Plasticising

Focus
Plasticising
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Screws - cylinders - non-return valves:
Suitable for every application!
Genuine ARBURG components
Genuine ARBURG components: long service life,
100% in-house production: all products meet consistently high quality standards.
guaranteed.
Wherever components move and material is being conveyed, wear is unavoidable. This principle evidently also applies to plasticising units during injection moulding, with consequences for
component function and for the manu­
factured moulded parts. Developments
in the materials sector, particularly in
the field of engineering thermoplastics,
which are increasingly adapted specifically to a special range of properties,
place high demands on the wear protection for screws, cylinders and nonreturn valves. Based on our wide range
of experience and process expertise, we
develop and manufacture our products
to perfectly match your day-to-day requirements. We achieve our high quality
thanks to the in-house production of all
plasticising components. An advantage
from which you benefit directly in your
production through high levels of availability and a long service life.
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High of in-house production, best quality
A high ratio of in-house production, centrally organised production, one location:
All of these are part of ARBURG’s long tradition. This results in components that guarantee maximum reliability and suitability for
daily operation.
Starting with the raw material, all the production stages for screws, cylinders and
non-return valves are implemented centrally
at Lossburg. In the case of the screws, this
includes machining, heat treatment and
subsequent alignment, grinding and polishing. All dimensions as well as true running
properties are monitored as part of detailed
quality control. The same applies to the processing of cylinder tubes and the manufacture of components for non-return valves:
Here, too, the quality of all production
stages is monitored continuously. This results in outstanding durability, robust performance and high precision throughout a
long service life. For all applications.
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Variety of geometries: the optimal screw for every application.
Service hotline: immediate support via remote
diagnosis.
A decisive factor: manufacturer
know-how
As a manufacturer of high-end injection
moulding machines, ARBURG also possesses
extensive applications engineering and processing expertise. This expertise continuously
flows into the development of all the plasticising components. This has resulted in a
practice-oriented range for the processing of
diverse materials, which perfectly combines
a number of wear resistance categories with
a variety of geometries.
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Fast spare parts supply
ARBURG stands for comprehensive service
offerings, including the spare parts supply
of plasticising components. In-house production guarantees stock levels on a continuous basis, ensuring worldwide availability
of all components. In order to ensure the
prompt delivery of spare parts throughout,
the ARBURG headquarters and subsidiaries
are connected via an IT network. This ensures optimum supply to all customers, minimising machine downtimes. Plasticising
parts can be ordered directly from the headquarters in Lossburg, the subsidiaries and
representatives, or via an interactive catalogue on the Internet.
Analysis of defective components
If a plasticising component such as a screw
or non-return valve becomes defective during production, the customer can request
ARBURG’s repair department to analyse it.
Such components are appraised, checked,
measured and, if necessary, subjected to
material tests. The results of these investigations are submitted to the customers in the
form of a detailed statement which also
provides recommendations for replacing the
defective components. Once the reason for
the defect is known, appropriate measures
can be taken. For example, it may be advantageous to change to a different wear
resistance category in order to prevent the
problem in future.
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Wear resistance categories for plasticising compon
Highly wear-resistant: special non-return valve.
Comparison of structures: melt-metallurgical (left) and powder-metallurgical (right) steels.
All the components used to prepare the
melt are subject to a certain degree of
wear. This unavoidable effect is brought
about by a variety of overlapping mechanisms. In addition to mechanical
wear, i.e. abrasion, corrosion also plays
a significant role in the processing of
special thermoplastics.
In accordance with applicable requirements, we offer you plasticising components in a variety of wear resistance categories. You are able to choose from a
variety of screw/cylinder combinations
to cover the spectrum of materials to be
processed. The differentiating factors
here are, firstly, the materials used and,
secondly, the type of wear protection
applied, i.e. the type of surface treatment technique and hardening process.
Basics: abrasion and corrosion
In the case of abrasion, a hard foreign body
penetrates the comparatively soft surfaces
of basic metal bodies, forming furrows in
the material. These hard particles can be either a filler in the molten plastic or a solidified particle which has already become detached as a result of wear. Consequently,
abrasive wear occurs virtually throughout
the entire plasticising unit, i.e. in both the
solid plastic and melt areas of the unit.
