[MarcL]

What model M400 do you have?

Is it an original DC-drive M400 (gray console, 10" LCD, sealed keyboard flat in console face)?

A new-style DC-drive M400S (black console, 15" LCD, conventional or sealed keyboard on sloping shelf; DC brush servo motors)?

Or a new-style AC-drive M400 (same console as above, but AC brushless servo motors)?

If it is either DC-drive system, you can use DIP switches on the servo amplifier to defeat the limit switches. If you do this after you power up and home (being careful what you touch, of course) then you can run the machine and see if the error has gone away. If the error still happens with the limit defeater DIP switches thrown, then you know the problem is not in your limit switches or their wiring.

To defeat limit switches, toggle the DIP switches up away from the board. To enable limit switches (normal operation) toggle the DIP switches down towards the board. WARNING: if you try to home with the switches defeated, it will run through the limit/home switch and bottom out the axis.

If it is an AC-drive system, then a faulty limit switch cannot cause "full power w/o motion". A faulty switch on an AC-drive system can only cause "Z+ limit (#6) tripped", or words to that effect.

What values did you have in Parameter 15 (slow probing rate) when you got the error persistently, and what did you have when it ran without errors? Or, if you were using the feedrate override to slow it down, approximately what were the override settings?

I wouldn't expect "full power w/o motion" due to a too-high digitizing speed, but I wouldn't rule it out. When you are digitizing, and the probe touches the surface, the control stops the axis without the benefit of any deceleration ramp. This works fine at 2 to 5 in/min, but is a pretty harsh at higher speeds.

There is an option in Parameter 10 to enable a ramped deceleration in digitizing and probing. This is mainly intended for AC-drive systems, but could be used on a DC system as well. Set Parameter 10 to 4.0 (assuming it was zero before) to enable ramped deceleration in digitizing and probing.


Summary: If you have a DC-drive system and the error goes away with limits defeated, then take a hard look at your switches and wiring connections. If the errors continue with limits defeated, but go away at lower speeds, then either learn to live with lower speeds or enable ramped deceleration.