Missed step detection with MK2Clone r2!

Firmware for MK2Clone r2 is “under construction”.

I found a library for TMC2130 made by teemuatlut, and some implementation of sensorless homing in Marlin, but unfortunately, the software SPI is working only one-way and also the sensorless homing are not working like it should just out-of-the-box in spreadCycle mode. I’ve made a workaround with the software SPI, and found a fixes for the problem with sensorless homing, and now… I’m working on the part responsible for automatic rehoming the printer when the missed step will be detected.

The first, alfa version, on the video, dry run of the printer

I’m reading the Prusa MK3 firmware source, documentations for the TMC2130 and the source code of TMC2130Stepper, to get this thing working on the Marlin 1.1.8. I strongly believe it will work, eventually.

When the crash detection with TMC2130 will be done, there is the fan extender and external mosfet for heatbed waiting, and requiring a little modifications on the electronics-body.


TMC2130 is coming…

The printer should be ready soon, but… What I will be doing, if I finish? No…! I had to change something.

I decided to replace X, Y and E stepsticks with TMC2130. The Z motors will be still run by TMC2208. Why?

TMC2208 are great to run quiet the printer in stealthChop2 mode, without (mostly) lose of any steps, but even with the UART interface which are provided, there is no great function called stallGuard, which are available in TMC2130. This, and already a not bad support for this in Marlin, caused me to go for them. As right now the only true advantage is sensorless homing, and it’s only software feature, to add the Prusa MK3 style rehoming while missing step will be detected. For extruder it will also act as additional sensor for the filament – when the filament will be clogged printer can pause the print and trigger the filament change.

I don’t know, why Trinamic didn’t made yet a stepstick with the upgraded stealthChop2 mode and the stallGuard working it it. Maybe the next product from them will be like that? I hope so, as unfortunately the stealthChop in TMC2100 and 2130 are losing steps very often (unless the speeds and acceleration are low), and also to enable stallGuard it’s needed to turn off stealthChop and go for the louder mode, the spreadCycle.

The TMC2130 on MK2Clone r2 will be connected by software SPI from unused ports on RAMPS, to make the connecting easier than soldering cables to LCD expansion board. Additionally, after tests, I figured that connecting TMC to the hardware SPI used also by SD card reader on LCD board, causes random initialization problems for the memory card.

Moreover, not only the TMC2130 is something new. There will be also RRD fan expansion used to control the fans – as I dont like when the printer finish the job and the fans is running, until someone turns off the printer, and external mosfet board for the heated bed – because the mosfests which are installed on most chinese RAMPS boards are not big enough to power the bed.

Chinese quality vs price

While the r2 is still in beta, I’m looking for parts which have best price/quality relation. There are many chinese bearings, pulleys and other parts, with very low prices but mostly those are unusable.

Linear bearings

From the cheapest LM8UU only 30-50% of them are good enough to use them. The rest have so big looseness, which make the positioning of nozzle to be just a random, and it has very big impact on print quality. Currently I’ve ordered few bearings made by chinese brand FUSHI, those have very good opinions on Aliexpress, and I believe those will be good, without exceptions.


Almost all of the cheap chinese pulleys are just crap. The internal bore, which should be 5mm, are always 5.1mm or even more. They will rotate, but those will be always non-linear on the 5mm motor shaft. It will make the dimensions of printed objects a little bit inaccurate, and as well it will have a impact on print quality. From pulleys on Aliexpress I found good reviews of those made by POWGE, and currently I’m also waiting for them. From many cheapest ones, there is none accurate enough to be used in the printer.


Fortunately, even the cheapest Arduino + RAMPS boards are fine. But apart for that, I found that chinese brand RobotDyn are making great quality electronics, all the solders are made excellent. I strongly recommend to get those. There is one disadvantage – their Mega 2560 has a usb-micro port instead of the classig big usb-b port, but probably everyone has at least one this type of cable, as its commonly used in mobile phones.

Apart from chinese parts

The bill of materials (available on github) are constantly updated, I’ve added links to the needed products, to find them more easily.

I decided to modify the Marlin again, the added options which are worth mentioning are calibration menu and instant xyze moves from lcd. The full changelog and the source code as well are available on github.

