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2.4r2 "Probe samples exceed samples_tolerance" error

B20bob

B20bob

Member
Hey guys, I'm having an issue on my 2.4r2 350mm. It has been printing great for about 454 hours but now I am constantly getting "Probe samples exceed samples_tolerance".

So I built a new klicky probe and replaced the microswitches in both the Z-endstop and the klicky-NG (New switches are: D2FC-F-7N). At first this seemed to resolve the issue, the first 3-4 prints ran with noticeably better tolerances on both QGL and Auto-Z calibration, and without errors. Then last night it randomly began throwing the same error as before, and now it won't even finish the QGL process because it's cancelling due to the probe readings being so far out of tolerance. If it does make it past QGL then it fails on the Auto-Z calibration.

I have checked the Z belts, they are sufficiently tight and as equal in tension as I can get them. I have also snugged the bed screws. This has me scratching my head, I can't think of what to check next... Anyone here had an issue like this before?
 
Check if your magnets are not going out, causing probe to be attached improperly or at an angle. Even if you used superglue, it tends to release in hot environment. Alternatively you can try PCB Klicky and see if it improves. Or fall back to inductive probe for a while. This will help determine if problem is in motion, or Klicky itself.

Just a sidenote - do not snug all 4 bed screws. Tighten only the one in corner next to endstop, other 2 leave tightened just lightly, and leave fourth one free or even remove it. This will allow bed to expand as aluminium heats up. When you tighten all 4 screws, unless you have kinematic mount, bed will have no place to expand and will warp and make mountain or a taco.
 
Make sure the part on the hotend is not moving. I had mine come loose after some time and cause me frustration.
 
Sanity Agathion said:
Check if your magnets are not going out, causing probe to be attached improperly or at an angle. Even if you used superglue, it tends to release in hot environment. Alternatively you can try PCB Klicky and see if it improves. Or fall back to inductive probe for a while. This will help determine if problem is in motion, or Klicky itself.

Just a sidenote - do not snug all 4 bed screws. Tighten only the one in corner next to endstop, other 2 leave tightened just lightly, and leave fourth one free or even remove it. This will allow bed to expand as aluminium heats up. When you tighten all 4 screws, unless you have kinematic mount, bed will have no place to expand and will warp and make mountain or a taco.
Click to expand...
Thanks a lot for the reply.

I didn't notice any perceivable movement in the probe when attached to the toolhead and probing, but of course with the tiny tolerances here I probably wouldn't be able to see it with my bare eyeballs anyways I guess.

I have a PCB klicky on the way now so I'm hoping that will solve it.

Also, thanks for reminding me about the bed screws.. Now that you mentioned it I remember reading that in the build docs. I'm pretty sure I only heated the bed to 60c with all screws snugged. I hope I didn't F my aluminum plate...
 
NoGuru said:
Make sure the part on the hotend is not moving. I had mine come loose after some time and cause me frustration.
Click to expand...
Good idea. I did check this part by trying to wiggle it with my fingers but I think I'll take the toolhead apart and check the screws while I'm waiting for my PCB klicky to get here.
 
B20bob said:
Also, thanks for reminding me about the bed screws.. Now that you mentioned it I remember reading that in the build docs. I'm pretty sure I only heated the bed to 60c with all screws snugged. I hope I didn't F my aluminum plate...
Click to expand...
I believe it will be OK.
 
I'm around the same print hours. (Stealthburner) I was about to take the toolhead apart to clean it from any filament dust and go over the rest of the parts. I'm not getting the same error (though it does happen a couple of times during a QGL, but will recover just fine).

In my case, I attribute it to a modestly sticky linear slide. So I was going to clean it out and re-lube it.
 
Ok so after some time messing with this thing I have now replaced the klicky-SB adapter with a freshly built beefed up modded version. I also replaced the PCB Klicky with a freshly built unklicky (heatset version).

At first it again seemed like the issue was resolved. I did about 5-10 prints to set the probe offset for auto-z without errors. I Them ran a 15ish hour print with PLA without errors. Then when I tried running it again it began constantly throwing the same error as before, I tried about 5 times and it failed every time.

So I started the print and watched the terminal output as it was going. All probing moves were within tolerance (0.0075) until it got the second phase of auto-z where it measures the bottom of the probe body against the Z endstop/sexbolt.

The fact that all other probe points are within tolerance makes me think it's not a rail issue.

I played with the probe on the SB adapter and could not feel any play or wiggle, it feels solid. The SB adapter is most definitely tight to the toolhead. I'm having a hard time figuring out why it's failing, or where my play could be coming from.

I do have the auto-z touching the head of the screw that's on the front of the Unklicky, just because the z-probe can't reach the bottom of the Unklicky body without crashing the nozzle into the bed. I don't have enough length on my wires back there to move things around.

That said, I am going to build an unklicky sexbolt tonight, although I'm not confident it will change anything, I'm kinda just throwing things at the wall at this point to see if maybe something will stick. Should I use the longer pin when I build it? The one intended for kinematic bed mounts? or will this cause different issues with offsets and tolerances?

Another idea I had was to Print a short pin and glue it to the bottom housing of the Unklicky probe to try to avoid having to probe that screw head.

Any thoughts? I'll post another update in the near future.


Update:

I tightened all the belts even more, now they are considerably tighter than I've ever had them. Also moved to UnKlicky Probe and UnKlicky Z-Endstop. So far I've been able to print but it does still error out I'd say maybe ⅓-¼ of the time.

Another thing I was thinking about, what Should I have my retry tolerance set to? The default from the LDO example config is 0.0075. What should I have that set to?
 
Last edited:
are you using the stock Z-belt tensioners at all 4 corners? - I'm having similar issues and found that one of mine isnt as stable as I'd like and have since ordered a tool-less CNC version off aliexpress.
 
tx_wombat said:
are you using the stock Z-belt tensioners at all 4 corners? - I'm having similar issues and found that one of mine isnt as stable as I'd like and have since ordered a tool-less CNC version off aliexpress.
Click to expand...
I am. I've managed to get mine more reliable by really tightening the Z belts and going back to the normal micro switch Z endstop from the unklicky one. I still get the error once in a while but thankfully it's been much better.

I'm gonna look into those CNC ones you mentioned though. Do you happen to have a link to the ones for ordered?
 
Sanity Agathion said:
Check if your magnets are not going out, causing probe to be attached improperly or at an angle. Even if you used superglue, it tends to release in hot environment. Alternatively you can try PCB Klicky and see if it improves. Or fall back to inductive probe for a while. This will help determine if problem is in motion, or Klicky itself.

Just a sidenote - do not snug all 4 bed screws. Tighten only the one in corner next to endstop, other 2 leave tightened just lightly, and leave fourth one free or even remove it. This will allow bed to expand as aluminium heats up. When you tighten all 4 screws, unless you have kinematic mount, bed will have no place to expand and will warp and make mountain or a taco.
Click to expand...
i was having this same issue and it was indeed the magnets in my sb tap! was trying everything else for hours, glad i saw this suggestion
 
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