dxf scaling - trying to understand

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gregh
Posts: 2
Joined: Thu Sep 24, 2015 7:34 pm

dxf scaling - trying to understand

Postby gregh » Thu Oct 13, 2016 9:03 pm

I have an svg which I want to laser cut and I need a dxf format (my software won't accept any of the other suggested formats)

I read a few articles that said you need to select the scale as px in the export but although I see the sizes updated, they are still not right.

Steps to reproduce:
- I created a box using http://www.makercase.com/ with outside dimensions 200mm
- I downloaded the svg
- Open the svg in Inkscape 0.91 r13725
- I convert Object to Path so I can make my own customisations
- When I select a single item, the properties say "Width 710 pixels at 90.00 dpi "so that equals 200.37mm. OK close enough, there are various settings in the box maker that may affect the exact dimensions.
- Document properties specify default units as mm, but I don't think that makes a dif.
- "Save as a copy"
- select Type "Desktop Cutting Plotter (AutoCAD DXF R14)"
-select use ROBO-Master, deselect use LWPOLYLINE
- Set Base Unit px
Desktop_Cutting_Plotter_2016-10-13_11-57-22.png
Desktop_Cutting_Plotter_2016-10-13_11-57-22.png (8.67 KiB) Viewed 4265 times

-Open resulting dxf in AutoCad and measure length
------result 282.85mm
-repeat with other base units:
-Set Base Unit:mm; result 79.82mm
-Set Base Unit:in; result 3.143mm
-Set Base Unit:pt; result 226.28mm
-Set Base Unit:pc; result 18.85mm

right now it looks like my immediate solution will need to be Open in AutoCad and rescale before resaving dxf.

Anybody know what I am doing wrong, or have an alternative plugin suggestion please?

Thanks in advance for any advice.

Regards,
Greg
Attachments
Box Parts.svg
(5.54 KiB) Downloaded 204 times

tylerdurden
Posts: 2344
Joined: Sun Apr 14, 2013 12:04 pm
Location: Michigan, USA

Re: dxf scaling - trying to understand

Postby tylerdurden » Fri Oct 14, 2016 2:16 am

Howdy,

I tried a couple of tests:
    Using the original file
    Using test rectangle files in in and mm
    Pasting the largest box panel into a new document (using mm)
It seems the original document may be wacky, because the other files export properly to dxf in their respective units.
Have a nice day.

I'm using Inkscape 0.92.2 (5c3e80d, 2017-08-06), 64 bit win8.1

The Inkscape manual has lots of helpful info! http://tavmjong.free.fr/INKSCAPE/MANUAL/html/

tylerdurden
Posts: 2344
Joined: Sun Apr 14, 2013 12:04 pm
Location: Michigan, USA

Re: dxf scaling - trying to understand

Postby tylerdurden » Fri Oct 14, 2016 7:16 am

tylerdurden wrote:Howdy,

I tried a couple of tests:
    Using the original file
    Using test rectangle files in inches and mm
    Pasting the largest box panel into a new document (using mm)
It seems the original document may be wacky, because the other files export properly to dxf in their respective units.
Have a nice day.

I'm using Inkscape 0.92.2 (5c3e80d, 2017-08-06), 64 bit win8.1

The Inkscape manual has lots of helpful info! http://tavmjong.free.fr/INKSCAPE/MANUAL/html/

gregh
Posts: 2
Joined: Thu Sep 24, 2015 7:34 pm

Re: dxf scaling - trying to understand

Postby gregh » Fri Oct 14, 2016 8:42 am

Thanks for your response. I really appreciate it.

So I tried your 2 further tests (cutting & pasting as well as drawing a test rectangle) and I got the same result as with the original svg. The 200mm object in inkscape measured 282 in Autocad.

So to be clear your result was the same as mine with the original svg, but not with the cut & pasted version or the test box?

The weird thing is that I had other parts of the box which I customised in a separate file, and that came out even larger -what should have measured 200 was something like 700 +. I rescaled both files in Autocad and I have a cuttable dxf now, but I'd love to figure this out.

Maybe I should start with re-installing in case I have a corrupt file somewhere.

tylerdurden
Posts: 2344
Joined: Sun Apr 14, 2013 12:04 pm
Location: Michigan, USA

Re: dxf scaling - trying to understand

Postby tylerdurden » Fri Oct 14, 2016 10:07 am

gregh wrote:So to be clear your result was the same as mine with the original svg, but not with the cut & pasted version or the test box?

Correct.

My test rectangle scaled properly, as did the large box piece (200x150).

FWIW, I used no checkboxes in my export... that seems to work better in SheetCam.
Have a nice day.

I'm using Inkscape 0.92.2 (5c3e80d, 2017-08-06), 64 bit win8.1

The Inkscape manual has lots of helpful info! http://tavmjong.free.fr/INKSCAPE/MANUAL/html/

v1nce
Posts: 696
Joined: Wed Jan 13, 2010 4:36 am

Re: dxf scaling - trying to understand

Postby v1nce » Thu Nov 10, 2016 11:26 pm

Post original svg (before you edited it with inkscape)
It looks like someone inverted the width and height in the viewport
29.7/21 x 20 = 28.25


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