HSS Takes Aim At Injection Molding

The Holy Grail of 3D printing (aka additive manufacturing) is fast production speed with traditional engineering plastics.

A new technology coming from England claims to have the right stuff. It’s called High-Speed Sintering (HSS) and uses inkjet printing and infra-red heating instead of the lasers and scanning mirrors used in selective laser sintering (SLS).

In the patent drawing, 12 refers to the radiation source; 18 is the powder, and 30 is the printhead.

In the patent drawing, 12 refers to the radiation source; 18 is the powder, and 30 is the printhead.

 

According to Neil Hopkinson, one of the original developers of the approach, the main advantage is speed. In SLS, the laser has to scan backwards and forwards, very time consuming especially when there are a lot of parts or large parts. In HSS, the inkjet printer puts infrared-absorbing ink on a bed of plastics powder (nylon 12 is used in a promotional video). Then an infrared lamp passes and energy from the ink is absorbed and melts the power particles underneath. A new bed of powder is deposited and the process repeats until a three-dimensional structure emerges.

Hopkinson tells us: “On our small machine we can often turn round shallow builds in 10 minutes or so. The process currently takes under 20 second per layer irrespective of how much material we sinter in a layer.”  Hundreds of parts can be made in 10 minutes.

That rate is competitive with injection molding, says Hopkinson. It appears to be a significant improvement in the 3D printing universe, and it may have a role. Three hours are required for machine warm up and cool down.

In terms of types of materials used, Hopkinson comments:  ”We are receiving a lot of interest from materials companies and have made parts with a wide range of polymers.”  Materials used to date are generally confidential, but it’s been disclosed that nylons and thermoplastic elastomers have been used.

What size build envelope is possible?

“We currently run a small machine making parts of maximum size 145mm x 45 mm x 80 mm but we have previously worked a build volume over 300mm x 250mm x 300mm and we envisage much larger build volumes in future.”

How do the economics compare with competing processes?

“We have conducted a lot of cost analyses and High Speed Sintering always looks very attractive compared with other ways of making complex geometry parts.  Mostly we benchmark economics against injection molding.”

Candidate geometries for the process include intricate parts ranging from closures for healthcare products to a wide range of parts in automotive such as dampers, housings and pipes.

How soon will a part be commercialized?

“We routinely make production standard parts but we prefer not to sell these parts direct and instead allow licensees to develop a large market for this technology.”

HSS may be cost competitive for at least some types of large-volume series production, particularly if customization is involved. It’s also clear that engineers can envision designs without regard to the rules that limit injection molding. Undercuts and other features require expensive tooling. Also—and importantly—the process creates the potential for whole new design concepts, such as curving internal channels not possible with molding.

It’s a niche process, but it could be an important one.

The technology was developed by Loughborough University Enterprises Limited (Loughborough, Leicestershire, Great Britain).  The U.S. patent was awarded last fall.

The Loughborough process is now being commercialized by a University of Sheffield spin-out that is publicly funded.

 

 

 

About Doug Smock

Former Chief Editor at Plastics World and Senior Technical Editor Design News

Aircraft, Automotive, Consumer Goods, Design, Europe, Injection Molding, Prototyping ,

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