Plastic meets aerospace requirements

An EOS Electro Optical Systems (UK) product story

Edited by the Engineeringtalk editorial team Jul 24, 2008

Rapid manufacturing and prototyping specialist, Ogle Models, has introduced a flame retardant plastic to the range of materials that it uses to produce components for customers.

Ogle Models is using the PA 2210 FR flame retardant plastic in its laser sintering machines The polyamide was designed to meet the flammability, smoke and toxicity standards of the civil aerospace industry.

Aircraft manufacturers like Boeing, Dassault, Embraer and others have successfully tested the new material.

To achieve a fire retardant rating of UL94 V-O, a minimum 2mm wall thickness is required.

In the telecommunications industry, Ogle producrd a fire retardant, fibre 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 centre 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.

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, said 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 a larger EOSINT P 730 with a 700 x 380 x 580mm build volume and a smaller 200 x 250 x 330mm capacity Formiga P 100.

Willmott said: "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 parts".

"There is less of a problem in X and Y as shrinkage is linear, but it is nonlinear 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 moulded 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.

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

An early contract fulfilled by Ogle using this machine was for a customer in the medical sector, whose fine tolerance, nylon parts were previously made by SLA and vacuum casting with a longer lead time and at higher cost.

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 realised 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.