In August 2017 AutoRIM were approached by Rabchog, a member of the Buddhist community at Kadampa Art studio. Formerly a building surveyor he had been given the task of finding a solution to the manufacture of large rotationally cast polyurethane mouldings, sometimes as heavy as 80kg.
At that time the manufacturing process was one of hand mixing and physical lifting to pour into moulds. Inevitably the production rate was not as high as desired and Rabchog was looking to improve the process by the introduction of purpose designed mixing equipment.
The brief was to build an AutoRIM RIM-mix machine to process a 2 part formulation with a 200% content of Omya Whitting (Calmote) CaCO3 fine filler in the polyol giving a final viscosity of 26400mPas and a density of 1.76g/cm3. This mix required a pre-blend batch blending system for the polyol and a 2 part elastomer mixing machine with vacuum on both 200 litre day tanks for degassing. The added challenge was the space restrictions for a machine in the Art Studio.
Following our meeting AutoRIM introduced Rabchog to a recently retired chemical industry expert for his advice and provided some light reading in the form of one of our most borrowed technical library books – Polyurethane Handbook by Gunter Oertel.
Many telephone calls, discussions and meetings later culminated in finalisation of the brief in Autumn 2018 and having given our considered advice on support equipment including extraction, working practices and production rates the RIM-mix 2-part elastomer machine was constructed, and Rabchog and fellow members of the community visited for F.A.T. at AutoRIM in early Spring 2019.
The RIM-mix was duly delivered and commissioned since when it has since been delivering improvements in consistency and repeatability of the production process of a 2 part urethane reaction of highly filled polyol component using a hardened pump with motor drive unit. Using a conventional MDI mixed with filled polyol at a pour rate of approximately 100g/second closed mould injected into stationary moulds by a mix head supported by a modified boom for up to and over 60 seconds following which the mould is rotated for up to 18 minutes to ensure even distribution during initial curing. A large amount of Calmote filler improves mould detail definition and reduces shrinkage and after final cure in ambient conditions the casts are then hand trimmed and painted by volunteers from all corners of the world in the Art Studio.
A variety of casts of different shapes and sizes are produced and after completion are destined for the worldwide Kadampa Buddhist community. Rarely has there been a more delightful project to design and manufacture a polyurethane machine; _/_