6 Planetary Mixers - Herbst Planetary Mixer

6 Planetary Mixers
6.1 Review
6 Planetary Mixers 68
Planetary mixers are mainly used to mix medium viscous to high viscous medias, i. e.
liquids, pastes, creams, suspensions or dry powder mixtures, which are being processed
in the chemical, pharmaceutical, cosmetic and food industry.
There are planetary mixers for laboratory requirements with bowl sizes from 2 litres up as
well as for production purposes with more than 1250 litres. Furthermore existing bowls
can be fitted with a top mounted planetary mixer as an addition.
An optimal mixing is achieved by the characteristic movement of the mixing tool. This
moves on a circular path and at the same time around it’s own axis and in addition a
wall scraper moves along at the same time. This way no dead zones exist in the mixing
bowl which results in guaranteeing a thorough mixing even at low revolutions and little
energy needed. This is of highest importance for instance with shear sensitive products.
Up to now a double planetary mixer had to be operated when the effect of specific shear
forces on the mixing product was needed. Today there is a cost saving alternative. A
newly developed mixing tool provides an optimal adjustment of the shear force to the
product by means of a variable slot width.
The shear of a planetary mixer normally is not sufficient for the production of fine dispersed
emulsions. A Rotor-Stator-System (Homogeniser) provides the necessary forces.
The product is drawn out of the bottom valve of the mixing bowl then axially sucked in
by the homogeniser and radially pressed through the slots of the rotor-stator-system. The
product is then pumped back into the mixing bowl through the outside pipes.
The intensity of the shearing strain can be influenced by adjusting the slots and the
speed. The use of the homogeniser can be extended considerably by adding a product
pump prior to the entry into the bowl. The possibility of a dust-free dosage of powders
into the rotor-stator-system also is of advantage.
An almost continuous operation is obtained by using several mixing bowls. While stirring
takes place in one bowl, a second bowl can be emptied, cleaned and refilled. This reduces
the operating cycle considerably so that the production rate can be increased or seasonal
fluctuations can be controlled. In most cases this alternative is more economical than the
operation of a larger mixer.
If requested, all planetary mixers can be equipped with a jacketed bowl with electric
heating, a vacuum installation and further accessories.
All machines parts in contact with the product are normally made of stainless steel.
Special materials or surface coatings, such as Hastelloy, Teflon, etc. are also possible, as
well as mixers suitable for use in explosion zones (ATEX 94/9).
The suitable electronic control technology - from control cabinet to fully automatic control
- is also available. The standard of the machines complies with the regulations of BG
Chemie and GMP/FDA regulations.

6.2 Construction Types
6.2 Construction Types 69
One differentiates between three different models, up-right support construction, stand
construction and the planetary mixer with hydraulic lifting column.
Figure 45 shows the planetary mixer in it’s classic tripod construction. A normal bowl
capacity ranges from 7 to 120 litres. A typical aspect is that the bowl can be moved up
and down whereas the mixing head with the drive is stationary.
Figure 45: Vacuum Planetary Mixer HRV 50 in up-right support construction
With regard to the stand construction of the mixer it is possible to move the main drive
unit, which consists of the bowl cover, the stirrer drive and the stirrer devices, up and
down. As a rule the bowls are fitted with rollers; sometimes they are equipped with
suitable lashes for fork lift trucks. There are three alternatives with stand mixers: the
wall stand, the floor stand and the mobile stand. Figure 46 shows the planetary stirrer
with wall fixing.
Figure 47 shows a 120 litres planetary mixer combined with a rotor-stator-system (Homogeniser).
This new construction is available for a bowl capacity of 100 to appr. 1500
litres.
The lifting column of the mixer which lifts the complete head with drive and stirrer tools
hydraulically represents a new development. Disadvantages of a folded coat respectively
grease lubrication are being avoided by a dry running lifting column. A specially simple

6.2 Construction Types 70
Figure 46: Planetary Mixer HRV-S 120 in stand construction
Figure 47: Planetary Mixer HRV-K 120 HO with hydraulic lifting column

6.2 Construction Types 71
and effective cleaning of the complete mixer is possible in combination with the smooth
stainless steel surface of the machine housing. It stands to reason that also the mixing
space which has contact with the product as well as the stirring tools are constructed
”easy-to-clean”. After lifting the drive head the bowl, which is fitted with rollers, can be
moved to other parts of the site.
These two construction types are being used specially with larger bowl capacities because
the bowl does not need lifting.
6.2.1 Product Models HR-S 2 to HR 10
The planetary mixers HR-S 2 to HR 10 are designed for use in laboratories and small
production runs. The effective mixing volume lies approx.. between 0,4 and 1,6 litres for
the planetary mixer HR-S 2 and between 2,0 and 8,0 litres for the planetary mixer HR
10.
The stainless steel mixing bowl of the planetary mixer HR-S 2 (see Figure 48) is either
single or double jacketed with a volume of 2 litres. By using a glass mixing bowl, the
mixing process can be viewed through the glass jackets which is especially advantageous
in the research and development field.
Figure 48: Planetary Mixer HR-S 2
a) stainless steel mixing bowl, b) glass mixing bowl
The driving unit with the planetary gear is fixed on top of the mixing bowl cover. The level
adjustment of the cover is manual; for weight equalisation purposes a counter weight is
installed on the inside of the column. Alternatively the level adjustment can be regulated
electrically by a linear drive.

6.2 Construction Types 72
Starting with the large planetary mixing unit, all known standard mixing tools can be
used for stirring purposes; complete with a wall scraper made of Polyamide, Teflon or
stainless steel.
A double jacketed bowl can be cooled respectively heated by an external system. The
unit can also be equipped for vacuum operation.
The support column, floor plate and all parts in contact with the product, with the
exception of the scraper, are of stainless steel construction. The bowl cover and the drive
unit are, for weight reasons, made of aluminium.
Figure 49 shows a 7 litre vacuum planetary mixer unit HRV 7. The bowl is fixed to the
Figure 49: Vacuum Planetary Mixer HRV 7
vacuum cover by means of a bayonet lock. An illuminated sight glass fitted with a wiper
permits observation of the mixing process.
An especially user friendly design of a stand construction is shown in figure 50. The double
jacketed, electrically heated, bowl is fitted onto the stand base plate. The complete mixing
head can easily be manually lifted by means of the guides fitted with ball bearing and
a counter weight in the stand column. A hydraulic, electrical or pneumatically operated
level adjustment can also be provided. Figure 63 on page 84 shows a 3 litre vacuumplanetary
mixing unit with an electric level control.
The 7 litres planetary mixer is fitted with a protection hood. The speed is controlled by
a mechanical control gear and not by a frequency transformer.
A customised basis standard version of the mixers – as illustrated in figure 51 – can be
fitted onto a mobile stainless steel trolley together with a 2 ltrs. vacuum planetary mixer
and an external heating/cooling system.

6.2 Construction Types 73
Figure 50: Planetary Mixer HR-S 7
Figure 51: Vacuum Mixing Plant HRV-S 2

6.2.2 Product Models HR 15 to HR 120
6.2 Construction Types 74
These planetary mixers are designed foremost for use in production units, but are also
suitable as laboratory units. The available mixing capacity is between approx. 3 and
100 litres. These mixers can be constructed as classic stand version or the more versatile
stand model. Figure 27 shows a 15 l vacuum planetary mixer with homogeniser HRV 15
HO as a classic version. Figures 45 to 47 show design variations.
Figure 52: Vacuum Planetary Mixer with Homogeniser HRV 15 HO
6.2.3 Product Models HR-S 100 to HR-S 1250
These planetary mixers are designed foremost for use in production units. The available
mixing volume varies between approx. 20 to 1000 litres. These mixers are designed as
free standing mixer units, but are also optionally available as wall or floor mounted units.
The free standing version with an integrated lifting column and a mixing bowl volume of
up to 500 litres is also available.
Figure 53 shows a free standing planetary mixer. The complete drive unit is electrohydraulically
lifted to permit the removal of the mixing bowl after termination of the
mixing process.

6.3 Customised Designs 75
Figure 53: Planetary Mixer HR-S 400 (stand construction)
6.3 Customised Designs
6.3.1 Double Planetary Mixer
Where higher shear force entry is required in the mixing process, a special mixing tool
(see also chapter 6.4.4) or a double planetary mixer can be used. The special design and
position of the two mixing tools provide the necessary shear forces for a free revolution
and an effective mixing operation. The level of the shearing strain is dependent upon the
rotating velocity and the clearances between the mixing tools.
6.3.2 Detachable Planetary Mixer
Suitable bowls can be retrofitted with a detachable planetary mixer. The planetary mixer
unit would then be attached to the centrally located bowl flange.
6.3.3 A Combination of a Planetary and a Central Mixing Unit
In the research and development field it is often of great importance to cover the largest
possible functional range with only one mixer. To achieve this the planetary mixer can
be fitted with an additional connection for a central agitator shaft.
Figure 54 shows a combination of a planetary gear with a central agitator shaft. On the
left is the planetary gear with the planetary mixing tool and wall scraper, the centrally
located drive spigot for the agitator is clearly visible.

6.4 Machine Technique 76
Figure 54: Planetary Gear with Connection Provision for a Central Agitator Shaft
The Figure on the right shows the same planetary gear unit with a connected central
agitator shaft. A high-speed dissolver plate serves as mixing device.
The machines in the following illustration were designed for colour pigment operation
in the printing industry. The left one shows the operating mode of a central mixer.
The agitator shaft, dissolver plate and the pulled down mixing bowl supports are clearly
visible. The bowl is fixed by means of a tension strap (not visible in the illustration).
On the right is the same mixing unit, however, converted for the operation as planetary
mixer. The bowl fitting is pulled up and a 40 litre bowl is fixed therein. The matching
bowl carriage holds the smaller 15 litre bowl which can also be operated by this planetary
mixer by merely exchanging the mixing device and the wall scraper.
Low as well as high viscose products can be processed in this mixing unit.
6.4 Machine Technique
6.4.1 Planetary Gear
The characteristic movement of the planetary mixing tool is provided by the planetary
gear. The movement course of a specific point of the mixing tool can be seen in figure 56.
Construction of a planetary gear is shown in figure 57.
The rotating shaft is sealed by means of radial seal rings. For special duties additional
O-rings can be provided for gearbox seals.
6.4.2 Totally enclosed Planetary Gear
The new planetary gear is designed specifically for use in contamination sensitive areas
such as Pharmaceutical, Food and Cosmetic industries.

6.4 Machine Technique 77
Figure 55: Planetary Mixer with additional Central Agitator Shaft HR-S 15-40 Z
Figure 56: Plotted point of a Planetary Mixing Tool

6.4 Machine Technique 78
Figure 57: Construction of Planetary Gear
The standard design does not provide an absolute separation between the product area
and the transmission interior (see fig. 57). This disadvantage is eliminated by the total
encapsulation of the planetary gear. Total enclosure is ensured by the installation of
standard seals (see also centrally mounted mixers) or the use of slip rings. The use of
quick-release couplings allows for a quick and trouble free exchange of the various mixing
tools.
6.4.3 Equipment Design
Planetary mixers are normally fitted with a variable speed adjustment. The speed adjustment
can either be reached by a frequency converter or a mechanical variable speed
gear box.
The level of the mixing bowl for stand mounted planetary mixers is normally adjusted
hydraulically, however, a number of mixer types have the possibility of a hand or foot
operated hydraulic adjustment.
The mixer bowl and the planetary mixer head are built as a correlated unit to ensure the
correct all clearance between mixing bowl, mixing tool and wall scraper. The scrapers
are usually of either Polyamide or Teflon and are pressed onto the bowl jacket by the
product during the mixing process, thus preventing product adhesion. A stainless steel
scraper can be supplied but this requires a manual adjustment to provide the necessary
wall clearance.

6.4 Machine Technique 79
Single or double jacketed bowls can be supplied. Jacketed bowls are usually fitted with
electrical heating elements which heat the transfer medium (water or thermo-oils). The
temperature is controlled by a thermostat. By operating temperatures above 60 ◦ C
additional insulation around the mixing bowl must be fitted. Operating temperatures of
above 90 ◦ C and up to above 200 ◦ C require a thermo-oil as heating medium. External
heating/cooling unites or steam heating, complete with the necessary safety precautions,
may also be used.
It is recommendable to install an additional heating/cooling coil in the jacket should it
be necessary to heat or cool the product during mixing.
The temperature indication of the vessel jacket does not present a problem, however, the
product temperature indication is a different matter. There are a number of possibilities,
i. e. the temperature element may be fitted into a tube which penetrates the inside jacket
of the bowl, or is extended into the bowl which then requires the wall scraper to be cut
out to the extent of the thermometer.
In case of planetary mixers with homogeniser the temperature element may be mounted
inside the bottom discharge of the mixing bowl as the total product is circulated during
the homogenising operation.
Both described mounting methods have accuracy problems. Should correct product temperature
control during the mixing operation be essential then the installation of a temperature
element on the mixing tool itself is the optimal method as the measurement
values are transferred by infrared technology; alternatively a slip ring transmitter with
higher temperatures can be installed (see section 3.5.2, page 24).
6.4.4 Mixing Tools
Figure 58 shows some standard planetary mixing tools.
The fitting of a quick release coupling allows for a trouble-free change of mixing tools to
suit the specific need of various products.
Figure 58: Standard Planetary Mixing Tools
Form F1 is often used to stir creams, ointments and pastes, F2 for light substances, F3 for
solid substances and powder mixtures. Form F4 is used to process emulsions and foams.

