Homing newly converted CNC G0704 setup with Mach3

I've spent hours reading and trying various ways to "home" my axis's on a newly CNC converted G0704 mill. I've successfully tuned the motors and can jog them around. I do not have mechanical switches.

Everything I have read has said to manually jog the axis's to their locations and hit the "Ref All Home". Hitting this button doesn't seem to store anything, as when I hit it, the axis start to move to other locations. Where they are moving to, I have no idea. I usually have to estop it before it hits the max limitations on the axis. I've entered "soft limits" as well, but they hit the limits at what appears to be random places, so I am assuming that is because the home location is not established correctly or known.

Any help appreciated...getting SO close to being able to use this its driving me insane!!

P

The real question is: Why would you home a mill without a tool changer? I'm not being flippant here, there really is no reason to do it.

You are going to set your G54 0,0,0 to the workpiece anyway. You might want to set a G53 ''parking position'' to move the table and head to a convenient location on job completion to facilitate measuring or part load/unload. On my mill the machine coordinates are always the same as the work coordinates, and move around with a new job, and the G53 varies with the job.

This does preclude using soft limits, so it's up to you to insure the machine is going to work within the acceptable work envelope.

G54 is closely tied to MCS, and MCS 0, 0, 0 is the location where it was homed.
If you home "in place" - w/o home switches - your WCS could be anywhere.
In case of tool breakage, power failure, ... you will never establish your WCS again at the same place.

Quote:

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Originally Posted by cetagloh454

I've spent hours reading and trying various ways to "home" my axis's on a newly CNC converted G0704 mill. I've successfully tuned the motors and can jog them around. I do not have mechanical switches.

Everything I have read has said to manually jog the axis's to their locations and hit the "Ref All Home". Hitting this button doesn't seem to store anything, as when I hit it, the axis start to move to other locations. Where they are moving to, I have no idea. I usually have to estop it before it hits the max limitations on the axis. I've entered "soft limits" as well, but they hit the limits at what appears to be random places, so I am assuming that is because the home location is not established correctly or known.

Any help appreciated...getting SO close to being able to use this its driving me insane!!

P

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I'm only using soft limits at present too.
Mine doesn't move when I hit 'ref all home'. All it does is zero my machine axis co-ordinates to wherever I've moved the table to for my home position to be.
Home is relative to the zero position of soft limits.
If I want the machine to move home at all I have to use G28 in midi.
This is prob a better way of having it if you have no physicals.

I can't remember how this above was achieved tbf ie: which contig settings to change.

Be careful with G28 codes in your Gcode files. If home isn't right... It will bite you and break.

Quote:

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Originally Posted by ZASto

G54 is closely tied to MCS, and MCS 0, 0, 0 is the location where it was homed.
If you home "in place" - w/o home switches - your WCS could be anywhere.
In case of tool breakage, power failure, ... you will never establish your WCS again at the same place.

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I guess I have been doing it wrong for all of these years. :rolleyes:

On my mill with no tool changer, it makes no difference where the WCS is, as long as it is within the work envelope of the machine. Once the job is set up, then that establishes the WCS, and once set, MCS = WCS = CAM WCS. If needed, I can easily reestablish the WCS within the limits of my measuring capability, a couple of microns. Power fails are quite common in my area, but I don't break tools quite as often as I used to. ;)

Now on my lathe, I do use home switches as a rough location, with the final home position set with the encoder index pulse, +/- 1 micron. Why do I use a fixed MCS on the lathe? Because I have a 10 tool turret and a tool setter, thus need to establish the offsets from a fixed location.

Awesome, thanks for all the info guys. This definitely helps. I am totally new to the CNC world, so I am learning lots daily. -Paul