Heißkanaldüsen Typ SLT/-DLT Customer information

Heißkanaldüsen Customer information 

Typ SLT/-DLT 

B. Braun builds a high-tech production line for infusion solutions with 

GÜNTHER Hot Runner Systems using innovative valve gate technology 

In its implementation of a challenging project, B. Braun 

relies on the innovative valve gate technology from 

GÜNTHER Heisskanaltechnik GmbH. 

As one of the largest infusion solution manufacturers in 

Europe, B. Braun Melsungen AG has started up a new 

high-tech production plant for infusion solutions in 

Melsungen, Germany. Under the name of L.I.F.E. 

(Leading Infusion Factory Europe), Braun has planned 

three new production lines to produce and fill infusion 

solutions, and completed implementation of the plan by 

putting the third line into operation in April. 

The entire process runs online: from the manufacturing 

of bottles made of polyethylene through bottle filling and 

closing to automatic labelling, packaging and storage. A 

plastic cap is placed on the filled and closed bottle, which 

is then overmolded with PE in a subsequent injection 

moulding process. This creates a liquid-tight connection 

between the cap and the bottle. 

Ecoflac infusion solutions from the new 

high-tech production line for infusion solutions 

www.guenther-hotrunner.com 

4/11 Subject to technical changes 

When overmolding the cap/bottle, very even filling of 

melt into the cavities is necessary. There is otherwise a 

risk of overloading of individual cavities, which would 

lead to the rejection of bottles that are already filled. 

In conjunction with filling the cavities evenly with low 

injection pressure, very stringent requirements are also 

set for the gate quality, and importance is attached to a 

high level of process reliability and short cycle times. To 

be able to meet these demanding requirements, B. 

Braun formed a team in which specialists from 

GÜNTHER Heisskanaltechnik GmbH, Frankenberg, 

Germany, and the injection molding machine maker 

Arburg in Lossburg, Germany, were represented. The 

outcome of this cooperation was an injection molding 

machine specially suited for the tool and an efficient hot 

runner system. 

High optical requirements resulting from the use of a 

larger injection gate cross-section and the required 

reduction in cycle time make it necessary to use a hot 

runner system with valve gate technology. 

The hot runner system has to be able to fill 24 cavities 

with 1g polyethylene (PE) each with a minimum drop of 

pressure. Each of the five special injection molding 

machines has, divided into two rows, four 6-cavity molds, 

each of which can be replaced separately. The division 

into four molds results from the requirement of being able 

to change any of the units as quickly as possible in the 

event of a fault. 

This application uses the 5NLT type nozzle screwed to 

the manifold. This 230 V valve gate nozzle is excellently 

suited for confined installation spaces. The pluggable 

thermal and power connections of the nozzle allow 

replacements without having to completely dismantle 

the wiring. 

Each of these 6-cavity molds is equipped with a 

separately controlled needle actuation unit. The “sliding 

cam” actuation mechanism consisting of a lifting plate, 

specially coated guiding rail and a pneumatic drive 

cylinder ensures that the gates open and close precisely 

and evenly. Each drive cylinder can be removed without 

dismantling the mold. The positions of the needles can 

also be adjusted when still mounted. 

For any questions, please contact our Application Engineering department at +49 (0) 6451 5008-31 or -63. 

The information is given in accordance with our present-day knowledge and is meant to provide technical background. 

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View within the mold 

1.5. 2 

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Heißkanaldüsen Typ SLT/-DLT Customer information 



The melt is distributed through a main distribution similar 

to a stack mould, consisting of a manifold, a connection 

piece and heated transfer elements. These special 

transfer elements make it easy to replace the individual 

6-cavity molds. 

GÜNTHER valve gate echnology is distinguished by a 

long service life. Short cycle times and excellent gate 

quality without vestige can be achieved. Another 

advantage is that all parts subject to high wear can be 

eaesily replaced. Accordingly, problems such as nozzle 

clogging, poor part filling, gate stringing and inadequate 

gate quality can be avoided and shorter process times 

obtained. 

In comparsion to the plant previously used, it has been 

possible to reduce the cycle time and therefore also the 

process times by approx. 20%. 

Due to the many years of good experience that B. Braun 

has had with GÜNTHER Heisskanaltechnik and the 

convincing advantages of the valve gate system 

supported by the good technical service, the molds for 

the L.I.F.E. project were fitted with GÜNTHER hot 

runners. 

The L.I.F.E. project was implemented without delay. The 

project started in August 2002, and the first bottles were 

filled in February 2004. The requirements such as cycle 

time reduction, process reliability and the high quality of 

the injection gates have been constantly met since the 

commencement of the production. 

Dipl. Ing. Jörg Essinger 

Applications Engineering Manager 

Hot runner 

Cavity 

Segment of the mold 




Subject to technical changes 4/11





Conveying the containers through the testing machine and 

labeller to the packaging section. 

“Sliding cam” actuation mechanism 

ensures that the gates open and 

close with precise consistency. 



“Sliding cam mechanism” detail GÜNTHER 5NLT 

valve gate nozzle 



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Heißkanaldüsen Typ SLT/-DLT 



Customer information 







Smallest cavity pitches with the new micro flat nozzle type SFT/NFT 

A high number of cavities in a small space for micro 

articles made from technical thermoplastics is 

increasingly becoming one of the demands to be met 

today by modern injection molders. In order to enhance 

the economical efficiency in the production of such small 

articles, the trend today is going towards direct injection 

by means of a hot runner, in order to cut down on high 

sprue masses in comparsion to the part weight and to 

reduce cycle times determined by the sprue. 

GÜNTHER hot runner systems have always been 

especially well suited for these applications, on account 

of their excellent temperature control, outstanding 

thermal separation between the hot runner system and 

the mold, as well as technical innovations. The 

introduction of the SFT/NFT nozzle series has resulted in 

an additional wide range of possible applications. 

On account of their slightly different design as compared 

to conventional hot runner nozzles, cavity pitches from 

7 mm can be realized for open hot runner systems, and 

from 9 mm for hot runner systems with valve gate 

technology. 

The flat nozzles of the series SFT/NFT consist essentially 

of a metal tube with a tip, open passage or needle 

guide, a thermocouple and a nozzle body with integrated 

heating elements. The constant excellent temperature 

control of these nozzles with simultaneous high heating 

output in the area of the tip is achieved by the use of 

nickel-plated brass (CuZn) as basic material of the 

nozzle body and the two heating cartridges, which are 

operated via one control circuit. 



Thermal separation from the mold is achieved by an air 

gap and by means of a special titanium ring in the contact 

area of the tip. 

The standard diameters of the material channel of these 

nozzles range from 2.8 mm to 6.0 mm, and they are available 

in the lengths L of 60 mm, 90 mm or 110 mm. It goes 

without saying that custom/made solutions to meet 

special application requirements are also possible. In 

this case, we recommend contacting our engineering 

department. 

The advantages of this line of nozzles are shown in the 

following example of an interesting application. 

The task was to realize direct gating of a part made of 

PPS GF30 with a weight of 0.1 g. The part is a housig of 

an electronic component and must be molded onto a 

punch-out strip for further processing. The customer also 

wanted to have separate thermal control of each gate. 

Thus, due to the specified size of the injection molding 

machine and the required number of 64 cavities, the job 

of the hot runner system was clearly defined. 

The processing of this glass-fiber filled high temperature 

plastic requires the use of a nozzle tip made of a special 

hard metal alloy to reduce tip wear and the use of a 

thermocouple suitable for high temperature applications. 

In addition, the high temperature application also 

requires full insulation with a material able to withstand 

manifold temperatures up to 600°C, minimizing the heat 

dissipation from the manifold. 



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Smallest cavity pitches with the new micro flat nozzle type SFT/NFT 

The given dimensions of the punch-out strip resulted in a 

grid dimension with a distance of 122 mm between 

double rows of nozzles and a nozzle pitch of 

15 x 9.35 mm for the position of the gates. 

