Controlled Defence – Water Boiler Valve System
Malcolm Nicholls Limited (MNL) 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.
STL files were provided as design source. Stereolithography, (SLA) 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.