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Author Topic: Need help with fixtures / offsets  (Read 1965 times)

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Need help with fixtures / offsets
« on: January 11, 2011, 08:55:31 AM »
Greetings,

I'm very new to Mach 3 but have previous experience in CNC programming using AutoCad, NC Polaris and Router CIM. (yup, back then you had to use all three)

Mach has been truly amazing and I've had but one difficulty. I can't seem to work out how to run a project, shut down for a break (or overnight or weekend) and come back and restart and have the part cut in the same spot/fixture.

I have had a suggestion of using a reference spot on the table as an x-y home and reference my work from that, a good plan.

In my Router CIM days, an outline of the table was part of the drawing. I would draw my part on the table and when I'd create code, the positioning on the table was done. As long as I didn't move the fixture / spoilboard on the table, when I'd fire up the machine after a weekend or whatever, the part would be cut in exactly the same spot as before.

MY QUESTION:

How can this be accomplished in Mach 3?

OR,

Is there a way to have the part in the same spot each time it's run that you can recommend?

Thanks!

woof

Offline Hood

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Re: Need help with fixtures / offsets
« Reply #1 on: January 11, 2011, 02:06:10 PM »
The normal thing to do when you start Mach is reference(home) the machine, this will move it to a known position and set the machine coords zero position. The values you normally see in the DROs are the work offset coords, they can be the same as machine coords but usually are different but Mach references them to machine coords so that it knows where it is.

The normal procedure as said would be home your machine then jog to where you want the work to start and then zero the axis DROs. Doing that is you actually setting a work offset and the default is G54. If you then shut Mach down then it will normally ask if you want to save the offset, choose yes and next time you start you home then you can command a move to zero position and it will move to where you last zeroed your axis the previous time.

There are a few settings on General Config page that will affect things, so make sure persistent offsets are chosen along with persistent DROs if you are wanting the values to remain next time you start. Note however that although when you next start Mach  the DROs may show the position you were at when you shut down it may be slightly out of position due to steppers moving slightly whilst powering down and up. So always best to home each time you start Mach.
Hood

Offline RICH

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Re: Need help with fixtures / offsets
« Reply #2 on: January 11, 2011, 05:26:16 PM »
I may add a word of caution....
Should you or someone else manualy move the axis for some reason when all is shut down the program would never know that was done and
Mach would not know where you are, unless, you had limit switches and homed the Machine first back to 0,0,0.
RICH