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I want to create a 3D model which can be used in real life. When given some real life dimensions, can we make models in blender with the exact same measurement down to the millimeter? For example I want to make an external cover for a Samsung Galaxy S4. If I measure the S4's dimensions (mm, cm etc), can I use them to create an external cover which actually fits on the phone?

I know many suggests 'SolidWorks' for this type of CAD work but I want to know if this can be done in Blender.

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Yes, you can do this.

To get realistic measurements, go to the Scene tab in the Properties panel and then find the Units section and select Metric.

activating metric measurement

Keep in mind, though, that once you export, all the coordinates are still in "Fundamental Blender Units." There's no information stored in the model about what measurement system was used to make the model. The target system (SketchFab or Shapeways or whoever) will just make an assumption about what units the coordinates are in (often centimeters). You'll have to do a little testing to synchronize Blender's unit system with your target's unit system. It should be a very straightforward conversion, though.

I'd recommend making a unit cube in Blender and exporting that to whatever your target system is. See how they interpret its size. You can then use the Scale setting in that same Units section to control what unit a Fundamental Blender Unit maps to. If your 1m^3 cube is interpreted to be 1cm^3 by the target system, then you just have to adjust your scale by 10^3 or 10^-3 (I'm not sure which).

The smallest length Blender can handle is 1μm. It can't go smaller than that but that should be enough for your use. You can simply type in units (cm, m, mm etc.) but for μm you have to use "um".

It would also be worth your time to take a look at the addon measureit. It will make measuring things in Blender much easier.

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  • $\begingroup$ That was helpful. But the thing is I'm not sure how I can synchronize real world (e.g mm) measurement with blender (mm) measurement. Only way to 'test' is to print and check if it fits because there is no other 'target system'. Is there a authentic method of calibrating both systems? $\endgroup$ – Muhammad Ashar Jul 26 '16 at 15:23
  • $\begingroup$ Since I didn't ever print something using a 3d printer I can't tell you for sure, but there's a 'Scene Unit' option when exporting to .stl. It's description says that the current scene's unit (as defined by unit scale) is applied to exported data. Maybe that's what you're looking for. Also you could spend some time taking a look at the Mesh Analysis tool found in the properties of the 3d view (press 'N') when in edit mode. Here's a link to Blender's docs. And thanks @Matt for the edit, made things a lot clearer. $\endgroup$ – palkonimo Jul 26 '16 at 16:05
  • $\begingroup$ @MuhammadAshar Firstly, "Sync" != "Calibrate." I'm not talking about calibrating the printer. I'm only talking about making Blender and the printer use the same units. $\endgroup$ – Matt Jul 26 '16 at 18:36
  • $\begingroup$ @MuhammadAshar Secondly, you cannot print directly from Blender. You will have to use some other software. Either you have a printer and you'll use its software, or you're using a remote service and you'll upload using their software. Either way, you should have an opportunity to tell the software "use this scale." Even if you don't, remote services like Shapeways will tell you exactly how big it will be before you print it. If that size is wrong, it will be wrong by some factor of 10. Multiply or divide "Scale" by factors of 10 until you get the size you expect. $\endgroup$ – Matt Jul 26 '16 at 18:37

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