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High-Speed Shaft Assembly System

Hui Xu, Elijah Beard and Joshua Boyd

Danfoss Turbocor has created a project to assemble high-speed shafts for their TT series compressors. The TT series compressors are used by the HVAC industry to heat and cool large places crowded with people and equipment, including schools, offices and factories. 

Danfoss Turbocor is the first to develop oil-free compressors that run with shafts floating inside magnetic bearings. Danfoss Turbocor’s product lets the shafts in the compressors run up to 40,000 rpm, which is more than 10 times that of a car. These high speeds mean that assembling a balanced, strong and perfectly aligned shaft is important for the compressor’s performance. 

A shrink-fitting process is used to assemble the shafts whereby bearing sleeves are heated in an oven so that they expand and then pushed onto a smaller shaft with a press before the assembly cools. The bearing sleeves shrink as they cool which means they will form a tight grip around the shaft, completing the shaft assembly. 

Presses are expensive machines, so being able to use a small press saves money. The required press pressure is related to the sleeve temperatures because the sleeves expand when they heat up. If the sleeves expand enough, they will slip around the shaft without applying any pressure. We calculated this temperature so that a smaller press can be used, lowering assembly costs, increasing worker safety and helping avoid parts damage during the assembly. Safety equipment, including a Plexiglas guard around the press, a safety lock and insulated gloves, will be used to protect the press operator. The assembly process will be safe, simple and straightforward.

Team Members (L to R):
Hui Xu, Elijah Beard and Joshua Boyd
Patrick Hollis, Ph.D.
Danfoss Turbocor