Duet3 vs External Drivers for Mill

markz

I'm considering using a Duet3 for a Taig micro-mill and wanted some comparison with external drivers instead from folks who may know better.

The Duet3 drivers are pretty darn smart for 3d printing but how do they compare to like Gecko drivers? I don't really know if they're just amplifying power or doing other intelligent mill-related things.

The other issue I'm worried about is burning out a driver due to external electrical noise and doing things like hand-turning an axis.

I do know external drivers can pump more voltage for more torque and plan to use 32VDC or so on the Duet3 which should be ok.

Thanks, Mark

tenaja

@markz, the d3 can put out 6 amps, which is more than most motors for a mill that size can handle.

Be aware that the duet firmware has no backlash compensation, which is helpful in a mini mill like the taig--and required for any precision work. It also is missing tool offsets (extremely helpful), and uses nonstandard implementations of some codes. (They "meet" the technical "standards" specs, but not the traditional way standard cnc machines work.) For instance, iirc, "optional stops" are ignored, and this can be catastrophic on a cnc.

There is, however, a post processor (python?) on this forum that can add backlash comp to your gcode for you; do a search and it should be easy to find. You might be able to retrofit it to other missing features, too.

I haven't used a taig, or the d3, but between my experience with duet 2's, numerous Sherline cnc's, numerous other "nema 23" applications, and evaluating the d3 specs, it should work fine for a low budget setup.

It will take a lot of setup, since some things are counter-intuitive on cnc applications, being entirely printer-focused. My experience with Linux CNC on a few cnc machines was much faster than using a Duet on a "cnc" application. However, this forum is filled with very helpful people, so if you aren't in a rush, I'd say go for it, of you cannot afford a Linuxcnc (or BBB Machinekit) setup. A taig is small enough that many of these shortcomings may be moot, and a small control board is a definite advantage.

markz

@tenaja Thanks for the information. I'm just not really a fan of using a Linux app for something like this. I way prefer to have it on a small control board with a Windows PC for guidance - exactly the RRF paradigm.

I have a couple of things going for me.

I have a 3d printer that uses a Duet3 so I'm familiar with it. Also, I've already converted my CNC router to using a Duet2 with external drivers and the setup, which is at least as good as the original, was trivial.

Finally I already have RRF code that I run with my CNC that supports screw mapping and backlash compensation so I'm not worried about that.

Mainly I'm just wondering if (1) the Duet3 drivers are robust enough to deal with manual motor turning and the occasional electrical flash and (2) if the driver chips are doing anything intelligent (or not) that would make them clearly better (or worse) than an external driver.

Thanks. Mark

dc42

@markz said in Duet3 vs External Drivers for Mill:

Mainly I'm just wondering if (1) the Duet3 drivers are robust enough to deal with manual motor turning and the occasional electrical flash and (2) if the driver chips are doing anything intelligent (or not) that would make them clearly better (or worse) than an external driver.

The Duet 3 drivers are quite tough, but probably won't survive a short-circuit. Moving motors by hand is generally OK as long as you move them slowly.

Regarding intelligence, the Duet 3 drivers support stall detection and stealthChop (but not at the same speed) and microstep interpolation to x256. Most external drivers don't have those features; however some DSP-based drivers can detect and counter mid-band resonance of the stepper motor, which the Duet 3 drivers can't do.

markz

@dc42 Thank you for the reply.

I've gone ahead and ordered a Duet3 and I'm looking forward to the installation.