molding introduction

Fields of work
The injection moulding department currently has a staff of more than 25 engineers and technicians who, with the support of some 100 students, are engaged in the further development of mechanical, mould and process engineering. The following topics constitute the main focus of the department's work:
Mechanical and process engineering
Improved process control and closed-loop control systems are being developed and brought into a form where they can be suitably employed by industry. These concepts permit an increased productivity and a higher quality, and also serve to enhance the capacity of existing plant.

Computer-aided process simulation and mould layout
High-performance, computer-aided simulation techniques, such as the CADMOULD Version 6 program package developed at the IKV, together with the practical investigations that are being carried out, provide assistance in establishing the optimum design of injection moulds.

Quality assurance / process control
On-line quality monitoring and control, plus quality documentation for all the moulded parts produced, constitute key areas of our development work which we are pursuing in cooperation with our partners in industry.

Special processes
Processes such as the fluid assisted injection moulding, in-mould decoration, powder injection moulding and co-injection moulding are being subjected to both analytical and practical investigation in a bid to provide the user with guidance in the assessment and application of these processes. New, special processes are also under development, and concepts for combining and integrating processes are being implemented.

Polyurethane processing: process optimisation of reaction injection moulding (RIM, R-RIM, S-RIM), development of special processes (multi-component RIM, bladder RIM), process characterisation using ultrasound, process development for phenolic foams
Plant organisation
Solution concepts are worked out with allowance for the interplay of the different technical, organisational, personnel and economic aspects involved. These take in the costing of injection moulds and also staff training, for example.




Machine development: micro injection moulding machine



Computer-aided process simulation



Rapid Prototyping
Cooperation with industry
The practical orientation of the IKV's research work is reflected in the large number of projects that are being implemented in cooperation with partners from industry. These include: the computational layout of components and moulds for the automotive and aeronautical industry
the optimisation of shrinkage and warpage in components for the electrical engineering sector
enhancing moulded part quality and ensuring a constant process through direct cavity pressure control
energy consumption and reproducibility analyses for all-electric and hydraulic injection moulding machines
quality assurance measures for the processing of regrind
the powder injection moulding process for metal, ceramic and PTFE processing
the production of medical articles in resorbable plastics
compilation of a skills development concept for production staff in injection moulding companies


Services and facilities
One of the IKV's prime tasks is the implementation of the latest scientific findings in industrial practice. Assistance is provided for partners in industry in forms ranging from consultations, research and development contracts, and joint projects that are conducted in cooperation with a number of partners from industry.

In addition to a large number of conventional injection moulding machines, the injection moulding department has co-injection and fluid injection units, an all-electric machine, a micro-precision injection moulding machine and the appropriate equipment for the injection moulding of thermo-plastics, elastomers and thermosets at its disposal.

The Institute has a large number of injection moulds in stock, ranging from simple geometries, for analytical investigations, through to complex-shaped industrial parts. The machines and moulds are equipped with the latest measuring technology. A stereolithography unit for rapid prototyping rounds of the facilities available. The CADMOULD Version 6 software and a number of different CAD/CAM systems are available for mould layout and process simulation.





For further information, please contact:
Dipl.-Ing. Oliver Grönlund
Head of department Injection Moulding
Tel. +49 241 80-93827
Fax +49 241 80-92262
email: groenlund@ikv.rwth-aachen.de

Machine and mould technology
The developments that have taken place in the field of machine and mould technology have considerably extended the potential of injection moulding technology over the past few years. The focal points of the IKV's research are set out below. These are being worked on in cooperation with machine builders and plastics processors.

Machine selection
The optimum alignment of an injection moulding machine to the product range is of decisive importance for injection moulders in the light of the keen competition that prevails. The criteria employed in the selection of an appropriate injection moulding machine have so far been the size of the production run, the moulded part geometry and the characteristic values of the machine, such as clamping force and shot volume. To enable the aspect of moulded part quality to be included in the selection process as well, the IKV is developing a classification system for moulded parts, based on quality characteristics. This will permit conclusions to be drawn as to the requirements on the injection moulding machine.


Drive concepts
Different drive concepts are available on the market for injection moulding machines, yet there is frequently a lack of information on the energy consumption, noise emission and reproducibility of these different drive concepts. These criteria are being studied at the IKV in an independent analysis of the operating behaviour of all-electric and hydraulic injection moulding machines based on different concepts.


Demands on the moulded part


Keltool cavity


Principal mould with backilled insert



Dynamic mould temperature control
When injection moulding thermoplastics, it may be necessary to ensure not only rapid cooling of the moulded part but also short-term or local heating. The methods available for dynamic heating are fluid circuits at different temperatures and supplementary electric heaters. With both these solutions, cycle time can be chiefly influenced in the heating phase. Electric heating is more effective, since it allows selective heating of individual areas of the mould. Inductive heating has a higher efficiency on account of its heat transfer mechanism. Their advantage is that the mould surface can be selectively heated for a short period of time. Temperature control concepts of this type are currently being investigated at the IKV.


