Aerospace Friendly Flame-Retardant Plastic

Rapid manufacturing and prototyping specialist, Ogle Models, has introduced a flameretardant plastic to the range of materials that it uses to produce components for customers. Designated PA 2210 FR, the powder is produced by EOS for use in its lasersintering machines. Ogle operates three, two of which were bought in June 2008 as part of a £1 million ($2.53 million) investment.

The company believes it is one of the first RM/RP bureaus in Europe to run the fire-resistant material in its machines. Already it has produced two sets of parts for the cabin and fuel tank of an aircraft in quantities ranging from 50-off to 200-off, says David Bennion, sales and marketing director.

The polyamide PA 2210 FR was especially designed to meet the flammability, smoke and toxicity standards for the civil aerospace industry. Airplane manufacturers like Boeing, Dassault, Embraer and others have successfully tested the new material. PA 2210 F R typically qualifies for "flying hardware" with wall thicknesses down to 2mm.

In the telecommunications industry, Ogle has for some time been producing a fire-retardant, fiber-optic tray for communications towers using a combination of stereolithography (SLA) and vacuum casting. The process used to be time-consuming and relatively expensive. The same part is now laser-sintered in one operation using PA 2210 FR in quantities up to 180-off, without the need for tooling, resulting in a 30% cost saving for the customer.

Recent investment at Ogle's product development service center in Letchworth has seen a near doubling of floor area, giving more space to develop both the traditional model making and CNC prototyping sides of its business. Clients include many blue-chip organizations such as Bentley and GlaxoSmithKline as well as leading design, building and architectural firms including Laing O'Rourke, Arup and KPF.

The first EOS plastic laser-sintering machine, an EOSINT P 385, was installed at Letchworth in 2000, but for the last 18 months it has been working to capacity, 24 hours a day. Ogle's Rapid Prototyping Director, Steve Willmott, comments that, "the machine has been upgraded twice by EOS to take advantage of improvements in laser-sintering. The result has been a 30% increase in productivity and a 50% improvement in component quality."

A step-change in performance came with the installation of the two latest machines, a larger EOSINT P 730 with 700mm x 380mm x 580mm build volume and a smaller 200mm x 250mm x 330mm capacity FORMIGA P 100.

"New control software makes these machines much easier to operate, as no guesswork or experience is needed to set the scaling factor that allows for shrinkage of the part," Willmott says. "There is less of a problem in the X and Y axis as shrinkage is linear, but it is non-linear in Z. The latest EOS software applies compensation in all three axes automatically, making it quicker to set up a new job. The twin-laser P 730 is 40% faster than earlier laser-sintering machines, producing components that look as though they have been molded and with better dimensional accuracy and surface finish. Key to the improvement is the 0.12mm standard layer thickness, down from 0.15mm on the P 385.

Similarly, the FORMIGA P 100 does everything that the large machine is able to, but within a smaller work volume, yet to even higher accuracy thanks to the 0.1mm layer thickness.

Series production of laser-sintered plastic components is becoming the norm at Ogle, in addition to ones and twos for prototype applications. A good example is the manufacture of parts in batches of several hundred for a thermal imaging camera used in search-and-rescue work.

From a CAD model supplied by the customer, laser-sintering is used to make the chassis that supports the thermal imaging screen and the electronics. No hard tooling is required, so any alteration in design is easily accommodated without additional expense.

A big advantage of additive layer manufacturing by laser-sintering is that the process is fully self-supporting, allowing parts to be built within other parts and with complex geometries that could not be realized any other way. These attributes lower the cost of production and at the same time offer unfettered freedom of design. Moreover, the resulting components are strong and rigid enough to be used in places where they may be subjected to mechanical and thermal stress.