Good Karma at AutoRIM
In August 2017 AutoRIM were approached by Rabchog, a member of the Buddhist community at Kadampa Art studio. Formerly a structural engineer, Rabchog had been given the task of finding a solution to the manufacture of large rotationally cast polyurethane mouldings, sometimes as heavy as 10kg
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 polyurethane 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 books from the AutoRIM technical library – the Polyurethane Handbook by Gunter Oertel
Many telephone calls and 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 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. It has since been delivering improved consistency and repeatability of the production process of a 2 part urethane reaction of a highly filled polyol component using a hardened pump with motor drive unit. 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 concluding with in-mould rotation for a further 60 seconds to wet out all surfaces before it stands to cure. A large amount of Calmote filler improves mould detail definition and reduces shrinkage and after final cure in ambient conditions the mould is hand trimmed and painted by volunteers from all corners of the world in the Art Studio.
A variety of moulds of shapes and sizes are produced and after completion are destined for the worldwide Buddhist community. Rarely has there been a more delightful project to design and manufacture a polyurethane machine; _/\_