Breakout analysis of plastic material jetted moulds for injection moulding

Additive Manufactured plastic moulds for injection moulding produced by vat photopolymerization or material jetting are gaining interest in the industry, because they can be used to produce inexpensive inserts overnight. As a trade-off these inserts can only be used for small series of about 100 parts or less. Many technology providers simplify the expected number of shots by defining different material categories going from easy to mould materials (e.g.: PE, PS, PP, ABS, PA, TPE, etc.), and more difficult to mould materials (e.g.: PA, POM, PC-ABS, PVC, etc.) In this paper a breakout analysis is conducted on a case study moulded in PA6 material. Inserts are produced on 2 different material jetting machines, a Stratasys Objet 350 Connex 3 and 3D Systems ProJet MJP 3600 using respectively Digital ABS and VisiJet M3-X materials which are suited for injection moulding inserts. To minimise mould loading, simulations are used to select injection moulding parameters (injection temperature and material flow) which cause the lowest injection pressure. The insert breakout points correlate well to the positions where the highest injection pressure occurs and thermal hotspots occur in the mould, according to simulations. Furthermore, hotspots are also confirmed by thermal imaging. As both injection pressure and hotspots are material as well as insert design related, these results suggest that besides the injected material, the insert design is of importance for the reliability of the mould, which is here quantified by the number of shots which can be obtained before failure. In general, this paper is a starting point for understanding breakout of material jetted inserts. As future work, the injection point (gate) dimensions and location will also be investigated to help increase the number of shots. In this context, first simulations show that a different gate location should result in less shear force at critical locations, however this is not yet tested.

ISBN:978-989-20-8809-9

Jaar van publicatie:2018

Toegankelijkheid:Open