RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)
Would you mind giving us a short write up on the whats and whys? That would be greatly appreciated.
RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)
First one is during homing, when moving X to home it tries to keep pushing once it reaches the far left, the printer then reboots. I do recall you had the same issue, unclear as to what to change in the firmware.
Without a means of reading the Trinamic stallguard values, I initially tried varying velocities upward then downward for the homing. Eventually got to the figures currently in my firmware. Those gave me the most consistent and reliable homing. The only thing I do now is check belt tension is in normal state after one of my rebuilds. If there is a failure post rebuild, it's usually a slightly low belt tension. 1/4 turn on my Bear x-end and fixed.
These days, I basically never get a homing failure unless I tear down the machine for parts testing
Still using a Moon's 0.9 on X, but overall, things have been quite reliable for months.
You linear rails
RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)
Good luck, sounds like a lot of work.
Just some clarity on the homing and crashing - with default software just modified for BMG and 0.9 steps, the crashes and homing errors doesn't happen, I only get it with the firmware from here - https://github.com/guykuo/Prusa-Firmware/tree/0.9-Degree-Stepper-Support
So in this case I don't think it is hardware related at all.
I'll play around with the stallguard settings and homing speeds.
RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)
Tuning the current proved interesting, though. It made no difference at all until I went from 31 to 32, at which point the noise just disappeared. I'm guessing it has something to do with the change in Vsense from 1 to 0 at that point (`tmc2130_setup_chopper(...)` in `tmc2130.cpp`), but I don't understand why that would make a difference. At any rate, the drivers hit thermal shutdown about 40 minutes into a test print, and I wouldn't want to run them that hot over the long haul. It's all starting to make a _little_ sense, but I'm still a long, long way from an expert. I certainly don't understand how the current configuration works in the firmware.
There can be a jump in driving current (up or down) when going from 31 to 32, because the two sense resistors aren't as exact as the ADC in the driver. An increased drive current will make large motors run smoother. I've increased the drive current even for the Trinamic -049's by about 30% to get even more linearity.
Plus last time when we talked about inductance, I totally forgot to factor in the 0.9 degree step size. That doubles the apparent speed to the driver and thus puts additional demands on it even in terms of overcoming the inductance, like if it doubled. Plus there is additional inertia, so heating up drivers are not surprising. You may succeed by gluing heatsinks to the back of the Einsy and/or using one of the fan mods for the Einsy case.
RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)
I'll play around with the stallguard settings and homing speeds.
Yes, that would really be the only places that should be behaviorally different from Prusa's current MK3 firmware. Most of the other stuff in my firmware is for trinamic tuning - not likely to be causing software crashes.
BTW, you DID install heatsinks for the TMC2130's right?
RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)
Yup using rpi heatsinks
RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)
@vojtech-p6 I've got a good deal on two of the Trinamic motors. Is there anything I should be aware of? You wrote "increased current by 30%", is there a quick guide on how to do that (I know how to compile my own FW). I guess higher current absolutely needs heatsinks then, right? What about default current, are heatsinks neccessary for the Trinamics?
RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)
@fynn-a,
I don't want to speak for vojtech, but I'll at least _try_ to answer the part of your question about adjusting stepper current. Usual disclaimers apply: I've been working with this for about a day and a half, so don't count me an expert. If I get it wrong, please jump in and correct me!
The section of the code that defines the stepper holding and run currents looks like this in your variant file, defining `TMC2130_CURRENTS_H` and `TMC2130_CURRENTS_R`. The order, I believe, is `{X, Y, Z, E}`. It's a number from 0-63.
To understand what that number means, you'll need to dig into the TMC2130 datasheet. The numeric value is actually the current control scaling (cs) value, not current in amps. It determines the actual current in combination with the vsense setting and a sense resistor. Vsense can be 0 or 1, and determines if you'll use a larger or smaller scale. The sense resistor sets the fundamental size of those scales. Our Einsy has a 0.22 ohm resistor, so look at p. 55 of the datasheet and you'll see that we go up to 0.53A with vsense=1 or 0.96A with vsense=0. The RMS current in milliamps can be approximated with,
max * ( 1 + cs ) / 32
But wait, didn't I say that the firmware's code takes a single number from 0-63? That's because the Prusa engineers start with the smaller scale vsense=1 from 0-31, then automatically switch to the larger scale vsense=0 from 32-63. When they do that, they also bitshift the cs value to the right by one (basically dividing it in half, rounded down). I'm guessing that's not just for simplicity, but also because Trinamic recommends cs values at or above 16 for good microstepping performance. Kinda clever.
