Author Topic: DXF Dimensions  (Read 428 times)

nibbler

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DXF Dimensions
« on: November 06, 2018, 11:40:39 PM »

I just tried my first DXF and what can I say, just as my former experiences with that filetype: it sucks.

Anyway, to the problem, I followed Zax´s  Inkscape DXF guidelines. First I had no scaling options in Inkscape 0.91 so I upgraded
and set the document to mm 160x160 scaling 1, then I exported just having the "px" selected in DXF export.

Opening in T2Laser it would help to see the dimensions (i.e. in the lower left corner right to "Ready") ?
Output size says something about 500x500mm

I took a look in the G-Code and it starts moving to 400mm ! So the scaling is absolutely wrong.

I was not sure if the output size is the document size or the drawing size so I did the math

160x160 mm document size end up in 547.2x587.7 mm that means the output size should be the drawing but
that is 133.323x150mm

587.7 / 150 = 3.918
547.2 / 133.323 = 4.104

That means the drawing is even distorted ? Did I mention that I hate DXF?

100mm are 283,464 pt
100mm are 3,93701 inch

So that would be close to an inch/mm problem but the settings in inkscape are mm.
T2Laser Force Conversion in Override DXF Units turn out

13899.0 x 14926.6 that is much closer to what it should be, just factor 100.

Choosing mm in Inkscape DXF export turn out 144.8 x 155.5 mm in T2laser.

So what is the trick, apart from hating DXF? ;-)



 

Zax

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Re: DXF Dimensions
« Reply #1 on: November 07, 2018, 04:37:11 AM »
You should get accurate sizes in DXF, that's the beauty of the format - real world dimensions.

First, make sure your machine is calibrated. Use my test files in the Help / Samples menu and check it, calibrate in the menu if needed. If you change the belt tension (or just over time as they stretch) you'll need to re-adjust the calibration but it's simple using my menu.

I believe the latest version of Inkscape works if you select mm for the output, with T2Laser override options disabled.

Draw a simple square with the lower left at 0,0 and say 100 x 100 and experiment with the export to get it correct. Once you have it worked out the DXF format is very reliable.

nibbler

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Re: DXF Dimensions
« Reply #2 on: November 07, 2018, 07:51:04 AM »
I haven´t made a program to paper comparison yet but the "output size" in T2laser are the outer dimensions (rectangle) of the drawing, am I right?
Then I probably should work with mm in output.

Zax

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Re: DXF Dimensions
« Reply #3 on: November 07, 2018, 08:30:41 AM »
Everything is mm as that's what Grbl uses.