I’m waiting to get all the (better quality) chinese parts ASAP, to finally publish the build as – at least – Realase Candidate 🙂

MK2Clone r2 beta tests

The “beta” of r2 is assembled. And it’s really rigid! If you will try to push the frame on the top, the whole printer will move, there is no looseness at all. In comparison to Original MK2, its like day and night.

The available build space: around 25x21x20, thanks to chinese MK42 heatbed, made from aluminium, with PEI surface on top.

The first test print:

Owl statue, scale: 40%, 0.2mm layer height, with linear advance enabled and profile for MK2, sliced with Slic3r PE, printing time: 1h 22m, filament used: ESUN PLA+.

Assembly instructions are still in progress, If you have already a previous experience with building printers, the instructions may be even obvious for you. Anyway, those can be found there: https://mk2clone.dozuki.com/


Revision 2 is coming!

After few months usage of the current MK2Clone with good results, I’ve decided to go further and create a… MK2Clone Revision 2 (r2).

All the parts was reviewed – modifications, some smallers and few biggers was made. There is a new frame, designed to be lasercut from 10mm plywood. Spool holder taken from MK3, adjusted to fit 10mm frame. Parts refined to be more easily printable. Fixed a lot of misalignments in the stls due to differences in mechanical parts.

There will also be a lot quieter printing, thanks to Trinamic stepper drivers and quiet-enough SUNON fans. Additionally, filament runout sensor integrated with extruder body – no more ruined prints due to end of filament.

Unfortunately, the printer will be not as cheap as the first one. Trinamic stepper drivers are more expensive than the standard a4988. Original E3D Hotend, bigger heatbed, even the SUNON fans – all that parts will make the printer far more expensive. For the people looking for cheaper version, there will be still a option to use cheaper parts, I’m planning to publish a list of cheaper replacements.

Additionally, there will be a full guide describing how to build the r2 step-by-step, with photos.

All the parts for r2 (it’s still beta!) can be found on MK2Clone on GitHub in master branch (the master branch should be called dev for this repo ;)) – https://github.com/q3ok/Prusa-i3-MK2-Clone/tree/master

Stay tuned.

New firmware, summary and more


Current state of MK2 Clone build

The “Original” thing

Josef Prusa already announced and started sale of the Original Prusa i3 MK3 printer, with a whole bunch of new sensors. Unfortunately, as he was publishing almost everything to the community, currently his company is making everything by themselves, and its hard to buy the things from other suppliers. It was already same with MK2, but there wasn’t so much parts like that as now.

What about firmware?

There are already new versions of Marlin firmware available (1.1.x) which has a lot of new functions, with Unified Bed Leveling on top of them, and also skew correction algorithm. As the firmware which I made for MK2 Clone wasn’t stable enough, and also the X/Y skew was only the calculator, not the true algorithm to compensate it – I decided to abandon it. Additionally, the chinese MK3 aluminium heatbeds are not perfectly cutted, so the results wasn’t good enough.

-> Configuration files for Marlin 1.1.8 are available in the MK2 Clone GitHub repository


Freshly compiled software

Skewed Z axis

As dulouie noted that the x-end-motor and x-end-idler made by achim_boers has lightly skewed position for brass, he made also a new parts, which are linked in Bill of materials, and available on GitHub as well.


Skewed Z axis

Make it quieter

Most noises are made by stepper motors driving X and Y axes. The cheapest way is to replace the A4988 stepsticks with Trinamic TMC2100, even the chinese cheapest ones. When inserting the TMC2100 then the active cooling for electronics is almost a must, otherwise the stepsticks can skip steps due to protection agains overheating.


Electronics active cooling

What’s next?

Even more quieter: the second loudest noises (in my opinion) are made by the 30×30 fan which is responsible for cooling the hotend. I’ve already found the 30×30 fans made by TITAN, and the manufacturer declares noise level on 21dB. Sound promising.

Sensors! As the MK3 few new interesting sensors, I’m planning to put some on the MK2 Clone. Prusa Research are making a lot custom electronics right now, and I want to focus on electronics generally available on the market, to allow everyone to make the MK2 Clone in their homes.