TMCs and rubbing sound during mesh bed levelling

Hello guys,

I had some people reporting a rubbing sound on X and/or Y axes after installing the external driver board. It turns out that the TMC drivers cause some strange vibrations on the prusa motors with speeds higher than 130mm/s . Looks like on every printer it’s different, some have it louder, other don’t have it at all. Maybe due to frame upgrades etc. It can be felt during mesh bed levelling before every print. The only solution for now is to print at lower speeds (I personally believe MK2S prints better with speeds lower than 100mm/s) and lower the speed between point measurements during bed levelling. The last requires firmware adjustment as it’s hardcoded in Marlin_main.cpp :

  • int XY_AXIS_FEEDRATE = homing_feedrate[X_AXIS] / 20;

That “/20” at the end shoud be adjusted to “/30” to get lower bed level speed.

I have adjusted and re-compiled the latest versions for MK2S and MK2.5 and uploaded them here:

Feel free to contact me if you have any questions.


Ext. driver board with TMC2208

Hi guys, good news. I’ve completed testing my board with TMC2208 from Watterott.

So, why using TMC2208? Mainly because:
stealthChop2™ No-noise, high-precision chopper algorithm for inaudible motion and inaudible standstill of the motor. Allows faster motor acceleration and deceleration than stealthChop™ and extends stealthChop to low stand still motor currents.

Benefits of using stealthChop2:
– Significantly improved microstepping with low cost motors
– Motor runs smooth and quiet
– Absolutely no standby noise
– Reduced mechanical resonance yields improved torque
– Reduced motor working temperature

I highly recommend using these instead of TMC2100. The main reason is the increased torque and lower motor temperatures. Here’s the manual on how to do it:

Note on MK2S motors temperature and Vref with TMC2100

Hi guys, I often get the question for the high temperature on the motors. Yes, it’s normal, TMCs use different algorhythm in StealthChop mode and it’s also doing 256 steps instead of only 16. So the motors run hotter. It’s the same on MK3. Pucture below is my X motor temperature during print of PETG. If you’re running with the stock LM8UU bearings you can try to lower the Vref on both motors to 0.85 V. After that watch for layer shifting. You can go even lower if you don’t have layer shift. If it appears you’ll have to increase Vref again step by step up to 1V so you get to a safe point. Mine get very hot during print, but no problems so far, motors are able to take a lot more temperature, Jo Prusa said it himself. If you’re running with IGUS bearings you will most probably get layer shifting after lowering the Vref. This is due to the nature of the plastic bearings and the usual problem with getting the rods perfectly parallel. At the end you’ll have to find the sweet spot for yourself and your current build. You can always contact me if you have any questions.


Important news about the TMC2100 drivers!

Hi guys, thanks to a friend named Craig Johnson now I know why the original Watterott TMCs are whining. It’s because they run in SpreadCycle mode and we all have been running in StealthChop mode with the chinese drivers with black PCB. No matter if the jumper on my board is soldered or not they run in StealthChop mode. They have little mini jumpers on the back that are being left open. This leaves CFG1 and CFG2 floating and the driver is runnig silent. Now this is not automatically a bad thing, you don’t have to do anything if you don’t have problems with layer shifting. I’ve been running mine since I created the first prototype board and never had problems with the VREF set to 1V. So if you’re using the chinese clone MKS drivers, you don’t have to do anything. If you’re using the original Watterrott TMCs just desolder the jumper on my board and they will be running StealthChop, too without any whining/hissing. Of course you can run in SpreadCycle mode (noisier), but then you need to solder CFG1 and CFG2 jumpers on the back of the chinese clone drivers. If you have any questions feel free to contact me.

New shorter box for the external driver board!

Hi guys, it turned out the first box I designed is a bit taller if you install it on stock MK2S. It’s because I used custom front and rear brackets for the Y axis and they are taller than the original ones. So I made 6mm shorter version. If you’re still using original MK2S parts use the SHORTER VERSION of the box.

MK2(S) Ext. Driver Board rev.2.3 testing update

Hello guys, quick update. I’ve been testing a new revision of the board which will be compatible with all current and future MK2 Prusa upgrades (MMU and MK2.5). The best thing is it’s working with the official firmware from Prusa, I’m very excited about it. The old revision 2.1 will support all upgrades, but will need a very simple modification of the firmware which I will provide. So all of you guys who now have the old board, you’re in the game, too 🙂 Next batch will be ready in maybe 3 weeks, I’ll keep you updated.