Should Design Models be in MM?.... and Conversion Issues

3D Fabrication
#1

Hi,
I use Fusion 360 hobby version, and I have a few simple designs like custom spacers and holders/clips and things. I typically create my design in inches as the unit of measure.

While I was able to get one design to print, I’ve had issues with my most recent.

  • Is it just EASIER thinking of the whole process; to have a design in mm??
  • like… exporting the STL, importing the STL and slicing it and exporting it to geocode then importing it to print…
  • Does anyone know - if in Fusion 360 you can simply convert your model in inches to MM?
  • Fusion has an EXPORT screen, and in the export screen it gives you an “option” for the units of measure for the export. If my model is in inches and yet I select MM as the unit of measure for the export - does FUSION 360 do a conversion?

It’s rather frustrating to take the time to design something, and then run into issues trying to slice it and print it.

Thanks In Advance for Suggestions and really Answers Here

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#2

Can’t speak to the specifics of Fusion360 >> 3D slicers, but I do laser cut designs and the lasers are also all about that metric system.

I find it depends on…

  1. feel for metric
  2. one’s measuring tools

I designed … a lot … of sheet metal parts in a prior career using imperial so my feel for metric isn’t great. But one can adapt and as more things are specified in metric it’s not hard to adapt

Measuring tools are a bigger stumbling block in some ways. I’ve got rulers, tape measures, calipers in imperial. And getting decent measurements is important. So if it’s something I need tight measurements on I tend to design in imperial for simplicity’s sake.

Now, doing my work in a 2D autoCAD clone it’s pretty simple to take a finished design file, scale globally by 25.4, then proceed to produce production files. Not sure if Fusion360 can do this - either by migrating units (with associated re-dimensioning) or a global scale factor.

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#3

Absolutely. Design it in whatever units you want (inches, for instance), then just change the units.

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There are a lot of ways to get a file out of F360 so you can use it. For 3D printing, my favorite is to right click on the component (or body) and then Save as Mesh. This will give you an stl file and it’s a lot faster than waiting for the cloud-based export translation. If you didn’t set your units to mm in the document settings you can set it here for the stl file. The final dialog box will allow you to save it to your computer.

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EDIT: It’s not obvious from your sketch what’s wrong with your model. One thing you could do is to convert your solid to a mesh, then repair it, then save that as mesh (stl). Either way, some people suggest using NetFabb to repair all stl files before printing.

  1. MESH / CREATE / TESSELATE
  2. MESH / PREPARE / REPAIR
  3. Right click on body / Save as Mesh

Can you do a cross-section cut (Solid / Inspect / Section Analysis) and post that here so we can get a better idea what your model looks like?

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#4

@John_Marlow Thank you so much!!! I converted all my designs to mm, just to eliminate any issues in the slicing and printing process. We’ll see how it goes.

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#5

I claim that my two rules of thumb are all you need to know for 3D printing.

  • A quater inch is 6mm.
  • An inch is 25mm.

With Fusion 360, I stay in mm but often enter a dimension as 1.5". It takes it and displays the dimension as metric.

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#6

As suggested, I can just model in Fusion in inches and use the tool itself to convert, as the screen prints demonstrated. Hopefully that will make the slicing and printing process easier.

Good Rule of Thumbs

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#7

Ditto on Chris’ use of Save as Mesh. Works great.

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#8

I let openSCAD work in mm, and some things I enter in mm, and others I have a constant poorly named as mm that is set to 25.4, so I can simply set something as for example 4*mm, and get the proper 101.6 mm for my 4 inch part.

I also keep a metric dial caliper where I do most of my 3D designs.

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