size for rapid prototyping

i’m designing a piece of jewellery in blender and i want to export it to an stl file and get it rapid prototyped. does anyone know how blender units relate to real measurements in this situation?

most rapid prototyping systems just do the scale with the software before it starts.

You would definitely save time if you knew a scale, sorry I have never used blender for that, only Silo and Zbrush models.

It is best to just export a unit cube (keep in mind the default cube is actually 2 units wide - see the Dimensions properties.

Then give that file to the prototyper and ask THEM how physically big that would be, and see what they say. If they say as mmph sez and tell you it all depends, then you are free to use whatever scale you want.

Blender’s only limit is that around .01 blender units it gets dicey, so you want that as your finest level of detail.


where do you print it at? if you want me to check your STL I can do that.
i can open it in Rhino and make sure dimensions are right.

also a small tip would be to have a reference object. lets say you include a cube
which should be 1 cm. export that cube as a separate stl file. in case they need to do scaling they can apply the scaling from the cube scene to the ring scene and have the correct scale ratio.
it is low-tech but saved me some trouble when not having a CAD app at my hands.

I would also offer you to print it at your liquid polymer printer. the costs would be quite low. the polymer we use is fine for investment casting.

taking a reference cube to the shop makes sense, i’ll try that. thanks.

when you model the dimensions in blender correctly you should not have any problem.

this means:

  1. NEVER scale the object, only scale the mesh in edit mode.
    thus make sure you applied scale/rotation in case you did it by accident.

  2. mesh length is not linked to object length. this means when you have an edge of 2 unites and you scale the 3d object by 50% the edge is still 2 unites long and not 1.


If you do a lot of Blender modeling for manufacturing you must read this PDF by Robur.


Sykonort… Let me know what the default cube’s size turns into in stl… I’ve visited a fablab recently and the people there are really interested in that sort of thing.

Once I know what one blender unit (default cube = 1x1x1 blender unit) becomes in stl I can easily write a little script that can convert any blender model to a proper size for exporting.

Then you can just run the script and tell it that one blender unit should be 1cm when you export for instance.


you can simply define the unite in the print software.
there you can set one blender unite equal one inch, cm, mm or what ever.

it is just very important that the 3d object never gets scaled.

thanks for the tip about only scaling in edit mode. i’ve been having some problems with models where i’ve scaled them up and sometimes it works and sometimes it doesn’t. that must have been dependent on whether i scaled them in object mode or edit mode. really useful tip. also, it’s good to know that the print software can be told that one blender unit = one millimetre, that’s a big relief.

fantastic link, thanks for that mate. i’ve done a lot of freeform stuff like subsurf modelling, but i’m not so good at the precise technical stuff. this guide looks really helpful for that kind of stuff. it’ll be good for rapid prototyping and cnc machining.

there was a topic about this
I write my experience there with jewels+3d printing
I dont remember the topic name…

endi we should make those sticky

Here’s the link for Endi’s thread: