WICKERT Special Thermoset-Material

Different Processes Compared: 

Robot-assisted Dosing and Predrying Increase 

the Efficiency of Press Plants 

special 

Thermoset-Material 

The production programme of Schwab in Reutlingen covers among others also toilet seats. This plastics processor ordered for this purpose 

since 1998 five manufacturing plants for the processing of moulding masses of urea resin. Stipulated in the agreement for the 

supply of these plants was that initially only one was to install. During an optimizing phase the machine and the production process 

was to be utilized for the design of the remaining plants achieving thus the ultimate efficiency. 

The demands made on the press manufacturer 

in regard to efficiency and quality 

of the finished product were most 

exacting and the constructive method 

proved to be an unmitigated success. The 

four plants incorporating the experiences 

won produce now more than the five 

plants originally planned for. The plants 

as result of these endeavours offer a higher 

productivity, lower piece costs and 

essential improved product characteristics. 

This investing strategy: Entrusting 

the construction of the plants to people 

who are not only experts in their field 

but also solve problems innovatively and 

creatively certainly paid for itself. Innovated 

was thus a machine providing for the 

best possible process. 

The Initial Press 

Concept 

After a throughout market 

analysis and based 

on extensive experiences 

with the presses already 

in use the company 

at home in Reutlingen 

awarded WICKERT 

Maschinenbau with a 

contract for development 

and design. Installed by 

Schwab GmbH was a 

press of the Type Series 

WPA 5500 with volumetric 

roller dosing and 

hopper preheating. In 

this model the moulding 

material was distributed in lumps, all of 

the dosing parameters were manually 

adjusted. A downtime of four hours was 

necessary after a change of mould. Such 

changes took place three times weekly 

during three shift operation on 250 week 

days involving thus 600 unproductive 

cleaning hours. An optimization was thus 

regarded as dire necessity. The second 

important aspect was an investigation 

into an improvement of the cycle time. 

Alternative Press Concept for Multiple 

Advantages 

The operators, technicians and engineers 

participating in the development and 

testing of the pilot press focused their 

efforts foremost at the potential in optimating 

of cycle time and cleaning dura- 

special: Thermoset-Material 

tion. This was to be accomplished prior 

to delivery and installation of the four 

subsequent machines. The easy way for 

the WICKERT team would have been to 

resort to its experiences by simply improve 

the existing design. Another procedure 

as adapted: 

The initial machine was redesigned and 

a completely new production process 

realized. Three further plants should prove 

to be adequate to reach the desired 

production capacity. End of May 1999 

WICKERT suggested a solution, which 

originally increased the investment by 30 

% in comparison to the initially supplied 

version. What was the idea behind it? 

The roller dosing was to be replaced by a 

gravimetric one and the mould material 

distribution conceived as continuouslypath 

controlled. By this system the moulding 

material could be better adapted to 

the product geometry and shorter flow 

paths were achieved. Warranted by this 

method was an improved reproducibility 

and mould material distribution. 

Reproducibility without 

Compromises 

All of the parameter were manually 

selected for the roller dosing machine. 

This bears the risk of operating errors. 

This task is in the new machine concept 

in the responsibility of the SPS control. 

The batch-dictated parameters can now 

be the plant called up preselected with 

the SPS. 

The new version differs also by the defi- 

Wickert Maschinenbau GmbH · Wollmesheimer Höhe 2 · D-76829 Landau/Pfalz · Tel. ++49 (0) 63 41 -93 43 - 0 · info@wickert-presstech.de · www.wickert-presstech.de

ned drying of the granulate with the 

Duroline dryer which replaces the former 

hopper predrying. 

Predrying with Many Merits 

The processed urea resin moulding 

material is during the processing with 

predrying less exposed to postshrinkage. 

Improved is also the impact resistance, 

further more density and hardness, 

which positively influence the application 

scope. Even the flexibility is essentially 

improved. Predrying shows even at a first 

glance a visibly better surface gloss. 

Less Tool and Plant Wear, Savings 

in Material, Energy and Production 

Time 

The predrying of the granulate as part of 

the drying process allows for a reduced 

pressure. Press and tool being thus subject 

to considerably reduced wear and 

tear. 

The improved material properties and 

thinner wall thickness due to predrying 

will save not only on energy and time 

but equally on material consumption, 

with urea resins the predrying allows for 

curing times reduced by about 25 to 35 %. 

Advantages also for the Environment 

The new methods enable contrary to 

other predrying systems extensive automation. 

