Questions on using a moving gantry style mini-mill...

[Ger21]

2 Jobs tested and in production :) 2nd one much less stress ;)

2010 screen-set, tool change routine...

On this job I did exactly the same as before but the first cutter seems to have run about 0.2mm lower than it should, made a bit more mess out of my bed but i'm not worried about that as it's buggered anyway ;)

The next two tool changes worked perfectly and did not gouge the bed.

Anything that can cause this?

Didn't you have this issue before?

[Davek0974]

Didn't you have this issue before?

That was when the coolant stopped and the cutter loaded up, i was also pushing much hared back then as the feeds/speeds were off.

This job was only 3mm aluminium, I was taking a full depth cut though. Odd that it was only the first cutter, which went back in later to do a final full depth pass around the edge.

I will have a look at the shank and see if there are any skid marks.

Also have another to make today.

[Davek0974]

Next run went fine, apart from a boo-boo ;(

I've seen this behaviour before on the plasma table - something goes wrong, you press stop on the Mach screen, I know your supposed to press feed-hold but i wanted something between e-stop and feed-hold as the coolant failed to come on (duff relay) so i knew it would load up and break and so pressed stop.

Fixed the issue, wound the code back to the last M05 stop and set next line.

Pressed cycle start and the cutter goes down where it is and shoots off to X+ at cut speed, snapping the tool off. It should have gone back to where it started last time and re-cut the partial slot and then finished normally.

Looking at the DRO's the X machine position is off by 226mm which i think is the setting that it was stopped at so now the cut start was not X5 as it should be but X-221 or something like that.

As i said, this has happened on the plasma and as here, the only way back is scrap the part, re-home and start again. I failed to note the X/Y positions for job location so i couldn't reset it and try again.

Some sequence of events throws Mach positions into a tizzy and it shits the bed. On the plasma no harm usually but on the mill = broken tool :(

Oh well, the next part finished perfectly, no bed gouging, if anything it was running too high now - the material miked up at 2.91mm, i programmed the cuts to 2.90mm and there was still a good skin left at the base. Something seems a little variable on height setting possibly?

[Ger21]

Any time you press Stop, you MUST re-home the machine before doing anything else.
And I'd highly recommend using Run From Here, unless you know exactly what state mach3 is in when you use Set Next Line.

[Davek0974]

Thanks for that, explains a lot then ;) Don't think I've ever used RFH...reaches for manual ;)

I think for what I am doing - small batch production - saving the offsets is a good idea??

All the raw plates are pre-cut to the same size and pre-drilled for fixing to the bed so each part will always start in the same position or work-offset.

Is that what offsets are for?

Could I then have re-homed the machine and loaded the offset then carried on with part I had stopped on??

Lots to learn....

[Ger21]

If you don't close Mach3, the offsets should still remain after homing. (I think)
Yes, if you have a specific part that you always run in the same place, use an offset like G55,G56,G57...
Add the G -code to the beginning of your code, and save the offsets. Then when you turn on your machine, you just home, load the code and run.

[Davek0974]

Sounds good, an offset will do what i need, i have never checked if the work position remains after a home, something else to check.