Czech-based additive manufacturing company Innomia has designed new tool insert with direct metal laser sintering (DMLS) for creating the central front armrest in a Škoda car. Innomia used EOS technology to implement conformal cooling in the mould, reducing injection moulding time by 17 per cent and improving component quality.
Direct metal laser sintering is an additive technique that builds up a part layer-by-layer by sintering metal powder with a laser. Innomia’s engineers supported automotive supplier Magna in optimising cooling of the mould in the project for Škoda.
Injection moulding of the glass fibre reinforced plastic component is difficult, as uniform dissipation of heat throughout the tool has a significant effect on minimising distortion and improving component quality as it solidifies.
Moreover, temperature control plays a major role in minimising the production cycle time, as the quicker heat is removed, the sooner a component can be ejected and the next one produced.
The tool insert previously used was made of beryllium-copper alloy, which has a high thermal conductivity. Cooling was possible from one side of the insert only, so temperature distribution was uneven. As the temperature differential between the water and the mould was high – around 120°C – the elevated humidity accelerated corrosion, necessitating costly, intensive cleaning of the mould every one to two weeks.
Designers from Innomia developed the new tool insert cooling system with integrated conformal cooling channels. This is an established application using DMLS technology and one that only additive manufacturing can achieve. An EOSINT M 270 system from EOS was used to sinter Maraging Steel 1.2709 metal powder
Innomia was able to increase the hardness through post-treatment to more than 50 HRc, leading to high wear resistance and low maintenance costs.
Luboš Rozkošný, CEO at Innomia, explained: ‘The DMLS process enabled us to manufacture an extremely durable component, while at the same time successfully retain the proven advantages of AM in terms of design flexibility.’
The temperature distribution and associated heat dissipation are now substantially more homogeneous. Since the heat leaves both the tool and the component more quickly, a water temperature of 60°C is now sufficient for cooling. The insert surface temperature does not rise beyond 90°C and the consequent fourfold reduction in temperature differential has removed the air humidity problem and reduced energy consumption.
The uniform cooling channels mean that the production cycle is now 17 per cent faster than previously. Component deformation is no longer a problem, raising quality and repeatability. After 370,000 cycles, total cost savings amounted to around €20,000.
Pavel Strnadek, head of tool maintenance at Magna, added: ‘There is stiff competition in the European automobile industry. That is why it is very important for us to be able to produce components to the highest quality standards at the lowest price.
‘The issue of injection mould cooling was something that we have been trying to deal with for a long time. Additive manufacturing has allowed us to make the breakthrough and we are very happy with the results at every level.’