Solved Z-Axis Auto Leveling Routine Inconsistantly Starting

I downloaded the firmware from the Robo3D firmware page under Support -> Technical Support.

I'll add your start code modification as soon as the current print finishes.

 

This also happens with the firmware that MatterControl tells me is the latest available, which isn't the same one as what's on the Robo3D website, so whatever it is, it's common to both.

What I haven't done is try to see if preheating the bed/extruder affects it. I'm wondering if the wait for everything to come up to temp is somehow affecting it. Sometimes I preheat, sometimes I don't, and now I think that might be related.

 

I just read about someone else with the exact same issue on another forum, so at least it's not just me!

 

Ok, it's almost certainly related to the delay when heating.

I turned on the printer, then loaded a print using your modified G28. Instead of going to the center and waiting there, it went to the front-left, which I prefer instead of dead-center. When the extruder comes down, it always leaves a plastic booger that I try to remove before the printing starts.

I did not preheat the bed and extruder; I let the system do it all. When it finally reached temperature, the print began at the same z level as it was when it finished the last print - about three inches off of the bed. No bed probe, and the extruder never went down at all.

I preheated the bed and extruder, then tried the print again. The bed probe occurred, and the print was successful.

I did it again, waiting until the extruder cooled to about 180, then started the print again. After the wait for the extruder to heat up, the bed probe was again skipped and the print was a bit too close to the bed.

One last time, I preheated the bed and extruder before starting the print, and it bed probe worked exactly as expected.

I think I'm going to try to move the M109 command to the top of the start code list and see if it fixes my problem. It shouldn't matter that the extruder heats before the machine finds its home positions, right?

 

Ok, that's the trick!

Moving the M109 to the beginning of the start code seems to fix the problem.

The G28 Xo Y0 modification also seems to be desirable, since it keeps the head from leaving dribbled filament in the center of the bed.

I'm going to keep using this for a few more prints and see if the problem is resolved. If so, I'll mark the thread as such.

Thanks a ton for helping me figure this out. I don't know if I'd have been brave enough to start monkeying around with the start code without a lot more research.

 

*cough*

 

Yeah I'm pretty sure matterhackers have absolutely no idea what they're doing

 

After moving the M109 line to the top of my start code, I've been able to print a number of times without the bed probe being skipped. Thanks to Ziggy and Mike for helping me home onto the problem.

 

I encountered this issue last night. While trying to print using MC and connected to the computer via USB, I've never had an issue with the auto level (only had the printer for 3 days now so might just not have encountered the problem yet)... Unfortunately, about 40 minutes into the print USB connection was lost and the print stopped... After screwing around for half an hour, I finally got the software to recognize the SD card and got the file onto it. hit print, and trying to run the file from the card, no auto level was performed and it started to print just as described in the very first post in this thread...

I will double check the file on the SD card tonight and check to see how the gcode looks compared the file on the computer to what you guys are doing here, make suggested adjustments as recommended and see what happens.

 

I'm not exactly sure why it happens, but it seems as if the printer with the latest firmware "forgets" that it found the X/Y home settings if it spends too much time heating up.

The stock MatterControl start code runs perfectly only if the printer is preheated. I have not spent too much time trying to figure out what that threshold is, but if it takes more than a couple of minutes to come up to temperature, the X/Y home positions are lost and the bed probe G-Code is skipped.

Ziggy's suggestion of the G28 X0 Y0 solves this issue, as does simply rearranging the original qG-Code start code order. Either one of these solutions will cause the printer to find the X/Y home positions after the printer has reached the target temperature. I personally like Ziggy's suggestion because it moves the filament goop that is always there when the printer heats up to the front-left corner, instead of right in the center of the bed.

 

Well, snap, that finally explains everything!

The only reason that I would want to move the temperature command higher up would be to avoid having 2 sets of homing movements. I've already mentioned that I find G28 X0 Y0 superior because it places the extruder in a better position than the stock start code. Instead of having two G28 (non Z) commands, I only use one now, the one you recommend, after the temperature is reached.

I'd be willing to try something other than MatterControl, but I've been having such good results with my machine that I haven't seen the need yet. I was getting some Z ribbing, but I adjusted the left threaded rod which was very wobbly and I get nice, straight sides now.

It's running so well that even my kids are using it with no trouble, with a spool of black ABS. Now that the auto level is taken care of, the printer is running almost constantly - though my wife isn't too happy about it, being in her kitchen and all...

 

Excellent explanation. I reworked my "start g-code" in MC tonight before I tried my first print from the SD card, and it worked flawlessly. Only one hic-up but it might have been something I did. Not enough to cause problems though.

Thanks everyone that put in their input to this thread, it's worth reading, and fixed my problem.

 

I get the same thing... strange... sometimes it just starts up and skips the g29... sometimes it does it. More often does it than not.
Have considerable problems with it if I try to use straight Gcode files. Usually have to go in and edit them.