Question about metric vs. imperial units

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Question about metric vs. imperial units

Brant Merryman
Hi. I'm trying to work with a company that does laser cutting. I have been using OpenSCAD for a while and I'm pretty comfortable with it, so I decided that perhaps the easiest way to specify what I want him to cut for me is using scad.

I created a 2D object representing the piece I want to have cut. I removed all of the holes that I need to have cut, as well as created the outline. As with my other scad projects, all the sizes were in millimeters.

I exported the file as a dxf and emailed it to the gentleman. He was importing it into Rhino3D.

He replied to my email and said that while he could read the file, it was huge.

The reason I suspect this might be a metric vs. imperial issue is that I once saw a post from someone who had put an STL file on Thingiverse who had a similar problem in that when people imported his file into Blender it was very small. He said to scale it by 25.4x in order to get it to come out right. So, I scaled his files by 2540% and they came out what appears to be the correct size when I printed them on my 3D printer.

So, based on that tiny bit of knowledge, plus the fact that the laser cutting guy said my object was ' much larger than 32" ', I'm thinking that perhaps it might be the exact reverse of the problem I had with the other parts.

Does someone maybe have knowledge of this issue who can explain what is happening in more detail and tell me if there is a way (perhaps some SCAD command) to set or translate the file into a different units?

Thanks!

Brant Merryman
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Re: Question about metric vs. imperial units

kintel
Administrator
On 2013-03-05, at 15:39 , Brant Merryman wrote:
>
> Does someone maybe have knowledge of this issue who can explain what is happening in more detail and tell me if there is a way (perhaps some SCAD command) to set or translate the file into a different units?
>
It sounds like his Rhino3D is configured to default to inches for DXF import. Since we don't specify the units in OpenSCAD, the default is chosen instead of millimeters.

Rhino can be set up to use millimeters, see e.g. http://faculty.etsu.edu/hemphill/entc2170/assign34.htm
It would be interesting to know if that works - then we would know what the problem is.

It could also be possible to encode mm as units in the exported DXF files. However, I'm not certain that's the best idea since other people might consider OpenSCAD's unitless designs in any unit of their choice.

In any case, you can always use a top-level scale() in OpenSCAD to scale your entire design.

 -Marius