The generation of dust is for 

the benefit of the environment and the 

products greatly reduced. Reduced is also 

the emission of formaldehyde. With a 

precise adjustment of the granulate residual 

moisture rejection of parts caused 

by distortion are excluded the same way 

as shrink phenomenon’s. This bears great 

merit as to the consumption or recourses. 

Calculations of Economics are Convincing 

WICKERT produced an unambiguous 

comparison of plants with roller dosing 

and hopper predrying and plants with 

robot-dosing and Duroline predrying. 

The extra costs of 31 % per press are more 

than compensated by the capacity increased 

by 45 %. Of consequence are also 


the described product and process advantages. 

Finally could with the realization 

of the new concept the number of plants 

be reduced from five to four. Decision is 

further facilitated by: The initial plants 

without Duroline predrying and robotdosing 

could at a reasonable price be 

converted by Wickert to the sophisticated 

version here described. In conclusion this 

proves that at about equal investment 

volume the four presses now installed 

offer ample capacity reserves and at 

the same time the technically superior 

production of essentially improved endproducts. 


Pressing of Thermoset-materials to a New Standard 

Cycle Times reduced by up to 30 % Improve Product Properties 

But a few years ago it was predicted that 

thermoplast will entirely replace durable 

plastic materials for their more efficient 

processing methods employed. Investments 

in production plants for thermoset-materials 

ceased thus also almost 

completely. Thermoplast can, however, 

not replace thermoset-material in all 

applications, in fact experts speak of a 

come back of the latter material. 

The contemporary problem: The machines 

in use are generally outdated and 

deficient in efficiency and productivity so 

that the machining of thermoset-materials 

lacks economy and cannot compete 

on this special market. Enormous improvement 

potentials apply especially to two 

process stages, potentials to be exploited 

if competitiveness is to be restored; that 

is dosing and drying. 

Automatic Dosing 

Material suitable for pouring can, for 

instance, be gravimetric or volumetric 

dosed and be passed into a hopper with 

fully automatic closing flaps. The hopper 

is then passed into the open mould, 

opens the closure and carries the dosing 

out. The material mass can thus be per- 

fectly dosed and matched 

to the manufacturing conditions. 

An improved distribution 

of the mould material 

bears finally down in a 

better product. A further 

advantage being presented 

by the change of 

moulds and material. It is 

quite feasible to automate 

process steps as partial 

evacuation and blowing 

out of the mould. 

Drying Reduces Cycle 

Times by up to 30 % 

This has been convincingly 

demonstrated with urea 

resin mould material where 

by intelligent preheating 

respectively defined 

material drying at a dew 

point of –50°C this time 

saving can be actually 

attained. The new Duroline 

presses preheat the mould material 

to a reproducible dry state in conjunction 

with an exact material dosing and 

an additional dedusting – and allow 

thus for reproducible product properties. 

An efficiency not possible achieved 

with the conventional presses. It 

is hardly surprising that these presses 

attracted the attention of the market. 

Their operation not only results in a 

higher productivity but also provides 

for an essentially better mould quality 


through a controlled molecular surface 

moisture. 

The Duroline presses and the sophisticated 

Siemens S7 control allows a problemless 

operation. 

The Duroline presses are outstanding for 

the accessibility from four sides for all 

handling activities or the maintenance 

and cleaning chores. The design of the 

closing unit in down-stroke four-column 

design makes this possible. 


Injection Moulding with Recycled Plastics 

The ever increasing consumption of plastics calls urgently for a sensible recycling of waste. Foil wastes e.g. of agricultural and industrial 

activities and waste, collected by communal enterprises, are processed to regranulates or agglomerates, which provide difficulties for 

conventional injection moulding machines. 

The injection moulding machine of the Type WPM, first introduced 

at the FAKUMA 97, closes this gap. A special for recycling 

plastic developed injection moulding unit and a unique ratio between 

clamping force, mounting surface and shot volume (3.8 to 

23 l) are basic characteristics of this machine. 

An uncomplicated and efficient utilization of plastics waste 

has been given top priority by the recycling and waste disposal 

legislation. A target which can be effectively approached with 

the injection moulding machines of the Type WPM, machine 

conceived for this purpose. By this method plastics waste disposal 

by incineration called “thermal disposal” can be avoided. The 

machines can also cope with badly contaminated, unclassified 

and unsorted material and convert it into high grade technical 

mouldings. 

