Model to Scale

So I am new to Blender, I am using 2.8 and I have a question about modeling to exacting scale. I create items for scale models that I then 3D print, so getting the size accurate is an understatement. I am getting up to speed with the Scene panel and I am wondering if I am on the right track?

So say I am modeling an object that will be for a part that is going on a 1/32 scale model. I already know that this scales to 0.794mm. So am I correct in assuming if I set the unit system to Metric, the Length to Millimeters and then set the unit scale to 0.794 I will be modeling my Blender project to the correct scale for sending to the 3D printer?

Hope that was a clear enough question? Any advice or help would be highly appreciated!

It’s more complicated than that, but also simpler. The word “scale” repeats itself 3 times, and all are relevant to what you’re doing

  • working scale, the unit you use and the model dimensions, in the viewport
  • object scale, a multiplier. If it’s anything other than (x,y,z) 1,1,1 when modeling and exporting, you’re looking at a model that has its mesh in different dimensions than what you see in the viewport. Not good, so whenever you scale an object or change its dimensions, apply its scale
  • unit scale, also a multiplier. Can be applied to the model when exporting

Thing is, the unit doesn’t export, and you can decide the working scale until such time you want the model in correct dimensions. You could use the default unit, decide it’s millimeters, model, apply object scale, export, and tell the importing application it’s millimeters.

Or, if you use the dimensions of the full size object, decide a suitable unit. Then scale down the model 32x smaller, apply object scale, export.

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Thanks for all the details, very helpful for sure. I do see the Unit Scale tool tip talks about converting Blender units and dimensions, whatever that means. I think with what you said here I can get close at least and run a few test pieces and get this figured out. Thanks for setting me up, really appreciate it!

Yes, testing with something is a good idea. Don’t have to print it, probably enough to check what it looks like in the slicer. If you output an .stl in ascii, you can also open it in a text editor and see if the values makes sense.

The unit doesn’t export, only the vertex coordinates. Default cube is 2x2x2 BU, which in metric is 2x2x2 meters. Exporting it will put coordinates like -1, -1, 1 and 1, 1, 1. When you import it, you could tell the application it’s in millimeters, and you get a 2mm^3 print. If the coordinates are an order of magnitude off, then something went wrong.

You can pretty much forget about the unit scale. The scale can be applied with that too when exporting, but you don’t need it for working and it’s easier to just look at the object dimensions and make sure its scale is 1,1,1. Which you have to do either way.

The viewport has clipping settings, which will need adjusting if you start working too small or too big. If you model for 3D printing a lot, and the scale you work in doesn’t change much, you might want to use an actual unit, perhaps even set up the startup scene so it uses mm by default.

Using an actual unit does give you the ability to input with an unit, it also does conversion so you can input 3in even if you use mm. Blender unit, or none unit, means you can decide and start working right away - It could be mm, cm, inches, or if the reference photo has a coin as size reference, could also use currency as the unit of measurement. Switching to real world unit then scaling or setting the dimensions afterwards should be straight-forward enough.

Most input fields can also do calculations, which can help when sizing the object. It also knows what pi is, if you need to input a circumference.

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Lots of great info here, thanks for taking the time to help me out! The scales I build for range from 1/700 up to 1/24 but not exclusively either direction. I have quite a few printers but mainly use either DPL or SLA because of their high detail prints and I have several PLA printers for applications that dont need super rich detail.

I have been using Zbrush, Maya and Fusion 360 along with some others as well as some dedicated slicer softwares for the finishing touches. The idea here is I would really love to find a solution where I can cut out all that overhead and in a perfect world find one software solution that while maybe not handle all of the workload, at least enough I can cut out most of them and become more proficient with one. Not only that it gets expensive buying 3rd party plugins and addons for all of these so I can extend my toolbox. This is why I am hoping Blender can help me because with the upcoming release of 2.8 my research is showing me this has become a serious contender for 3D design and development and so far I am finding 3rd party support and the community to be one of the best I have seen in my 25+ years working with 3D applications.

Again, thanks a ton for the great information and feedback. You have given me some great information I can use.

Hi, I do a lot of model building. 3d and in scale. What works for me is to simply model in real world scale in 3d. Then save out the part I want to print as an STL file and scale it in mesh Mixer.
That way I only have one master file and I can print it out to any scale I want.
Here are a couple of online scale converters I have found useful

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By the way you might find this video interesting also. Vaughn Ling shows how to create support structures for 3d printing in Blender. He does it in 2.79 but it works in 2.8 also.

Quick 3D Printing Support using Blender’s Skin Modifier

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Thanks a ton for all this info Mash3d, this is some excellent information and I will put it to good use. I like the idea of building at 1:1 and then scale it to my needs. Just that I do custom work for clients who tell me what scale they want, so I tend to just build to the exact scale that I need to print at as its one less thing to deal with. Especially given these models are super high detail and that gets to be problematic when scaling down and would mean I need to leave the model at a low res until after the fact, so again more work. Meshmixer has always been my last step before going to print, but thanks for reaffirming that to be the best call.