Page 38 - ITA Journal 3-2018

Technical Papers
Printed sand mould for a large diesel cylinder head from MAN: the mould with dimensions of 1,460 x 1,483 x 719 mm was manufactured additively in 29 hours by the binder jetting process using a sand printer.
world leaders among 3D printing manufacturers include Concept Laser (metal), EOS (metal and plastic), SLM Solutions (metal) and Voxeljet. Voxeljet has spe- cialised in foundries and markets 3D printers for the production of sand moulds and cores as well as of plastic models for investment casting by the lost-wax process.
In order to produce a casting, what are needed are a mould and the appropriate cores to form the cavities in the component that is being cast. In classic sand casting, the moulds and cores are made from quartz sand, which is strengthened by a special bonding agent. While fully automatic moulding machines and automatic core shooting machines are stand- ard features at modern foundries for the mass production of car engines, for example, it is rarely an economic solution to use auto- matic equipment for prototypes and small batches. 3D printing is an increasingly common alter- native here. Sand moulds and cores of any complexity are man- ufactured from the CAD dataset via a layering process. Toolless manufacturing of this kind pro- vides high exibility as regards numbers, design and versions and permits the production in exactly reproducible quality of complex moulds and cores with practically any geometry. Voxeljet talks about cost savings of up to 75 per cent in the 3D printing of moulds and cores made from sand for small batches.
The printing of sand moulds and cores is a highly suitable option for development operations. The iron foundry Düker with locations in Karlstadt and Laufach in Germany, for example, does not use models any more in the casting it carries
out for customers. The CAD dataset is all that is needed to produce the sand moulds that are manu- factured additively. As a result, new products can be implemented in castings from computer les within a short time and can then be machined for trial purposes. Geometric adaptations are simple to carry out and recasting is then possible once the design data have been changed and another mould has been printed. Düker reports that development time is reduced signi cantly by this process. It is apparently standard procedure to produce initial samples within a few weeks, for which months are needed in the series process.
Die casting with reusable moulds made from tool steel bene t from 3D printing too. “Additive manu- facturing is creating tremendous opportunities for die casting com- panies”, as Dr. Ioannis Ioannides, CEO of the die casting machine manufacturer Oskar Frech, who is both Board Chairman of the VDMA foundry machine trade associa- tion and a member of the board of the VDMA additive manufacturing task force, stresses in an interview with the magazine Giesserei. For example, Frech uses 3D printing to produce a complex key com- ponent for its low-sprue FGS tool technology that economises on recycled material (e.g. aluminium or magnesium).
The mould plays a key role in the die casting process. It is impor- tant that the castings solidify as quickly as possible. The process time for a component can be shortened by faster cooling, while the quality of the casting is improved at the same time too. This depends on adequate heat removal in the casting mould, which is traditionally achieved
Large diesel cylinder head: cast iron part weighing more than one tonne.
ITAtube Journal No3/October 2018
38