Project makes prototypes with 3D printed moulds

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Hype about 3D printing replacing mass production is way off the mark, argues James Snodgrass, but the technology could help develop ‘midi manufacturing’ thanks to 3D printed injection moulds.

Anyone who remembers the first wave of internet mania, when preposterous start-up companies were injected with millions in venture capital and clustered in “incubators”, will also remember how the story played out. The tech bubble burst in 2000 and only the strongest companies survived. Large slices of humble pie were swallowed by mouthy young CEOs who, in the mid 1990s, confidently predicted the death of traditional businesses, only to find their start-ups swallowed up – for a fraction of their peak market capitalisation – by those very businesses they sought to undermine (or, to use today’s parlance, “disrupt”).

3D printing is the “disruptive technology” of the plastics industry. Wild claims have been made – mainly in a mainstream media whose tendency towards sensationalism blinds it to the reality that scientific and technological advances are usually made in small, incremental steps not giant breakthroughs. It has been suggested that 3D printing will make factories obsolete and that we’ll be able to make everything we need, from an iPad to a new fuel injector for a 1975 BMW 2002i, in a household device the size of a microwave oven.

Reality is again upon us. 3D printing has now plummeted over the parabola of the Gartner hype cycle. In September 2012, European Plastics News reported that rapid-prototyping veteran Todd Grimm, of TA Grimm and Associates, warned that 3D printing was reaching the “peak of inflated expectations”. “At any time soon, the 3D printer will not become a staple in the household,” predicted Grimm. His predictions are borne out by the slower-than-anticipated sales of consumer 3D printers, now that they are on the shelves of mainstream high street retailers.

As Grimm pointed out, 3D printing has been used for prototyping for nearly 30 years. And it will continue to have uses in specific, very specialised, applications: particularly medical and dental applications. But the dream of the home factory is a long way off.

“I tried a 3D Printer and All I Made Was Plastic Goo”, is the title of a recent article by Seth Stephenson in Slate Magazine. There is a group on the photo sharing site, Flickr, called “The Art of 3D Print Failure Pool”. Technology blog Gizmodo has published an article entitled “11 Spectacular 3D Printer Failures”. 3D printing reality, for early-adopting consumers, is not matching 3D printing hype.

The argument of 3D printing evangelists is that 3D printing represents a sea change in manufacturing. That it will lead to an inevitable shift in the relationship between consumer demand and manufacturing supply. The twentieth century, they say, was about creating a demand for mass produced goods. The twenty-first century, they say, is about people making the products they actually want (wilfully ignoring the fact that not everybody is a Giorgetto Giugiaro or a Jonathan Ive).

In last year’s 3D printing feature (April 2013), European Plastics News looked at the small UK-based model train company, Flexiscale. What that company is doing – 3D scanning real locomotives and rolling stock and making 3D prints from the point cloud, at whatever scale the customer required – provides genuine value for railway hobbyists. By targeting a niche within a niche, making items that could never be produced by injection moulding (because the market is too limited for the tooling costs to be economical, and intricacies in the subject would have to be simplified for the sake of mould geometries), Flexiscale found a pertinent case for using 3D printing.

But what of larger niches? Production runs that are too small to justify the cost of tooling for injection moulding and too large for the yield rate of 3D printers (not to mention the high cost of 3D printing polymers and resins, compared with the cost of conventional polymers). Arburg’s recently-introduced Freeformer 3D printer impressed the crowds at K 2013, with its ability to print in 3D using conventional polymers. It will keep the polymer costs down but the yield is determined by the time it takes to print, whilst also bearing in mind the cost of the machinery.

An innovation from Stratasys’s Objet business points towards a halfway-house manufacturing technology, one that marries the concept-to-manufacture quickness of 3D printing with the speed and repeatability of conventional injection moulding. Having developed a 3D printer material that can withstand the heat of conventional molten polymers, Stratasys is pointing to a future not of unique one-off production, or mass production, but “midi manufacturing”. Such a development enables injection moulding runs of hundreds or thousands, thanks to moulds that have been 3D printed.

Short-run injection moulding requires a substitute for costly moulds made of tool steel. Aluminium, for example, is the material used by UK company Protomold to make moulds for low volume production. 3D printing with engineering plastics now looks set to contribute to market development of short run moulding.

This new manufacturing paradigm has firmer foundations than the multi material printers that will churn out the latest games console in our living room at the touch of a button. And it has already been used to prototype an injection moulding tool before going to the metal.

The team of Dr József Gábor Kovács, head of the Department of Polymer Engineering Laboratory, Budapest University of Technology and Economics, in Hungary, was commissioned to design a general purpose electric fan that could provide enhanced cooling at a significantly reduced noise level. The fan design had to pass safety tests and perform under extreme load conditions including intense temperature, multiple hours of operation, and high rotation speeds.

Kovács’s team needed to make injection moulded prototypes of the fan from the same material as the finished product. But they did not have the budget – either financial or temporal – to produce multiple injection moulding tools. So Kovács turned to the Objet350 ConnexTM 3D Printer from Stratasys, which was used to make prototypes of the fan designs and also prototypes of the injection moulding tools.

Three prospective fan designs were created using the 3D printer. Within hours, the prototypes were ready to be placed onto an engine axis for testing. Kovács then chose the best performing fan design for the next stage of development.

During the next two days, he designed and printed a three-part injection mould from Digital ABS material. The mould was then mounted onto an Arburg Allrounder 70 tonne injection moulding machine and several thermoplastic fans were produced from polyoxymethylene (POM).

The prototypes not only passed the required safety tests, they were also able to increase cooling performance by 20% while reducing the associated noise level by 7dB.

Reflecting on the experience, Kovács commented that the Stratasys PolyJet technology provided the team with a “complete end-to-end solution without incurring major cost or time”. And he was satisfied with the quality of the end material, saying that the prototype was “just perfect, there was no need for post-processing”.

As the photographs of Kovács’s work indicate, there is still the evident banding that is the consequence of the layer-by-layer printing process, and this passes from the mould to the injection moulded product. But as 3D printer resolution increases, this banding will become less evident, and this promising technology might graduate from prototyping to help usher in a new era of midi manufacturing.          


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