Printing a threaded insert and accepting piece

[mthompson239]

I’ve printed many parts with threads and have made several observations about doing it. I can easily print 3/8-16 Bolts, Nuts and threaded Bosses, as shown below.

1. The resulting threads (for me) have always been good enough to mate with intended part (nuts, bosses, etc…).
The fit between mated parts of compatible threads also depends on Shrink and without some thread ‘chasing’ binding can occur. Optionally, the parts can be scaled up/down to compensate for the (common) 2% shrink (generally on the part with the internal thread).

2. The print-process parameters can be dialed-in to get ‘good enough’ parts, especially using ABS and PLA. PETg has some problems but, can also be dialed-in for a useful part.

3. If holding strength is needed, I can accomplish this by one of two way’s (or a combination of them): Increasing the number of Shells and/or Post-Processing with a real Thread-Tap or Thread-Die to ‘chase’ the threads.

Some dialing-in of Shells and Density is needed but, if planning on ‘Chasing’ the threads with Tap/Die, then I make that element of the part as a separate design and print with two processes (no point in printing aspects not needed on other features). They are printed at the same time (as two parts in their correct location in '3-D space'.
Use Concentric infill!

Examples:
The square with center boss: Has two outer shell and the boss has 6 inner and 6 outer shells for cutting threads with a real Tap.

The screws/bolts, black mount with boss have printed threads as does the large Bolt/Nut.

good luck

Thanks for the details reply. Rather not have to tinker with figuring out an X scaling down factor if not needed; but will do so if no other options. I default to 3 shell for all my prints. My ending thread that I will be using is a 1 3/4 so would rather not have to go out and buy a tap for a 2nd process. I default to rectangular, but will give concentric a go. Will also try to print a bit slower as well. The final piece that will have this thread is fairly large so an additional process would be added to accommodate this additional speed variance. Hope to give it a go tonight...will report back.

Thanks

If you need more strength use Owen and go to the glass point value and down.

Sorry...Owen? Glass point value and down? Never heard this verbiage before.

[Raise3D Pro Plus 2]

For strength about to 40% more like with steel parts. The same method to reinforce material.

[greybeard]

Thought I clarify my comment about two parts printed with two process at the same time to produce desired results - hopefully the picture saves me a thousand words

( the Nut is embedded in the Box - done in CAD (in this case, FreeCAD). When printed in a single print with two process, the result is One part with both Box and Nut co-joined as 'One Part')

[mthompson239]

For strength about to 40% more like with steel parts. The same method to reinforce material.

Thought I clarify my comment about two parts printed with two process at the same time to produce desired results - hopefully the picture saves me a thousand words

( the Nut is embedded in the Box - done in CAD (in this case, FreeCAD). When printed in a single print with two process, the result is One part with both Box and Nut co-joined as 'One Part')

For a smaller thread...yeah, i'd do that and call it a day but my final project is for a 1 3/4 thread. Plus the added weight of a nut that size would be bad for the application lol. I've actually done this in the past for a project for my son...worked out great since I had the hardware already.

[zemlin]

Using a .4mm nozzle, I'd go to a .5mm extrusion width. The plastic expands a little coming out of the nozzle, so if you are running an extrusion width equal to your nozzle diameter, the plastic stream needs to be stretched a little during printing. 20% over the nozzle diameter seems to be a good number to get the plastic to stay put on corners and rounds. Also, a 1:2 ratio on your width to layer doesn't allow for a lot of overhang. 1:2.5 on your width to height will help with the overhang builds.

[dkightley]

My tuppence worth...….

One thing nobody has so far mentioned is that if you take a subjective view of a thread, what you're really printing is a very shallow sloping section. It's twisted round into a spiral...but its a shallow angled sloping section. And one thing the FFF printing method is not that good at.....is shallow angles! What you get is a staircase effect...so you're fighting an uphill task even before you start.

The nearest we can get to a SMOOTH thread is going to be a thread with very tiny steps in the surface. So.…..if your threaded hole is printed vertically, make the layer thickness as thin as you can get away with. If the thread is printed horizontally, then extrusion width will be important.

I've never tried printing many threads. I cheat by tapping threads into undersized holes.....but I've never wanted a thread bigger than 8BA, which I challenge anyone to try and 3D print!!

[zemlin]

There are a lot of overhang test prints out there which might be helpful in testing your setup. Here's my version of an overhang test - continuous from 40 to 80 degrees. For a standard thread you'll want to find a setup (layer thickness to width) that will be stable beyond 60 degrees. Also, make sure you're printing your perimeters from the inside out.

https://grabcad.com/library/a-test-part ... -printer-1

[rsworden59]

I printed internal threads in PET-G and used support as another poster mentioned. I was afraid the support would be difficult to get out. but actually it broke loose easily and the support basically unscrewed out of the part. It worked well and gave pretty clean threads. Give it a try.