LV8729 guide + comparison with TMC drivers

I’ve previously tested the TMC2100, TMC2208, TMC2130, but still wanted to try out the LV8729 as a ‘silent’ upgrade option. Especially since there is an opinion that TMC drivers are not suitable for use in the extruder.

This video is a step by step to fitting the LV8729, including mainboard jumpers, VREF and firmware changes for both 1/16 and 1/64 microstepping. The steppers are tested in terms of print quality and volume.

Finally, I try to summarise which applications each stepper driver might be most suitable for.

Some notes:
- Never plug in stepper drivers or stepper motors while the power is on.
- Set VREF with the 12V/24V power connected, not 5V from the USB.
- Set VREF with the stepper unplugged.
- Stepper current should be as low as possible to limit heat. If too low, the stepper motors will skip steps. If too hot, they will be too hot to touch.
- The VREF values shown were correct for my Ender 3. Always go through the calculations yourself rather than simply copying mine.
- I am not liable for any damage your cause to yourself or your printer from following this guide.

Previous videos in the series:

Shopping for drivers:

Take a look around and if you like what you see, please subscribe.

#lv8729 #3dprinting #stepperdrivers

[oleurgast]

The reason LV8729 are recomended for the extruder is quite simple: Higher microsteps means less torqe per microstep. As an extruder needs much force to actualy move the filament, on 256 microstepping you might get inconsistent extrusion (the well known issue 602 on prusas mk3). The difference between skipping steps and "skipping" microsteps due to low torque is: The torque of microsteps "accumulates". So on full step the full movement (normaly 1.8°) will be fullfilled. But on the 127/256 is there realy a movement 127/256*1.8°? Maybe not. Maybe the the 125/256*1.8° movement has succeded, but the next sucessful microstep is 131/256*1.8° (just an example).
So the goal of using an LV8729 for the extruder is simply to find the microstepping with enough torque to actualy move the filament reliable for a constant extrusion, there every microstep succed in moving the filament. This might be 1/32 or 1/64 microstepping - but mostly not 1/128 and for shure not 1/256 microstepping like an TMC uses.
Also the TMC only uses 1/16 as input and interpolates - and the interpolation might be wrong speed on the beginning and the end of an extruded line.

As on the other side the extruder should use as many microsteps as reliable possible - you want a "smooth" movement of the extruder motor, no "pulses" of pressure. The movements of the gear(s) moving the fillament are very slow while extruding (as long you do not use huge nozzle diameters). So using 1/64 "native" (=not interpolated) microsteps are no problem even on 8-bit boards.

So tuning in a LV8729 needs more testing. You have to find the optimal microstepping for not "loosing" microsteps to avoid incosistent extrusion, but also moving smooth. The option to do 16, 32 and 64 microstepping give more options than a driver fixed to 16 microsteps or fixed doing 256 interpolation.

Of course nowerdays this is mostly theoretical: Using a Titan or a Bondtech BMG with gear reduction from 3:1 you already reduce the possible inconsistance by a factor of 3; making it mostly invisible (as the molten plastic in the nozzle works as damper smoothing out partly the inconsitancy - on a bowden system also the filament in the bowden smooths out inconsistencies, so the issue is mostly relevant to direct extruders - the reason it got prominent at the mk3).
On a remote direct drive (Nimble, flex3drive) with gear ratio of 30:1 / 40:1 its completly irrelevant (use TMC there, because extruder motor moves fast so 256 interpolated microstepping is usefull to reduce noise).

So in summery:
On a direct extruder with TMC and inconsistent extrusion you might try a LV8729 with 16, 32 or 64 microstepping. This might solve the problem. If you do not have an inconsistent extrusion issue, you do not need to solve it :-) so stay to the drivers you already have. But with an ungeared extruder having the issue, also check to switch to a geared extruder (like the Bondtech BMG/ Bondtech mk3 upgrade). It might be the only solution (without SMD soldering) in some situations anyway, as if an original Prusa mk3 is effected the TMC at the einsy board are soldered...
Also you can reduce weight this way (pencake stepper) which is always nice (even if the bed on i3 style limits the speed, less weight is good for reducing stress on the mechanical parts).


