The advent of additive manufacturing has given engineers across industry new and exciting ways of designing and manufacturing components and finished parts.
In the field of injection moulding, the additive manufacturing process has given us the ability to develop a new generation of tooling that offers considerable scope to improve the quality of finished mouldings, while improving cycle time and productivity.
This is primarily due to the ability to design true conformal cooling paths that run through key areas of each mould tool. As we’ve explained in previous blog posts, conformal cooling channels traditionally have had to run in straight lines. Additive manufacturing, where a tool insert can effectively be grown layer by layer, enables us to create highly complex cooling channels that follow – or confirm to – the exact surface geometries of the moulded part. As a result, we can cool the mould tool precisely in areas where a reduction in temperature is critical.
Additive manufacturing
Although additive manufacturing using direct laser metal sintering (DLMS) is not always faster than traditional subtractive or CNC methods of producing injection mould tool inserts, it enables operations such as drilling, EDM and other finishing processes to be eliminated. This is especially true of hybrid AM systems such as the ones that we use, as these automatically smooth the surfaces of each AM part as it is grown; this overcomes one of the early criticisms of AM, that parts had relatively rough surface textures that required subsequent finishing. Having a smooth surface for conformal cooling channels is clearly important to avoid unwanted turbulence in the cooling liquid as it flows during the injection moulding process; of course, for some tools, induced turbulence will be advantageous to improve the cooling effect but this is carefully controlled by the addition of internal features such as ribs.
In principle, there is no limit to the complexity or structure of conformal cooling channels produced using AM techniques. In practice, considerations such as part design, cost and production time will dictate the final design.
Nonetheless, design engineers now have a powerful set of tools at their disposal.
Best practice
Not every injection moulded part requires conformal cooling. In general, however, parts with extensive curved surfaces or complex geometries are ideal candidates for this process. To achieve optimum results, it pays to work with an injection moulding company that has experience of manufacturing conformal cooled mould tools.
Although this may sound obvious, not all moulding companies have an understanding of the best ways to design and engineer conformal cooled toolsets that produce the best outcomes. The latter depends on a range of factors – material choice, the chemistry of plastic recrystallisation, the choice of coolant and the physics of heating and cooling – together with a number of often unpredictable variables. Much of this knowledge can only be gained through practical experience and depends on working with a partner that specialises in injection moulding, toolmaking and additive manufacturing.
Our latest white paper has a full analysis of testing we carried out that looked at heat transfer, cycle time and quality, and the effect of using additive manufacturing and conformal cooling.