Sensing Distance from Work Piece

Quality of product depends on the ability to detect the distance of the cutting tool from the Work Piece. The nature of this sensing problem changes depending on the cutting tool.

Plasma Torch

Here is a great article on controlling Torch to Work Distance. The quick story is that voltage between the torch and the work piece increases as the torch gets further away from the material. There is a discussion of building a z-controller here-- some of the content may be helpful. From that is a potential collaborator.

Notes from Tom

There is a lot of information about torch tables using plasma torches, but I haven't seen much about those using acetylene torches.

The articles about plasma torches seem consistent:

• Torch height should be regulated to optimize cut pattern:
  • If too high or too low, the cut will have beveled edges
  • Most torch head damage results from head too low
• Initial torch height should be 150% - 200% of height after cutting has been initiated.
• Height can be sensed by voltage of plasma arc: Torch height is proportional to arc voltage. Open circuit voltage is around 300vdc, cutting voltage ranges from 80vdc to 200vdc, depending on operating current and cutting height.

Relevant articles:

CamSoft Torch Height Controller

Hypertherm Torch Height Controller