While on a Creality board due to low flash and no free I/O a bigger board with stepper drivers in sockets is a little more expansive but give you other benefits, so track down traces might be a bit to big an effort, there are other printers (like the Anycubic Predator) with closed source 32 bit board and touch screen but loud soldered A4988, there tracking traces and soldering wires to external modules might be very profitable - changing the board would not only costs the price for a new board, but also problems finding the right settings (as you can not take a look to the original firmware) and also changing the touch display. Actually I ordered the Predator yesterday and tracking down Step/Dir/En will be one of the first things to do after assembling and doing some testprints (there of course all 4 drivers, as it has 3 fast moving axes and the extruder will also get fast as soon as the nimble arrives)

[satyrn]

Hi Michael! Thanks for all your great instructional videos! I am in the midst of doing a MKS Gen L with TMC2130s. Doing the loom for SPI was daunting (great difficulty with the Dupont connectors seating in the jackets, and wires coming dislodged when trying to force them) but your guides have made the process easier for sure. Thanks!

[robertvega]

I did have skipped steps on the extruder with the 2208s in stealthchop2. I went 2208's in stealthchop2 for XYZ and 2208 with the One Time programable spreadcycle for E . Since I did this upgrade I feel deeper in love with my Ender 3. Thanks for the great videos!!!

[carlhaw]

Watched your stepper drivers videos I upgrade my ender3 with the mks gen L board with tmc2100, tft 3.2 inch touch screen, and dual extruders I followed your vids to a tee and had flawless performance.

[dougpalmer]

Michael, thank you. You are a valued contributor to our community.

[iteerrex]

I'm a new bee to 3D printing and very much like these technical videos.Thank you!
For other noobs.. cnc kitchen is also a good technical source.

[mareksz]

Regarding the Vref. It's good to check the actual resistor on the driver. The Formula for my LV8729 was assuming 100 ohm but there was a 220 ohm.

[dimitripapadopoulos]

Hi Michael, thanks for the series. I use the tmc2208 also for the extruder. Works like a charm.

[braccopls]

the loud sound you hear with LV8729 is just the firmware going into quadstep mode because the MCU can't keep up, thus going down to 1/16 and maybe skipping some steps

LV8729 are meant for 32 bit controllers. 32 bit + LV8729 is a much better solution than 8 bit + TMCs

So a 32-bit board like the SKR V1.3 should be able to handle 1/128 stepping without any issues? How would that compare to stepping interpolation on TMC2208?

[deceitive]

Excellent summary Michael, thanks for all your testing!!

[louis-ericsimard]

This was an incredibly useful and meticulous series. Thanks a lot !

[Rsm]

Congrats you have over 50, 000 subscribers on your channel!

[toraryugraphiperso]

clearly... I see all this stepper motor driver and I just die... with you, all is perfect now! more understandable ! thanks!

[zoltankorossy]

There are two versions of LV8729 drivers, each of which requires a different vref. That's probably why there were skipping problems with them in the video. If the bottom of the driver has R100 resistors, then, as in the video, the vref is (A/2). However, if there are R220 resistors then vref is (A*1.1). There's a very good chance you actually needed 0.83V for XYZ and 0.99V for E.

[zeealpal]

Great video, I'm looking forward to the TMC2209's, with StallGuard, sensorless homing while in StealthChop2 and CoolStep apparently! 👌

[emmanuelauffray]

Would be keen to have your views on another popular combo. SKR 1.3 (32 bits with Marlin 2) and tmc2208 at least in uart mode. Considering this master?

[BenEBrady]

I just upgraded my Ender 3 this evening to an MKS GEN L board with TMC 2100 stepper drivers. It's scary quiet now.

[Niklas]

Always send M502 (load default values = the values from fw) followed by M500 (save values to eeprom) after flashing fw. Just to make sure to load the new values and save them to eeprom to make everything in sync. You will not need to do manual changes like you do in the video (sending M92...). The eeprom settings will be used before the settings in the fw (and flashing will not change eeprom) so making them the same after config changes could remove some unnecessary headache

[DarkMetatron]

I just changed from TMC2208 to LV8729 for my extruder because i had constant issues with TMC2208 in stealthchop mode for the extruder. Changing the TMC2208 to another mode needs soldering and my soldering skills need training bevor I would try that.


No my ender 3 runs perfectly with an MKS Gen 1.4 and three TMC2208 for x/y/z and one LV8729 for the extruder.