@david_kelly In VCarvePro, you should be using either grbl inch or grbl mm. The mm one will give you better resolution. You can still design in inches in VCarve. The output file will be a .gcode file.
@david_kelly I realize this is the finishing toolpath, so the full picture isnāt here. Right at the start of your file I see this:
G0Z52.000
G1Z0.000F42000.0
Thatās a plunge of 52mm (again, with this being the finishing path, not necessarily an issue). The concern here is the Plunge Rateā¦42,000mm/min. That is way too fast. Now, your machine will cap that based on your grbl settings, but you probably donāt want to max that out.
That feedrate is only for the initial plunge. Right after that you go to 3600mm/min. I donāt have a longmill, but Iād guess thatās still fast for your Z.
Iād still recommend the jog testā¦up and down on the Z to see if any position is lost or if there is anything unusual. If you can, run the Z up and down at different locations on the XY plane. Especially in the XY location you think things go wrong. Thereās always the possibility of an issue with you wiring/connections.
Another question I shouldāve asked earlier. The gcode makes this more obvious. Do you have enough Z height for this project? Looks like youāre working with 50mm thick material, plus an endmill that is at least 50mm. Are you sure youāre not running out of room and crashing the Z at the top of itās range?
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Every time Iāve ever had a problem with a cutter going too deep itās because of the collet and the bit coming loose and digging in deeper.
Just saying, I didnāt see anyone mentioning that. Sometimes it can be sawdust in the collet.
It would be helpful if you could check your z zero after this happens and make sure the bit is where you set it.
Maybe youāve done that alreadyā¦
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Hello,
Paul: Thankyou for your thought. Iāll have to do that next time. Iāve moved it too much to find zero again.
David
Witās End!
Since last post,
- Iāve replaced all the stepper motor cables with shielded cables and grouneded the shields.
- Replaced the spndle cable with a shielded cable and grounded the shield
- Revisited all joins, soldering them before screwing them in tightly
- Grounded to a common (Buzbar) source on the
a) the Z carriage
b) the x rail
c) the y rails
d) the Longboard
e) the embedded steel wire in the dust extraction hose
There is no resistance showing betweeen any of the componets, including the casing of the spindle
After 35 minutes, the machine suddenly dug 8mm into the model!
Attempting to bring the bit to the previous X=Zero, Y=zero, Z =Zero, the machine thinks it is 8mm too highā¦i.e. when the bit is on the bed of the machine, it;s reading Z-8mm
I canāt suggest anything else to solve your problems but I would like to address your point #3 ā¦ It is a no-no to solder the wires before inserting them into a connection and tightening itās set screw.
The solder will wick up the wire and you create a failure point.
If you want to do something as far as those screw connections is concerned then use ferrules on the wire ends before tightening down those set screws.
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thanks for the expert advice Jens.
Hi David,
HAving never had this kind of issues, I o prolly cannot contribute other than redirect you to (a lot) of entrys in this here forum on the same subject.
Somewhere hidden in there might be your answer?
https://forum.sienci.com/search?q=plungeing
@david_kelly You may want to read @NeilFerreri 's post and look into what he had to say, if you have not done so already. 
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Super Long Board component failure?
Thanks for the feedback.
Iāve been through Neilā posts ad revisited all ote helpful comments.
- The bit is not pulling itself into the material ( I managed to catch it plunging at the end of a pass before it went into the material.
- Iāve tried several (probably 50) times testing the up/down motion at various parts of the work. Itās fine and always returns to the correct Z zero point.
- The Z gantry is running in mid range, and is nowhere near any limits.
- Somewhere, after half an hour or so, this always occcurs.
- Iāve spent a month with no product and spent nearly $1K on electricians and cabling. In my view, we have properly shielded absolutely everything and grounded absolutely everything.
- The only consistent thing is that after a certain amount of Z movement, usually about half an hour or so, this fault occurs. If the starting passes donāt have many Z movements, then the time before failure is extended possibly to an hour.
- I reduced the Z axis movement speed to 10 mm/second in Vectric. It has made no difference
- My suspicion returns to the possibility of a capacitor discharge (or something like that) in the Z control in the SLB. Normal testing of the SLB would never pick this up, because it is random and seems dependent on the number of Z movements
Posted in error. David
Iāve just thought about Nielā comment about the Z movement being 3000mm/sec. I hadāt realised this setting is in the firmware settngs.
I have adjusted the firmware settings
102 from 3000 to 200
122 from500 to 200
Iāll try that before I blaspheme any more about the SLB!
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Iāve just run the router with all the Z axis movements at a crawl. itās made not a bit of difference. Iāll ask CIENCI for a replacement SLB, to confirm or eliminate that possibility.