Rapid prototyping / Rapid tooling
Simultaneous engineering requires prototypes so that design errors can be detected at the earliest possible stage of product design, thereby cutting back on the cost and time involved in modifications. The IKV has a stereolithography unit at its disposal for the production of prototypes. This means that models for design and assembly tests can be made available within a very short period of time (rapid prototyping). For functional prototypes, by contrast, use is made of prototype moulds which permit the application of series material in a series process for the production of a limited number of prototypes (rapid tooling). The IKV is currently studying and evaluating processes for the direct production of moulds and for mould production via a process chain.


The IKV staff will be pleased to provide advice or engage in cooperation in the form of joint projects.


Special injection moulding processes 1
Injection-compression moulding
The injection-compression moulding process combines elements of both the injection moulding process and the compression moulding process. It permits a clear reduction in filling pressures and leads to less anisotropy in the properties of the moulded parts. This should be an advantage for thin-walled mouldings, mouldings decorated with textiles or films and optical, transparent mouldings.


In the case of parts decorated with textiles or film, it is the residual foam thickness that remains after moulding that is the main focus of attention. The injection-compression process not only gives higher foam layer thicknesses in absolute terms but also ensures a more homogeneous distribution of the layer thickness along the flow path.


With thin-walled mouldings, dimensional stability is of key importance as a quality criterion. This is influenced to a decisive extent by the shrinkage of the moulded part. Investigations at the IKV have shown that thin-walled mouldings with wall thicknesses of between 0.5 and 0.7 mm, display less shrinkage when produced by injection-compression moulding.


Injection-compression moulding has already gained considerable importance for the group of optical mouldings. This process is used especially in the production of optical lenses. Over and above this, it can also be employed for large-area optical mouldings, since these benefit not only from the better shrinkage compensation but also from the reduced filling pressure. Study results show that optical properties such as distortion and birefringence can be improved with the aid of injection-compression moulding.


The IKV is developing new application potential for this process in research projects and in direct cooperation with industry and is also compiling the necessary process knowledge. This know-how is then implemented in products on the basis of feasibility studies.


Textile decorated moulding part produced with injection compressing moulding


Injection compression moulded thin-walled part


Comparison of GAIM/Extrusion for bent pipes


GAFIM test specimen for bursting pressure material PA, braiders made of PA-fibres


Gas injection technique
The gas injection technique (GIT) generates cavities through the selective injection of an inert gas in specific, still molten areas of an injectionmoulded part, thereby creating a uniform gas pressure inside the moulded part. The gas injection technique became established for the production of thick-walled and rod-shaped parts many years ago. It is used particularly with ribbed and highly integrated parts, in order to minimise warpage and sink marks.


A logical step towards saving costs is to use the gas channel as a functional cavity for media lines. GIT offers particular advantages in cases where conventional production processes, such as extrusion or thermoforming, would involve a number of production operations. Costs can be reduced by comparison with 3D blow moulding for the manufacture of branched or highly integrated media lines and through the use of multi cavity moulds. The integration of media lines in a complex component is also possible.


Media lines suitable for the gas injection technique are being defined through market analyses and through cooperation with industry, and new variants of the gas injection technique are being developed at the IKV. One example of a product-oriented development of this type is the GAFIM process (Gas-Assisted Fibre Braid Injection Moulding), which can be used to meet stringent requirements, such as a high bursting pressure at high temperatures and good low-temperature impact strength.


Additional IKV processes, such as GASIM (Gas-Assisted Sequential Injection Moulding) for rigid/flexible combinations, GACIM (Gas-Assisted/Gas Counter Injection Moulding) for high volume lines and the CorePush process for branched lines will extend the range of applications still further.


Special injection moulding processes 2
Thermoset injection moulding
Information on material behaviour can be obtained by measuring the pressure loss with the aid of a newly developed standard measuring nozzle which incorporates a slot-shaped measuring section. The nozzle can be mounted directly on the injection moulding machine. In addition to this, information can also be obtained on flow behaviour, which is of key importance for processing in general, as well as on the behaviour of the material over time, which is significant for cold runner technology. Now that this standard measuring nozzle has proved successful in practice, it is to be implemented on a versatile measuring mould that can also be used to conduct investigations into curing behaviour.


The injection-compression moulding process holds much greater significance for thermoset processing than for thermoplastic processing. The chief influences on mechanical and optical properties in these processes have not, however, been quantified in their entirety. This is why injection-compression moulding is one of the focal points of IKV research, with particular emphasis on the processing of glass fibre reinforced phenolic resin moulding compounds.