It was no problem to implement the required nozzle pitch 

of 9.35 mm. However, the distance of 15 mm between a 

pair of rows and the separate control of each gate necessitated 

developing a “twin flat nozzle” 3SFT60S. 

This “twin flat nozzle” 3SFT60S consists of a nozzle body 

incorporating two material tubes with hard metal tips and 

two separately controlled heating elements. It was 

decided to do without full balancing because of the low 

part weight and the consequently increased dwell time of 

the material in the hot runner system. Due to the low part 

weight and the minimal pitches, the calculation of the 

pressure drop in a partially balanced hot runner system 


has resulted in a very small pressure difference whith no 

negative impact on the production process. 

This complete hot runner system requires 66 control 

points, 64 for the individual cavities and 2 for the 

manifold. As a “Hot Half”, i.e. with the clamping plate, 

frame plate and cavity nesting plate, the system was 

completely wired, assembled and tested before delivery 

to the customer. 





Stable and Material Saving Processing of Flame Retardant Polyamides with 

GÜNTHER Hot Runner Technology 

As a world leading supplier, Moeller GmbH (Bonn) pro- 

duces components and systems for automation, command 

and control devices. Diverse electrical and electronic 

components made of plastic are used in these systems. 

Fig. 1 Pushbuttons in command and control equipment 

(photo: Moeller GmbH) 

For a long time now Moeller has been using molds with 

hot runners for sprueless production of these parts. The 

advantages of hot runner technology over a conventional 

gating system include savings in material and a 

reduction in cycle time. 

When selecting a plastic for electronic components, it is 

often necessary to take account not only of the design 

requirements but also of statutory provisions and standards. 

In the electronics industry, for example, plastic 

components that are in direct contact with live parts must 

conform to the IEC Standard (International Electrotechnical 

Commission) etc. A further requirement is 

that the plastic must be capable of extinguishing itself 

after catching fire. Here, Standard 94 of the Underwriters 

Laboratories has established itself throughout 

the world as the authoritative standard for classifying 

flame retardance in plastics. The classification in standard 

94 of UL depends on the rate of combustion, time 

needed for extinction, formation of drops and afterglow 

time. Depending on the component's function, the 

following criteria must be met: 

UL94 V2: Vertical test specimen; self-extinguishing up 

to 30s after withdrawal of the flame, drips of flaming 

particles allowed; afterglow max. 60s. 

UL94 V0: Vertical test specimen; self-extinguishing up 

to 10s after withdrawal of flame; no drips of flaming 

particles; afterglow max. 30s. 

Moeller usually uses PA66 reinforced with 25% fiber 

glass with flame retardant for housing of electrical or 

electronic components. This type of material complies 

with UL94-V2 combustibility grading as well as other 

standards. 

A lot of devices from Moeller are also used in areas subject 

to the ATEX directives (ATEX = Atmospheres Explosibles 

= potentially explosive atmospheres). Here the requirements 

set for flammability have recently been 

tightened so that these components must now meet the 

requirements in combustibility class UL94-V0. On 

account of this more stringent requirement Moeller has 

had to replace the type of plastic it had previously used in 

a lot of components by an appropriate one classified in 

conformance with UL94-V0. 

Depending on the polymer, various flame protection systems 

are necessary to make a plastic flame-retardant. In 

the case of the PA66 used here, red phosphorus is used 

to give flame retardancy. The combustibility class is 

usually influenced by the quantity of the flame protection 

system used. Depending on the quantity, the red phosphorus 

used here reacts more or less strongly to temperature. 

Accordingly overheating during processing can 

cause thermal damage to the flame retardant. The gases 

arising as a result can form deposits on the mold and lead 

to corrosion. Occasionally the gases can even inflame. 

The PA66 with 25% glass fibers originally used by 

Moeller (combustibility class in conformance with UL94- 

V2) could be processed easily with the existing hot 

runner system. However, after changing to a PA66-GF25 

conforming to combustibility class UL-V0, serious problems 

arose when processing with this hot-runner system. 

In spite of the processing temperatures of 275…295°C 

being appropriate for the material, extremely severe deposits 

appeared on the molds. The molds had to be 

cleaned every 30,000 to 35,000 shots. In addition to 

cleaning the mould deposits, the mold inserts had to be 

replaced after every 250,000 shots because of 

corrosion. The reason for this heavy formation of 

deposits and corrosion in the mold was the significantly 

excessive rise in temperature in the hot runner nozzles in 

connection with the higher quantity of red phosphorus in 

the PA66. With a temperature of 290°C set at the control 

unit, temperatures of approx. 360°C were sometimes 

measured in the nozzles. This caused a reaction in the 

flame retardant. 



. 



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1.5. 7

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At that time GÜNTHER Heisskanaltechnik GmbH, 

specialized in the processing of demanding plastics, was 

given an order by Moeller to test an optimized hot runner 

system, at first for a 2K component. For the trial Moeller 

selected the “button insertion guide“ for holding a 

pushbutton (Fig. 2, 3) made of a flame-retardant PA66 

(with 25% glass fibers) and a TPE. 

Fig. 2 Pushbutton insertion 

guide for a pushbutton, 

made of PA 66 Gf25 

(Moeller) 

Fig. 3 Pushbutton 

(Moeller) 

The following criteria were set for selecting the hot 

runner system: 

� � �processability of a PA66 with glass fibers and 

flame retardant (red phosphorus / UL94-V0) 

�consistent temperature profile over the whole 

length of the nozzle 

�no massive temperature increase in the nozzle 

�low level of shear stress on the melt in the hot 

runner. 




The hot runner nozzle with a two-part shaft developed 

and patented by GÜNTHER Heisskanaltechnik GmbH 

(Fig. 4) has been selected. 

Fig. 4 Nozzle with shaft 

(Photo: GÜNTHER Heisskanaltechnik GmbH) 

This hot runner nozzle is setting standards in precision 

and economic efficiency. Various design features in the 

two-component shaft of the hot runner nozzle ensure 

excellent insulation in the front area of the nozzle and 

keep heat losses between the hot runner nozzle and the 

cavity extremely low. 

Due to this thermal insulation between the hot runner 

nozzle and the mold there is no problem in processing 

engineering plastics and high temperature polymers. 

From the lowest shot weights, as of approx. 0.019 g up to 

shot weights of approx. 5000 g, a wide range of 

applications in technical and precision injection molding 

are covered by the GÜNTHER hot runner technology 

portfolio. 



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1.5. 8 






Material 

tube 

Heater 

Air 

Gap 

solidified 

plastic 

Melt 

Shaft made of 

titanium alloy 

Open nozzle tip 

Fig. 5 Detail 

Nozzle with shaft and open nozzle tip (DHT nozzle) 

The optimal thermal insulation minimizes the heat loss of 

the nozzle through heat conduction. This assures 

consistent temperature control in the nozzle and prevents 

an excessive rise in temperature at which the temperature 

measured in the nozzle is much higher than the 

target temperature. This prevents any possible damage 

of the plastic melt or additives (flame retardant) caused 

by an excessive rise in temperature. 

To keep the shear stress on the melt as low as possible, 

the nozzle was provided with an open nozzle tip (Fig. 5) 

instead of a torpedo tip. This allows an unobstructed melt 

flow through the nozzle and intermediate gating into the 

cavity. As the parts are filled through a sub-runner, the gate 

vestige at the injection point is of little importance. 

Compared to a nozzle with torpedo tip the residual sprue 

is slightly bigger. 

Fig. 6 Vertical construction of the hot runner system for 

“pushbutton insertion guide“, Component 1 (PA66- 

GF25): 4-drop, 2x 5DHT50 nozzle on sub-runner 

The opening characteristics of the nozzle are critical for a 

reliable process. Tests have shown that both nozzles 

with an open nozzle tip give an even filling pattern at the 

same temperature. These filling patterns carried out to 

different filling degrees can be reproduced over a large 

number of cycles. Figures 6 and 7 show the result of the 

filling analysis at 25% and 50% filling. 





