Auto Tool Zero Crashes Bits??

Trying to figure out what the heck is happening here, its been working fine for a day or so then today i changed bits and grabbed the probe and put it on the work surface and clicked auto tool zero, it came down slow like it always did, touched off on the probe, but then instead of retracting up it tried to ram the bit into the probe, snapped the bit and gouged the probe doing this.

So i put a piece of wire in the chuck so i had a disposable part to test it again instead of an expensive bit and again the same routine, touch then drive it down into the probe. It used to touch, then retract up a bit above the surface.

I checked the button script, it hasn't changed, the probe thickness is set correctly, i'm just plain stumped!!

If i manually set the bit to just touch off the material surface and zero it manually everything is fine with the machine, but the auto tool zero doesnt work and i cant figure out why because it used to.

What am i missing here??

What script are you using?
Are you in incremental mode when you try to zero? (G91)

Usually, if it crashes like that, you have a bad auto zero script.

Here is the script that i am using, got it off the forum, note i am working in MM.

CurrentFeed = GetOemDRO(818) 'Get the current feedrate to return to later

PlateThickness = 19.500

If GetOemLed (825)=0 Then 'Check to see if the probe is already grounded or faulty

DoOEMButton (1010) 'zero the Z axis so the probe move will start from here

Code "G91 G4 P2" ' two second delay

Code "G31 Z-10.0 F5" 'Z goes down a max of 1.0 at 5IPM

While IsMoving() 'wait while it happens

Wend

ZProbePos = GetVar(2002) 'get the axact point the probe was hit

Code "G90 G0 Z" &ZProbePos 'go back to that point, always a very small amount of overrun

While IsMoving ()

Wend

Call SetDro (2, PlateThickness) 'set the Z axis DRO to whatever is set as plate thickness

Code "G4 P0.25" 'Pause for Dro to update.

Code "G90 G0 Z25.4" 'retract Z to 1.0 inch

Code "(Z axis is now zeroed test)" 'puts this message in the status bar

Code "F" &CurrentFeed 'Returns to prior feed rate

Else

Code "(Z-Plate is grounded, check connection and try again)" 'this goes in the status bar if aplicable

Exit Sub

End If

look at what i posted to you on mach3 forum

I saw your post over there but wasnt sure what you mean by it...

The confusion is this DID work, for like two days solid. Then suddenly it started ramming down instead.

you need to have the Z home position 25 mm /1 inch above where you use auto zero.
or the machine Z home 25 mm / 1 inch above the work pieces.
so eye ball your Z zero on your work pieces move Z up 25 mm /1 inch plus probe plate or what ever you use for z tool zero ref all home then it should be ok just do a dry run first with no cutter in the spindle see if it help.
I will dig out the code I use that does not have this problem late an post it.

Ahh ok, i gotcha... I will try that in a bit, working on cleaning up the workbench and measuring it up for an enclosure right now.

If you got better code i would definitely want to see it, i understand what your saying now.

Ok, i tried putting the Z about 50mm off the work surface and using my little piece of flexible copper wire in place of a bit i tried it again, sure enough now it works again with smashing down into the probe plate and it does retract.

Only problem is i was planning on using the work surface itself when i start making PCB's, but i guess unless the code is changed to be better i could just make sure its about an inch off the surface then hit auto zero as well.

I took a piece of thick Lexan and milled out a pocket to make sure its parallel to the bit, eliminating any variances in the table, then i made four corner hold downs on my 3d printer that keep the blank board in place, one of the corner hold downs has a spring loaded contact pin that will make contact with the surface of the PCB material and i have a small breakout box that i made for the probe so i don't have to use my large probe plate, just flip a switch to make the connection to the PCB surface and i already have the entire machine grounded to the controller, so once the Z axis comes down and touches the PCB it sets Zero and a LED lights on my breakout box so i know it touched off.

Just have to massage the script a bit so i don't have to worry about the preset height before hitting Auto Zero and i should be in business!