Since it is not possible to recycle thermosets via the molten state on account of the irreversible chemical crosslinking process that takes place, the IKV has looked into particle recycling as a means of reuse. Comprehensive investigations have been conducted into the influence of particle size distribution in the regrind on the resultant properties of the moulded part. The results have shown that coarse recyclates and, in particular, the addition of up to 30% coarse recyclate does not pose any problems.


Different sensor types are to be studied in respect of their suitability for quality assurance and quality control in the thermoset injection moulding process. It would be conceivable to use pressure sensors or optical sensors to establish the optimum switchover points, dielectric sensors for monitoring curing processes, and also all-in systems available on the market.



Injection compression moulding


Influences on moulding properties with particle recycling


Mould for micro injection moulding



Injection moulded honeycomb structure: web thickness 2,5 µm, height 20 µm


Micro-injection moulding
Micro-injection moulding can be employed to produce micro-structured moulded parts in high volumes on a cost-effective basis. Studies are being conducted into questions concerning appropriate materials, the necessary plant and mould technology and guidelines for the generation of microcavities and for process control. Honeycomb structures with a crosspiece width of 2.5 µm and a structural height of 20 µm have already been produced here using a specially developed standard mould unit and the requisite peripherals.


A machine for injection moulding micro-components needs to fulfil different criteria from a conventional injection moulding machine. High clamping forces are not required; instead of this, special attention must be paid to the precise metering and injection of very small quantities of melt. The peripherals that generally go with the mould can be integrated directly in the standard mould unit in some cases. The IKV is working on a practicable concept for an injection moulding machine of this type.


To enable microsystems to be produced in a hybrid design, it is also necessary to have the appropriate handling systems and a suitable form of process control. The IKV is looking into micro-assembly injection moulding and injection riveting. The process engineering, process analysis and process optimisation are also being developed by the IKV.

Quality assurance
The steadily increasing competition from low-wage countries is forcing European producers of injection moulded parts to reduce their production costs by a considerable margin again and, at the same time, to increase their production efficiency. The process control methods that have been developed at the IKV to this end, on the basis of state-of-the-art automatic control strategies, make it possible to achieve the requisite uniformity in the production process and moulded part quality.

On-line quality monitoring
Quality documentation is gaining increasing importance. By calculating all the relevant quality characteristics of a moulded part from measured characteristic process parameters, it is possible to document the entire production process without need for the elabo-rate measurement of quality characteristics. Apart from documentation, online quality control is also employed for the elimination of rejects.


The implementation of quality documentation is greatly facilitated by the use of neural networks. Investigations at the IKV have shown that attributive characteristics, such as scorch and sink marks, can also be calculated with a high precision using this algorithm, which has been taken from the field of neuroinformatics research.


Quality control
Online quality control forms the basis of the automatic quality control system developed at the IKV. The machine setting parameters are corrected automatically with the aim of achieving optimum quality. There is then no need for the machine operator to intervene with this control system. The moulded part properties that are calculated by the online system are fed back to the master computer on the injection moulding machine via a state controller. Optimum machine setting parameters are then available from one cycle to the next.


Experimental moulding glasses, IKV Aachen


Series production moulding, company Mann + Hummel, Ludwigsburg


Quality control with neuronal networks


Adaptation of the cavity pressure controller over 6 cycles in the injection phase



Cavity pressure control
Apart from quality control covering all the machine cycles, a cavity pressure control system within each individual cycle constitutes an appropriate means of ensuring uniform moulded part quality. By contrast to the process engineering employed to date, where a velocity profile is specified for the injection phase and a pressure profile for the holding pressure phase, the cavity pressure control system requires a pressure profile to be specified for the cycle as a whole. A characteristic feature of this profile is a constant gradient in the injection phase which will generate a constant flow front velocity and hence constant morphological properties over the flow length.


A model-based predicative control concept has been developed at the IKV. This generates adjustment signals for the hydraulic valves or adjusting motors of the screw drive in real time and thus aligns the cavity pressure to the specified pressure curve online. The system includes an adaptive component to make allowance for process changes, such as material fluctuations. This adapts the controller to changed process conditions from one cycle to the next.


Plastics for innovative applications
Powder injection moulding
Powder injection moulding (PIM) is well established for the production of ceramic or metal parts in order to obtain the highest degree of design freedom and product automation. As it is a near net-shape technique, secondary finishing is reduced to a minimum and high output rates are typical. For metal injection moulding a small sized metallic powder is mixed with a wax-polymer binder that allows shaping in a thermoplastic injection moulding machine. After shaping, the wax-polymer binder is removed, usually by heat, and then the structure is sintered in a manner similar to traditional powder metallurgy or ceramics firing.


