Loss of Z reference over drilling operation

[joco-nz]

I am having an issue where at a random point in a drilling operation the firmware or the ccc-gcode-controller is losing the correct current Z value. At some point it stops drilling deep enough. In fact it usually only just touches the cooper. So if the travel height is 5mm and the drilling depth is -2.5mm it has actually returned to a travel height of ~7.5mm as at the end of a drilling plunge to Z-2.5mm the drill bit has just nicked the cooper.

I did a trial with the Autoleveling check box OFF however it still happens.

Anyone else experiencing this?

I'm using the Marlin from the Cyclone 2 repo. Although it might be from just before the V2 official release.

[ve3sjk]

It almost sounds like the same issue i have seen with the auto level. If i auto level it seems to just end up barely scratching the copper. the last test board i cut was with auto level off. I have seen it just stop in mid code a couple of times. Both times it just said. end stop hit Z in the lcd display. The software loses communication at that point that has happened twice. I wonder if its not noise on the floating z-min input to the ramps when disconnected from the tool before cutting. A false hit i believe would re zero the z axis. I usually put 0.1uf caps across the contacts of the limit switches for debounce, i wonder if the same can be done to the z-min input. I am using the newest version of cnc-gcode-controller with the dynamic zero tool options.

[joco-nz]

I just did a test in Pronterface and had the same issue again. At a random point it loses the the Z height. If I stop the process and type in G1 X0 Y0 F200 then G1 Z1 F200 the drill tip is about 3 - 3.5mm above the copper surface not 1mm as it should be.

It could be a floating input I guess. But wouldn't the pull resistors on Mega deal with the floating aspect?

Either way something is happening and its not tied to controller software.

[ve3sjk]

@joco-nz are you leaving a probe lead on the copper or removing both before cutting. I had one lead attached to the copper, thought it was ground but i think it was the input lead instead. I think it was getting ground through the tool tip during cutting. Are you getting anything in the status line of the display that any z endstops were hit. Maybe losing steps, what happens if you half the feed rate. Is the captive nut floating on the x carriage, i was having problems with z until i glued it in. Perhaps its moving during a drill and throwing off the axis position if it raises out of the slot it will spin a couple times before dropping back in, could change it a few mm's quickly.

[joco-nz]

Good things to check out @ve3sjk. I'll make sure both leads are clipped to plastic. I had been doing it with the ground lead on the copper and the signal lead on the plastic (I think).

I don't have an lcd display attached to the RAMPS. So no messages coming from Marlin in that path. I will check what is happening on the serial comms (if possible) see if can see what is happening.

I don't "think" the Z nut is floating. But I will do a test and watch for just that issue.

[joco-nz]

Test performed and you were right. I must have (at some point) swapped the leads over and left the signal wire attached to the copper and it was randomly being grounded via the Dremel at some point. If I had the leads around the other way (which I had before) the problem had been happening. So following good practice and clipping BOTH wires to the plastic tabs on the frame and no issue.

[ve3sjk]

@joco-nz i am happy you were able to find it quickly. Intermittent are a nightmare sometimes, like looking for a shiner in the the telecom industry. Another caveat is the proximity of the +5 volt line where the limit switches attach to the ramps. I inadvertently connected down one row, pretty sure i have to change the voltage regulator on that mega board now the board will just power up by usb but its dead off the 12volt inputs.I am going to cap that row at some point to prevent doing it again in the future.

[joco-nz]

Yeah I'm paranoid about those connections. I use a 3 pin plugs but with only the 2 wires just to try and prevent that type of mistake. It's not perfect but at least it makes me think each time I connect something. Doing a test mill with new settings. Its already looking MUCH better. Will post progress on my build log in the google groups fourm.

[CarlosGS]

This is indeed an annoying problem with the firmware. For Cyclone I wanted to stay with minimal modifications of Marlin, but enabling "endstops only for homing" was giving some issues with the autoleveler. I'll try to fix it so it eventually, for now stay with the solution of clipping the electrodes away. Sorry for not specifying this well, great that you solved the issue so quickly!