Double Engraving Problem - NOT A MECHANICAL ISSUE

[daveman]

Results of the oscilloscope testing confirms what I thought. All 3 of the DM series drivers I tested in the machine are the low budget version of these drivers that have the smoothing features enabled but lack any way to tune or disable them. They don't have a RS232 port for programming with ProTuner nor dip switches for disabling these features. What that appears to do is apply acceleration control in the driver itself which throws off the timing of the firing of the laser. The controller applies acceleration and then it is compounded with the acceleration in the driver making the pulses get out of sync and the motor steps lag behind. Here is a diagram of what testing with the oscilloscope shows:

When the controller fires, the carriage is slightly lagging behind due to the acceleration applied in the driver itself. Since the ramp up is only at the very beginning of the movement, it does not deform the image, it just shifts it a little opposite the direction of travel. This is even worse for bi-directional etching because the image doubles and the shifting occurs in both directions.

So this was a lot of testing, trial and error, and headache to come up with a very simple answer, don't buy cheap drivers!

I ordered some good ones today from LightObject and looking forward to wrapping up the build, photos to follow.

[daveman]

SUCCESS!! Installed the new DM422S stepper drivers and everything works great, no double imaging. Since I could disable the smoothing via dip switch I was also able to confirm the issue is the smoothing in the prior drivers. If I turn it on maximum (sw9&10 on) the DM422S I get the exact double engraving I did with the prior drivers. I turn it off (sw9&10 off) it works perfect. Back to having my nice clean install with the smaller drivers. Pictures coming tomorrow to show how it all turned out. Only thing about the DM422S drivers is the aggravating connectors, I prefer the screw terminals as they are much easier to deal with. Once I swapped with smaller gauge wire and stripped a little extra they went right on.

Thanks for your patience and assistance Marco!

[Tech_Marco]

Excellent!

Mau be you can share your story on our Facebook group : Lightobject Laser Lab


Great job!

Marco