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How do I add the correct spacing around a mate?

Question asked by Pepijn De Vos on Jul 30, 2018
Latest reply on Jul 31, 2018 by Glenn Schroeder

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I'm sure this is a super dumb question, but I just don't know the right terminology to google my answer.

So I've made a case for a product with a battery cover that clicks in with some clips.

I want to 3D print both the case and the cover, but some random dude in a Youtube video mentioned that a classic rookie mistake is to make them the exact same dimension, which will produce a really tight fit, or no fit at all.

But I can't find out how to avoid this problem.

So far I've tried to manually make my cover 0.5mm smaller (no idea of this is a reasonable number), but that gets really nasty around all the clips to make their alignment and size correct, because now I have to "spread" this difference along the edges of the cover.

So I gave up on that, as I simply could not get it right, and things kept clipping or have too much space.

I found some videos on tolerances, which is more about variance than the tightness of the fit.

What I want is basically design my cover to the exact dimensions and then apply some "inset" to make it fit smoothly.

This is such a common thing that I'm sure there are smarter ways to do it than manually adjusting all your dimensions by small fractions of a millimeter.

Glenn Schroeder Jul 30, 2018 11:23 AM

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Welcome to the forum. This isn't something I do very often, but one option might be to create a second configuration of your Part and use the "Move face" command to enlarge the Part on each side by the desired value (suppress this feature in the original configuration). Be sure to select each exterior face when using the feature.

Someone else will likely have a better idea, but if not this might be worth trying.

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Glenn Schroeder Jul 30, 2018 11:23 AM

Someone else will likely have a better idea, but if not this might be worth trying.

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Pepijn De Vos @ Glenn Schroeder on Jul 31, 2018 7:06 AM

Thanks, this works great. I have one problem: After moving the faces, the dimensions for the prongs rebuilt themselves based on the new moved faces, moving them to the wrong spot. How can I prevent this?

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Glenn Schroeder @ Pepijn De Vos on Jul 31, 2018 8:23 AM

Pepijn De Vos wrote:

Thanks, this works great. I have one problem: After moving the faces, the dimensions for the prongs rebuilt themselves based on the new moved faces, moving them to the wrong spot. How can I prevent this?

As I said above, this isn't a feature I use regularly (in fact, I believe doing research to try to help you was the first time), so I'm afraid I can't answer that. Without seeing the Part file I doubt if someone that is more familiar with it could answer it anyway. Can you attach the file here? See How can I attach a file to a forum post? if you aren't familiar with the process.

You might also want to un-mark my earlier answer as correct. With the Discussion marked as answered people will assume you no longer need help and might not look.

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Newell Voss Jul 30, 2018 11:46 AM

A number of variables go into determining appropriate size/fit (feature/material/resistance force needed/etc..) Average printers will get you around .005"-.010" accuracy (.5mm is about .020"). The best method is to make an educated guess (start small as you can manually refine a 3D print to get an idea how far off you are.), print and then refine the design based on your tangible prototype. You only need to apply clearance where you will have contacting surfaces that need it such as lips/grooves, snap features, etc. Dont scale/clearance your whole model if you dont have to. The move face command is very helpful as Glenn mentioned.

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Kevin Chandler Jul 30, 2018 12:28 PM

Hello,

Another factor to consider is whether there will be post-printing operations.

If you require a finer finish than what can be provided by the printer (or at least at the print resolution you're willing to wait for), then you'll have to clean up the surfaces.

This will take away some material...whether it's enough, that I dunno.

Cheers,

Kevin

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5 Replies

Glenn Schroeder Jul 30, 2018 11:23 AM
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Correct Answer
Welcome to the forum. This isn't something I do very often, but one option might be to create a second configuration of your Part and use the "Move face" command to enlarge the Part on each side by the desired value (suppress this feature in the original configuration). Be sure to select each exterior face when using the feature.

Someone else will likely have a better idea, but if not this might be worth trying.
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- Pepijn De Vos @ Glenn Schroeder on Jul 31, 2018 7:06 AM
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  Thanks, this works great. I have one problem: After moving the faces, the dimensions for the prongs rebuilt themselves based on the new moved faces, moving them to the wrong spot. How can I prevent this?
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  - Glenn Schroeder @ Pepijn De Vos on Jul 31, 2018 8:23 AM
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    Pepijn De Vos wrote:
    
    Thanks, this works great. I have one problem: After moving the faces, the dimensions for the prongs rebuilt themselves based on the new moved faces, moving them to the wrong spot. How can I prevent this?
    
    As I said above, this isn't a feature I use regularly (in fact, I believe doing research to try to help you was the first time), so I'm afraid I can't answer that. Without seeing the Part file I doubt if someone that is more familiar with it could answer it anyway. Can you attach the file here? See How can I attach a file to a forum post? if you aren't familiar with the process.
    
    You might also want to un-mark my earlier answer as correct. With the Discussion marked as answered people will assume you no longer need help and might not look.
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Newell Voss Jul 30, 2018 11:46 AM
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Correct Answer
A number of variables go into determining appropriate size/fit (feature/material/resistance force needed/etc..) Average printers will get you around .005"-.010" accuracy (.5mm is about .020"). The best method is to make an educated guess (start small as you can manually refine a 3D print to get an idea how far off you are.), print and then refine the design based on your tangible prototype. You only need to apply clearance where you will have contacting surfaces that need it such as lips/grooves, snap features, etc. Dont scale/clearance your whole model if you dont have to. The move face command is very helpful as Glenn mentioned.
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Kevin Chandler Jul 30, 2018 12:28 PM
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Hello,

Another factor to consider is whether there will be post-printing operations.
If you require a finer finish than what can be provided by the printer (or at least at the print resolution you're willing to wait for), then you'll have to clean up the surfaces.
This will take away some material...whether it's enough, that I dunno.

Cheers,

Kevin
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How do I add the correct spacing around a mate?

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