Mthompson
Posts: 15
Joined: Sat Jan 03, 2015 1:07 am

Printing a threaded insert and accepting piece

Mon Dec 10, 2018 2:23 am

So I designed an insert which will be used to screw two 3d pieces together. The insert prints out 100% proper. However the threads on the accepting pieces print poorly. Using a .4 nozzle for reference. Printed at .2 layer and speed of 40mmm with 30 and 60% infill. Cant seem to get the internal threads to print nice. I have attached a pic from my testing of doing threads. Thread size for reference on the 2" OD part was 3/4-6. Am I asking too much from a .4mm nozzle? I dont think so as I have printed nut/bolt pieces in the past downloaded from Thingiverse.

What factor am i missing here?

Much thanks for any assistance as this is now holding up a final design to be completed.
Attachments
20181210_021908.jpg

Mthompson
Posts: 15
Joined: Sat Jan 03, 2015 1:07 am

Re: Printing a threaded insert and accepting piece

Mon Dec 10, 2018 2:26 am

Maybe this is a better pic to show what I mean on internal threads coming out poor quality.

Raise3D Pro Plus 2
Posts: 66
Joined: Thu Oct 25, 2018 3:03 am

Re: Printing a threaded insert and accepting piece

Mon Dec 10, 2018 3:14 am

Few things and possibilities... The first dry filament, second try to print calibration cube. To check walls quality. You can run over extruded... or opposite. I'm not too sure by the picture. Try layer height 0.1000 mm.

airscapes
Posts: 325
Joined: Tue Mar 06, 2018 10:35 am
Location: Philadelphia PA Area

Re: Printing a threaded insert and accepting piece

Mon Dec 10, 2018 8:43 am

Assuming the basics are set correctly (starting height, extrusion multiplier, speed, temp, cooling if required etc) you may need custom support.. I have made a Kwawu arm for a coworkers daughter who is missing most of her arm from the elbow down. The hand connects to the arm with a 25mm thread and to get those inside threads to print well I have to use supports. I set the support to 40% and generate, then go into custom and remove so I have full support from bottom to top every so often. The attached is printed at 35% infill. You may also want to check your model with 3d Builder for errors, OpenSCAD messes up these threads when it is used to size the files, which I then have to fix with 3dBuilder before printing.
Below I have attached a the factory file of the arm so you can see what I mean. You need to flip the build plate upside down so you are looking up from under the plate to see the the supports inside...
20181210_083150.jpg
Last edited by airscapes on Mon Dec 10, 2018 9:40 am, edited 1 time in total.

mroek
Posts: 147
Joined: Mon Oct 26, 2015 1:47 pm

Re: Printing a threaded insert and accepting piece

Mon Dec 10, 2018 9:33 am

@Mthompson: I actually think your print looks decent. Printing threads is always a bit tricky, and the ones in your picture should function just fine, even if they look a little rough.

wirlybird
Posts: 1238
Joined: Sun Jul 17, 2016 1:32 pm

Re: Printing a threaded insert and accepting piece

Mon Dec 10, 2018 9:36 am

What material? I'd try slowing a bit.

mthompson239
Posts: 84
Joined: Wed Mar 16, 2016 6:19 pm

Re: Printing a threaded insert and accepting piece

Mon Dec 10, 2018 11:01 am

All other prints come out 100% proper. I have a few different machines (Flashforge/PowerSpec/Mono Price) that are basically all the same (clones), and it occurs on the few machines that I tried to print it on. Also, using the spools currently printing with..I dont keep filament long enough to dry out..I print alot.

Material is PLA; should have noted that.

I shouldnt need supports for these small pitches.

What is the suggest speed to print threads? I know kinda dependent on threads..but what might be a good rule of thumb?

mthompson239
Posts: 84
Joined: Wed Mar 16, 2016 6:19 pm

Re: Printing a threaded insert and accepting piece

Mon Dec 10, 2018 11:18 am

Additional pics. And event tried a different size for testing.

*Edit, cant seem to add anymore pics..

greybeard
Posts: 178
Joined: Mon Mar 02, 2015 1:23 pm

Re: Printing a threaded insert and accepting piece

Mon Dec 10, 2018 2:06 pm

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
Attachments
threads.png
3D Print Parts
https://www.thingiverse.com/Still_Breathing/designs

Raise3D Pro Plus 2
Posts: 66
Joined: Thu Oct 25, 2018 3:03 am

Re: Printing a threaded insert and accepting piece

Mon Dec 10, 2018 3:02 pm

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

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