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1.5. 9

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Fig. 7 Filling pattern with 25 % mold filling 

Fig. 8 Filling pattern with 50 % mold filling 

The good insulation of the 5DHT50 B nozzle used allows 

the material to be processed at a nozzle temperature of 

265...270°C to significantly reduce the emission of gases 

from the flame retardant. The intervals for the necessary 

maintenance work have been extended from < 35,000 

shots before to > 50,000 shots now. With the previous 

system the inserts were worn after approx. 250,000 

shots due to corrosion but now with the GÜNTHER hot 

runner system, more than 1.2 million shots have been 

possible without corrosive wear. 




Fig. 9 2K-mold for insertion guide (4-fold) 

Although nozzles with open nozzle pieces are used, the 

plastic melt does not drool when the mold opens. One of 

the reasons for melt drooling is imprecise temperature 

control in the hot runner nozzle. Excessively high 

temperatures in the hot runner can cause the melt to 

expand and plastic can exude even when the mold 

opening times are very short. In practice this effect is due 

to a very narrow process window: There are often only 

approx. 5K between the freezing and the explosion-type 

opening of the nozzle and the associated drooling of the 

melt. 

The changeover has had another effect, too: Using this 

hot runner nozzle has prevented the formation of streaks 

around the injection point. 

In the meantime the process capability of the GÜNTHER 

hot runner systems has been proving its worth for more 

than a year. Meanwhile, Moeller has equipped two 

further molds for processing this PA type (PA66 25% GF; 

UL-V0) with GÜNTHER hot runner systems (5DHT50B 

nozzles). Here, too, this type of material can be 

processed without any problems. 





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1.5. 10 



Preventing flow marks on injection molded parts 

The requirements set on molded parts in the visible area 

are high, a clean injection point is indispensable. This is of 

particular importance for components which are backlit, 

as it is the case with light covering panels. Flow marks 

caused by flow separation of the melt in the nozzle can 

lead to quality problems. To ensure process reliability, 

nozzles with multi-purpose pluggable tips are used by 

Werner Langer Metall- und Kunststoffverarbeitung, a 

metal and plastics processing company. 

A PMMA-type material, optimized for transparency and lack of 

streaks, is used for light covering panels (between the mold 

halves). 

Plastics processing company Werner Langer produces 

three different kinds of light covering panels for Simon & 

Schelle, a lighting manufacturer. The production started 

in early 2007. “Our customer's quality standards as well 

as the requirements on the light covering panels were 

clearly defined,” says Werner Puppe, technical manager 

at the plastics processing company from Meschede- 

Berge, “a clean injection point, no flow marks or weld 

lines, little warpage, absolutely no sink marks on the side 

flanges of the covering panels, and a high-quality surface 

finish. After all, the light covering panels shall be used as 

mirror lightings in the bathroom.” 

Use of conventional nozzles is problematic 

Standard nozzles with screwed-in tips, sufficient for most 

of the injection molding applications, could not be used for 

production of light covering panels because their use 

goes together with flow separation of the melt. This would 

have caused flow marks on the opaque covering panels 

which would be visible when backlit. In search of a 

solution, the company contacted hot runner supplier 

GÜNTHER Heisskanaltechnik. 





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“Since we have been in contact with this supplier since 

1988, and have always appreciated is good consulting 

services and technical support, we were looking for 

collaboration on this application as well. For this 

purpose, we made the 3D design data of the part 

available for the hot runner specialist. As a result, 

GÜNTHER came up with a proposal to use a nozzle type 

with a multi-purpose pluggable tip.” This relatively new 

type of the tip enables the melt to be mixed in such a way 

that there are no longer flow marks seen on the molded 

part. This is a unique selling point of the multi-purpose 

pluggable tip on the market. 

“The design of the nozzle tip yields a very low shear 

potential,” says Walter Ehlert, in charge of consulting and 

sales at the hot runner specialist. “Competitive products 

do feature some design principles which should result in 

flow marks being avoided; however, these techniques 

often increase the level of shear stress in the melt, which 

may lead to degradation of the plastics. This can often be 

seen in the form of streaks on molded parts.” This 

problem arises particularly in the case of light covering 

panels: The molded part is very long, so it must be filled 

quickly. The multi-purpose pluggable tip, designed with 

its maximum depth of clearance, produces minimal 

pressure drop together with a very low level of shear 

stress. 

The new multi-purpose pluggable tip, here in a nozzle of the 

SET60S type, enables the melt to be mixed in such a way that 

no flow marks appear on injection molded parts. 

1.5. 11


Preventing flow marks on injection molded parts 

Apart from flow marks being avoided, two further quality 

features of the manufacturing process have caught Mr. 

Puppe's eye: “Virtually no warpage and no sink marks on 

the whole length of the light covering panels, this is really 

amazing. We would not have been able to get such a 

result with conventional nozzles.” Last but not least, the 

design of the new nozzle enables particularly fast color 

changes. This is because the melt channel is designed to 

optimize flow so that the material comes to rest nowhere, 

which results in an optimal melting process. 

„Without a nozzle type with a 

multi-purpose pluggable tip, we 

would have had to use a 2-drop 

manifold for this application, “ adds 

Puppe, „this would have forced up 

the prices. The costs of a nozzle with 

a multi-purpose pluggable tip are 

only marginally higher than those of 

a conventional nozzle. Thus, better 

Werner Puppe product characteristics are 

technichal manager, combined with decreased process 

at Werner Langer, costs.“ 

a plastics processing, 

company from 

Meschede 

Molds on hand can be retooled 

The multi-purpose pluggable tip is intended primarily for 

parts that have to meet demanding requirements for 

optical clarity, such as, for example, applications 

involving polycarbonate or PMMA, or perhaps POM 

homopolymers. “No applications using fiberglassreinforced 

plastics have been implemented so far. 

However, they are also possible if the tip is made of hard 

metal,” says Ehlert. 

The customer of Werner Langer chose an opaque white 

shade for the light covering panels, which limited the 

selection of the material right from the start. A PMMA- 

type material, optimized for transparency and lack of 

streaks, is used for this application. 

Since the part is closed on the one side and open on the 

other, different flow paths in the mold are the result. To 

obtain a proper nozzle position, a mold flow analysis was 

carried out to come up with an off-center positioning of 

the nozzle. “During the sampling inspection as well as 

when starting up the mold, there was not a single 

problem with the hot runner nozzle,” says Puppe. 

“Plug&Play”, this is how he describes the change-over to 

the new nozzle concept. 

The tool is installed in an Engel injection molding 

machine, type 1050/200, with a clamping force of 

2,000 kN. A linear handling device takes the parts and 

puts them on a conveyor belt where they are manually 

packaged. Molds on hand can be retooled with the new 

kind of nozzle. In fact, the installation of a nozzle with a 

multi-purpose pluggable tip requires just a little 

modification of the mold contour. “However, only very 

small modifications are necessary to replace a 

GÜNTHER hot runner nozzle,” says Ehlert. 

Wide range of applications 

It is only natural that recently developed products, such 

as the multi-purpose pluggable tip, which are relatively 

new on the market do not immediately become 

widespread in applications. First of all, it is necessary to 

gain experience, and test the basic applications in longterm 

studies. For one and a half years now, the multipurpose 

pluggable tip has been included in the product 

range offered by GÜNTHER. The market entry phase is 

over, and Ehlert sees large areas of application, for 

instance, in the automotive industry, as well as for every 

application which requires optical parts. 

For Werner Langer, the testing phase is over for some 

time already, at least with regard to the light covering 

panels; the production is a complete success. Puppe is 

confident: “When it comes to the production of optically 

demanding parts, we will continue using the nozzle with 

a multi-purpose pluggable tip.” 



1.5. 12 

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The light covering 

panels are manufactured 

on an 

Engel injection 

molding machine, 

type 1050/200, 

with a clamping 

force of 2,000 kN. 