Apart from compounding, process management of injection moulding is particularly important for achieving the highest possible product quality, since it is at this stage of the process that key component properties are determined. For this reason, the analysis of the injection moulding process constitutes one of the focal points of the IKV's research work. In the course of fundamental process analysis investigations employing statistical methods, the correlations between process control and part quality as well as part defects are being established and described in both quantitative and qualitative terms.


Combining ceramic injection moulding with special plastics processing methods constitutes a further point of focus. By using gas-assisted injection moulding the amount of expensive raw material required can significantly cut while the stiffness of the part remains on high level. Consequently, considerable savings for debinding and sintering time can be realised due to the lower material input, thereby giving a more economic production process. Moreover, gas-assisted powder injection moulding enables new applications as well as an improved degree of integration. For example, ceramic pipes of complex geometry capable of carrying aggressive fluids or fluids at high temperature and pressure can be produced by use of this technique.


Powder injection moulding


Gas-assisted powder injection molding


Processing of thermoplasts by use of the gas loading technique


Foam from polyeactide produced within the gas loading process


Biodegradable plastics
Biodegradable plastics make a key contribution towards waste avoidance and material recycling. The material costs are still high, however, and special processing techniques are required. One way to reduce costs is to produce biodegradable foams. Research at the IKV is focusing on the influence of processing on moulded part properties for injection moulding and extrusion.


The resorbable plastics constitute a special group amongst the biodegradable plastics. These materials degrade into non-toxic substances in the body and are then eliminated. A large number of medical applications require implants that will remain in the body for a limited period of time. By using resorbable materials, it is possible to avoid having to perform a second operation to remove these temporary implants.


To satisfy the complex medical requirements, the so-called CESP-process (Controlled Expansion of Saturated Polymers) was developed at the IKV. This process permits amorphous thermoplastics to be moulded at temperatures below 40° C. In this way, temperature sensitive additives, such as proteins or antibiotics, can be incorporated.


The examples set out illustrate the benefits of conducting research into special materials for other fields in plastics processing as well. The IKV staff will be pleased to provide advice or engage in cooperation in the form of joint projects using the results of research already conducted.

PU Technology
Plant and process behaviour
It is only possible to implement in-process production monitoring in the manufacture of high-grade technical polyurethane (PU) components by the RIM process if all the influences acting on the process are known. Against this background, a modular simulation program has been developed at the IKV, which can be used to describe the metering behaviour of any desired RIM plant in mathematical terms. Investigations and trials were conducted with different statistic modelling methods, based on measured process parameter curves, in a bid to achieve a complete description of the complex process sequence and to predict the moulded part properties. It is then possible to estimate the influence of plant design on the process right at the planning stage of a RIM plant.



Foam characterisation
In moulded PU foam production, process parameters such as the degree of mould filling and the mould temperature, have a direct influence on component properties, such as the density structure. Different methods for analysing the process behaviour of PU foam have thus been developed at the IKV.

Mould filling behaviour can be investigated on different test settings using different in-view moulds. Ultrasonic measuring is used to analyse the foaming and crosslinking of PU systems during processing. Mechanical, thermal and rheological measuring equipment is available for assessing component properties and processing behaviour. The foam structure can be evaluated in quantitative terms with the aid of an optical analysis system developed at the IKV.



Influence of tube length on the isocyanat index k


Optical analysis of the foam structure


Numerical warpage compensation




An experimental analysis of the processing and component properties has formed the basis of a mathematical model of PU processing. By integrating the models in FEM and FDM processes, it is possible to simulate the filling behaviour of RIM mouldings and calculate the temperature and density development in moulded foams. In addition to this, the fibre orientation and mechanical component properties can be calculated for short fibre reinforced mouldings (RRIM).
PU sandwich mouldings: warpage behaviour
The shrinkage and warpage behaviour of PU mouldings is essentially influenced by the chemical and physical processes that take place during moulding. Sandwich mouldings in rigid PU foam with a reinforced outer layer are particularly prone to warpage on account of their anisotropic material properties.

Against this background, a mathematical model for describing warpage behaviour was developed at the IKV and implemented in an FEM environment. In this way, it is possible to optimise the component at the concept and design phase already, and also to cut back on cost and time-consuming prototype investigations.

PU development plant
The PU development plant at the IKV has three high-pressure metering units which can be used to process both compact PU systems and PU foam systems, as well as short-fibre reinforced systems by the RRIM method. Mouldings with continuous glass fibre reinforcement can also be produced by the SRIM process. Three mould holders and different test moulds are also available in the development plant.

IKV staff will gladly answer your questions regarding the possibility of cooperation in joint research projects and advise you on PU technology.