Alternate Z Axis Control

Discussions and help on this commercial controller.

Moderator: twehr

Alternate Z Axis Control

Postby twehr » Mon Oct 10, 2011 1:40 am

I completed the long-waiting z table automation last week, but I wasn't completely happy with the way the DSP controller manages the Z axis. Specifically, I don't like the required and slow Z axis reset. But, I did want to have the table move up automatically between repetitions of a job (for cutting thinker materials).

I discovered the DSP does not actually do part I wanted, but I did find a way to make it happen and improve the whole Z axis setup. In short, I use the DSP's U axis to control the Z axis of my laser. Here is a video of the setup in use.



You can read more about how I did it here.
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Re: Alternate Z Axis Control

Postby andrewblanejr » Mon Oct 10, 2011 2:51 am

great work tim! i really really appreciate that you took the time to post a blog article (how-to) about the whole thing.

I assume that your edges appear much more square/perpendicular than not steping after each pass? When i used my previous laser blaster, my acrylic cuts/edges definitely had a slight "slant" to them, this must mitigate that tremendously...right?
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Re: Alternate Z Axis Control

Postby BenJackson » Mon Oct 10, 2011 6:44 am

I also control the table with U (in EMC2) so that Z can be used to trigger the laser. Z<0 is one of the ways to fire (if M3 is on) which lets me use random CAD programs without having to tweak the setup or post-process to add laser commands.

However there is so much slop in the table axis on the 2.x that I would never try to adjust it between passes. It's designed to have slop to avoid binding. I've done linear cuts with a table move (to verify focus in thicker materials) and the cuts are verry wobbly.

Even if you preloaded it to basically track one or two of the rails you'd have to have the threaded rods adjusted very carefully. I was thinking that a makerslide-based guide (together with the existing lift system) might make it possible to retain table registration while moving.
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Re: Alternate Z Axis Control

Postby bdring » Mon Oct 10, 2011 11:15 am

My original laser had an upgrade to the Z axis that provided very good stability. This was done for the 3D printing. It was basically more V rail like you mentioned here. Since the z lift plates have play the threaded shafts motion does not affect the table.

A few other people are talking about doing a Z upgrade on the 2.x

viewtopic.php?f=16&t=135&start=160#p1294
viewtopic.php?f=16&t=261
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Re: Alternate Z Axis Control

Postby twehr » Mon Oct 10, 2011 12:25 pm

andrewblanejr wrote:I assume that your edges appear much more square/perpendicular than not steping after each pass? When i used my previous laser blaster, my acrylic cuts/edges definitely had a slight "slant" to them, this must mitigate that tremendously...right?


I did not take any measurements to be sure, but visually they look very straight and square to the surfaces. I'll try to look at them tonight and report back. I will tell you I am getting the cleanest cuts in acrylic that I have ever gotten; very little waviness and crystal clear.
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