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> This is a laser cutter that takes its "print jobs" as a PDF file and uses its vector drawing commands to drive the cutting head. This means that it is impossi

> This is a laser cutter that takes its "print jobs" as a PDF file and uses its vector drawing commands to drive the cutting head. This means that it is impossible to use it to print a wheel. You'd need to attach the output to a lathe and sand it down to be round so it actually functions as a wheel rather than as a vibration source. Respectfully, I don't think you're limited by the PDF format if you're talking about a laser cutter. And... Circular motion doesn't spring forth naturally from gantry CNC laser cutters -- they're rectilinear in design. It's circles not existing all the way down. Using it as a CAD format with inherent fundamental shapes missing seems kind of funny, though.

itishappy 3y ago
Epilog claims (up to) 1200dpi resolution. Another comment mentioned the "standard bezier curve representation" is accurate to 0.03%. This means errors should start being observable with a circle as small as 3in. These are probably wildly optimistic assumptions, but it's still 10x smaller than the bed of their largest unit, and there's nothing to stop people from creating arcs of circles with radii even bigger than that!
- photonerd 3y ago
  Observable is pushing it. Technically observable, sure, but ~1dpi misplaced is… unlikely to be noticeable. Plus, if that level of accuracy is required simply adding more nodes improves accuracy exponentially. Not least, the “standard” approximation really should be updated in software, as modern 4-node approximations are down to 0.005%, almost an order of magnitude better.
  - ars 3y ago
    If you are misplaced by 1dpi, then your "1200 dpi" is actually 600 dpi. If you got a machine that's accurate to 1200 dpi presumably you want 1200 dpi and not 600.
    - photonerd 3y ago
      That’s not true in this case. It would still be 1200 dpi but the approximation of one curve is off by 1 dpi in some dimension. If all the lines were off, then yes, kinda. Ish.
  - itishappy 3y ago
    Oh, I completely agree! "Observable" is pushing the limits of the word past absurdity. 1200dpi would put the resolution of the system at just twice the wavelength of their laser. I feel like that's about the limit of what's possible due to physics [citation needed]. I'm fairly confident their actual performance is less.
  - versteegen 3y ago
    > simply adding more nodes improves accuracy exponentially According to another comment, it actually improves at O(n^6).
    - photonerd 3y ago
      I stand corrected! Polynomial..ly
- amluto 3y ago
  Last time I used one, Epilog’s software was pretty terrible. It seemed to designed around a workflow in which you either design your cuts in CorelDraw and then print to a Windows print driver. I sincerely hope that the upcoming Windows third-party print driver deprecation kills this. (Also, what’s wrong with them? Even ignoring cost, I would rather have a Chinese printer that had a publicly known control interface and supported Lightburn than a “nice” American laser printer that was only operable with bad proprietary software.)
- mlyle 3y ago
  The 1200DPI resolution is for engraving using rasterization, so, not really the same thing. When you're cutting things on a laser, there's myriad sources of error. Odds are the optical path isn't completely square, so there's some cross coupling between axes. There's drive belts. The laser is often pulsed. There's taper.
somat 3y ago
The shape is there. postscript(and I assume PDF) has an arc primitive. however it is rasterized(drawn) in the reference implementation using bezier curves. Now the postscript to servo control program(g-code?) interpreter might use the same bezier curve approximation, but it might not. I think if it were a formal complaint they would have to positively assert that their machined circles are following an inferior profile rather than just assume they are. g-code sort of sucks as a language. It is very primitive. I always thought it would be cool to have a postscript dialect that supported more than two axis to use as a low level language on computer driven machine tools.

itishappy 3y ago

Epilog claims (up to) 1200dpi resolution. Another comment mentioned the "standard bezier curve representation" is accurate to 0.03%. This means errors should start being observable with a circle as small as 3in. These are probably wildly optimistic assumptions, but it's still 10x smaller than the bed of their largest unit, and there's nothing to stop people from creating arcs of circles with radii even bigger than that!

photonerd 3y ago
Observable is pushing it. Technically observable, sure, but ~1dpi misplaced is… unlikely to be noticeable. Plus, if that level of accuracy is required simply adding more nodes improves accuracy exponentially. Not least, the “standard” approximation really should be updated in software, as modern 4-node approximations are down to 0.005%, almost an order of magnitude better.
- ars 3y ago
  If you are misplaced by 1dpi, then your "1200 dpi" is actually 600 dpi. If you got a machine that's accurate to 1200 dpi presumably you want 1200 dpi and not 600.
  - photonerd 3y ago
    That’s not true in this case. It would still be 1200 dpi but the approximation of one curve is off by 1 dpi in some dimension. If all the lines were off, then yes, kinda. Ish.
- itishappy 3y ago
  Oh, I completely agree! "Observable" is pushing the limits of the word past absurdity. 1200dpi would put the resolution of the system at just twice the wavelength of their laser. I feel like that's about the limit of what's possible due to physics [citation needed]. I'm fairly confident their actual performance is less.
- versteegen 3y ago
  > simply adding more nodes improves accuracy exponentially According to another comment, it actually improves at O(n^6).
  - photonerd 3y ago
    I stand corrected! Polynomial..ly
amluto 3y ago
Last time I used one, Epilog’s software was pretty terrible. It seemed to designed around a workflow in which you either design your cuts in CorelDraw and then print to a Windows print driver. I sincerely hope that the upcoming Windows third-party print driver deprecation kills this. (Also, what’s wrong with them? Even ignoring cost, I would rather have a Chinese printer that had a publicly known control interface and supported Lightburn than a “nice” American laser printer that was only operable with bad proprietary software.)
mlyle 3y ago
The 1200DPI resolution is for engraving using rasterization, so, not really the same thing. When you're cutting things on a laser, there's myriad sources of error. Odds are the optical path isn't completely square, so there's some cross coupling between axes. There's drive belts. The laser is often pulsed. There's taper.

somat 3y ago

The shape is there. postscript(and I assume PDF) has an arc primitive. however it is rasterized(drawn) in the reference implementation using bezier curves. Now the postscript to servo control program(g-code?) interpreter might use the same bezier curve approximation, but it might not. I think if it were a formal complaint they would have to positively assert that their machined circles are following an inferior profile rather than just assume they are. g-code sort of sucks as a language. It is very primitive. I always thought it would be cool to have a postscript dialect that supported more than two axis to use as a low level language on computer driven machine tools.