First Layer Adhesion – 3D Printer Bed Mesh Levelling Mods – Prusa Mini+ & i3 MK3S+

This post will be a simple account upon the bed levelling modifications for the Prusa Mini and Prusa i3. These are in my opinion essential modification, especially for the mini but will greatly improve both first layer print adhesion for larger models on both printers.

For Mini+

In this video I’m going to go through the workflow for the bed levelling mods for the Pura Mini+ and Pura i3 MK3s+. I’ll start with the Mini, which before doing any bed levelling mods, you’ll need to ensure your printer is set up square and un-skewed.  Follow this official guide from Prusa or watch my video here which I made before the official Prusa guide was available.

It is also worth selecting the location where the printer will be positioned, and to avoid moving the printer if possible. And if you must lift the printer, do this from the base and avoid carrying from the Z axis or cantilevered arm.

This is the workflow guide that I used, which was written by a gentleman called Benji – to whom I am greatly thankful for sharing: Prusa Mini Silicone Bed Leveling Mod – User mods – OctoPrint, enclosures, nozzles, … – Prusa3D Forum and this is the updated version

And I followed this with only slight variations and use of different tools. Instead of using Silicone tubing and longer machine screws, I bought M3 shim washers, the sizes of which come in 0.1mm, 0.25mm, 0.3mm and half a mm, which can be combined to make up whatever variation of adjustment is needed. 

I should also mention that I’ve not tried the silicone version of the mod, so I can’t say there’s any real advantage to using the shim method other than it worked for me. Silicone has very good heat resistant properties and may also contribute to dampening vibrations. I did wonder though, for ease of adjustment if I could have installed helicoil style inserts into the aluminium y carriage and using longer countersunk machine screws in a similar way to the i3’s nylock mod, to adjust the heat-bed height without the need of the fiddly M3 nyloc nut underneath the aluminium y carriage.  I had a look at the DXF file for the mini’s aluminium y-carriage and the mounting holes are same size needed to tap the inserts to the coils size needed so this could have been an option. But I’ve committed to shim washer and will carry on.

Tool wise, I needed a 2.5mm stubby hex keys, and a 5mm nut spinner along with the T10  torx key. I then followed the stages from point 12 onwards to generate the first height map in Pronterface, inputted those numbers into a GitHub app described as G29 absolute to relative value converter & plotter. Prusa Mini Silicone Bed Leveling Mod (

Essentially, once the nozzle and heat bed have gotten up to temperature, G28 homes the three axis and G29 performs the bed mesh levelling. You will get some sums in the console which can be copy and paste into the input box and converted usable information.

Taking my queue from the raw values segment of the app, I can remove or positioned the appropriate number of washers between the standoff and aluminium base, to make up the distances.

So I’m just taking off the heat bed off the prusa mini to show you how I got the platform level. I’m using a torx 10 tool to unscrew these countersunk machine screws. And what I did was place the shim washers underneath the hex standoffs around the edge where it was necessary. And the only place I didn’t do that was for the centre because that is the refence point.

And to highlight as described in point 6 of the instruction – leave the centre screw and spacer alone, although you might find you need to tighten this – this is the reference point for the other 8 fixing positions. I’ve already completed my mod some time ago but will demonstrate removing a shim-washer to further reduce this deflection. I unscrewed the centre right stand-off and checked the washers with my vernier calliper. I then discarded one washer and began reassembling.

I also checked all the other standoffs had not rattled themselves loose since I last did this. After which I reassembled the print bed, and performed the same workflow to generate the G29 mesh levelling values.

And here you can see how those values have changed. I performed the height map several times, adjusting the number of washers, until I was below 0.2mm of variance. Removing the washers has lowered that value to closer to the 0mm reference point.

After which I completed the first layer calibration. Before doing this, prints would lift along the righthand side of the print bed, and I found I had to limit the print sizes well below the maximum advertised capacity.

This mod, and the squaring guide have greatly improved the printing quality and my experience using the prusa mini. So, I highly recommended performing these tasks. Alongside this, reducing the first layer print speed improved first layer adhesion, and moving to an alcohol and silicone free anti fog lens cleaner for degreasing the print bed will also help improve print adhesion.