Heißkanaldüsen Customer information Typ SLT/-DLT 

Hot runner technology for medical 

products: Precision millions of times 

Mini-Spike and Transofix, these are the names of two 

products manufactured by B.Brown, a healthcare 

company. These medical products are provided with 

protective caps which, manufactured with high precision, 

are required in millions of units every year. To guarantee 

a trouble-free production, the company trusts in systems 

supplied by GÜNTHER Heißkanaltechnik. 

The first product serves as a withdrawal and injection 

spike for multi-dose containers, the second one as a 

transfer device for sterile liquids, e.g. for drug admixture. 

In spite of the high number of pieces, precision has the 

highest priority when producing protective caps. „The 

force fit of the protective caps must be manufactured in 

such a way that on the one hand the caps do not get lost 

during transportation of medical products, but on the 

other hand can nevertheless be easily withdrawn,” says 

Stefan Moser, a project manager at B.Braun Melsungen 

AG. “And this must also be possible when the user is 

wearing Latex gloves which can additionally be 

moistened with liquids like solvents.“ 

Until the conversion of production at the beginning of 

2007, the company had manufactured protective caps 

using two conventionally designed multi-cavity molds 

with multi-tip nozzles. 

Picture: Parting line 1 of the tandem mold is intended for manufacturing 

the Mini-Spike protective cap, parting line 2 (pictured) 

for manufacturing the Transofix protective cap 

The conversion of production was triggered by the fact 

that, first, those molds with a low number of cavities 

could no longer provide the required production 

volume and, second, the Mini-Spike tool had reached 

its wear limit. 

The tandem technology seemed to be appropriate to 

solve the quantity problem. By this method two 

different parts can be separately and individually 

injection molded in an overlapping injection cycle on 

an injection molding machine using a tandem mold 

provided with two parting lines. The volumes and the 

quantity of pieces can be set individually for each 

parting line. The gating system of the tandem mold 

consists of an alternating slider with a bayonet socket, 

with one of the sides respectively locked and the other 

one unlocked for opening. “The design of the system is 

simple, rugged and not susceptible to malfunctions,” 

says Joachim Hammer, a machine setter and quality 

controller at the supplier from Melsungen. 

For any questions, please contact our Application Engineering department at + 49 (0) 6451 5008-31 or -63. 




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Picture: Stefan Moser, project manager (left), Benjamin Koch, 

responsible for machine optimization (middle), and Joachim Hammer 

(right), machine setter and quality controller at Braun Melsungen 

1.5. 13

1.5. 14 

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Implementation of tandem technology requires an 

injection molding machine with a relatively high 

installation height of the mold and adapted 

programming. B.Braun decided to use a machine of the 

type Engel 200/90 V Electric with an electrical injection 

unit. 

“The hot runner system is the highlight of the tandem 

mold,” emphasizes Stefan Moser. “This system does not 

only guarantee an equal filling of the cavities on both 

sides of the mold, but also a faultless gate point at the 

protective caps.” “Because of the high number of cavities 

24+48 in the tandem mold, we first focused on a 24+48drop 

hot runner system with individually controlled open 

single nozzles,” says Walter Ehlert, responsible for 

consulting and sale at GÜNTHER Heisskanaltechnik. 

For about 20 years B.Brown has been trusting in 

components provided by the company from 

Frankenberg. 

Picture: Open multi-tip nozzle of the type 26ZHT – all in all 24 nozzles 

are installed in the two parting lines of the mold: 12 of them with two 

tips each on the Mini-Spike side, and 12 of them with four tips each 

on the Transofix side 

Picture: Mini-Spike, a withdrawal and injection spike for multi-dose 

containers (above) and Transofix, a transfer device (below), each of 

them with a protective cap (green color): Such a protective cap made 

of polyethylene (Lupolen 3020K) barely weights 0.5g 

“But it would have been too demanding and expensive to 

install such a system within the planned compact mold,” 

Walter Ehlert continues to explain. Since the hot runner 

with multi-tip nozzles did function well in the mold in 

stock, this technical alternative solution has finally come 

into view. 

Ehlert describes the advantages of multi-tip nozzles for 

tandem production in the following way: “These nozzles 

have a very small structural shape, therefore they allow 

very small patterns in the mold, keeping the controlling 

effort low.” However, the use of multi-tip nozzles is often 

a compromise because there is only one control zone for 

four gates. Therefore the user cannot control the details 

of the process so well as with single nozzles. However, 

with “simple” materials this feature can be compensated 

for without any problems. 

The concept of the hot runner system comprises twelve 

open multi-tip nozzles per parting line; the ones of the 

type 26ZHT18/2/67-S with two tips on the Mini-Spike 

side, and the others of the type 26ZHT18/4/67-S with 

four tips on the Transofix side. Valve gate technology 

was originally planned only for the sprue bar. However, 

since the mold was thought to work with a stiff sprue bar 

which moves away when the parting line 1 opens, valve 

gate technology was also provided for the injection 

molding machine along with the needle valve in the 

sprue bar. 








This has the advantage that the machine is able to 

continue conveying even with the sprue bar moving 

away to eject the parting line 1. 

“However, at the beginning of the series production it 

was problematic with this configuration to evacuate the 

pressure quickly enough from the hot runner system, 

remembers Moser. In principle, due to tandem 

technology, the material for each injection molded part 

has to be injected and conveyed, and finally the pressure 

has to be removed again from the system in half of the 

cycle time. With the protective caps, the material 

squeezed out of the system on the injection side, and the 

parts initially showed extreme stringing.” 

The problem was basically solved with the following 

measures: The machine valve gate nozzle was replaced 

by an open nozzle, the inner cross-section of the 

connecting nozzle was enlarged, and the machine 

program was optimized. Today, the cycle time of the 

single part has been reduced by 10%, with two parts 

being produced at the same time due to tandem 

technology with alternating injection and cooling. 

To sum it up, good filling performance for all cavities, no 

stringing, good tear-off behavior are the parameters for 

which the hot runner system supplied by the 

Frankenberg company is substantially responsible. 

The company was founded 25 years ago. Today it 

employs about 200 people, and operates together with 

its partners all over the world. 





iA 

Picture: “Hot half” with view on the multi-tip nozzles 26ZHT with 

four tips 

1.5. 15


Hot runner systems for plastics filled with 

metal or ceramic powders 

The MIM (Metal Injection Molding) and CIM (Ceramic 

Injection Molding) technologies use injection molding 

process to produce metal and ceramic components 

which could not, or only with considerably more effort, be 

produced by machining. With these methods threedimensional 

components, e.g. for medical engineering 

products, can be molded in only one working step with no 

need of subsequent machining. Without well adapted hot 

runners it is hardly possible to ensure manufacturing 

process reliability. 

Metal and ceramic powder filled plastics are used in 

many different fields. Examples of use of MIM are 

components for consumer products like ballpoint pens or 

for medical engineering products. Products 

manufactured by CIM are in demand where ceramics are 

required for insulation, often in conjunction with high 

temperatures. Sample applications can be found in the 

lighting industry. Both of the processes are relatively 

easy to use and make it possible to produce components 

without subsequent machining. Complex components 

can be manufactured this way. 

An application example for the MIM technology is an 

implantable infusion pump used in pain management for 

chronically ill patients. This device, installed in the 

abdominal wall, is applied for the measured dispensing 

of pain medication into the human body. 

The base plate was formerly manufactured by machining 

from a special, relatively expensive titanium alloy. This 

method was not only time-consuming but also expansive 

because of swarf. However, to realize the idea of 

manufacturing this component by MIM was not so easy 

at the beginning. Although it is normally quite easy to 

manufacture three-dimensional components by injection 

molding, the difficulty in this case was that the base plate 

had a large diameter and significant changes in wall 

thickness. 

This problem has been solved by injection molding the 

component with three parallel hot runner nozzles. It has 

resulted in short flow paths and more even pressure 

distribution to yield a component which is manufactured 

in only one working step without the necessity of 

subsequent machining. Lower production costs are yet 

another compelling factor. 

With the MIM and CIM processes, a metal or ceramic 

powder is mixed with a binding agent, often polyethylene 

or polyoxymethylene, and a special wax, and then 

granulated. 

