Vacuum cast pipework fittings repeatability of the +/- 0.05mm accuracy was paramount

Controlled Defence

Product development prototypes produced via vacuum casting….

In brief

Malcolm Nicholls Limited used enhanced rapid prototyping techniques to aid a boiler manufacturer develop a safety valve system for mains water inlet.
The system's aim was to provide protection from pressure surge and negative pressure boiler evacuation on a highly efficient domestic water heater.

Model requirements….

The customer required 30 sets of valve based components for water board approval testing. The components needed to be highly accurate with some tolerances as tight as +/- 0.05mm

Tight Tolerances

Some of the tolerances required were as tight as ±0.05mm. High precision metal inserts within the silicon tooling maintained the tight tolerances required in some of the bores.

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Perfect screw threads

The ultra high resolution SLA machine producedsmooth and accurate threads. The screw threads that can be seen here were all cast in without need for post machining.

Urgent Timeline

Scaled down simplified data of the engineering plant was broken down into many sections representing the differing areas of the plant. Several SLA printers and SLS printers were utilised simultaneously to speed up the process.

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Urgent Timeline

Once the pieces were built, supports were carefully removed. As budget was limited, parts were given a light sandblast and a quick coat of paint, the colour depicted the various sectors of the plant.The parts were mounted to a custom built display board. All in all the project was completed in just over a week

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How it was achieved…

STL files were provided as design source. Ultra-high resolution SL masters were built at the ultra-fine layer thickness of 0.05mm. The silicone tooling needed to produce the 30 sets of polyurethane castings was enhanced with high precision metal inserts to maintain the tight tolerances required in some of the bores. (Tolerances as tight as ±0.05mm can now be repeatedly held.) The screw threads that can be seen here were all cast in without need for post machining.
The prototypes were put to use in engineering evaluation, fit and function tests and regulation approval. An increase in the test pressures for water board approval meant that initial polyurethane samples failed. However, subsequent castings, from the same silicone tools, in glass-filled polyurethane resin completed the high pressure tests at an internal pressure of 15 Bar.

Detailed Views

The screw threads that can be seen here were all cast in without need for post machining.

All 30 sets had to have repeated accuracy with tight tolerances.

Some of the tolerances required were as tight as ±0.05mm.

Not all projects require the level of accuracy that was required in this project. Some of the tolerances required were as tight as ±0.05mm.

Why MNL?….

In this instance the key point for using MNL's expertise was accuracy. Combining MNLs in house high res SLA 3D printing system and the precision inserts within the silicon tooling ensured that all 30 sets were within the tight tolerances that were required.

In conclusion….

Almost anyone can 3D print a model it’s what you do with it after is where MNL stands out from the crowd, with a selection of 3D Printing processes and a skilled model making team, make for a perfect project partnership.

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