Printing hole for tapping

1. If I printed this object in PLA and needed (3) 1/4-20 threaded holes as shown, and (2) non-threaded holes approximately 1/8" in diameter (for pressed pins) how would you accomplish that. If this was aluminum or steel the drill size for a tap would be 13/64".

2. Is there a way to "beef up" the cross sectional area around the circumference of ALL the holes in the model itself? I don't want to print this completely solid.

3. How much should I under size the printed holes?

4. Is the over hang on the left and right going to be a problem from a printing perspective? If so, is it solvable?

Afterwards I will do some destruction testing on it, braking forces and maybe even some frozen type temps. I believe Polylactic acid has a crystallization temperature but varies with its purity.

Thanks in advance (if you are in the know),
-JW:

 

I am using ROBO PLA filament. I've never used a Slicer. I use MatterControl and it's been printing flawlessly so far (actually impressive). I also haven't played with shell, infill or generated any supports before.

What is the Slicer forum called?

-JWW:

 

Thanks,

So ... there's no way of doing something like this (in yellow) and have it print. Printing the solid cylinders inside the model with a hole to give it some meat.

 

So I gave this a shot but I didn't have supports configured correctly. I didn't save after I selected generate. Thanks to someone off-line via email educating me. I was totally impressed with the print up until it wasn't able to print the overhang. Now that I understand what I was doing wrong any suggestion on the settings I should use to lessen the supports, have it print that "area" well with the minimum amount clean up? It "seems" to me there would be a lot of clean up necessary with my current settings. I also am posting of few pics of the print. Being new to 3D printing I am quite impressed.

 

1) For 1/4"-20 threading you can actually print the threading into the part and not need to tap it at all. If you want to tap it either increase the perimeters or use a 2 body trick
2) For a 2 body essentially you have 2 shapes. The ring you want to tap into being one piece and everything around it as another in the same STL file, like so:


For this I chose 3 perimeters, so that's a total of 6 for it to go around both sides, thus that's 2.4mm thick. Adjust based on the number of perimeters.


This gives you a total of 9 max perimeters around the circle, 6 for the piece you made and 3 surrounding it. This will give you ample material to tap into without needing to use either a super high perimeter thickness or high infill

2) yes the overhang is a problem. You'd either need to print with support, rotate the model so that face is on the build plate, or add a piece of material on the ends to do a bridge

 

Mike,

Thanks for the suggestions. Questions, that's what I thought I tried to do in my model. I drew TWO cylinders, one for taping the other to beef up the taping? Two cylinders instead of a square and a cylinder as you suggested? Maybe I forgot to union them or something.

I did try putting some supports in but the clean up on the top size wasn't that great, pics below. I only printed a "small section" of the overall model. Doing so could of created some other problems too since the model was so small therefore retaining the heat more. At least you can see what I am talking about on the "supports" in the second image below. The first images the supports cleaned up acceptable, in the second image they did not.

 

The square can be any shape you want. You could do 2 concentric rings if you wanted but it's a bit unecessary as you won't be tapping into that much of the material.

The thing you need to make sure is to not merge the geometry. You should be able look at the mesh and see a division between the two.

Supports with PLA can be a real pain. Simplify3D does a good job but can still leave some ugliness. I usually just get some files and grind it down by hand.

Where are the stresses going to be on your part? Do you absolutely need to print in that orientation?

 

Thanks, I'll give that a shot next time I print it. I normally machine these out of aluminum, just wanted to print a similar prototype model is all. I figured a bull barrel type approach would work on the tap scenario. Ignoring stress for now, this seemed to be the best configuration to print it. Are you suggesting this?

I wonder if I could simply design support in the modeling program to begin with.

-JW:

 

PLA ... I didn't think it would be able to print the arc without support. I might look into Simplify3D someday but right now the default is working fine for my intended purposes.

 

Printing with a smaller layer height also helps with that.
I'd still print that with support to get a nicer finish, but should break away cleaner

 

Also, sometimes when i'm putting screw holes in prints, I print them a tiny bit small and then heat my screw up and it self threads it in when the screw is hot.