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3D Printing - Tolerances To Create An Assembly

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I've got to produce a prototype of an assembly for my project. Our University uses 3D printing, but the finish quality isn't amazing, the models always have ridges on the surface.

 

I've got an assembly in solidworks with concentric and tangent mates that are of equal diameter/size to their parent component and was wondering if and by how much I should reduce the inner component size by to make sure they are functional when the prototype is finished... Should I combine the parts into one part file with a tolerance or prototype each component separately and assemble by hand (which would require a redesign of the assembly)?

 

Any advice will be much appreciated!

 

Mike

 

post-50737-0-35345700-1304863396.jpg

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In my experience their is no hard and fast rule for this. 3D printing is a generic term, every different process and machine will have different levels of fidelity in all 3 axis (usually very fine in X and Y and coarser in Z which results in the stair stepping effect).

 

You can try to align your part when you print it so that you get the most accurate dimensions where you need it, but that may not always be possible.

 

It looks like you have some flexible joints and living hinges. You may need to account for the brittleness of the printed parts which will not be the same as a natural material. Typically when I model SLA parts I will give .5mm on each side for anything that needs to fit together. Also keep in mind that if you are going to paint or prep your parts afterwards, sanding will remove additional material and painting will add material.

 

The best way to do this is usually to mock up a sample part that is very simple, but create a few different offsets to test how much room you need in your 3D to get a good fit on the actual parts. Usually if they charge you, that little test part will be cheaper than making your full model, finding out it doesn't fit together, and having to print it all over again.

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Hi,

 

I have an Objet 30 printer, for gaps between working components I leave a gap of 0.1mm (which is 3 times the layer thickness). If you are interedted I run a printing bureau in the UK. I have only just launched, and will have a new website up and running soon (the current one is not great). The address is www.3dprint-uk.co.uk if interested. I also offer free 3D prints in a monthly competition - upload and you may win!!

 

Best of luck with the rest of it!

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