Pitting-type corrosion, in contrast, is generally attributable to combined chemical and
mechanical attack. Corrosion is often preceded by abrasive wear processes. The primary cause of corrosion are the volatile constituents of the melt. For example, corrosion
can be caused by water from inadequately
dried granulate combined with oxygen.
However, the metal surfaces are also attacked by aggressive, corrosive constituents
contained in plastics with additives or which
occur through the thermal breakdown of
polymers. As these volatile constituents are
only released under processing conditions,
corrosive wear occurs primarily in the area
of the metering zone (extrusion zone) and
on the components of the non-return valve.
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Wear-influencing factors
•Process parameters (rotational speed / back pressure / temperatures / material dwell time)
•Filler type (glass fibre / carbon fibre,
mineral fillers)
•Filler content
•Additives (flame retardants / dyes)
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ents
Wear resistance
categories
Component
Wear protection
Screw
ARBID
Cylinder
Bimetal
Non-return valve
High-alloy
tool steel
Screw
High-alloy PM steel
Cylinder
Bimetal
Non-return valve
High-alloy PM steel
Wear-resistant
Highly wear-resistant 1)
Area of application
Unfilled plastics / plastics with
a low filler content
(< = 25 %)
and low corrosion tendency
Plastics with high
filler content
( > = 25 %)
and high
corrosion tendency
Temperature
range up to
380 °C
450 °C
1) Standard from injection unit 800 upwards:
A suitable wear resistance category for
each material
The wear resistance of the different screws
and cylinders depends not only on the absolute surface hardness, but also on the
depth of hardness, i.e. the progression of
the hardness across the diameter; this is
also a decisive factor in determining service
life. Selection of a wear resistance category
depends largely on the material being processed. However, injection moulding machines are generally used in day-to-day production operations for manufacturing a
wide variety of products made from differing materials. Consequently, the wear resistance category selected for the injection unit
must be of a universal nature in order to
achieve maximum protection against wear.
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Long service life: bimetallic cylinder (BMA).
Wear-resistant cylinder modules
(ARBID - BMA)
The wear-resistant screws sold under the
brand name ARBID feature very high boundary layer hardness and excellent mechanical
properties thanks to the hardening process
employed by ARBURG. Highly wear-resistant
bi-metallic cylinders (BMA), in which two different materials are combined, are also available. A hardened alloy is applied in the cylinder, which is made from conventional steel.
With a thickness of 1.5 to 2 mm, this layer
has a high degree of hardness and offers an
optimum wear reserve
Highly wear-resistant cylinder modules
(PKV - BMA)
A high-chromium, powder-metallurgical
steel (PM steel) is used for the highly wearresistant PKV screws. Compared with conventional melt-metallurgical materials, the
structure of PM steels is significantly more
uniform, more finely grained and non-porous. PKV screws are characterised by high
abrasion and corrosion resistance and,
thanks to the hardening process employed,
have a significantly higher wear reserve
than the wear resistant ARBID screws.
.
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Special plasticising components for thermoplastics
Problem-free processing: special thermoplastic screw geometries and designs.
The right choice of screw geometry can
also prevent or reduce wear to your
plasticising components. We therefore
recommend the use of screws with an
adapted compression ratio and special
cylinders in the case of special thermoplastics. Problems caused by highly
adhesive plastics can be remedied by
means of special component surface
treatment. Ensuring that your production always runs smoothly.
Packaging sector applications: barrier screw.
PVD-coated components
Highly adhesive plastics, for example polycarbonate (PC), tend to form a coating on
the surfaces of plasticising components.
This generally causes superficial flaws on
the surface of transparent components.
PVD coatings from chrome nitride (CrN) on
screws and non-return valves prevent the
formation of these coatings. This form of
surface treatment, well known in the metal
cutting tool sector, provides additional
wear protection.
High-compression screws
The use of a screw with a relatively high
compression ratio (HC screw) can prove
­expedient in improving fusing during the
processing of semi-crystalline thermoplastics
such as POM. During the processing of materials with poor granular feeding properties
or the addition of regranulte material, a
more deeply cut inlet feed zone will also
prove advantageous with respect to process
stability. HC screws are available in a highly
wear-resistant quality (PKV).