6.4 Machine Technique 80
The stirring tool F4 is also applicable for a double planetary mixer and so is F5, which
can be used for solid and viscous products.
The straight-arm paddle agitator F5 can be combined with the shearing frame F5.1.
This frame is fixed to the mounting support for the scraper. The stirring tool will comb
through this shearing frame at every revolution. The result can be compared to the
one of a double planetary mixer, whereas the relative speed between the stirring tool
bars is lower. The value of the transferable shear forces depends also on the fixed slot
width and the revolutions, and this money saving alternative is mostly sufficient for many
applications.
The planetary stirring tool F6 is specially suitable for stirring oil-in-water-emulsions.
Specific designs can also be provided in addition to the standard mixing tools application.
Figure 59 shows a helical stirrer.
Figure 59: Helical Planetary Mixing Tool

6.5 Application Examples
6.5 Application Examples 81
6.5.1 Vacuum Laboratory Mixing Unit HRV-S 2-ex
A further development of the vacuum mixing unit HRV-S 2 (figure 51) is illustrated in
Figure 60. The mixing unit is housed in a stainless steel cabin with two wing doors. The
Figure 60: Vacuum Laboratory Mixing Unit HRV-S 2-ex
cabinet of the Ex-zone 1 construction is located in a non Ex-proof area. Operation of
the mixing unit is only possible with doors closed. The large glass windows in the doors
enable a perfect sight of the mixing process inside. The cabin interior is vented by an
external exhausting system in order to remove solvent vapours.
The vacuum pump, the circulation thermostat and the main control box as well as the
control panel are located outside of the cabinet.
The special construction of the mixing unit permits the selective operation of the highspeed
central mixer or the low speed planetary mixer. The fitted guide rail allows for
horizontal movement of both mixing units. The integrated counterweight permits an easy
vertical movement of the mixer driving gears.

6.5 Application Examples 82
In addition, the mixing unit is fitted with a simple bowl discharge device. The build-in
discharge aid, shown on the right side ofFigure51, which is manually operated by means of
a threaded spindle. This discharge aid permits the product paste to be discharged directly
from the mixing bowl into a double chamber cartridge for which a special acceptance
device has been integrated.
6.5.2 Vacuum-Double-Planetary Mixing Unit HRV-S 2 DP
Figure 61 shows the Vacuum-Double-Planetary Mixing Unit HRV-S 2 DP used in the
production of dental compounds.
The elevation adjustment of the mixing heard by manual means is assisted by the installation
of a counter weight housed in the support column and the carriage is mounted on
ball bearings.
Figure 61: Vacuum-Double-Planetary Mixing Unit HRV-S 2 DP
Employed are intertwine operating mixing tools of a straight-arm agitator design. All
parts as well as the internal jacket of the bowl, which are exposed to the product, are
coated with polyamide.

6.5 Application Examples 83
6.5.3 Vacuum Double Planetary Mixer HRV-S 2-4 DP
The planetary mixing unit shown below in figure 62 is fitted with a double jacket glass
bowl. This bowl enables the product to be cooled with water and allows easy observation
Figure 62: Vacuum Double Planetary Mixer HRV-S 2-4 DP
of the mixing process, ideally suited for development work.
The possible use of two different bowl sizes allows for a wider range of applications.
6.5.4 Vacuum Planetary Mixer HRV-S 3
The vacuum planetary mixer, shown in figure 663, is used in the process development of
new tooth past recipes and in trial operation. The stainless steel bowl, which is mounted
on the base plate of the stand, has a volume varying between. 0,6 to 2,4 litres. An
electrically driven linear gear is installed to control the level adjustment of the machine
head.
6.5.5 Vacuum-Planatary Mixer HRV-S 7
The Vacuum-Planetary Mixer in image 64 is used for the production of gels. The single

6.5 Application Examples 84
Figure 63: Vacuum Planetary Mixer HRV-S 3
Figure 64: Vacuum-Planatary Mixer HRV-S 7

6.5 Application Examples 85
jacket bowl is fixed on the stand floor plate. The level adjustment of the machine head is
manual. The mixing process can be observed through a sight glass.
The machine cover is designed for the operation with different bowl sizes, whereby only
the mixing tools and the bowl scraper have to be exchanged.
6.5.6 Planetary Mixer HR-S 25
Figure 65 shows the stand version of a basic planetary mixer. The 25-liter bowl is fitted
Figure 65: Planetary Mixer HR-S 25
with a trolley. The height of the machine is manually adjustable.
6.5.7 Vacuum Double Planetary Mixer HRV-K 30 DP
The characteristics of the planetary mixer (figure 66) show the two separate drive units,
which allow the operation of the slow rotating planetary stirrer without being dependent
on the high-speed dissolver. The two drive units have an independent variable speed
adjustment, as required by the product mix.

