4. Materials and building strategies
A variety of different metal materials are available for EOSINT M machines, and new materials are continuously being developed [4]. The most relevant material for series production tooling is a high-grade 18 Maraging 300 type steel (1.2709, X3NiCoMoTi18-9-5) which is marketed in powder form under the name EOS MaragingSteel MS1. This material is fully melted in the EOSINT M machine to produce fully dense parts with a hardness of 36 – 39 HRC as built, which can be easily post-hardened (6 hours at 490°C) to increase the hardness up to 53 – 55 HRC and produce an ultimate tensile strength of more than 1900 MPa. Tool components built in this material can be machined, eroded, polished etc. in a similar way to conventional tool steel materials. The middle and right examples of Figure 7 were built in EOS MaragingSteel MS1. In cases where lower strength and hardness are sufficient, often the material of choice for DirectTool is a proprietary bronze-nickel based alloy material called DirectMetal 20. This material has the advantage that it is very quick and easy both to build and to finish, and is therefore very popular for prototype tooling and low-volume production tooling. The high build speed is achieved partly by using processing parameters (laser scan speed etc.) which produce a partially porous structure inside the parts, whilst the outer surface region is built with higher density. The projects shown in Figure 1 through Figure 3 and Figure 6 were produced using this material. Other DMLS materials may also be useful for DirectTool applications in some cases, for example stainless steel materials are available which can be beneficial for moulding corrosive plastics. EOSINT M systems build parts on top of a metal plate called a build platform. When building mould cavities, the platform is typically integrated into the cavity design so that the DMLS geometry is melted directly onto the platform. Figure 8 (a) shows how multiple tool inserts can be built on one platform (these are components for the tool shown in Figure 6(b)). The individual inserts are cut out, typically by sawing or wire cutting, to produce inserts or onserts like those shown in Figure 1 and Figure 2. In cases where it is not convenient to integrate the platform, for example loose inserts or cooling pins, these are built on a support structure which attaches the DMLS geometry to the platform, and which is removed after building.
Figure 8: An example is shown in Figure 8 (b), which also shows how long parts (in this case 305 mm) can be built lying down to save time. Figure 8 (c) shows a case where standardized cooling pins were being produced as a series product by EOSINT M. Here the most efficient and cost-effective method was to build large numbers of pins standing up – in this case 200 pins fitted on one half of a build platform and could be produced fully automatically (unmannedoperation) in just 30 hours. They can be efficiently separated from the build platform by wire cutting.
Figure 9: Use of an Erowa Powerchuck clamping system in an EOSINT M machine. Left: chuck in machine. Such a system based on the widely used Erowa Powerchuck 150 system is available as a commercial option for EOSINT M systems (see Figure 9), which is particularly relevant for users who have this system on other machining stations. But various other solutions have also been implemented, according to requirements and wishes of particular users. The process software of the EOSINT M system includes a feature to enable easy alignment of the machine coordinate system to any suitable mechanical reference. |
