[A_Camera]

Hi,

just one more user of the eBay tb6560, and I would like to share my experience and my measurements. Going through this very long thread, one of the main themes is about the shortcomings of the design with respect to the timings and noise of the pulses after the optocouplers.
My motors tend to loose steps at more than 600 mm/s, and indeed, the oscilloscope shows a rather sloppy rise time in the step input of the tb6560. The levels seem quite OK to me:

Attachment 304904

As a test, I tried following someone's advice to connect a 1K pull-up resistor to each optocoupler, and the waveform becomes much, much better, with a reasonable rise time:

Attachment 304916

I did this for all the dir and step optocouplers, which is a pretty simple operation, and I noticed that the motors sound somehow smoother and the machine can run up to 1500 mm/s. I'll keep them at a safe 1000 mm/s, which is more than enough for my needs.

Seems a big improvement, and in the next weeks (eh, free time is what it is...) I'll do more testing after installing the new spindle, as I already destroyed two dremel-like spindles by doing relatively intense carvings...

The other big improvement that I had experienced some time ago was to wire only half of the motors' coils, to lower the inductance. At the time the max speed I could achieve was ~200 mm/s, which was quite disappointing.
My motors are marked 57BYGH603B, and seem to be quite common in cheap eBay kits. They have a very large inductance, which may explain the difficulties in driving them.

I hope that my experience is useful to others, and I wish to thank all those who posted the very useful info and explorations in this forum.

Here's a photo of the mod with the 1K resistors, I'll be happy to check if other people with the same issues as me find any analogous improvement by mounting them.

Attachment 304932

Cheers
fbx

Those optocouplers are of no use, they give you a false sense of safety. Remove them all together and your performance will increase more. Another thing is that I don't think you run at 1500mm/s, possibly 1500mm/min... and if that is really the case then you are really lucky. Even 1500mm/min is a very high speed for those drivers, assuming you are using a ball screw with 5mm pitch.