There was a project that I wanted to try and finish and with my big CNC now operative THIS IS THE TIME!
But let’s start from the beginning
Like me there are a lot of people with a delta 3d printer that are using DRV8825 as stepper driver into their electronics. And there is a change they saw some strange ghosting effect in their smooth curvy 3d printed pieces. This strange effect is also called Salmon Skin.
You may have the best mechanical delta, and with no reason you saw that strange watermark on you piece.
Who is the murder… I mean the guilty?
Long story short, DRV8825 stepper driver has an intrisic bug, that is more evident while they are working at low feedrate (aka low freq), and this bug can cause a missing micro stepping issue.
HERE you can read a more complete and nice explanation. And from this web site I get the schematic of the little circuit I’m going to make 🙂
The circuit is quite simple: we have to put 2 couple of antiparallel diods on each phase of a stepper driver motor. And now I have a working CNC, and I have some spare single side copper board for PCB prototyping.
I just need to buy a bunch of diods and some PCB screw terminals.
And after some work with Eagle I’m ready to start to cut the PCB!
There was a lot of soldering job to do… but that was quite simple 🙂
Following a short video about the making process 🙂 If you felle nice please like the video and subscribe 🙂
The following 2 photos are about a cylinder printed WITHOUT the TL-Smoother. DRV8825, 1/32 microstepping. Mini delta printer. Ramps 1.4.
If you look you can see the salmon skin rising and crossing the shell of the cylinder.
The other 2 following photos are about the same GCODE FILE printed ON THE SAME MACHINE with the only diffence that I used the tl-smoother on this run.
The salmon skin effect is less visibile. Still there… but less visibile.
Comparing the 2 object.
You can see the difference… but it’s not so huge.
- the printer is not quieter than before… just a little bit maybe
- they don’t become so hot. Maybe this kind of diods can handle the heat much better
- I have to try to print at higher speed to see if there is some difference
- I have to calibrate a better the DRV8825 current to see if there is some change in the print quality
for the moment that’s all folks.
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