Free cross-section
LM = Metering zone
Free cross section
Metering zone
LK = Compression zone
Feed zone
LE = Feed zone
LMLKLE
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Application
Screw geometry
Thermoplastics (general)
Standard three-zone screw
Shear-sensitive materials, e.g. PVC
PVC screw (low-compression)
Semi-crystalline thermoplastics, e.g. POM
HC screw (high-compression)
Self-dyeing
High-speed parts
Three-zone screw with mixing section
Lengthened screws with mixing section or
barrier screws
Rhomboidal mixing element: for use in the case
of high material throughputs and melt qualities.
Low-compression screws
The use of low-compression screws is recommended for processing shear-sensitive
materials. In addition to a reduced compression ratio, these screws also have a
longer compression zone which provides
milder fusing. Such screws are used primarily for processing PVC. In the event of overheating, PVC liberates highly aggressive
HCl (­hydrochloric acid), which can result in
corrosion to the plasticising components.
For this reason, low-compression screws are
only available in a highly wear-resistant PKV
design which has a high resistance to corrosion. Another typical application is powder injection moulding (PIM), used for processing ceramic or metal feedstocks.
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Lengthened cylinder modules and
­barrier screws
Lengthened plasticising units with L/D ratios of 22:1 to 25:1, usually combined with
rhomboidal mixing elements, have proven
suitable for meeting high demands with
regard to material throughput and melt
quality. An alternative to the lengthened,
3-zone screws are barrier screws, which
are used primarily for processing PE and PP
for packaging applications.
Range for thermoplastics
•Screws and non-return valves
with PVD coating
•High-compression screws
•Low-compression screws
•Lengthened plasticising units
•Barrier screws
•Rhomboidal mixing elements for
melt homogeneity
Rhomboidal mixing elements
Plastics are generally not dyed until the processing stage on the injection moulding machine. Master batches and liquid dyes are
typically used for this purpose. Rhomboidal
mixing elements ensure homogeneous mixing of the melt in order to prevent streak
formation. Optimal homogenisation also
makes it possible to reduce the proportion
of additives and consequently lower material
costs. Rhomboidal mixing elements are
available for screws with diameters exceeding 30 mm and a L/D ratio greater than 20.
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Special plasticising components for cross-linkable
Highly specialised: screws for moist polyester and granular thermosets.
A significant distinguishing factor in the
processing of cross-linkable moulding
compounds compared to thermoplastics
is the cylinder temperature control.
Whereas cylinder modules for thermoplastics are heated electrically, liquidmedium (water or oil) temperature-­
controlled cylinder modules are used
in the case of cross-linkable moulding
compounds. The screw geometries and
­non-return valves employed also differ. ­
Our range therefore also includes special plasticising units for the processing
of cross-linkable moulding compounds.
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Thermoset processing
Thermosets are processed almost exclusively
with fillers and reinforcing materials. There is
consequently a high risk of abrasive wear to
the plasticising units. The screws of cylinder
modules for thermoset processing operate
without compression and feature a relatively
small L/D ratio owing to the material feed
positioned further forward than its normal
location. Granular materials are processed
without a non-return valve; in ­the case of
BMC compounds, a specially-designed
­non-return valve is used. Thermosets are
processed almost exclusively with fillers and
reinforcing materials. The ARBURG range
includes highly wear-resistant cylinder
modules for this purpose.
Elastomer processing
Screws for processing elastomers are designed purely as compression-free conveying screws and are equipped with an
adapted non-return valve. The feed area is
specially designed for the processing of
band material and features a corresponding
feed yoke.
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moulding compounds
Highly precise dosage: disc-type non-return valve
Reliable closure: needle shut-off nozzles for processing LSR.
for LSR processing.
Liquid silicone processing (LSR)
Compression-free conveying screws are
also used for the processing of LSR. Because the two components are fed to the
screw in liquid form, the screw channels
are cut very flat. Due to the low viscosity
of LSR, these screws are combined with
special, disc-type non-return valves which
allow precise dosage and secure closure.
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Needle shut-off nozzles
The low material viscosity makes it necessary to use needle shut-off nozzles on all
LSR cylinders. This prevents the liquid silicone rubber from leaking out when lifting
the nozzle. Depending on the mould design, numerous shut-off nozzle versions
are available.
