New A20M with 3D Touch - Nozzle hits bed

[mleeber]

Just assembled the A20M, added the 3dTouch, uploaded the firmware to support the 3DTouch and homing or autoleveling puts the nozzle into the bed and the Z motor starts clicking. Ordered this from 3DPrintBay. Printer has while accents instead of blue and there is no glass bed, did I get an old model? Any ideas on how to fix the nozzle/bed thing or should I just send this back?
Thanks!

[Jdbye]

Just assembled the A20M, added the 3dTouch, uploaded the firmware to support the 3DTouch and homing or autoleveling puts the nozzle into the bed and the Z motor starts clicking. Ordered this from 3DPrintBay. Printer has while accents instead of blue and there is no glass bed, did I get an old model? Any ideas on how to fix the nozzle/bed thing or should I just send this back?
Thanks!

Mine also came with a plastic bed and white accents. I contacted the seller and it turns out Geeetech stopped shipping the glass bed because of issues with it getting damaged in shipping. Which seems like a silly reason to me, as everything in the box was packed extremely well EXCEPT for the bed which only had a very thin sheet of foam above it instead of the thick hard foam that protects everything else. And nowhere on the product page did it mention this (in fact it said it came with a glass bed)
A small redesign of the padding material to have more padding on top of the bed and slightly less on the bottom protecting the metal frame should solve this issue.
Anyway, they agreed to ship me a glass bed. Haven't received it yet though. I suggest contacting the seller and asking them for assistance or contacting Geeetech directly if you want a glass bed.

Anyway, you should use the bed leveling paper included with the printer, lower the Z axis onto it so that the nozzle is providing a good amount of resistance when you pull on the paper. Then without moving the Z axis adjust the probe so that it's 2mm from the bed (in the retracted position), make sure the probe is as straight/level as possible. You can use a 2mm allen key or anything else that's exactly 2mm to measure the distance between the bed and probe, just see if you can move the allen key (or other object) back and forth underneath the probe and see if there's a visible gap.

Once you've adjusted and tightened the probe, you should adjust the Z offset. Before doing this it may be a good idea to manually level the bed using the screws, although it shouldn't be necessary, it's just that manually leveling the bed later on will result in having to adjust the Z offset again. Disable software Z endstop in firmware (change #define MIN_SOFTWARE_ENDSTOP_Z to //#define MIN_SOFTWARE_ENDSTOP_Z in Configuration.h) and upload the firmware. Do auto home/bed leveling, then move X/Y to 128/128 using the menu. Start slowly lowering the Z axis using the menu and using the bed leveling paper lower it until the nozzle provides good resistance again. Look at the Z position on menu at this point. Negate it (if it's positive it becomes negative and vice versa) and this is your new Z offset that you should set in the menu and save settings afterwards. Without adjusting the Z offset my printer would often fail during the calibration process as it wouldn't move down far enough to touch the bed, seems like the Z endstop would trigger as a safety mechanism before the probe reached the bed.

Once you have the Z offset saved you can test if it works. Do auto home and bed leveling again and again move to X128/Y128. At this point your Z axis position on the menu should be showing the offset you set. Then repeat the process moving the Z axis down until it provides good resistance on the bed leveling paper. It should provide good resistance at exactly Z 0, or maybe Z 0.1 (in my experience the Z axis is not that accurate so it can be off by 0.1)
Any time I move the printer I do this process again to make sure the Z offset is still correct, and adjust it up or down by 0.1-0.2 if necessary.

Finally, you can re enable MIN_SOFTWARE_ENDSTOP_Z and upload the firmware again.

My Z offset ended up at -1.74 ish. This means that Z 0 is 1.74 mm further down than it is by default. It seems like this is the offset between the nozzle and the probe and that the paper is likely 0.26mm thick, adding up to the 2mm distance from bed that I measured using an allen key.

I saw a few different methods for measuring the Z offset, all of them gave different results and this is the only one that worked for me.

If the probe isn't mounted exactly 8.2mm from the bed with the nozzle touching the bed the probe won't function right. Sounds like it not reaching the trigger point at all. Another common misunderstanding is that people don't remove the original z endstop when they install a probe.

8.2mm sounds like a lot. I've never heard of that, seems to be working fine for me with 2mm distance to bed.
I have my original Z endstop unplugged, but as I understand it, it shouldn't really matter - this endstop triggers after the probe does, and none of the instructions I've found say to unplug it either. But as it was flashing and flickering a lot, I decided to unplug it anyway thinking it might be why my auto leveling was failing (it wasn't). I think the flashing and flickering that occurs is just a side effect of it being connected to the same pins as the probe on the board, so when the firmware sends data to the probe it causes the endstop to flicker.
On other printers you would need to unplug it to plug the probe into the same port, but Geeetech has a separate port for the probe and their own instructions don't say anything about unplugging the original endstop.

[knewton]

I have been struggling with my a20m for about a month now. I had the same thing happen from the above site, white instead of blue accents and no glass bed, the endstop slamming into my bed, and I also unplugged the original endstop because of the auto level.

It was working fine until the nozzle had a backfeeding issue and clogged up. After we worked on it and replaced the nozzle, we haven't been able to get a single print. I've tried corners, auto level, anything I can think of but I'm fairly new to this. I've been exposed to printers for around 6 months, but have only really gotten into printing my own stuff in the last month.

I'm going to try to do the steps listed above and report any issues/success I have. If the OP ever got his glass bed from the seller, I think I'll reach out and try to get one as well.

[Meierme176]

removing the z endstop is required due to the probe and endstop being on the same pin failure to do so will result in accuracy loss and false triggering as well as the endstop being a physical blocker preventing any proper probing from happening.
disabling #define MIN_SOFTWARE_ENDSTOP_Z is a horrible idea you should have just used the disabled soft endstop command.
http://marlinfw.org/docs/gcode/M121.html

Where do you insert that command?

honestly i don't know why i even bother answering posts anymore.
i should just let people struggle for months like i did let them figure it out on there own the hard way.

That's not a good way to look at this. People come here for help for a reason.

[Meierme176]

console access of your choice & i repeat my self 1000s of times and no one seems to ever listen.

I'm sorry, I'm very new to this. What do you mean by console access?

I do believe that "people not listening" has more to do with this forum's UI than people not actually listening. I have looked around for the past two days for solutions to this problem and this is the only forum post that keeps coming up. However, I am grateful for your help.

I posted my own question kind of similar to this one at:
https://www.geeetech.com/forum/viewtopi ... 08&t=68810
but I provide a bit more information as to what's actually going on.