Prusa Mini Silicone Bed Leveling Mod  

RE: Prusa Mini Silicone Bed Leveling Mod

I've added a plot to the PMSMBL converter to help visualize your bed without having to use any additional tools.

https://bbbenji.github.io/PMSBLM/

RE: Prusa Mini Silicone Bed Leveling Mod

@danielsan3318

Sorry, ich habe vielleicht nicht erwähnt, dass die Grundplatte der Z-säule etwas angefast werden muss:

Ansonsten passt die Freimachung für den Schrittmotor.

RE: Prusa Mini Silicone Bed Leveling Mod

@ Benji

Thanks for updating the github with the graph.  It was a great help.  Below is my final result.

RE: Prusa Mini Silicone Bed Leveling Mod

Octoprint is a fine thing, but not essential for leveling the bed. Since the Prusa MINI, unlike the MK3, displays the offset when you drive over the entire bed. So I leveled my bed and it's faster, at least in my opinion, checked everything with Octoprint and everything is perfect and within 0.05mm.

RE: Prusa Mini Silicone Bed Leveling Mod

@benji

This looks very similar to this tool BLV , which I use as Octoprint Plugin.
In any case a very useful and helpful tool!

RE: Prusa Mini Silicone Bed Leveling Mod

@karl-herbert

Yes, we both used the same library to create the visualization. Plotly.

RE: Prusa Mini Silicone Bed Leveling Mod

@karl-herbert

What is the uncompressed spring length, 10 mm?

RE: Prusa Mini Silicone Bed Leveling Mod

@rockytoptim

For this I used these springs: https://www.federnshop.com/de/produkte/druckfedern/d-117a.html

Gutekunstfeder-D117A

RE: Prusa Mini Silicone Bed Leveling Mod

@karl-herbert

Thanks for the link.

RE: Prusa Mini Silicone Bed Leveling Mod

I am planning this mod on my mini as well. I have actually already done a slight variation of it. Basically found some scrap silicone tubing I had around the house, pulled up the bed and put tubing donuts around all the existing spacers, and it gives you a few milimeters of play adjusting the tension of the existing screws. Got my bed significantly more level than it came from the factory, but not perfect, so sourced all the parts to do it per these instructions.

For those having trouble sourcing the parts, the most trouble I had was finding the torx screws. I couldn't find a single source of them in the US. The person selling them on amazon is shipping them from China. So I've already got all the parts but the torx screws which are currently somewhere between China and here.

Screws https://www.amazon.com/gp/product/B01DEUBWMM/

Nuts https://www.amazon.com/gp/product/B003Z6VHE4/

Tubing https://www.amazon.com/gp/product/B07PMHH6YJ/

RE: Prusa Mini Silicone Bed Leveling Mod

If it wasn't for the fact that my y carriage seems to be slightly warped, the back right corner where the wires come into the bed seems to be higher than any other spot even with just that corner screwed down tight to the standoff, and all the others backed off a tiny bit to compensate for that high corner, I still can't completely level it. I am just about running the stock screws out of the standoffs on the left side.

This mod however should solve that since it eliminates the stand offs everywhere but the center. I contemplated trying to bend that corner down by hand slightly, but figure my luck i'll just make it worse in the other direction.

RE: Prusa Mini Silicone Bed Leveling Mod

Posted by: @d0ug

If it wasn't for the fact that my y carriage seems to be slightly warped

@d0ug

I too had a similar problem, in my case the back left arm was lower than the rest. I checked this by using a straight edge on the y carriage frame. It was causing me print issues, I suspect because the auto level firmware was finding it hard to compensate for tenths of a mm. I did the mod and now I have variation of no more than a few hundredths of a mm. The prints are much better. No more first layer issues or prints coming off the bed.

This is consistent and has been so for a few weeks, no variation. I have found the suggestion to make sure the hot end is lifted well clear of the bed after print / calibration important in keeping the inductive sensor (MINDA) cooler helps too in making sure the calibration is consistent. So I modified the end of print code to lift the Z axis well clear of the bed (as suggested elsewhere).

A big vote of thanks to all those involved in the mod and the suggestions in this thread.

Good luck with your mods @d0ug

Roger

RE: Prusa Mini Silicone Bed Leveling Mod

@benji,

Thanks for adding picture of where the the point is on the actual mini bed when you hover over the data points you pasted in.

RE: Prusa Mini Silicone Bed Leveling Mod

@benji

There may be an issue in the code for your tool.

I recently received and installed the SuperPINDA so the first order of business was dialing in my silicone mod.

I followed the instructions from the tool and initially it was guiding me towards 0 error and the plot was showing 0.00-0.05. Awesome!

Unfortunately, I *kept* following the instructions and my offsets started drifting up so now the plot is showing 0.23-0.28. What?

I'm not really sure what to do here other than tighten them all equally to get back to 0 and start over.

I've attached the log of the G29 outputs and you can see the numbers decreasing for the first half of the runs and then increasing for the second.

RE: Prusa Mini Silicone Bed Leveling Mod

I got the rest of the parts to do my silicone bed leveling mod today. After about 3 hours. Got it to this point. I think i'm either fighting against thermal expansion/contraction of the bed, or MINDA probe errors at this point. No matter how much I play with it, it's not getting much better than this. I do have a SuperPINDA ordered and just shipped today. Should be here Fri, so we'll see what difference that makes.

RE: Prusa Mini Silicone Bed Leveling Mod

@straylit
I will take a look today.

@d0ug
I don't think you'll be able to get it any better than that! Even if you did, the improvement to the first layer would be extremely negligible. Great job!

RE: Prusa Mini Silicone Bed Leveling Mod

@straylit
Actually your bed looks just fine! The difference between 0.00-0.05 to 0.23-0.28 is exactly the same. Keep in mind the converter outputs values relative to the center point values. I am not exactly sure what happened here, but your measurements of the center point went up drastically between the first and last measurements. A small change is expected because the Mini does not actually probe the exact center, so the converter averages the 4 surrounding points. A possible answer might be that your SPINDA moved up I guess... Anyway, I will take a closer look at your output later. Having said that, your bed looks great!

RE: Prusa Mini Silicone Bed Leveling Mod

I am thinking i'm just dealing with errors that just aren't going to be easy to correct. I am using my smooth sheet, and literally flipped the sheet over and get this result

Flip it back over and the result looks similar to the original

RE: Prusa Mini Silicone Bed Leveling Mod

@d0ug
Note that the plot is exaggerated.  You have an amazingly level print bed, both sides of the steel sheet 🙂

@straylit
On second thought, the SPINDA moving would not make a difference. Anyway, you also have a great bed!

RE: Prusa Mini Silicone Bed Leveling Mod

@benji

thanks for confirming and thankyou for your efforts. Not sure why my center point is drifting up... Very odd.

The center screw is nice and tight so there's no play there, same for the SPINDA.

I wonder if prusa still needs to release a firmware update to properly support the new probe on the mini.

@d0ug

You bed is twice as flat as mine on that one side... I think we are both approaching the range of being within the measurement error of either MINDA or SPINDA.

I've been doing all my leveling cold so far to reduce extra variables.

@all

From what I can tell so far, the improvement between the MINDA and SPINDA was more about reducing the amount of temperature induced drift and less about improving the absolute accuracy.

I've attached a comparison from running G29 ten times on a cold heatbed just prior to and just after installing the new probe.

As you can see the readings bounce around quite a bit for both.