difference in work object size.

[Welshexpat]

Hi good people. I have been using Inkscape for about a year for laser  cutting with no real difficult issues. Bur after reading a post in another forum i saw that the problem I get of importing a saved DXF file into lasercut 5.3 ( yes i know it's not the best but it works fine) and find the size changes usually to a smaller version of the original.
 I have been rectifying this by altering the size in lasercut and then continuing this is ok but sometimes the total selected area in inkscape maybe e.g. 231.226 x 231.226, that sort of thing so it's quite a few numbers to write down or to retype.
 This doesn't take a great deal of time but it would be nice to have it exact.. I assumed this problem was due to lasercut being ....well lasercut, but it seems that there could be something I am not doing in inkscape when saving as DXF.
I always use mm and set this on document properties. When I save in dxf or svg I accept the defaults that come up on screen.
So any suggestions would be greatly appreciated.
Regards Tony.  in advance

[Moini]

Can you share the factor by which the cutting is off?

Is it maybe 72 : 96 ? -> Use a pt template (File -> New from template...)
Is it about 1 : 4 ? -> See here: https://inkscape.org/en/learn/faq/#inkscape-092-my-drawings-are-just-quarter-their-original-size-when-i-open-them-program-xyz

[Welshexpat]

Hi thanks for reply. For example 3 squares 150mm 100mm 50mm same centre. In lasercut they  became 39.6, 26.4,  13.2 respectively. I usually save the file as dxf and svg but of course it's always dxf to lasercut. Inkscape is set up for mm. There is only one dxf in the save as menu as far as I can see. Desktop cutting plotter autocad dxf R14.
Regards

[Moini]

Okay, please see the corresponding FAQ item (your plotter program doesn't support the complete SVG standard):

https://inkscape.org/en/learn/faq/#inkscape-092-my-drawings-are-just-quarter-their-original-size-when-i-open-them-program-xyz

[Welshexpat]

So sorry for not replying sooner. Thanks for the link. After changing the settings a simple 105mm square became 104.9735 mm in Lasercut. That works for me!! Thanks again. 

[Moini]

You can increase Inkscape's precision in the settings, if you should ever need it to be more precise. All those conversions' imprecisions add up (or rather, multiply).
Edit > Preferences > Input/Output > SVG Output