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Author Topic: Home location/limit switch problem  (Read 3548 times)

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Home location/limit switch problem
« on: December 16, 2007, 05:41:24 AM »
I'm building a moving-table type router table but I'm not certain where the X axis limit switch should be. As you look at the table, with the Y axis running towards you, I have fitted the switch to the left end of the X axis. However, I'm having trouble setting the axis travel so that the distance moved shows as a positive value in Mach3. Have I got  the switch on the wrong end of the axis?
This relates to the ' conventional' Home location (if there is such a thing) for the X and Y axes. Should that be at the left end of the table or the right?
I think I'm missing something obvious here, I've looked at some of the videos and searched this forum but can't fined an answer.
All help gratefully appreciated!

Offline Hood

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Re: Home location/limit switch problem
« Reply #1 on: December 16, 2007, 06:25:09 AM »
You can position your home switch where you want, I have mine at the left end (X minus). You can mess around with the settings in the Homing and limits page for the X axis to get it right, you can reverse the axis and also you can tell it to home negative or positive. If you have the limit switch at a position other than the axis extreme you can tell Mach that by putting a Home Off figure into the Home Off box, again on the Homing and Limits page.
 You can also reverse an axis by changing the Dir Low Active setting in Ports and Pins, Motor Outputs. But I believe some drives dont like this so be aware of that fact if things go weird.

Re: Home location/limit switch problem
« Reply #2 on: December 17, 2007, 10:52:30 AM »
Thanks for that, Hood. I'm sure I'll get there eventually, but it makes my brain hurt!

Offline jimpinder

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Re: Home location/limit switch problem
« Reply #3 on: December 17, 2007, 01:15:52 PM »
Richard -

The home switches are just a way of telling the machine where it is. They can be anywhere. If you set the automatic zero option then the "machine co-ordinates" will zero at that location.

The location might be no earthly use to run a program from - for instance my machine is a lathe, with a milling machine attached. The home switches are as far left (under the spindle) and as far towards me as the table will move.

All my lathe programs tend to be written with Z0 at the end of the work peice, and X0 on the center line of the lathe. My milling programs tend to be 0,0 at the bottom left hand corner of the table. To facilitate this you have an offset table G54 to G59 and there are many available under G59 (255 I think - but I might be wrong).

You home your machine, which sets the machine co-ordinates at 0,0 then select the appropriate offset as your program co-ordinates. The table can then move to the correct position to interpret your program.

Is your brain still hurting???
Not me driving the engine - I'm better looking.