Been a long time away..... back and can't rememember anything!

Hi all

My poor old MPCNC is a bit worse for wear. Rusty bearings, juddering movement etc
Looks like some TLC required.

Now… I thought (wrongly apparently), that G28 X/Y/Z homes the CNC back to the left hand front corner using the limits switches. And it does this.

So, I then move the head to say the centre of the table and set the values to zero using G92 X0 Y0 Z0.

This is the new origin correct? The LCD indeed shows X0, Y0, Z0.

So why does G28 then send the CNC back to the left front corner to reset the origin?
Clearly I am using the wrong command.

So… how do I tell the head to go back to the 0,0,0 origin I set in the middle of the table?

Repetier host is running my cutting routine, but not returning the Z height back to where it started and I cannot work out why.
Therefore, it’s making it very difficult to get accurate repeat cuts.

Hmm

Yes, G92 will set the position.

G28 tells the machine to auto home. You are telling the machine, you have no idea where you are, use your end stops to figure out where you are.

G00 X0 Y0 Z0

or if you don’t want your Z to go back to 0
G00 X0 Y0

What are you using the make the gcode file? Estlcam? You may have setup ending gcode to do something.
https://docs.v1e.com/tools/milling-basics/#__tabbed_1_1

It’s not uncommon for us to probe for Z either manually or with a touch plate before starting each job.

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Thanks. I have added the code to the Repetier ‘End’ macro that drops the Z height 5mm.
This puts it back where it started.

Getting old sucks… I seem to have forgotten everything!

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Yea, the ‘drop Z height’ macro I added in Repetier just plunged the bit into the piece… fail.

Having a hard time dialing this in. Seems like lots of things have changed or failed.

For instance, my Z height sensor now shuts the CNC down with an emergency stop error message, rather than set the Z height. No idea why that has changed.

I was trying to carve some 3mm Dibond. Not very successfully either. The bit clearly needs to be fairly thin for text. I only have straight bits here.
I am guessing a tapered round end bit would be better… say 0.5mm?

But, at £10+ for a bit… I may as well just have someone make the label for me. Been 3 hrs sitting here already.

Something is screwy somewhere. I set the GCODE up in Esltcam, and then use Repetier to run the CNC. But the Z height is doing all kinds of weird things.

For instance, it will carve the text, then when it moves over to the next item to carve/cut, it starts 10mm too high… no idea why that would be.
It doesn’t seem to be able to run from what was set as Z0 at the start.

Hmm

As part of the same gcode file? Or are you doing each letter as a separate job?

If you run the same file twice, does the machine behave the same way (even if wrong)? This will help determine if it is hardware or software problem.

Check for extra resets of Z in the Gcode.

G92 Z0 with or without X and Y parameters will tell the machine to set zero wherever it currently is. This messes up a lot of jobs.

Other ways I can think of is G10 L20 Z0 and I’m sure there are other ways. Following what the machjbe thinks its height is on an LCD is a good way to check for this.

G28 returns to the table 0/0 not your set origin. If you start up and never home, wherever the tool was when you powered up is table 0. If you home bottom left, that’s the table 0.

Just g28 should take you to that point in all 3 axis.

For the z problem, i found lots of ways to screw up using estlcam. The only fix often was to kill the entire program and start from 0.