Offset issues with an iDraw H SE/A3 machine

[drskullster]

I'm having offset issues using saxi with an iDraw H SE/A3 machine.

The plot will start fine, then slowly start to offset on the X or the Y axis. The issue is not exactly consistent (the offset can vary from really bad to barely noticeable) but it is happening on most of the plots.

I pinned down the issue to saxi by creating a test plot and trying it with different tools: Axidraw Inkscape plugin and their CLI tool. Both tools will plot the file flawlessly. When I plot it with saxi, I get an offset on the Y axis:

I tried with all the different settings in saxi (changing each one at a time), including speed which I think plays a role but even at painstaking low speeds the shift starts to happen eventually.

I will have a look at the code because I really want to include saxi in my setup, but if anyone has an idea to where I might look at first it will help a lot (especially since the testing is very slow, it takes around 10 minutes before I can start noticing the issue).

[drskullster]

happy to report that increasing the microstepping resolution fixed the issue!

Switching this:

saxi/src/server.ts

Line 167 in 70b5b2f

await ebb.enableMotors(2);

to:

await ebb.enableMotors(1);

did the trick.

If you have an opinion on how to parametrize that I'm all ears. I don't think it should be in the UI as it's too advanced, I was thinking to add a microsteppingMode CLI parameter. What do you think @alexrudd2?

[alexrudd2]

Is there any observed downside to the increased micro stepping resolution you've noticed?

Can you tell what the Inkacape plugin / aixdraw Python uses?

If there's not a downside (say, maybe some Axidraws can't handle the higher resolution?), we should just change it across the board.

[drskullster]

Interesting @alexrudd2, the Axidraw plugin seems to use 16x microstepping by default:

https://github.com/evil-mad/axidraw/blob/master/inkscape%20driver/axidraw_conf.py#L118

https://github.com/evil-mad/axidraw/blob/master/inkscape%20driver/axidraw.py#L974

[alexrudd2]

Thanks for checking (I'm on a phone or I would have myself. :/) .

I'd say we match the others for consistency and accuracy plotting. The only tradeoff is a bit of speed. In my mind, the only people who would care about super-long plot times (I've heard of hours) would be plotting something so intricate that they'll need the precision anyways.

Go ahead and change the default (with a comment, please)

[alexrudd2]

@drskullster Looking at the machine you have, it's a different setup from an Axidraw. Cool that it works directly!

You might consider doing some tuning specific for that device (see the profiles in planning.ts

[alexrudd2]

See also: nornagon#120