This mixture, called a "feedstock", can be processed by 

injection molding like any conventional plastic material. 

The plastic material is then removed from the molding, 

the so-called "green part", by heating. After debinding, 

this component has a porous structure because of the 

removal of the plastic material and is called the "brown 

part". 

By sintering of this brown part the metal and ceramic 

constituents are baked together to form a component 

with a homogeneous structure whose density and 

resistance does not differ from a conventionally 

manufactured steel or ceramic component. 

The advantages of e.g. a metal component, like high 

mechanical resistance and high conductivity, are 

combined with a relatively simple way of manufacturing. 





iA 

Picture: The titanium alloy base plate (below) of an implantable 

infusion pump was formerly manufactured by a complex 

machining process. Today the MIM technology allows for scrap-free 

manufacturing without subsequent machining. (Photo: TiJet) 

1.5. 16




Basically, conventional injection molding machines can 

be used for CIM and MIM. But if a manufacturer wants to 

use these processes on long term, wear-resistant 

cylinders, screws and non-return valves should be used 

because these components are submitted to an 

increased abrasion due to metal and, even to a higher 

extent, ceramic powders. Discussions with feedstock 

manufacturers and plastic processors have shown that 

80 to 90% of the parts produced by using MIM and CIM 

are manufactured by means of a cold runner with a sprue 

rod. A big fraction of the sprue rod can be recycled, 

nevertheless it would be very promising to avoid this 

production step by using hot runner systems. 

A very homogeneous temperature control in the hot 

runner is required, since the materials have a very small 

processing window. Variations of the temperature lead to 

a segregation of binder and powder which results in 

shrinkage differences and finally in the formation of 

cracks in the component during the sintering process. 

For these applications, GÜNTHER Heisskanaltechnik 

GmbH recommends using its hot runner nozzles e.g. of 

the _HT type which are designed to meet higher 

requirements. 

The patented two-stage nozzle shaft guarantees an 

excellent isolation at the forward section of the shaft, 

providing for an extremely low heat loss between hot 

runner nozzle and cavity, and for a very homogeneous 

heat distribution within the nozzle. 

1.5. 17 

Material tube 

(25 W/mK) 

Heater 

Air 

(0,04 W/mK) 

Gap solidified 

plastic 

(0,2...1,2 W/mK) 

iA 

Picture: The two-stage shaft of the SHT type nozzle and the frozen 

plastic material which forms a "cap" around the nozzle provide for 

optimized isolation towards the cavity and therefore produce a 

homogeneous temperature profile in the nozzle. 

Melt 

Shaft made of 


(7 W/mK) 


(100 W/mK) 

In addition, the frozen plastic material forms a "cap" 

around the nozzle, thus providing thermal separation 

between hot runner nozzle and cavity. 

However, this feature produces quite the opposite effect 

for metal filled plastic materials because of the metal 

powder conductivity. In this case the mixture of plastic 

material and metal powder would draw the heat off the 

nozzle. That's why the supplier equip the nozzles used 

for MIM with special insulating caps made of a highly 

heat resistant plastics like polyetheretherketone (PEEK) 

or polyimide (PI) to provide thermal separation. A tubular 

titanium shaft located around the hot runner nozzle 

additionally improves the insulating effect. 

This is a certain distinctive feature of the products 

supplied by Günther, since most of the hot runner 

nozzles on the market have no two-stage shaft and 

achieve the sealing by direct metallic contact with the 

material tube in the mold insert. This leads to a very high 

heat loss which has to be compensated by a higher 

temperature in the hot runner nozzle. This causes an 

excessive rise of the temperature as well as temperature 

variations, and therefore the materials cannot be 

processed in a reliable way. 

With the MIM technology, the parts are often molded by 

direct gating, and not via a sub-runner. Nevertheless, a 

relatively large gating point must be used in this case to 

obtain the necessary throughput and to transfer 

sufficient heat into the gate point. This is necessary 

because the metal-filled material transfers some of the 

heat into the cavity, and the melt freezes quickly due to 

the high filler content. 

However, with the CIM technology a sub-runner is often 

used. Here, too, a large gate point is of importance in 

order to cause as little as possible shear stress and to 

transfer the melt as quickly as possible into the cavity. 

With regard to wear resistance, hot runners have to meet 

severe requirements, for both MIM and CIM. The 

products of Günther Heisskanaltechnik have nozzle tips 

made of hard alloy to provide reliable wear protection. 

For this reason high life times are possible with no need 

to change components of the nozzle. 








A further quality increase can be achieved by hot runner 

nozzles and manifolds which are heated by a fluid. 

It is well known that in particular for the processing of CIM 

feedstock a very homogeneous temperature control is 

necessary in order to avoid segregation and 

inhomogeneities of the melt. This may cause void 

formation in the component. Because of the inertia of the 

fluid, a nozzle heated by a fluid provides an even more 

constant temperature behavior than an electrically 

heated hot runner nozzle. 







iA 

Picture: Hot runner nozzles which are heated by a fluid provide a far 

more homogeneous heating as electrical heaters, and maintain 

the temperature at a considerably more constant level. 

1.5. 18


Hot-Runner Systems for High Injection Speeds 

When Speed Counts 

When delicate parts with thin walls and long flow parts 

are required, quick injections are essential for reliable 

production processes. Rapid injection processes are 

often indispensable for large-volume parts too however. 

An adapted hot-runner technology allows perfect 

processes and products here. 

Even in conventional injection moulding processes high 

injection speeds are often necessary but there are two 

variants that set particularly high standards: expansion 

injection moulding and physical foaming. In expansion 

injection moulding the melt is compressed in the screw 

antechamber or in the hot-runner and used as a pressure 

storage medium. As shown in the PVT diagram, the 

plastic melt can be compressed approximately 10 % at a 

pressure of about 2000 bar. This behaviour is used 

during expansion injection moulding. It is necessary for a 

reproducible process however that the pre-compressed 

melt volume be kept constant. For that purpose the 

screw must be held in an exact position after 

compression because it would otherwise be subjected to 

high pressure at the opening of the valve gate nozzle and 

an excessive amount of melt would enter the mould. This 

pre-condition is satisfied by electromechanically driven 

injection moulding machines, permitting an optional axial 

positioning within the system's confines and the 

maintenance of this position even under high pressure. 

If a hot-runner system is used in expansion injection 

moulding, a pressure of up to 2500 bar is built up and 

maintained for a defined time. This ensures an even 

pressure in all cavities. 

For the successful use of expansion injection moulding, 

an absolutely even opening of the needles is essential. 

Once the needles open, the melt that is precompressed 

in the hot-runner can expand like an explosion and fill the 

cavities evenly, allowing very thin-walled components to 

be filled. 

In physical foaming, for example with the MuCell 

process, the system is fed a physical blowing agent, 

which first dissolved in the melt under pressure. On 

injection into the cavity, the pressure reduces, the 

blowing agent expands and the melt foams. Here too it is 

necessary to be able to inject the melt at high speeds into 

the cavity in order to be able to foam the part selectively 

in the cavity. A light-weight component with a closed 

outer skin and foamed core emerges. This process can 

produce foam structures with walls thinner than one 

millimetre. 



iA 

The internal pressure that arises as a result of the 

foaming process acts on all points of the component, 

whereby to a certain degree it takes over the task of the 

holding pressure and in this way can balance out or at 

least reduce sink marks, shrinkage and warpage. 

For both processes the injection moulding machines 

must be adapted to the altered requirements. In 

expansion injection moulding an electric injection 

moulding machine is necessary for a precise dosage and 

injection. The MuCell process requires a special screw 

and special units in order to be able to inject the blowing 

agent in the super-critical state into the melt. Both 

processes – with just a few exceptions – can be 

conducted with all common polymers. LCP cannot be 

processed with the MuCell method but it is very suitable 

for expansion injection moulding. 

