Rapid tooling enables Space Station mission

The unique Low Cost Tooling for Composites system (LCTC) developed by Boeing and RenShape Solutions tooling division, has achieved another first.

The unique Low Cost Tooling for Composites system (LCTC) developed by Boeing and RenShape Solutions tooling division, has achieved another first - with an application to build tools for the thermal radiation shields for a world-first superconducting magnet on the International Space Station.

A consortium of RenShape Solutions, Technical Resin Bonders, a Finnish tooling company Artekno and Amber Composites, one of RenShape's UK distributors, has undertaken the Space Station project.

The project was commissioned by Space Cryomagnetics, based at the Culham Science Centre in Oxfordshire.

The LCTC process is quick, simple and economical.

Using RenPaste RP 4040 patties, it provides a new solution for prepreg tooling and is designed specifically for use in an oven or autoclave to make prototype and pre-production prepreg parts.

Tools can be made in one simple step - from CAD data to tool surface.

The RenPaste RP 4040 process is based on making an undersize aluminium honeycomb core, onto which a layer of RP 4040 paste is applied, heat cured and then milled back to the final dimensions.

For the Space Station application, two large 'doughnut' shaped tools, measuring over 3m in diameter were required to mould the prepreg laminates that will comprise the mouldings for the radiation shields of the super conducting magnet.

RP 4040 was particularly suitable for this project because its CTE closely matches that of aluminium and, as the additional central part of the tool was made from aluminium, it was important that the two materials had similar linear expansion characteristics The base of the RP 4040 part of the tool was produced at Artekno using low cost commercial grade aluminium honeycombs, machined to around 15mm below the projected final tool surface.

Artekno then manually applied the RP 4040 patties to the honeycomb taking care to work each patty into the next so as to eliminate any voids or joint lines.

Prewarming the patties to 60C helped facilitate this process.

The tools were then ready to be post cured up to 135C.

Because of the large size and the need to avoid creating undue stress in the structure, the heating and cooling processes carried out progressively over some 70 hours - considerably longer than normal.

The RenPaste RP 4040 process also allows for any late design changes to the tools.

These could be achieved simply by applying additional patties to the parts of the tool to be modified, and supporting these during the application and curing processes with metal mesh and plywood shuttering.

The tool was then ready for the final operation - creating the final tool surface.

To achieve this the RenPaste RP 4040 was milled to the final dimensions using a CNC-driven five-axis machine equipped with carbide tipped cutters.

Initial inspection of the tool indicated a very positive outcome.

The tool was then subjected to a number of additional ambient curing cycles and again, after final inspection, all critical dimensions were within tolerance.

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