Sheetcam - DXF or SVG

Discussion in 'Cutting Systems' started by SignTorch, 4/11/15.

  1. SignTorch

    SignTorch Artist

    Roles:
    • Vinyl CuttingVinyl Cutting, CNC RouterCNC Router, Designer / ArtistDesigner / Artist, Hobby / PersonalHobby / Personal
    Brands:
    • Corel DrawCorel Draw, Adobe PhotoshopAdobe Photoshop, V-Carve ProV-Carve Pro
    Location:
    Vidor, TX
    First, the golden rule for vector graphics is NEVER USE DXF UNLESS YOU HAVE TO OR WHEN YOU "KNOW" IT WORKS BETTER (for some reason)

    In sheetcam you can import SVG files, so you don't have to use DXF

    Some DXF files might work better than SVG, like SignTorch DXF files import to sheetcam perfectly - in that case you should use DXF - in which case you have to use sheetcam scale factor to size the DXF and you have to cut it as is because you can't really edit vectors in sheetam
    sheetcam-signtorch.

    But some DXF files, like if the format is R14 or greater and the DXF contains splines, like if exported from corel draw or inkscape or most ordinary vector graphics applications - then sheetcam doesn't handle splines very well at all and there will usually be some places that just don't come out right - in which case it's better to not use DXF - most of those applications also export SVG

    sheetcam-dxf.

    And, in sheetcam, even SVG format doesn't seem to import perfectly, but SVG usually comes out better than the equivalent DXF

    sheetcam-svg.

    And here is what all of the above is supposed to look like

    sheetcam-vector.

    The SignTorch DXF works because it has tangent continuous arcs that are ideal for CNC purposes which sheetcam can use as is

    The SVG has bezier curves - sheetcam has to convert that to arcs - accurate to within some finite error tolerance - because bezier curves cannot form perfect arcs - so there will always be some deviation - and sometimes there will be small but outright inaccuracies

    The DXF come out terrible because in this case it was an R14 DXF from inkscape which contains splines - which sheetcam obviously misinterprets in some places for some reason - and many CAM programs don't even do that good or don't accept splines at all - or some programs digitize splines into many tiny line segments - that only works if your machine has constant velocity and high acceleration

    sheetcam-lines.

    Ironically if we import the previous segmented DXF into sheetcam - it comes out as good or better than SVG

    sheetcam-lines2.

    The bottom line is that - in sheetcam or any other CAM software - your mileage will vary with different images in different formats in different software - the only way to know what works best is to test every option and never assume that what might work in one case will work the same in all cases.

    Even though SignTorch files and formats are very very consistent - so every file and format is the same and should come out the same in every CAM application that supports that format - that is not always the case - even if they were perfect - there would still be problems - because various combinations of software and image formats are not perfect..

    go figure.... anyone not confused by all that please take over and set us all straight.....
     
  2. SeanP

    SeanP member

    Roles:
    • Plasma CuttingPlasma Cutting
    Brands:
    • Corel DrawCorel Draw, HyperThermHyperTherm, Adobe IllustratorAdobe Illustrator, Mach3Mach3, Adobe PhotoshopAdobe Photoshop, SheetCAMSheetCAM
    Location:
    Co Kerry, Ireland
    That's a very good article there Gary, explains it well!
     
  3. kl fergus

    kl fergus registered

    GARY, YOU OPENED MY EYES - I HAVE SEEN THE EXACT EXAMPLES YOU ARE TALKING ABOUT AND I HAVE BEEN UNDER THE GUN TO PERFORM AND THAT IS ALWAYS WHEN IT HAPPENS. LINES NOT CONNECTING THE WAY IT SHOWS AND THEN THE NEXT TIME I USE IT- IT WAS PERFECT. SO GO FIGURE NOT ALL PROGRAMS WORK ALL THE TIME WITH OTHER PROGRAMS AND THE SAME PROGRAMS--NOW I AM GETTING CONFUSED I THINK YOU UNDERSTAND- YOU STARTED IT-- THANKS GARY I SLEEP BETTER AT NIGHT NOW , CAUSE I AM NOT THE ONLY ONE!!
     
  4. Pimp66

    Pimp66 member

    What if you use Adobe Illustrator to design? Does it still have the same issues?
     
  5. SignTorch

    SignTorch Artist

    Roles:
    • Vinyl CuttingVinyl Cutting, CNC RouterCNC Router, Designer / ArtistDesigner / Artist, Hobby / PersonalHobby / Personal
    Brands:
    • Corel DrawCorel Draw, Adobe PhotoshopAdobe Photoshop, V-Carve ProV-Carve Pro
    Location:
    Vidor, TX
    I would suppose so - afik the only sure fire way to avoid the issue(s) is to use DXF with (tangent) arcs - afik the only way to do that in illustrator is to use the exdxf plugin to export (R12 compatible) dxf with arcs - but I haven't tested that lately
     
  6. Pimp66

    Pimp66 member

    ok thanks for the info!
     

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