OGM
CAD being used for the design of complex moulds
Injection mould tools, traditionally manufactured in the Far East, can now be created in the UK in half the time required for conventional toolmaking, says Marcel Gowers of plastic injection moulding specialist, OGM. In the following article for BP&R, he outlines how.
Speed and quality maintenance are the holy grail of any industrial manufacturing process and nowhere is this truer than in the production of injection-moulded components. Traditionally, manufacturers have been looking to the Far East to cut the time it takes to get a design from concept to production.
However, even in the Far East, the manufacture of mould tools suitable for the high-volume production of complex parts is a time-intensive process; with lead times of up to four months between design sign-off and delivery of first part production in the UK. And the performance of a tool - especially its ability to cool parts effectively prior to ejection - determines the cycle time, quality and overall productivity of the moulding process.
Innovation cuts mould making times
Additive manufacturing is finding its way into toolmaking and a new technology - hybrid metal additive manufacturing and machining – is enabling moulds to be made quicker and more cost-effectively than ever before. The first of its kind to be installed in the UK at OGM, this new technology is creating waves in the injection moulding sector and is ushering in major change in the manufacture of plastic parts in the UK and beyond.
Two technologies, one machine
Hybrid metal additive manufacturing and machining is proving particularly popular with customers looking to achieve complex moulds quickly and cost-effectively. At the heart of the solution is the combination of hybrid metal additive manufacturing - using direct metal laser sintering – with conventional CNC machining. They have been combined into an integrated build process, with stunning results.
The system builds mould features from powder material layer-by-layer using a laser. After each layer is added, an automated secondary machining process rapidly removes excess material to generate the finished geometry of the tool. The result is high dimensional accuracy and a fine surface finish that allows core and cavity details to be manufactured automatically in one go. The material surface finish produced is also hard, often avoiding the subsequent need for heat treatment to produce production tooling. If required, a full range of textured or polished surface finishes can be applied in secondary processes.
Rapid Production Toolmaking technique compresses lead times by up to 50 per cent
To make the most efficient use of this hybrid metal additive manufacturing technology, OGM’s Rapid Production Toolmaking technique is also used to combine the process with conventional high-speed machining. The basic shape and simpler features of a core or cavity are machined first from a solid block of tool steel and this becomes the base structure onto which the more complex features are added. This approach compresses lead times by up to 50 per cent, with just a few weeks from order to first production parts, and produces mould tool inserts with good levels of surface finish and precision, to within 50 microns.
Better part quality and faster cycle time with improved conformal cooling
The hybrid metal additive manufacturing approach enables the production of mould features that would be extremely difficult to manufacture with any alternative technology. Notably, the production of conformal cooling channels in moulds with complex geometry.
In many components, cooling channels compete for space within the tool with other features, such as ejector pins or moving inserts. Although injection mould toolmakers have developed solutions to this problem they inevitably add to the time, complexity and cost of producing each mould tool or mould tool insert. The hybrid approach, by contrast, allows tools incorporating conformal cooling channels to be manufactured automatically in one hit, with no need for separate finishing activities. As a result, typical lead-times can be reduced from more than 12 weeks to less than six weeks.
With time being of the essence on any production job, being able to guarantee quality, whilst reducing lead times and improving cost efficiencies is good news for customers. Moulders want the shortest possible cycle time to maximise productivity and keep unit costs down and thanks to OGM’s use of hybrid metal additive manufacturing and machining, this is now possible.
About the Author
Marcel Gowers is Additive Applications Engineering Manager at OGM, with over 25 years of mechanical engineering experience. This includes 15 years at Smiths Group plc within a high technology environment.