Heitec Creating a standard production tool with a small injection point

Editor: Eric Culp

A German hot runner supplier worked together with a Swiss moulder and toolmaker and an injection machine builder to solve the problems associated with producing a tiny plastic part.

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The polypropylene part has a diameter of only 3.8mm, which means its production demands special processing requirements
The polypropylene part has a diameter of only 3.8mm, which means its production demands special processing requirements
(Source: Heitec)

Plastechnik AG, based in Bösingen, Switzerland, specialises in the production of technically sophisticated plastic parts and the design and manufacturing of injection moulds. The company had an inquiry regarding an application with an extremely small shot weight, so it approached Heitec Heisskanaltechnik, which is based in Burgwald, Germany. The company offers special solutions in hot runner technology, particularly in lateral injection and the production of highly specialized small nozzles. Since the moulder and toolmaker is located in Switzerland it talked with Heitech’s Swiss representative Daniel Jenny from E. Ramseier Werkzeugnormalien AG in Wangen, Switzerland.

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A miniscule shot size

The plastic article that is the focal point in the project is a very small bearing cage made of polypropylene. The tiny component is part of a flow meter and boasts an approximate weight of 0.007g. Plastechnik and Heitec collaborated on the development of a 4-fold series-production tool. The aim was to fulfill the demanding application with a hot runner. Despite the low material throughput of only 0.028g per shot, the hot runner system is said to enable reliable, precise and material-friendly processing.

Protecting the material

Heitec emphasised that the core task of hot runner technology is to ensure that the molten plastic flows into the cavity of the tool unscathed and with low-shear. For this reason, the company said it dedicates itself to continually refining existing products as a way to offer customers an advantage in regards to quality and efficiency. As a result of this optimization, the company explained that it has been able to cut the energy requirements of hot runner nozzle rows of various construction styles. The energy savings are dependent on the design of the nozzle, with the savings ranging between 25% and 60%.

Creating a tiny injection point

In the case of the mould’s hot half, which was produced at Heitec, the company used its hot runner nozzles from its First Series Type with a shaft diameter of 13mm and a melt diameter of 3mm. Thanks to the highly precise thermal profile of the nozzle, it was possible to obtain a very small injection point diameter of 0.32mm. The injection point reportedly received high marks and the outlines were optimal. As the manifold of the 4-fold application, a distributor nozzle – also known as a rotary distributor – was utilised.

During the sampling of the application, which was carried out on the grounds of German injection moulding machine manufacturer Arburg, Lossburg, very good results were said to be shown immediately. The chambers were evenly filled after the first shot, Heitec said. During the course of the sampling, the system was able to master a spray pressure of 600 bar, the company added.

Although it would be normally be expected with this type of plastic, there appeared to be no stringing, which was said to be due to the excellent thermal profile of the nozzle.

Plastechnik AG is reportedly very satisfied with the direct injection via the hot runner. If the quantity development increases according to plan, the aim is to create a 16-fold series-production tool with identical hot runner components.

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