Valve gate systems essential 

In both processes valve gate hot-runner systems must 

be used in order to build up and maintain the required 

pressure in the hot-runner system. In expansion injection 

moulding the hot-runner system not only has to 

withstand very high levels of pressure, it must also be 

ensured that all needles in a multi-cavity mould open 

exactly and simultaneously. This even needle movement 

enables a lifting plate, which works in accordance with 

the principle of the sliding plate mechanism. Here the 

hydraulic piston's axial movement is guided through 

connecting links into the plate's lifting movement and 

accordingly causes the needles to move. 

Fig. A slide lock, pneumatically or 

hydraulically actuated by means 

of an external cylinder, allows the 

simultaneous actuation of all 

needles 



1.5. 19


1.5. 20 

iA 


In an X-Melt trial conducted in cooperation with the 

injection moulding machine manufacturer Engel, 

GÜNTHER Heisskanaltechnik GmbH in Frankenberg, 

subjected a two-cavity mould to a pressure of 2800 bar 

for half a second and checked the system for leaks. The 

injection trials were conducted with a test strip made of 

various materials with a wall thickness of 0.5 mm. The 

time for shooting the melt into the cavity varied from 

material to material and was 0.1 s for polystyrene, for 

example, and 0.04 s for LCP. The following are the 

results of the trial: the hot-runner system remained 

completely leak-tight at 2800 bar. No melt came out of 

the valve gate nozzles. Both cavities were filled 

simultaneously. A very high level of reproducibility could 

be attained. An example of an application for expansion 

injection moulding is the friction disk. 

Fig. For the expansion injection moulding of the friction disk an eightcavity 

hot-runner system with flat nozzles of the type 4NFT60LA is used. 

Friction disk 

Material 

Particle weight 

Wall thickness 

Gate diameter-ø 0.8 mm 

Hot runner 

Pitch center 

LCP 

0.02 g 

0.15 mm 

8-fold NV 

Hot runner nozzle 4NFT60 LA 

14 mm 

Fig. The LCP friction disk weihing 0.02 g can be produced with process 

reliability only with the expansion injection moulding method. 

(Photo: Schiebl) 

As trials have shown, reliable processes are possible 

only with expansion injection moulding. In this 

application a plastic part is injected onto a metal strip 

serving as a substrate. The disk is made of LCP, weighs 

0.02 g and has a wall thickness of 0.15 mm. The 

challenge in this project was to inject the very small 

quantity of material with process reliability. As the weight 

of the shot is so low, only valve gate systems can be 

used. 

A hot-runner nozzle specially designed for LCP 

processing was selected. The nozzle's material tube 

diameter was made narrower to reduce the viscosity of 

the LCP as a result of the higher shear. 

Abb. 8-fold hot runner system NV - friction disk of LCP 

Reduced weights and costs 

An important factor in physical foaming is that instead of 

expanding in the hot runner, the melt does not expand 

until it is the cavity. For that reason the hot-runner 

nozzles must maintain the pressure in the system after 

the injection of the melt and the subsequent closing until 

the blowing agent stays dissolved in the melt. This could 

be confirmed in trials. An example of an application is a 

car door lock housing with a wall thickness of 1.1 mm 

made of POM, which is produced with MuCell 

technology. The customer's aims were to cut costs by 

using less material and to shorten cycle time and reduce 

warpage and sink marks. The gas in the melt lowered the 

melt viscosity, which allowed a quicker injection. The 

microcellular foam allowed homogeneous shrinkage 

behaviour, which made it possible to avoid sink marks in 

thicker walls. The hot-runner nozzle used was a type 

8NLT80 nozzle from the supplier. The needles were 

actuated by hydraulically activated single needle valves. 

The customer's aims were to cut costs by using less 

material and to shorten cycle time and reduce warpage 

and sink marks. The gas in the melt lowered the melt 

viscosity, which allowed a quicker injection. The 

microcellular foam allowed homogeneous shrinkage 

behaviour, which made it possible to avoid sink marks in 

thicker walls. The hot-runner nozzle used was a type 

8NLT80 nozzle from the supplier. The needles were 

actuated by hydraulically activated single needle valves. 







Fig. This car door lock housing made of POM is produced with 

MuCell technology (Photo: ITW) 

Door lock housing 

Method Mucell-technology 

Material 

Particle weight 

Wall thickness 

Gate diameter-ø 

Hot runner 

Nadelansteuerung 

Weight reduction 

POM 

49,0 g 

1,1 mm 

2,0 mm 

8NLT80 





Single valve (hydraulic) 

10 % 

When physical foaming is used, the needles are moved 

by means of single needle valves depending on the 

number of the cavities. MuCell technology made it 

possible to reduce the weight of the door lock housing by 

10%. 

Homogeneous temperature control is important 

The valve gate hot-runner nozzle with shaft (N_T nozzle) 

from GÜNTHER Hot-Runner Technology is very suitable 

both for expansion injection moulding and also for 

physical foaming. The advantages of this nozzle are the 

exact temperature control. In particular in the case of 

technical polymers, which are semi-crystalline plastics 

with a narrow processing window, it is essential to have 

homogeneous temperature control over the entire length 

of the nozzle. For the purpose of attaining a 

homogeneous temperature profile, the nozzles have a 

two-part shaft for insulation and the front area is made of 

a titanium alloy. 

Expansion injection moulding and physical foaming offer 

new prospects for plastic processing operations in terms 

of saving costs and optimising products and processes. 

Adapted hot-runner systems are indispensable however 

to process materials reliably. The GÜNTHER hot-runner 

technology range includes valve gate systems specially 

designed for this area of applications and they have 

proved effective in practice many times. 



iA 

In general it is important in all valve gate systems that the 

needle be centred exactly when closing and that it dip 

into the injection gate without the sealing area of the 

needle coming into contact with the needle guide. This 

counteracts wear on the system. The needle guide in the 

GÜNTHER hot-runner technology systems is made of 

powder metallurgical steel, which has a very high degree 

of hardness and strength. 

If an individual component is worn, it can be replaced on 

its own. As the needle guide dips down as far as the edge 

of the product, only the guide has to be changed in the 

case of wear. It is not necessary to work on the mould 

insert. 

Fig. To produce the car door lock housing, a four-cavity hot-runner 

system is equipped with type 8NLT80 nozzles. 

1.5. 21


Vliesolen – Bamboo Fibre Reinforced Plastics 

The firm of PMG Geotex in Chemnitz compounds 

plastics with exotic filling materials. 

Instead of the usual glass fibres special, they use 

bamboo fibres to modify the properties of polypropylene 

or polyethylene, for example. Depending on their length, 

the bamboo fibres can be used in different areas. For 

example, longer fibres are mixed into screed or concrete 

to prevent cracks forming during drying. The shorter 

bamboo fibres are compounded into plastics as 

reinforcement or filling material.These fibres, which are 

chemically linked with the polymer, make the plastics 

much stronger than those that are not reinforced. In 

addition this filling material also has an impact on the 

price of the product. 

The properties of a PP modified with 30% bamboo fibres 

rank between unreinforced polypropylene and 

polypropylene that is reinforced with approx. 20% glass 

fibre. 

There is no problem in processing these plastics 

conventionally with cold runners. However, more and 

more interested parties ask about the possibility of 

processing this material with hot runners too. 

The trials carried out by PMG and GÜNTHER 

Heisskanaltechnik GmbH together show that it is 

possible to process plastics filled with bamboo fibres with 

hot runners also. 

Three plastics (PP, PE–LD /PE-HD), each with 30% 

bamboo fibres, were available for the processing trial: 

- Vliesolen BF30, natural (PP-2/30-HM1) 

- Vliesolen BF30, black (LDPE-2/30-HS2) 

- Vliesolen BF30 (HDPE-1/30-HM1) 

These materials were tested in a test mould 

(2-cavity: 1-gr washer), which was equipped alternatively 

with 

- nozzles of tip (5SHT50S) or 

- valve gate nozzles (5NHT50LA 

Small sprue gates are not suitable because the bamboo 

fibres are longer than glass fibres and there is a risk of 

the sprue gate getting clogged up with fibres. 

