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Isel CPM3020 cnc machine - electronics rebuild

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philf:

--- Quote from: modeldozer on January 21, 2016, 08:59:28 AM ---Hi Chris,

When I built my CNC router i fitted 6 limit swithes in series and 3 separate home swithes.  The limits tiggers an E- stop and the3 homes go to three different inputs.  To be honest I never use the home switches as I normally set machine zero (X, Y, Z) to a datum on the part.

Cheers
Abraham

--- End quote ---

Hi Abraham,

Certainly with Mach3 it's advantageous for safety and for the sake of the machine to drive to home or limit switches as a reference before you start machining. By setting the soft limits up correctly (and enabling "Use Soft Limits") you will then never run into the limit switches and before Mach3 will run any code it does a check that the soft limits won't be reached.

If the table or gantry is moving fast it may not be able to stop quickly enough before running into a mechanical limit which, as Andrew has pointed out, could lead to a ballscrew & nut being destroyed or worse.

I too always zero on a job but Mach3 works with two sets of co-ordinates akin to Absolute and Incremental on a DRO. I always home the machine on switch on and then I zero the edges of my part in the 'incremental' mode but the 'absolute' mode still knows the safe distance to the limits and thus can give you a warning.

Hope you're taking all this in Chris! If you get stuck you know where I am.

Cheers.

Phil.

awemawson:
G54 Phil

raynerd:
As always, appreciate your replies. Really helpful stuff and I think I now understand. Based on the info, I was fiddling last night I can see how you can set limit and home all on one pin - very smart.

I fully appreciate Andrew, based on what you said, that in industry or with big machines a limit is critical for safety of the operator but equally safety of breaking parts.

Thanks again for your time.

raynerd:




The cnc machine is now up and running. I`m blown away with how fast and how accurate it is and how well it did with a 4mm cut depth in brass cutting some text.

philf:
Excellent work Chris!  :clap:

Phil.

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