With all that said: I used the Trinamic -049's for over a week with stock firmware and no heatsinks, including a few fifteen-hour overnight prints. Worked like a champ.
@vojtech-p6,
I'm glad you mentioned trying to boost the current with those Trinamic steppers, 'cause I've been trying just that! So far, so good. Heatsinks are warm but not hot.
I did finally get some good settings and good prints with the Moons HA6 as well. I just tweaked the firmware to let me use smaller cs values with vsense=0, then ran in the neighborhood of 350mA-400mA with tbl=2, toff=3, pwm_grad=4 and zero hysteresis. Worked in both spreadCycle and stealthChop modes, though stallguard values could use a tweak to be a bit more gentle. Thanks for your tips!
In order to optimize either of these steppers further, I think I'm going to have to dig out my oscilloscope and figure out how to connect it to a stepper motor. Anyone done that before and have some tips?
RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)
Hi,
thankyou, I just read your post and would like to help.
i created a bracket for the power supply side when I moved it out of the enclosure.
I noticed it improved the surface quality. Then I made other parts for filament management and the part fan, spline isolation in Z,
i have a case to mount to the z axis that holds the pi 3 board and a sensehat to monitor vibrations and temperature and humidity.
I also have an Einsy case that bolts the YAnd Z axis together. This case also has an active cooling setup for the vias side of the board.
These changes have improved part quality and I am now experimenting with other mods.
you can download these parts from prusaprinters and Thingiverse and pinshape
username carterm2
i will be looking into your motor solutionsoon
thanks for the hard work.
carter
RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)
evan38109 good to see continued work refining the Trinamics. Once you have it better characterized, we can also push it into my 0.9 firmware.
RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)
Do the 2130's report their temperature or are you using a flir camera?
Do the Vias exit the back of the board at a subsurface heat spreader? If it is necessary to add heatsinks, can you cover the vias? Is thermal double stick foam tape shipped on the heatsink safe to use?
Finally, I printed a rounded box 53mm X, 134 Y, and 208 Z with a .6mm nozzle and .3mm z steps (9 hours). adding video (part looks much cleaner in person) to show surface... is this showing VFA's or ... how best to evaluate my setup relative to VFA's so I can evaluate progress as I change motors, and printer setup.
Please look at ... https://www.prusaprinters.org/social/6839/prints. I worked hard on this in order to create better parts, I want to share here on Prusaprinters to help out but also to get feedback. So far, I am very impressed with the quality of Prusa's staff and the feedback I get from the community is very helpful. I just don't get much feedback and I really am serious about refining surface quality...
For Example, both Vojtech and Joan were pivotal in getting airflow over the vias, Joan suggested the idea and Vojtech supplied the technical knowledge to get things working... but no one as built the fan assembly or even mentioned cooling the 2130's until I found your post.
Regards,
Carter
RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)
@fynn-a,
I don't want to speak for vojtech, but I'll at least _try_ to answer the part of your question about adjusting stepper current. Usual disclaimers apply: I've been working with this for about a day and a half, so don't count me an expert. If I get it wrong, please jump in and correct me!
You're spot on. Couldn't have said it better.
With all that said: I used the Trinamic -049's for over a week with stock firmware and no heatsinks, including a few fifteen-hour overnight prints. Worked like a champ.
Same experience here. The Trinamics are a bit more sensitive to stall detection than stock, so raising those thresholds might be considered, but is not required on a smooth moving printer. Also they run cooler than stock, so increasing the current is possible to gain more linearity under acceleration load. I haven't needed heatsinks so far. I'm currently running at
#define TMC2130_CURRENTS_H {20, 24, 35, 30} // default holding currents for all axes
#define TMC2130_CURRENTS_R {20, 24, 35, 30} // default running currents for all axes
@vojtech-p6,
I'm glad you mentioned trying to boost the current with those Trinamic steppers, 'cause I've been trying just that! So far, so good. Heatsinks are warm but not hot.
