Power of print

A new powder printing process developed by

(DMU) in Leicester could one day be used to cut the cost of manufacturing a variety of customised consumer goods, such as motorcycle helmet liners.

A rapid manufacturing machine using the technology would build a 3D model from a CAD helmet liner design layer by layer at a high production rate. Polymer powders would be specifically selected and sintered for the process.

The process is being tested as part of a European project, Custom-Fit, that aims to produce personalised consumer goods cheaply.

The team is expected to produce sample helmet liners by the end of May.

David Wimpenny, director of the rapid prototyping (RP) and manufacturing group at DMU, said his research group is one of a small number in the world who have successfully produced layers using rapid laser printing techniques.

The challenge, he said, is producing layers fast and high enough. 'A couple of millimetres high was the limit of parts made using laser printing,' said Wimpenny. 'We've broken the 10mm barrier — which doesn't sound like very much, but it's the equivalent of sending a spaceship out of Earth's orbit.'

The goal is to obtain 2,000 layers/min, which will produce 200mm of material —the same as injection moulding.

Using a laser, DMU's process heats loose polymer powder material to fuse a layer on to a surface. Then it quickly cools that layer before the next one goes on top.

'The engineering has to overcome the cooling down of each layer so the fusing can be done quickly,' said Wimpenny. 'Then we will obtain the 2,000 layers/min target.'

One way to do this, said Wimpenny, was to build a laser printer that simultaneously forms multiple parts on multiple platforms. This, he said, will allow time for one part to cool down while you print on to another product.

DMU is working with UK rapid prototyping and tooling technology company Mining and Chemical Products (MCP) to commercialise its process by 2010.

MCP is delivering an industrial rig at the end of this month for DMU's team to experiment on. The rig will have multiple platforms and will process many parts in parallel.

The machine — originally engineered for high-speed printing on materials such as glass — is a huge departure from the converted office printers the DMU team was experimenting with.

Since beginning research in 2001 Wimpenny's team has had to overcome many technical challenges, the biggest of which was to find a way to deposit the material. 'In a standard laser printing process you only put one layer of ink on a piece of paper,' said Wimpenny.

'If you do that thousands of times you would find that after a few hundred prints no material had been deposited.'

He explained that the printing materials transfer onto the paper by an electrostatic charge. As a charge builds up, the printing material, whether ink or polymer, sticks to the print head. 'It does not want to come off so the efficiency drops quite quickly,' he said.

The team has developed a patent-pending method to dissipate the charge accumulation on the surface.

'At the moment the charge accumulation is limiting the application other groups are working on,' said Wimpenny. 'Our efficiency remains the same having laid down 10,000 layers as it is when we put down the first layer.'

The motorbike helmet is one of the case studies chosen for the Custom-Fit project. Other applications include the consumer goods market and medical applications such as surgical implants and prosthesis.

Wimpenny envisages a day — maybe five years from now — when you could walk into a major retailer, have your head scanned, grab a coffee and come back to collect a reasonably priced, custom-made helmet.

Using current RP machines, Wimpenny claimed that it costs £200 to make a customised helmet, whereas his process could cost £20.