Amazing article on Hackaday showing that not all stepper drivers are created equal. This could actually be the reason for the moire effect that I’m seeing in the deltas I work with.
http://hackaday.com/2016/08/29/how-accurate-is-microstepping-really
It was very interesting reading this comment and related link:
"Karl Hagström says:
August 29, 2016 at 1:34 pm
This guy solved the problem with the DRV8825 by using 4 diods in series with each phase! Great write up: http://cabristor.blogspot.se/2015/02/drv8825-missing-steps.html?m=1
"
@Eclsnowman I wonder if that trick would help with the print quality of the tall cartesian style printer that @Thomas_Sanladerer reviewed recently.
I’m getting really tired of explaining why 8825s suck in mixed decay mode. I’ve been saying it over and over for more than a year. Plug the motor specs and PSU voltage into my stepper motor simulator and you’ll see the current control failure as plain as day. https://github.com/rcarlyle/StepperSim
The stepper is fine. Microstepping is fine. The driver is fine, too. The problem is the driver settings being mismatched to the motor/PSU.
It’s a widely known and completely predictable problem that will come up with even a small amount of research. The 4988 datasheet even has a special note on the effect, which 4988s can also suffer from to a smaller extent than 8825s. Shame on TI for not mentioning it in their datasheets like Allegro does.
8825s are pretty much garbage with “fast” steppers often used in 3d printers – if you don’t use my simulator or switch to fast decay mode, you have a considerable chance of getting ripples in your prints.
SO MANY 3D printers have this problem. I see it in prints from Ultimakers and Airwolfs and many other high-end manufacturers. You can’t run a 24v printer with low-inductance steppers and Pololu 4988s or 8825s without getting rippling at low speeds. The decay settings Pololu uses (and thus all the 3D printer knock-off stepstick options) are simply wrong.
This is something Makerbot actually got right and the hobbyist community screwed up, believe it or not. The 4982s in the Replicator 1/2/2x line are configured correctly for 24v operation and don’t have ripple issues.
@Ryan_Carlyle For what it’s worth, I had altered my UM2’s controller board Sunday to ground the driver Rosc pins and it cleared up the problem I was seeing. Thank you for that information. Hopefully I’ll be able to post before & after pictures in a few days.
@Jeff_DeMaagd @Ryan_Carlyle yes, we know this now at Ultimaker as well. We didn’t know shit when we made the Ultimaker2 on this area.
We are looking into fixing this. As Jeff mentions, it’s a simple resistor swap.
i like this way to describe your products or technical information with HD Pics
@Ryan_Carlyle You mention 24v a lot, my printer is only 12v, is that just as bad? I can’t use your simulator thing as I don’t have access to excel or any kind of spread sheet software (unless google’s spreadsheet thing works).
@Steve_M as far as rippling / lost microsteps go, lower voltage is better. 8825s work better on 12v than 24v. They might still ripple but it’s much less.
Aside from 24v having better heater/wiring safety, with 12v you can’t run your motors as fast. But with typical low-inductance steppers that only usually matters if you want to use 0.9 degree steppers and/or have a delta where the carriages might have to run much faster than the effector.
Hui! Just modded the DRV8825 on my 12V driven CoreXY to ‘fast decay’ (those pins are TINY 
), what a differene! Details like the sign on the back of 3dBenchy are much clearer, surfaces are much cleaner, Z banding is reduced… You can even hear the smother moves, only at the cost of some high frequency noise.
@Volker_Klaffehn Yeah, I personally find the fast decay hissing to be pretty annoying. It’s more of an issue on Cartesian/CoreXY type printers than deltas. You should only really hear it while a motor is stationary at certain microstep positions, which is unavoidable with Cartesian type printers, but deltas never hold any motors still.
@Ryan_Carlyle Any thoughts on the TMC2100?
@Ryan_Carlyle the hissing comes mainly from my z axis, which already did that before, maybe because i have nema14 10.8V Motors on it.
@Ryan_Branch I don’t personally use any 2100s but various people around here like them. I do use the TMC2660 in the Duet Wifi which is similar and it’s really nice. SpreadCycle in 1/16th mode with 1/256 interpolation is plenty quiet. The SpreadCycle mode uses adaptive decay, so it SHOULD be pretty good for microstep angles. I don’t have a simulator for it though and I haven’t o-scoped it so I can’t tell you for sure.
StealthChop mode has issues in aggressive motion control, it’s really not intended for CNC equipment, but some people make it work in slow printers. I wouldn’t bother since microstep interpolation is barely louder.
I Like This Way Although I Don’t Know Technical As Well,But I Am As Oversea Salesman,I Must Know That A Little,Right?