One thing to watch for in Inkscape - by default, if you click on an element with the selection tool (the arrow), and look at the width and height, this will include not only the width and height of the geometric shape, but also the width of the stroke.
So, for example, if you draw a 10" by 10" square with the rectangle took, then give it a 1" stroke, you’ll find when you click on your square with the rectangle tool it will still show 10" by 10", but if you try the selection tool it will show 11" by 11" (not 12", because the stroke is centered on the edges of your square). This drove me crazy for a long time.
You can fix this by doing “Edit -> Preferences…”, then under “Tools” set “Bounding Box to Use” to “Geometric Bounding Box”.
SVGs can use real units (mm, inches, etc) but many programs create unitless SVG files. The 20”x12” thing is a hack to deal with those programs; whenever you import a unitless SVG into the Glowforge UI if the aspect ratio is 20:12 (5:3) It is automatically scaled to 20” by 12”. If the SVG uses real units no scaling happens. If the file is unitless but not ina 5:3 aspect ratio, the Glowforge assumes 96 “user units” (the default units in SVG) per inch.
Why? According to various discussions it was apparently a design spec for the software. Also apparently, it was implemented such that any Artboad with a 3:5 aspect ratio (h:w) will trigger absolute positioning.
Absolute positioning simply means that it loads such that (0,0) is the top left corner of the bed as displayed in the GFUI. The actual top/left position that the GFUI will allow to be cut is (0.01”,0.01”). Even though these art boards will load at (0,0), you can still move stuff around in the GFUI.
one of my problems was i didn’t have the most recent version of inkscape and one of the things they fixed from the last version was how the size issues export to other programs
It may end up a little bit off because of the “kerf” of the laser. Check and see if the hole you cut this out of is 33/32"? That sounds really big for a kerf width though - depends on the material, but it’s usually closer to 0.01".
Is the 31/32" the size as it’s imported in Inkscape or the size of the cut part? 1" square tool path will produce a smaller actual part because the laser has width just like a saw blade or router/milling bit.
If that’s the import size, older versions of Inkscape tagged files at 90dpi by default so when you open an SVG in another program expecting 72 or 96 dpi, the design gets scaled. Make sure the Bitmap settings in Preferences are set to 96dpi instead of 90dpi. 31/32" is pretty close to the decimal equivalent of 90/96.
it exported as 96 pixels at 96 dpi. The hole is 1"x1", so the kerf is about 1/32". Is there a way to change the settings if you cut centered on the line, or to the inside or ouside of a line? otherwise I will just change it in my drawings from now on to offset outside cuts 1/32"
You probably want to get a digital caliper instead of using a tape to measure it because an offset of .0313" (1/32") will make everything oversized. The laser kerf is only .006"-.01" on average depending on the material and laser settings.
The glowforge seems to always slice down the center, so in Inkscape where the lines have width you need to account for it. Unless they’ve changed something recently or I never figured it out.
If you make your own scale of squares in Inkscape and print it directly and then measure it you should have a scale you can use to enlarge the Inkscape Svg before exporting it?
I am still digging out where all the widgets are and I am sure that the details or the link to an explanation by other would be a way for everyone else who does not know to benefit