The conversion of plastics waste into moulded technical articles 

represents undoubtedly a sensible environmental protective 

utilization of waste which is thus possibly two to three times 

reconverted into base material. This is not only strived for from 

an ecological but also from an economical aspect as the recycled 

material or regranulate offers decisive monetary advantages for 

processors. WPM machines are a future-orientated investment 

for waste disposal and processing enterprises. 

The injection unit with screw preplasticing in combination with 

an injection plunger is highly wear resistant and will cope effectively 

with material greatly differing in composition, structure 

and staining. 

The machine commands of a servo-assisted plastification acting 

as adjustable friction force compensation in the injection cylinder. 

The plastification pressure in the cylinder can thus be matched 

to the conditions of the production process. The conventional 

injection units were exposed to risks in the processing of 

recycled material. The machine suffered frequently early dama- 

Locking bolts 

ges or even destruction by the abrasive aggregates, blocking 

often resulted in breakdowns. Contaminates such as metal, glass, 

paper, stones, fibres, aluminium residues and copper fragments 

are highly abrasive and produce material blockages. 

By combination of screw plastification and plunger injection 

operation can be conducted with large cross sections, which give 

access even to large foreign bodies. Equipment of these machines 

includes neither check valves nor retainer rings. Operation is carried 

out with locking bolts being hydraulically operated and cannot 

be inactivated even by such foreign bodies as steel screws or 

copper wire. The rugged machines offer thus a virtually troublefree 

operation despite being charged with problematic material. 

The also new design of the screw geometry enables a complete 

plastification at the possibly lowest temperature. The generation 

of gases and corrosive material being such extensively avoided. 

The highly wear resistant injection unit tolerates such stabilizers 

e.g. wood shaving, rubber meal and glass fibres. 

Injection moulding of large volume parts 

Recycled material and agglomerates from communal waste 

disposal, TETRA-PAK fraction 

Thermoplasts e.g. filled with wood shavings 


Screw plastification 

Plunger (ram) injection 


For Moulded Thermoset-material Parts: 

New Standard Presses and Automatic Machines for Top Productivity 

Wickert offers now machines with absolutely unique features for the manufacturing of moulded Thermoset-material parts. These 

machines provide for reduced cycle times and improved surface finish due to an intelligent press technique with effective predrying: 

Wickert has thus supplemented their programme in machines for the production of Elastoform parts with plants for the processing of 

Thermoset-material – offering sophisticated and extreme economical solutions. 

Used for the manufacturing of moulded 

Thermoset-material parts are hydraulic 

presses with which the required retention 

force can be applied. The mould material 

is in the machine heated with heat plates 

or by direct tool heating and attains thus 

the desired material properties. Up to this 

stage procedures for Thermoset-material 

and Elastomer parts do not essentially 

differ. 

The production of rubber mould parts 

offer great difficulties to automation 

while this represents the state of art 

where parts of Thermoset-material are 

concerned. The pourable initial material is 

for this purpose volumetrically predosed 

and then automatically fed into the cavities. 

In case of tools with multiple cavities 

or with large surfaces several lumps are 

predosed to achieve a better material 

distribution in the tool. The procedure is 

confronted with a number or problems 

e.g. cleaning of the plant is complex and 

time consuming i.e. changing of material 

of mould is difficult and frequently avoided. 

Yet multi-coloured are frequently 

specified for sanitary articles – which is 

by Thermoset-material processors correctly 

termed as disadvantage of this 

production method. 

Especially in the tools with large surfaces 

the “predosing in several lumps” does not 

effect an optimum distribution of the 

material into the cavities. 

A further problem being presented in 

the hygroscopic characteristics of the 

moulding material. It is for one due to 

the surface moisture (hygroscopic effect) 

and secondly to the bonded molecular 

moisture. The molecular moisture is used 

for the process and thus desired, surface 

moisture interferes with the processing. 

If the surface moisture can be reduced to 

a defined value prior to processing not 


only a higher quality is achieved for the 

product but also a cycle time reduced by 

up to 30 %. 

Besides many intelligent detail improvements 

the Wickert-Duroline above 

all provides for the Thermoset-material 

processors advantages as to dosing and 

material drying. 

A real novelty is presented with the 

newly developed Duroline dryer; the 

mould material is thus prior to processing 

reproducible predried. Next to the already 

mentioned briefer cycle time of up to 30 

% also an improvement of the physical 

properties, is achieved. 

Shorter cycle time and improved 

surface finish 

Intelligent press technique 

Effective preheating

WICKERT Special Thermoset-Material

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