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Optimal design of plasticising systems
1000
[kg/h PS]
100
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Maxim
10
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ARBURG’s database of expertise: a suitable
30
70
100
170
290
400
800
Injection unit size
1300
2100
3200
4600
Always ideal: optimum working range of injection units in relation to material throughput.
plasticising system for every application.
A common feature of all our
ALLROUNDER machine series is their
modular design. The same applies to all
our injection units. Various cylinder
sizes can be used on one machine without the need for elaborate conversion.
A correspondingly wide range of screw
diameters is available for this purpose.
This allows you to precisely match the
plasticising systems to suit your specific
operational requirements.
Optimal design of your plasticising system can contribute decisively toward
minimising wear. Our applications engineers will therefore provide you with
advice on all aspects relating to the design of plasticising systems. Combined
with application-specific wear protection, selection of the optimal injection
unit ensures the highest possible productivity and quality of your injection
moulding production.
Design basis: shot weight and dosage
volume
The process of designing a plasticising system initially involves determining the application’s shot weight and dosage volume.
The dosage path of the screw should lie
between 1D and 3D to avoid process-related fluctuations. Based on the dosage
volume, a range between 20 and 80 percent of the maximum screw stroke should
therefore be selected. In contrast, extreme
loading increases the occurrence of air
pockets and leads to excessively short
dwell times, non-homogeneous material
and un-plasticised granules.
The plasticising capacity factor
The shot weight and cycle time are used to
determine the plasticising capacity of the injection unit. In this instance, the ideal operating range of the screw should also be between 20 and 80 percent of the maximum
plasticising capacity. The reason for this restriction is related to material-specific para­
meters. The maximum possible plasticising
capacity of an injection unit is determined
by the screw’s pitch volume and minimum
dwell time, which should be approximately
30 seconds for most standard plastics and
approximately 60 seconds in the case of
technical plastics. When operating at the
lower limit of the plasticising capacity of
Calculation of the required plasticising capacity [kg/h]
Plasticising capacity [kg/h] = Shot weight [g] x 3.6
Cycle time [sec]
0.2 x max. plasticising capacity < required plasticising capacity < 0.8 x max.
plasticizing capacity
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Individually interchangeable: the injection units of all ALLROUNDER machine series are of modular design.
Minimal heat losses: Cylinder modules are
insulated in the feed area.
an injection unit, thermal damage to the
material due to excessive dwell times can
be expected. In the case of high injection
flows and pressures, such as those required
for thin-walled articles for example, a selection based on shot weight and plasticising capacity alone is often inadequate,
since the maximum attainable injection
pressure within the injection unit is reduced as the screw diameter increases.
In such cases, a change to the next largest
unit is recommendable.
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The plasticising flow factor
Finally, a check should be carried out to
­determine whether the plasticising flow,
which is dependent on the screw speed,
is adequate for dosing the required shot
weight within the remaining cooling time.
Selection of a larger injection unit may
also be necessary in this instance.
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International sales and service network: ARBURG is represented by its own organisations at more than
30 locations in over 20 countries and by trading partners in more than 50 countries
ARBURG GmbH + Co KG
Arthur-Hehl-Strasse · 72290 Lossburg · Tel.: +49 7446 33-0 · www.arburg.com · E-Mail: contact@arburg.com
Turkey, Hungary | Asia: People’s Republic of China, Indonesia, Malaysia, Singapore, Taiwan, Thailand, United Arab Emirates | America: Brazil, Mexico, USA
For more information, please go to www.arburg.com.
© 2016 ARBURG GmbH + Co KG
The brochure is protected by copyright. Any utilisation, which is not expressly permitted under copyright legislation, requires the previous approval of ARBURG.
All data and technical information have been compiled with great care. However we accept no responsibility for correctness. Individual illustrations and information may deviate from the actual
delivery condition of the machine. The relevant valid operating instructions are applicable for the installation and operation of the machine.
ARBURG GmbH + Co KG
DIN EN ISO 9001 + 14001 + 50001 certified
526421_EN_GB_092016 · Subject to change
Printed in Germany
With locations in Europe: Germany, Belgium, Denmark, France, United Kingdom, Italy, Netherlands, Austria, Poland, Switzerland, Slovakia, Spain, Czech Republic,