Cutting and Engraving not lining up

[jkittle99]

I'm still working the kinks out of my new laser cutter, but it seems like I'm still having DSP / LaserCad related issues. I'm hoping they are simply configuration related, but they're really starting to feel like software issues to me. For reference, I'm running LaserCad 6.71 with OS 130622.

See the attached photo. The outer box is 200mm x 200mm. I draw it in lasercad, and it cuts a box 200x200. So everything is fine so far. Notice the engraving in the middle, it's distorted (quite a bit on the Y axis), not centered, nor is the cut that surrounds it in the correct place, although the dimensions of it look ok.

Attached is the project file. Can anybody duplicate this issue, or give me some guidance on what might be going wrong here?

[Toasty]

I'm probably not going to be a lot of help and I'm sure Marco can point you in the right direction. But...

I doubt it's software or dsp related unless you simply have a defective dsp and even then I can't imagine it would do that.

You didn't mention what kind of laser engraver you are using so I'll assume it's a k40 of some type. From what I've seen on the forums it's probably a mechanical problem or a configuration problem (which I suppose IS actually software but I'm assume you mean an actual software error).

You might want to post what software you are using to create the design, what file format you're saving it to before importing in lasercad, etc...

The only reason I mention all of that is that I recently finished a job with 300 pieces of engraving plastic that were cut and engraved. The pieces had to be EXACT because they were attached to each other back to back when they were done.

I didn't have a single problem so the software seems pretty stable to me. I've actually been very surprised by it's features and how consistent it has been day in and day out.

I design in Coreldraw 10 and save as an .ai file which is then imported into Lasercad.

[jkittle99]

I'm using a homebuilt laser cutter based on the buildlog.net 2.0 design. I don't think it's a mechanical issue, if I tell LaserCad to cut a 200mm x 200mm box, it comes out perfect. It's when I start doing multiple 'layers' that I seem to be having isseus with the layers lining up. Also, if i have more than one object on a layer, it seems to have issues. Engravings look good, they're just in the wrong place, so I don't think it's an accelleration issue. It's just that things don't line up... by TONS.

Most of my desings are in autocad, and I import as DXF. They look perfect on the screen, its only when I'm cutting them that things go badly.

Josh

[Toasty]

Again, I'm just throwing stuff out there based on my experience but I would try a different file format. There are so many versions of .dxf that I've always hated working with them when a customer sends one to me.

I image it would be hard for the programmer of lasercad too.

.ai files exported from CorelDraw 10 work great for me but I also had good luck importing black and white .jpg images for the engraving (not cutting of course).

Does the drawing still look correct if you "simulate" the job?

[jkittle99]

I would think that if it looks right on the screen, that the file format is ok, but yeah I totally understand the number of versions of things. These started life as an autocad 2000 format DXF. I'll try and run a 'simulate' and see if it still looks ok on the screen.

Do you have a cutter? Care to try and run the job on paper and see what it looks like for you?

[Toasty]

I did download the file. My laser was tied up with work all day. I may be back in my shop tomorrow. If so I'll run it on paper to see what it does. I think I'm running an older version of the software though.

I did simulate it and it looks fine on the screen. I've found if it simulates right it runs right for me. The only thing was when I opened the file the design was way off my work space and I had to center it on my page. That's obviously because we have different workspace sizes (different machines).

One more idea. Do you have a very strong exhaust system or maybe running air assist? I've seen work move from air causing very similar problems, especially the elongated engraved part. It doesn't really make sense on the cuts though especially since it looks like the shape is closed properly.

Oh! And you mentioned layers. Are you using different layers in Autocad? I would try doing it all in a single layer then just select the objects in lightobject and change the colors. I've had customer drawings come in with layers and it does similar weird things to CorelDraw. Once they resend as a single layer all is well. Again, just throwing stuff out there.

My bet is on a configuration problem. Maybe a stepper is missing steps on the rapid move between shapes and while engraving? Probably something simple if it's not hardware. I'm sure Marco will chime in here soon.

[waltfl]

hi there
I did it today just on a piece of scrap wood and it worked fine no problem.
greetings
waltfl

I did download the file. My laser was tied up with work all day. I may be back in my shop tomorrow. If so I'll run it on paper to see what it does. I think I'm running an older version of the software though.

I did simulate it and it looks fine on the screen. I've found if it simulates right it runs right for me. The only thing was when I opened the file the design was way off my work space and I had to center it on my page. That's obviously because we have different workspace sizes (different machines).

One more idea. Do you have a very strong exhaust system or maybe running air assist? I've seen work move from air causing very similar problems, especially the elongated engraved part. It doesn't really make sense on the cuts though especially since it looks like the shape is closed properly.

Oh! And you mentioned layers. Are you using different layers in Autocad? I would try doing it all in a single layer then just select the objects in lightobject and change the colors. I've had customer drawings come in with layers and it does similar weird things to CorelDraw. Once they resend as a single layer all is well. Again, just throwing stuff out there.

My bet is on a configuration problem. Maybe a stepper is missing steps on the rapid move between shapes and while engraving? Probably something simple if it's not hardware. I'm sure Marco will chime in here soon.

[Toasty]

Same here. Just ran it on paper and it looks good.

[Tech_Marco]

In most case, it iis driver issue. Change Rising edge/ Falling edge may fix the issue

Marco

[jkittle99]

Thanks to all for the feedback and running some tests - it's encouraging that it looks good on your machines. I'll play with the rising/falling edge that Marco recommends and see if that changes anything. What else could it be? Is there such a thing as too much microstepping / aka running too high? Would the DSP care? I think I'm set for 1/16 microstepping, but I'll have to doublecheck that. It doesn't seem like I'm missing steps, but I'm open to the possibility that it's happening and I'm unaware of it.

Josh

[Things]

Microstepping reduces the torque of the stepper motors significantly, so it's possible that the motors do not have enough torque to avoid skipping steps. Engraving is a lot more taxing on the motors due to high acceleration, I'm betting 100% on this being a hardware issue.

One way to check is set an origin, and mark it with a pulse from the laser. Run the job, and see if the laser comes back to the same origin. If not, you've got a slipping belt or skipping steps.

EDIT: Just read a post from you further down about the laser never going back to it's origin - this is definitely a hardware issue. Motors skipping steps can be very audible, or not audible at all. One way to check for it is to hold your hand on the motor and run it, and see if you can feel any odd vibrations, especially during acceleration. Also make sure all your belts are tight (but not overtight, they should spring a little when you release them).

You haven't mentioned what machine you're using, but if it's one of the K40 machines, from memory the motors are very undersized for the job, it may help to get a higher power driver or even replace the motors if they are actually skipping steps. Reducing microstepping will also increase torque.