Toroidal Pick-Off

What is a toroidal pick-off?
This was a recent project to create a toroidal (doughnut) shape to surround a pelletron-chain in a high voltage machine with an applied potential. The cut-away section is to allow the chain to come out without damaging the part if it were to break while running.

Toroid 1

It was proposed that the part could be made by machining a face plate with four holes equal spaced. Use these holes to mark a 25mm plate of aluminium for drilling & tapping. Mount the 25mm plate off the face plate for turning in a lathe. The outside diameter would be turned to 108.4mm and bored to 54.8mm. A template could then be used as a guide for machining the front circular profile. The part would then be unscrewed, flipped and the back profile created. After the toroid was shaped a flat would be milled on the bottom and two mounting holes drilled & tapped. A section would be cut out and the ends would be hand shaped and the entire part sanded to a smooth finish.

That’s a lot of work for one part and would tie up a lot of man power so it was decided that the part would be 3D-printed in aluminium.

The printed part may seem expensive but compared to the labour for manual fabricating the part it is quite comparable. Other benefits are;

  • A more accurate part (~0.1mm or better).
  • More intricate part detail.
  • A hollow part.
  • Manpower can be allocated to other jobs.
  • Choice of exotic materials such as stainless steel, titanium or inconel (an aluminium alloy will be used in this instance).

Toroid 2

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