  • M140 S60 ; set bed temp
  • M109 R170 ; wait for bed levelling temp
  • M190 S60 ; wait for bed temp
  • G28 ; home all without mesh bed level
  • G29 ; mesh bed levelling

For i3 MK3S+

Now this is the Prusa i3 Mk3S+. and again, I’ve already completed the bed levelling mod previously, but will point out the sources and how this modification is a little different. I’ll also run the mesh levelling again and try further improving the accuracy.

I’ll begin my showing you the nylock standoffs – threaded onto the original machine screws, with a washer between the underside of the heat-bed and nut. These were just slightly loosened to allow them to turn without noticeably pivoting in the holes.

The Prusa i3 – despite it’s more antiquated electronics has more features. It has a simple skew compensation with magnetic zones providing X-Y Axis squaring references points. It also has a mesh levelling cycle that includes more grid points, and a higher number of probing cycles per point, which ultimately amounts to more accuracy.

The mesh levelling on the mini uses a 4×4 grid with two probe measuring plunges per point, compared to the i3’s maximum 7×7 grid, with 5 probe plunges providing you adjust this in the settings. Mesh bed leveling | Prusa Knowledge Base (

So the  last time I did this… so last time I did this, this section was a little low so I added some Kapton tape but I’m going to remove that now and redo the mesh levelling and see the difference.

I used this workflow with minor changes, such as placing the nylock nut the correct way around, with the addition of metal washers, and heating the nozzle as well just to make sure all variables were are similar as they might be to normal printing conditions.

I set the print bed temperature to 60, plus the nozzle temp to 170 and waited for these to (M190) to reach targeted temperatures. I then performed a G28 homing which on the i3 also performed the mesh levelling. After which I wrote G81 into the console to retrieve the levelling values. For subsequent mesh cycles I used G80 to perform the mesh-based z probe and G81 to retrieve the levelling status or values.

So the bottom right machined screw needs to move 130 degrees counter clockwise and place this protractor here and soon around 130. This one here going to move 137 anticlockwise. oops whoops, oops, oops, oops, oops….

Let’s do this again. This is going to 238, I’ve done 180 and now I’m going to do another 58. I’m going to adjust that one as well. So that is the 180 and adjust another 70. One of the issues with the printer, which is not easy to see, but I will flip this over in a moment when it’s cooled is that there’s two linear bearings supporting the print bed, on the left hand side, but only one in the centre on the right hand side. And what that means is if I over here, that doesn’t move so much and that has a little bit more flex.

So I’ve just done the mesh levelling again, and that looks really good now.

Now, doing a Z calibration macro. I’m pretty happy with that, but it’s unusual that the shape only occupies such a small part of the print bed – pretty much the same size as the producer Mini. Really, this should be to scale much further across to see if the calibration is worked on the edges.

  • M140 S60 ; set bed temp
  • M109 R170 ; wait for bed levelling temp
  • M190 S60 ; wait for bed temp
  • G28 ; home all and perform mesh bed level
  • G81 ; mesh bed levelling

Thread Repair Kit

Well I did buy a coil repair kit helical style. This is the drill bit for drilling the pilot half of the tab and these other coils which you screwed into place with this tool here. And you use the last tool to punch out a little tab at the end. So described in the manual here, a simple x-y carriage base. This is official press. I want to cost me a little bit and see about tapping these holes, nine of them with this kit.

I had to stop because I feel like I was going to bottom out and then thread that. I think I might just do this by hand.

Oops, Oops, oops. Whoops.

So it’s taken the thread quite well. And I feel like there is that ability to now use the new lock method with the Prusa mini. But this is a highrisk option because you have to tap the holes, thread them with the coil and basically try not to make any mistakes. I’m not sure if you would end up having to dismantle any of the sections to get access. Could be quite tight in places, but you will have that additional flexibility of being able to micro adjust in a slightly less fiddly way – anyway than other options.