6.5 Application Examples 86
Figure 66: Vacuum Double Planetary Mixer HRV-K 30 DP
If selective high shear forces are required for a product mix, these can be provided by a
dissolver. The planetary mixing tool provides well blended product mixes even at highest
viscosity.
The insulated jacket bowl is fitted with a screw-mounted electric heating element for the
heating media; with water as heating medium a product temperature of 90 ◦ C can be
realized. A vacuum pump for vacuum operation is provided.
The complete mixing unit is designed for easy cleaning. Cables are installed in one of the
two lifting columns.
6.5.8 Vacuum Double Planetary Mixer HRV 40-60 DP
A double planetary mixing unit is shown in figure 67.
This unit is intended for mixers fitted with 40 or 60 litre mixing bowls. The two mixing
tools interlace with each other, whereby the straight arm model (form F5) also provides
an upwards flow of the product. In addition a wall scraper is fitted which moves the
product from the jacket to the centre of the bowl.
The planetary mixer is used for the production of highly viscose pastes.

6.5 Application Examples 87
Figure 67: Vacuum Double Planetary Mixer HRV 40-60 DP
6.5.9 Planetary Mixer HR-S 100
The planetary mixer show in Figure 68 is used in the manufacture of abrasive products,
i e. mixing of powdery raw material with binding agents and hardeners.
The helical stirrer shown in Figure 59 on page 80 serves as mixing tool. When lowered,
it turns slowly into the product shortly before closing the bowl, thus avoiding a product
condensation below the stirrer.
After finishing the mixing process the product is being evacuated directly into forms by
means of the tilting bowl. The filled bowl can be tilted without problems more than 90
degrees by means of a special manual hydraulic.
6.5.10 Double Planetary Mixer HR-S 120 DP
The Double Planetary Mixer in image 69 is used for mixing different dry substances.
The mixer as well as the matching mixing bowl is movable. The bowl is fixed by a special
device which guarantees that it is at the right place at all times, which is important,
because the mixing tools are adjusted to the bowl and operate in a precise and walladjacent
method.
The bowl can be removed from the mixing unit by operating a floor switch.
Two interlocking straight arm agitators mix the dry substances. A circulating wall scraper
prevents the product to stick to the wall.

6.5 Application Examples 88
Figure 68: Planetary Mixer HR-S 100 with tiltable Mixing Bowl

6.5 Application Examples 89
Figure 69: Doppelplanetenrührwerk HR-S 120 DP
The control technique, which is integrated in the control cabinet, enables the projecting
of different process parameters and the course of a fixed mixing process and is operated
by a touch panel.
6.5.11 Vacuum-Planetary Mixing Unit with Homogeniser HRV-S 500 HO
This mixer is designed for use in the manufacture of biologically based cosmetics (see
fig. 70). The design allows for vacuum operation, an inline homogeniser and an infrared
product temperature transmitter.
The mixer is of free standing, floor mounted design additionally fitted with wall mounting
support installations. The electrically heated jacketed bowl is fixed to the base plate.
6.5.12 Vacuum-/Pressure Planetary Mixer Unit HRVD-K 700 HO
The mixer unit shown in fig. 71 can be operated either under vacuum or pressure. The
elevation of the mixing head is hydraulically adjustable. The lifting carriage support
column is non-lubricated (dry-running). Three CIP sprinkler heads are mounted on the
bowl cover which considerably ease the internal bowl cleaning operation, further assistance
is provided by circulating the cleaning fluid with the homogeniser.

6.5 Application Examples 90
Figure 70: Vacuum-Planetary Mixing Unit with Homogeniser HRV-S 500 HO
Figure 71: Vacuum-/Pressure Planetary Mixer Unit HRVD-K 700 HO with Homogeniser

6.5.13 Double Planetary Mixer HR-S 1000 DP
6.5 Application Examples 91
The double planetary mixer HR-S 1000 DP, as shown in figure 72, is being used by the
pharmaceutical industry for mixing predominantly dry substances. Special emphasis has
been placed on an easy cleaning of the mixing unit. Furthermore, CIP-spraying heads are
fixed to the bowl hood.
The mixing unit is fitted with two single jacketed bowls, which allow virtually a continuous
operation. The bowls are transported by a special bowl carriage, which may, if so required,
be fitted with a lifting/tilting device.
Figure 72: Double Planetary Mixer HR-S 1000 DP