I did finally get some good settings and good prints with the Moons HA6 as well. I just tweaked the firmware to let me use smaller cs values with vsense=0, then ran in the neighborhood of 350mA-400mA with tbl=2, toff=3, pwm_grad=4 and zero hysteresis. Worked in both spreadCycle and stealthChop modes, though stallguard values could use a tweak to be a bit more gentle. Thanks for your tips!
Congrats! 🙂 How's the quality (and noise) with those now?
In order to optimize either of these steppers further, I think I'm going to have to dig out my oscilloscope and figure out how to connect it to a stepper motor. Anyone done that before and have some tips?
That's going to be a bit tough.
First, you probably don't need to look at both the coils as the waveforms will be the same, as everything is symmetrical. But even a single coil is driven with a H-bridge, so you can't simply connect a single scope probe across it, that'd short-circuit it to ground. You could have some luck if you leave the printer or the scope floating, but you'd see a lot of noise in the signal as both have big capacitive coupling to mains. So either a differential probe, or use two channels on a scope and enable math on the scope to see the difference.
That'd let you see the voltages. But voltages aren't quite interesting, they correlate with the speed of the motor and are influenced by inductance. The important quantity is current, as that's what translates to torque and controls microstepping. It's also what the driver's feedback loop tries to set. For currents, you'll need a current probe or a resistor in series with the motor to measure voltage on. Perhaps the built-in sense resistor could be used, but I worry that thanks to chopping, you'd see both the channels on it mixed together. I'd need to examine the datasheet to confirm.
RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)
@vojtech-p6 I've got a good deal on two of the Trinamic motors. Is there anything I should be aware of? You wrote "increased current by 30%", is there a quick guide on how to do that (I know how to compile my own FW). I guess higher current absolutely needs heatsinks then, right? What about default current, are heatsinks neccessary for the Trinamics?
They run perfectly fine without any firmware mods and without heatsinks.
Everything else is just tuning to improve the performance even more. I did increase the current by modifying the line mentioned in my previous post and even with this, I haven't needed heatsinks and didn't trip the TMC2130 thermal protection. (No enclosure, a comfortable ambient temperature.)
RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)
Do the 2130's report their temperature or are you using a flir camera?
They have a two stage thermal alarm. The "pre-warning" is triggering at roughly 120 °C, and thermal shutdown follows at 150°C die temperature. The chip is still communicating after shutdown, but will not drive the motor. The Prusa firmware will detect the pre-warning and kill the print immediately, displaying
TMC DRIVER OVERTEMP
on the screen. So at least you know when you're driving the TMC's too hard and the printer will not let them heat up to the shutdown temperature.
Do the Vias exit the back of the board at a subsurface heat spreader?
Yes. That's where most of the heat is dissipated.
If it is necessary to add heatsinks, can you cover the vias?
Yes. Thermal contact with the vias is what's important.
Is thermal double stick foam tape shipped on the heatsink safe to use?
The foam part sounds odd. Foams are not usually thermally conductive. A thermally conductive double sided tape would be OK. Or a thermally conductive glue. Or a thermal compound in the middle and a bit of epoxy in the corners. I wonder if a M.2 heatsink would fit.
RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)
Vojtech,
"I wonder if a M.2 heatsink would fit."
The Prusa Mk3 case has 6mm ( https://www.thingiverse.com/thing:2699771) by jzkmath...
it also wisely has the vias side opposite the bed... cooler than next to the bed.
The case here ( https://www.prusaprinters.org/prints/1910-yz-case) has 8.9 mm
The M2 heat spreader here requires 5mm.
Carter
RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)
In the old Trinamic tuning thread, I used a current probe to look at the drive waveforms.
Forum has lots of information, but not much recall.
RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)
Sorry, Prusa case to Einsy looks like 6.9mm.
There are M2 copper heatsinks for $2.40 from China that are chocolate bar shaped... and appear to be 2-3mm tall.
RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)
Sorry, Prusa case to Einsy looks like 6.9mm.
There are M2 copper heatsinks for $2.40 from China that are chocolate bar shaped... and appear to be 2-3mm tall.
That's cool. Unfortunately the M.2 is too large in other dimensions. You can't stick it right on, because it interferes with some through-hole components that definitely should not be shorted to each other. So a modification to the heatsink or to the Einsy would be required.
RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)
Actually the chocolate one (red) fits well. It's just a tad too short. So perhaps one that has the right size can be found.