Issue With Bodies Fitting Together In The Real World Once 3D Printed

[Anonymous]

Thanks for reading my post. I'm out of ideas on how to fix my problem, and I'm really hoping someone has a simple answer that I missed!

I have been making a pendulum clock by designing it in Fusion 360, and then printing all the parts on my 3D Printer. However, the frame is much larger than my printer bed, so I cut the frame into pieces in Fusion and printed them separately. I added notches and holes in the split frame pieces so they would "snap" together once printed, and thus will become a sturdy, solid frame. 

Getting the pieces to "snap" together is where the issue comes in.

In Fusion the pieces articulate perfectly. The 6mm notch fits right into the 6mm hole, but that doesn't work in the real world once the parts are fabricated. All parts need a little wiggle room through either having a slightly larger hole, or slightly smaller notch. 

Is there a way in Fusion to automatically add extra space around all surfaces that articulate together, so that they actually fit together once fabricated?

Every space that touches another needs a little buffer room. This is true even with the most precise settings on my 3D printer, and is true when I make things with my amazingly accurate CNC machine. Currently I'm modifying each surface that snaps into another one at a time, and it is exhausting. Example being that the hole stays 6mm, and I use the "Q" (offset faces) function to make the notch have only a 5.8mm diameter.

• Screenshot 1 you see a few of the pieces fitting together in the geometrically perfect world of Fusion.
• Screenshot 2 you see the holes created to receive the notches from the other piece.
• Screenshot 3 you see the notches meant to go into the holes.
• Picture 4 is the front of the actual printed and assembled parts.
• Picture 5 is the back of the actual printed and assembled parts.

screenshot 1 - Multiple pieces of frame fitting together perfectly

screenshot 2 - One piece with added holes to fit with another part

screenshot 3 - Part with pegs to go into the holes of the other part

picture 4 - front of assembled frame parts

picture 5 - back of assembled frame parts

I am also open to other ideas that accomplish the same goal. I used the pegs and holes (of different sizes) because I could make it so them only fit one way. This helped reduce the chance of incorrect assembly when I was looking at around 75 different pieces for the whole clock. I ended up having to drill the holes slightly larger on all pieces, and sand the flat surfaces so the pieces fit flush.

I apologize if this is not the correct forum to post this question. I appreciate any help anyone can offer! 

Thanks!

[davebYYPCU]

It’s called Tolerance Testing, draw samples and test with them, when done,

adjusting the parts with known allowances for you Printer and filaments.

Quick fixes like non uniform scaling in the Slicer is haphazard.

Might help save time and plastic....

[Anonymous]

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Every space that touches another needs a little buffer room. This is true even with the most precise settings on my 3D printer...

Calibrating your 3D printer should alleviate or eliminate this problem. 

Try googling for information on how to calibrate your printer (or software that runs your printer) for dimensional accuracy.

[Anonymous]

This sounds exactly like what I'm looking for! Can you point me in the direction of some resources you recommend for learning about doing Tolerance Testing properly, AND also about how to universally adjust parts in Fusion with these known allowances?

Any direction would be greatly appreciated.

Thank you!

[Anonymous · Accepted solution]

I think I figured out how to do this better on my own! After reading a lot of threads that didn't fix this issue, but danced around it I tried a bunch of stuff in Fusion and finally stumbled across something that is FAST and works very well.

Here's the steps to follow!!!

1.  Without anything selected go to the "Select" drop down located in the top, horizontal menu.
2. In the "Selection Filters" area uncheck the box that says "Select All" and then check the box that says "Body Faces". NOTE: "Select Through" should remain checked.
3. Exit out of that menu making sure you are still using the Window Selection tool in general.
4. Now click on the face of one of your objects you wish to modify and hit the "Q" button on your keyboard. This will open the "Offset Faces" panel.
5. With this panel open now window select the entire area you wish to add a buffer to. NOTE: This action will deselect the face you initially selected before you hit the "Q" button  on your keyboard, so make sure to select it again while holding shift if it's a face you also want to modify.
6. Now in the "Offset Faces" panel you should have the following parameters:
   1. Where it says "Faces" there should now be all the faces you want to buffer all selected in one simple move (next to the arrow mine says "20 selected" in this instance).
   2. Where it says "Offset Type" you should select "New Offset" from the dropdown.
   3. Where it says "Distance" you should now enter what you need depending on the accuracy of your 3D printing operation (I used "-0.2mm" in this example which is important to remember, because it will remove material from both sides of your joint so you will lose 0.4mm total).
7. Now hit "OK" in the "Offset Faces" panel and be amazed that a little buffer room now exists all around your joint!
8. Export your STL file and print in the slicer of your choice.

This is going to be a game changer for my hobby 3D prints. No more ridiculous time spent individually selecting and offsetting the faces. No more time spent sanding and fixing my prints after they are made. They really will just fit together now.

As a heads up, even though this is way easier there is still a good chance you'll accidentally select one too many or one too few faces without noticing. So make sure to check your model thoroughly before exporting as an STL. It's also good practice to save a version before doing this that has no buffer and/or at least making a copy of all the bodies your going to mess with before altering them. 

I have not found another thread yet that actually gives an answer to this problem effectively. I hope a lot of people see it. Even an hour of Lars Christensen tutorials where the second video specifically addresses this topic doesn't actually help you do it this fast (videos sourced below).

https://www.youtube.com/watch?v=Zvvug3wK7SI&t=11s

https://www.youtube.com/watch?v=uTW78sIznUc

[Anonymous]

Hey, I had accepted your answer as the solution, but I had to take that back. From reading your answer I thought that you could change the tolerance within Fusion 360. You can change the tolerance in the CAM section, but since I'm 3D printing the CAM section is not helpful.

Still a big thanks to you for your reply. The term "Tolerance Testing" was new to me, and it lead me down a whole different Google wormhole. Piecing together that knowledge eventually got me to stumble across my own novel solution while trying various adjustments in Fusion 360. Sincere thanks, I could not have figured out a solution so fast without your help!