If the injection gate diameter is 1.6 mm (5SHT50) or 1.4 

mm (5NHT50LA), the above types of materials can be 

processed without restriction. 



The hot runner nozzles used in the test feature a two-part 

shaft in the front area of the nozzle. This structural feature 

provides excellent thermal isolation between the hot 

runner nozzle and the mold. This thermal separation also 

has a positive effect on the temperature control inside the 

nozzle. The hot runner nozzles are suitable for 

processing standard, engineering and high temperature 

plastics. When processing filled plastics, nozzle tips 

made of a hard metal alloy with good heat conductive 

properties provide very good wear protection. 

Material tube 

(25 W/mK) 

Heater 

Air 

(0,04 W/mK) 

Gap solidified 

plastic 

(0,2...1,2 W/mK) 

iA 

Fig. Standard hot-runner nozzle 

5SHT50 with two-component 

shaft (patented). 

Nozzle with excellent insulation 

in the front shaft area. 

Picture: The two-stage shaft of the SHT type nozzle and the frozen 

plastic material which forms a "cap" around the nozzle provide for 

optimized isolation towards the cavity and therefore produce a 

homogeneous temperature profile in the nozzle. 

Valve gate nozzles can be recommended to achieve 

flash-free gate quality of the part. These nozzles are 

characterized by a long lifetime and short cycle times in 

operation. 

Melt 

Shaft made of 


(7 W/mK) 


(100 W/mK) 



1.5. 22

1.5. 23 

iA 


Vliesolen – Bamboo Fibre Reinforced Plastics 

Another advantage is that all the wear parts can be easily 

exchanged. This can avoid problems such as clogging of 

the nozzles, poor part filling, stringing and poor gate 

quality, and achieve shorter process times. By using a 

valve gate nozzle, the cycle time can be reduced by up to 

20 %, depending on the application. 

Fig. Sample parts, produced with a 5SHT50 nozzle 

Thanks to the optimised temperature control in the hot 

runner nozzles the material could be processed at the 

temperatures recommended by the manufacturer. 

Depending on the base polymer and type of nozzle, the 

injection pressure fluctuated between 700 bar and 1100 

bar. 

On the whole, the parts make a convincing impression. 

The sample parts produced with the nozzle with tip 

showed a good gate quality. It was possible to realise a 

maximum tear-off height of approx. 0.15 mm. 

As expected, valve gate nozzles can achieve optimum 

gate qualities with these types of materials too. 

Fig. mop holder made of vliesolen 

The thermal resistance of the bamboo fibre reinforced 

polymers is relatively high; after a simulated machine 

idle time of 10 minutes there is no problem in starting the 

aforesaid materials with the two hot runner nozzles in the 

test again. It is not necessary to have any higher nozzle 

temperatures. The parts do not show any thermal 

degradation. 

To summarise, it can be said that we did not experience 

any problem when processing the three tested plastics 

with bamboo fibre reinforcement in the hot runner 

system from GÜNTHER Heisskanaltechnik GmbH. This 

makes it possible to manufacture a product economically 

with a good price-performance ratio. 








Nozzle design for injection moulding on tandem tools 

50% of cycle time can be saved by switching from 

standard injection moulding production to tandem 

technology. A precondition here is the ideal adaptation of 

the melt flow path and the nozzles to suit the altered 

process. To produce glass-fibre reinforced polyamide 

covers, GÜNTHER Hot-Runner Engineering developed 

within a very short time a nozzle construction that offered 

the advantages of low costs, reliable heat management 

and easy installation. 

Objectives which even in normal economic circumstances 

would rank among the most important for a new 

process are of particular significance in times of crisis. 

These are to manufacture components in as short a time 

as possible and at costs as low as possible. The fact that 

tandem technology in injection moulding can reduce 

cycle time by up to 50% induced a major German 

manufacturer of motor tools to change over to this technology 

for the production of glass-fibre reinforced 

polyamide covers for work tools. Tandem technology 

makes use of the unproductive cooling time in injection 

moulding. Ideally this doubles the output from a standard 

machine. The process runs as follows: after closing the 

first parting level of the mould and injecting the melt, the 

second parting level opens during the cooling process, 

the parts fall out of the mould, the parting level closes and 

the melt is injected. While the components are cooling in 

the second level, work can be continued in the first level. 

The advantages for the process of this overlapping are 

shorter time requirements and lower costs. 

Fig. Mould with tandem technology: One challenge is the melt flow 

path from the first to the second parting level. 



iA 

Before the process changed over to this technology the 

assembly, which consisted of two differently-sized 

components, was produced on two injection moulding 

machines in two different moulds. In tandem technology 

the production of the assembly could be combined in one 

mould so that there was no longer any need for a second 

machine. 

Keeping mould costs low 

To implement the technology, the injection moulder got in 

touch with T/Mould GmbH & CO KG, Bad Salzuflen, the 

sole supplier of tandem technology, at the beginning of 

2008. “A major challenge presented by such a project is 

to keep tool costs as low as possible”, explains Daniel 

Gersmann, who is the supplier's Project Consultant. 

“In the current project the main challenges were the 

design of the nozzle and melt flow path. The tandem 

technology side of the project did not present any great 

problems because the component geometry is relatively 

simple.” 

To find the best solution, injection moulders and suppliers 

of tandem technology drew on the know-how of Günther 

Heisskanaltechnik GmbH in Frankenberg (Eder). The 

hot-runner specialist developed a system for the 

application in which the functionality of the complete 2+2cavity 

mould could be produced with two nozzles. The 

alternative to this would have been a more complex hotrunner 

system with main manifold and sub-runners for 

injection for both components. The simple layout 

reduced the costs of the nozzle construction by more 

than half compared to the redirection system. 

Combination of hot-runner and cold-runner technology 

“Looking back, we actually built the system twice”, 

remembers Carlo Rasi, sales representative for the 

Frankenberg hot-runner specialist. “The first solution 

comprised a large hot-runner system with which the melt 

was conducted through main manifolds and sub-runners 

to the hot-runner nozzles; the transfer nozzle was 

constructed as a valve gate nozzle.” The original idea 

was that in addition to the nozzle in the first level, two 

nozzles with their heads lying against each other would 

be used in the second level. “However, this solution not 

only required a larger mould but also a larger injection 

moulding machine and would accordingly have 

increased costs. Furthermore”, continues Rasi “such a 

solution would not have been ideal because of the heat 

loss.” 



1.5. 24

1.5. 25 

iA 


Nozzle design for injection moulding on tandem tools 

To avoid these disadvantages, the hot-runner specialist 

in consultation with the heater supplier developed a 

special solution for the second level in the form of a 

transfer nozzle, which on the outside is identical to the 

suppliers' SHT nozzles with two-part shaft. Here, the 

basic idea of two nozzles was maintained and optimised 

so that they could be produced in just one component. 

Fig. The special nozzle design in the second parting level cuts costs 

and reduces the construction size. 

In the new system an open passage was fitted on the 

cold-runner side for the first parting level. During the 

injection into the first level a plastic plate with a defined 

wall thickness is formed which allows injection through to 

the second level. Before that this plate provides a closure 

between the first and second parting levels. When 

injecting into the second level, the melt pressure and 

enthalpy of the melt are sufficient to inject the melt jet 

through the plate to the transfer nozzle. 


Based on T-Mould's experience and the injection trials 

conducted in the hot-runner specialist's own pilot plant 

experimental facility, it was possible to define the wall 

thickness of the plate in a way that would ensure that the 

process would function perfectly as of the first shot. 

The process with the aid of the plastic plate has al-ready 

been in use in practice for a long time but so far usually 

with polymers that have not been reinforced. In the 

current case a semi-crystalline, glass-fibre reinforced 

material is used, which makes greater demands on 

process reliability. 

Low losses during thermal conduction 

In a very short time GÜNTHER and the heating supplier 

were able to find a solution in terms of the best possible 

way to heat the transfer nozzle. A two-component shaft 

with titanium cap as well as nozzle heating adapted for 

this application make it possible to minimise the heat loss 

in the nozzle so that only very little is lost in the conduction 

of heat to the nozzle tip. The nozzle heating 

consists of only one component so that there are no 

significantly cold areas. 

“A further challenge presented by this project was the 

short time available”, remembers Rasi. The individual 

parts of the nozzle were developed, designed and specially 

produced within four weeks. There was no time for 

any extensive tests before the installation of the nozzle 

assembly. Nevertheless the design functioned from the 

beginning without any problems occurring at all, which of 

course is very unusual for a completely new development. 

“From the first shot, the temperatures were a 

uniform 280 °C in the material manufacturer's default 

window. The pressure curves did not show any irregularities 

and there were no problems starting up again 

after an interruption in production. At no time were there 

any signs of damage to the material. The production of 

the new tandem tool commenced in the autumn of 2008; 

since then production has been running perfectly with a 

40% reduction in manufacturing costs. 

In the meanwhile GÜNTHER has implemented more 

projects with the new nozzle design, which is basically 

suitable for every family of mould if there is not too great a 

difference in injected weights in the first and the second 

levels 

Dipl.-Ing. Jörg Essinger 







Precision and costs under control 

Weißer+Grießhaber relies on BlueFlow ® Hot-Runner 

Engineering for Micro Parts 

Extremely thin-walled products with ultra-fine structures 

are a speciality of Weißer + Grießhaber. In a pilot 

application of the new BlueFlow ® hot-runner nozzles 

from Günther Heisskanaltechnik GmbH, the company 

has engineered a more cost-effective production of 

precision filters, a safety component for the automobile 

industry, with greater process stability. 

Already in the year 2009 the plastics processor Weißer + 

Grießhaber (www.Weißer-Grießhaber.de) from 

Mönchweiler, a town in the Black Forest area, was 

awarded “the innovation award for the promotion of 

innovative achievements in medium-sized industrial and 

skilled trade enterprises” for its directly injected filter. For 

the first time, filter screen fabric and threading were 

produced in pure injection moulding in one shot for these 

precision components for the automobile industry. This 

replaced the previous procedure, in which an existing 

metal or plastic screen fabric was overmoulded to obtain 

a ready-to-install component. The impact on costs was 

significant, which, depending on the product, sank by 

around 60 to 80 per cent. In the meantime, a large 

number of variants are produced, in quantities ranging 

from several tens of thousands to double-digit millions, 

for other industries too. Such polyamide filters with 

weights of about 0.1 grammes are used for example in 

ABS and ESP systems to filter out even the finest 

particles from the brake fluid and accordingly ensure 

reliable functioning. 

Fig. A particularly efficient and easily regulated heating technology 

allows slim high-performance nozzles. 





iA 

Thread thicknesses of 0.10 to 0.15 millimetres and mesh 

apertures as tiny as 0.07 millimetres are scarcely visible 

to the naked eye. Burring must also be reduced 

accordingly to under 5 micrometres. 

Weißer+Grießhaber spent about five years developing 

the directly injected filters. This concerned mould making 

above all and the moulds are still being constantly 

improved. The hot runner and control engineering as well 

as the adaptation of the process parameters have had a 

decisive influence on the qualitty and process stability. 

One of the decisions taken by Weißer+Grießhaber as 

part of the continuous further development was to use 

BlueFlow ® , the new heating technology developed and 

produced by Günther Hot-Runner Engineering, in their 

own manufacturing before the launch on the market and 

to evaluate the experience with it. The first obvious result 

of using the new nozzles”, explained Siegfried Kaiser, 

Head of Sales and Project Management at Weißer+ 

Grießhaber, was the much lower temperature and 

pressure levels compared to the systems used before – 

which had also ranked among the top technologies. The 

temperature window used during the process is much 

smaller; the average temperature sinks and becomes 

more stable.” That not only reduces the strain on the 

mould; it sustainably saves energy and substantially 

reduces downtime. Another aspect, which is at least just 

as important, is that the higher temperatures and 

pressure levels before used to cause unacceptable 

material damage and consequently rejects. Furthermore, 

not all cavities in the 8-cavity mould were filled and 

the reject rate reached double-digit percentage levels. 

These problems are now over: GÜNTHER's hot runner 

fills all cavities and the reject rate is less than 1 per cent. 

There is also a great improvement in injection gate 

quality. 

Fig. A micro filter (outlet valve for an automotive application) made of 

non-reinforced PA66 from Bada, injected in one processing step; 0.1 

grammes and 1,848 apertures measuring 0.07 x 0.07 mm. The 

maximum permissible burring is 4.5 µm. 

1.5. 26

1.5. 27 

iA 


Precision and costs under control 

Another aspect has been observed in practice: thanks to 

the fast heating and stable temperatures in the nozzles - 

nozzle temperature and setpoints are now at the same 

level for all eight nozzles -, the mould can be started up 

without any problem. Restarting after a fault is also easy 

now too. This also contributes greatly to reducing costs 

during the process and it increases process reliability. 

® 

Keyword: BlueFlow nozzle technology 

The core element in the new nozzles are the thick-film 

heating elements developed by Günther and a project 

partner. The dielectric layer and the heating conductor 

paths are applied to a stainless steel casing in screen 

printing under clean room conditions and burnt in 

afterwards. A covering layer insulates and protects the 

heating element from external influences. The most 

important advantage of the thick-film heater: the heating 

traces can be brought closer to the material, allowing a 

much more precise output distribution over the entire 

heating tube because 

the conductor paths can be varied in terms of width (and 

output) and positioning. This makes it easier than before 

to achieve a high concentration of power in the front 

nozzle area, for example. 

The entire heating element, is only about 1.00 mm. 

Compared to conventional brass heating elements, the 

new thick- film heaters are therefore much finer and have 

a narrower diameter. Other outstanding features in the 

heating elements are the high dielectric strength and 

non-hygroscopy, which puts an end to the previously 

customary slow heating to 100 °C and subsequent 

interruption in heating to drive water vapour out of the 

hot-runner systems. 

The bottom line ® 

The BlueFlow technology is fundamentally compatible 

with previous nozzle systems and retrofitting is possible. 

The slight increase in investment costs must be viewed 

against the direct savings and increased reliability in 

Weißer+Grießhaber applications: 

The bottom line 

The BlueFlow® technology is fundamentally compatible 

with previous nozzle systems and retrofitting is possible. 

The slight increase in investment costs must be viewed 

against the direct savings and increased reliability in 

Weißer+Grießhaber applications: 

• Less downtime due to the faster and problem-free 

start-up, even after faults. 

• Energy consumption is reduced by about to 30 per 

cent because the temperature is lower. 

• Significantly less rejects due to the improved temperature 

control in the nozzles, reduced process temperature 

and lower pressure levels. The lower pressure 

allows the use of a smaller injection moulding machine 

as an alternative, which further reduces costs. 

• Stable process with lower downtimes and accordingly 

a higher output. 

• Heat loss is reduced, not only by the smaller outer 

contours of the nozzles but also by the low heat 

conductivity of the two-part nozzle shaft (patent: DE 

412 70 36 issued on 4 May 1995) with ist combination 

of materials, steel in the back and a titanium alloy in 

the front. 

In addition, the new heating technology benefits from 

other features in the redesigned mould, such as the 

narrower diameter compared to that of conventional 

systems. This allows smaller nest spacing and 

accordingly smaller moulds or a greater number of 

cavities with the corresponding improved efficiency and 

yield. 

“A precise calculation of the cost per piece is not 

available for this application yet. However, the pay-off 

became evident in less than half a year”, said Siegfried 

Kaiser. 

Fig. Precision times eight – the newly-designed Günther hot-runner 

nozzles reduce process temperature and the required pressure, 

which is also gentle on the material. 

GÜNTHER Heisskanaltechnik GmbH 

Dr. Frédèric Zimmermann

Heißkanaldüsen Typ SLT/-DLT Customer information

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