Protoform prototyping speeds arms prototypes

Protoform’s Space Puzzle Moulding rapid prototyping system is being used by arms manufacturer, Heckler and Koch, to rapidly prototype/manufacture plastics parts for its products.

Protoform’s Space Puzzle Moulding rapid prototyping system, made up of tooling cost, timescale, production rate and item cost, suits military products ranging from 2g to 2.2kg shot weight and generally within the dimensions 800 x 400 x 200mm Quantities can range from prototype up to 3000 items from a single set of tooling.

The importance of ‘function without failure’ in the field of combat is ensured throughout production, from design and development through to final test and adjustment, which culminates in a human assessment of each product by experts even after the computerised phase of manufacture is complete.

In the supply chain, this close control extends as far back as the selection of barrel steel and other materials unique to H and K, supplied exclusively by an approved foundry.

H and K were seeking to take maximum advantage of plastic materials in their products.

This was not to save weight or to cheapen the product in any way: it was production-process driven.

For example, the manufacture of the frame of an H and K P-7 pistol from a solid steel billet involved around 100 milling operations removing almost 70 per cent of the original material.

It made sense to mould such frames in high strength polymers and H and K planned to install whatever plant and equipment was needed to achieve this technical advantage.

R and D on other functional engineering components had also shown up to a factor of 5-lifetime gain in reliability and maintenance from 2,000 to 10,000 cycles.

Moulding in plastics requires fully functional tooling to be created for each component right from the outset, since no amount of simulation can replace trials with production-intent materials moulded to the exact design specification.

Often these trials would highlight modifications to fine-tune the design before committing to the cost of full production tooling.

Toolmaker Konrad Hofmann, working for H and K, said that only the parts of the tooling that immediately formed the shape of the product needed to be produced, provided they could be surrounded and supported by a form of universal bolster, holding them accurately and securely for the injection operation to take place.

The assembly of these CNC-machined ‘Space Puzzle’ style tool-parts and the subsequent de-moulding of the component could be manually performed by a skilled operator since the quantity required by H and K at this stage was, at most, less than 100.

H and K engineers were supportive and, even though the process was in the earliest stage of development, placed tooling orders for examples of Space Puzzle Moulding (SPM).

Encouraged by their support, Hofmann perfected the bolster system, registering a patent on his invention and opening up a new market for rapid, low-cost prototype to low volume manufacture to full production-series quality.

Now, 20 years on and 10,000 industrial projects later, individual examples of such tooling have reached production volumes of 3000 plus.

All today’s SPM tools are designed to fit into one of a range of suitably sized, standard outer bolsters of unique, patented character.

The main parts of the tool that actually create the shapes and forms, the sliding cores and loose inserts, are precision milled on the very latest high speed, multi-axis, state-of-the-art CAD machines using tooling grade aluminium or steel.

They are finished on the external planes to a size about 20 per cent larger than the actual component itself, saving on material, time and therefore cost, but the benefits do not stop there.

In any early tooling, there needs to be flexibility to allow mould flow and post-moulding effects to be evaluated and if necessary adjusted.

SPM tooling accepts and facilitates such changes and adjustments, because the individual parts of the puzzle-like assembly are easily modified or replaced, doing so at the lowest cost and on timescales without impacting greatly on product flow.

Design versions and niche market variants can often only be accommodated by a change of inserts and it is not unusual for a single set of tooling to have multi-product capability.

This can be useful in a spare-part situation where a few pieces of an earlier design may be required at a later date, or perhaps the parallel introduction of high/low specification models with different requirements for control apertures.

SPM tooling strips apart easily when removed from its supporting bolster structure and has a near contact-volume envelope.

De-moulding is a slick manual-operation, since little automation is required to operate the core and inserts beyond a set of custom hand tools and extraction devices tailored to each component.

Space Puzzle Moulding is also a rapid tooling technique, giving production quality items in short-series manufacture.

Every H and K weapon now has plastic parts where appropriate.

related catagory other