Profile dies | machinery
Advances in modelling, production and design are helping profile extruders to get more out of their tooling. Lou Reade reports
latest in profile dies
Trial and error is still, unfortunately, an aspect of die design. The delicate relationship between the geometry of the die and that of the final part means that many iterations can be needed to get things right. However, a number of research teams are looking at
how emerging techniques -- either in simulation or production – might bypass this, and cut the time and expense needed to produce tooling. The Institute of Plastics Processing (IKV) in Germany, along with other research partners, have used additive manufacturing – also known as 3D printing – to create a profile extrusion die. They are part of a project called ‘Integrative production technology for high-wage countries’, which intends to speed up the process by which extrusion dies are designed and made.
Designing dies often requires many iteration loops in simulation and experiment, which considerable cost and time factor -- which can threaten the prospects of manufacturing in high-wage countries. The new approach aims to “replace manual trials
and evaluations with an automatic algorithm”, said the researchers. However, the algorithm supplies geom- etries that cannot always be replicated with conven- tional manufacturing processes. One possible solution is additive manufacturing, in
which steel powder is gradually turned into a solid part through local melting. Using optical machining processes instead of conventional mechanical process- es increases design freedom, said the researchers. Highly complex contours can be replicated, while
there is no restriction to the maximum machining depth. This means that a profile die does not have to be built up from numerous plates. This new production
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technique can save a considerable amount of develop- ment and production work. With this production technique, surface roughness
– caused by melting the powder – is unavoidable, but can be “both a curse and a blessing”. While the roughness must be minimised at the exit of the die – so that the produced plastics surfaces have an acceptable finish – it brings about a much better rinse behaviour: a laboratory trial showed that a colour change in a die made in this way can be achieved around 25% faster than with a conventionally manufac- tured die. As well as IKV, the project partners are Computer-
Assisted Analysis of Technical Systems (CATS), the Institute of Laser Technology (ILT) and the Laboratory for Machine Tools and Production Engineering (WZL) at RWTH Aachen University. The partners, from the fields of flow simulation,
additive manufacturing, tooling machines and plastics technology, designed the extrusion die as a demonstra- tor. It shows a production system in which the design is performed automatically without any time-consuming trials. At the same time, the die is produced in a single, fully automatic process step, so the number of assem- bly steps is reduced. The research findings will be further developed in a number of follow-up projects.
Optimised design US-based Plastic Flow has developed extrusion die optimisation software, which has been used improve the design of a square profile die with non-uniform wall thickness. The software successfully optimised the die’s geometry – and that of a sheet die – so that a uniform
June 2017 | PIPE & PROFILE EXTRUSION 25 On the block:
Main image: IKV researchers say 3D printing helps to
accelerate the design and
production of profile dies
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