Super hard nozzles - Test pilots

[PeggyB]

Do you have any results for stainless steel pla? I have a 125 gr. sample lying around, waiting for some nice purpose..
And I am curious how it behaves when changing between a lot of filaments. I am not a bulk user of a specific filament, but use a lot of different materials for testing and prototyping. so, how dirty will the side be?

[Anders Olsson]

Haven't tried stainless, it would be very interesting to see how that works!
You are on my list for a free nozzle, hope I will have them ready before easter.

The ruby nozzle should not be worse than a normal brass nozzle when it comes to changing filament.
I sometimes do the "atomic cleaning" when changing filament, feeding some Bridge Nylon into it and then pulling it out at 135 C, but that is mostly to speed up the process if I for example switch from Carbonfill to white or transparent filament.

[Blizz]

No worries, I haven't been wasting it. It's stuff I was planning on printing (wouldn't have bought a 2.2kg spool if I thought I wasn't going to use it).
Will examine the nozzle after my current batch of stuff is done and see for some pictures.

[LePaul]

Do you have any results for stainless steel pla? I have a 125 gr. sample lying around, waiting for some nice purpose..
And I am curious how it behaves when changing between a lot of filaments. I am not a bulk user of a specific filament, but use a lot of different materials for testing and prototyping. so, how dirty will the side be?

Is that the ProtoPasta stuff?

I haven't seen a lot of prints using that. I did a search on YouTube the other day looking for some. I thought in the robotic stuff I do, this stuff might be quite useful.

I would be really interested to know what Cura settings people are using for these filaments, too.

[PeggyB]

yes, it is protoPasta. I still have to think what to do with it... Saw some examples that were 'rusted'

What I like about these metal filled filaments is the weight, the prints don't look and feel as plastic anymore. Would be really interested in tungsten filament, not for the mechanical properties, but the weight and looks... (it has about the same weight as gold and uranium and melts at 3422 Celcius)

[LePaul]

For my builds, the ability to drill and tap into the finished material (as needed) would be great

[Amedee]

I am doing that quite often.

Unless you print at 100% infill, you need to have the holes in your design, otherwise you will not have any material to tap in (you need 'walls').
Taping (is this the right verb ?) plastic works well, you might even be successful without taping if your hole has the right size.

If you plan to screw/unscrew often or need to tight hard, then use an heli-coil (threaded insert)

[Roboduck]

I've had good luck with printing threads slightly undersized then chasing them with a tap later to clean up the threads. It helps tapping by not having as much material to remove. Also tapping under cold running water helps keep the taps from gumming up. Usually the printed threads are close enough that you can use them as is if you need a stronger thread. I've successfully printed threads as small as #0-80 although larger threads print much better.

https://www.youmagine.com/designs/inch-thread-test

Like Amedee said, if you are planning on threading/unthreading a lot or require strong threads you may want to look into thread inserts. I've used the heat-set brass inserts that work well for small tapped holes. I've also used encapsulated nuts before with success. Just use the "pause at height" plugin to pause the print just before the top of the nut pocket and insert the nut into the print. I usually cover the top of the nut with painters tape or PVA glue to help the filament print over the nut.

[LePaul]

Not to take us further off topic....but the problem with tapping in PLA is that the thread size I use is very, very fine. 4-40 thread (not sure the metric equivalent, maybe 3mm?). Drilling the hole then tapping into a 0.20 layer print is like threading into a thick stack of paper. No real grip for the machine screw.

Maybe 100% infill is better...that's a good idea

[Amedee]

When it come to threads, I'm lost with imperial things...
But to give you an idea, for an M3 thread, I would design a 2.5mm hole and tap it afterwards.
Just make a few tests to see what works for you -- e.g. in my case, I made a small bloc with 2.3, 2.4, 2.5, 2.6, 2.7mm holes and tried to find the best fit. Too big, your screw is loose, too tight you need to get too much material out and the wall becomes too thin.

[Roboduck]

I routinely print #4-40 and #6-32 threads using .1 and .12 layer thicknesses. They won't hold up as well as a brass insert or a nut but they work just as well as a drilled and tapped thread. With threads that small I just use a 1.2 or 1.6 Shell thickness to ensure the threads have enough wall thickness. Try printing my test block at different layer thicknesses to see which one works best for your threads. The block contains threads for #0-80 all the way to 1/2-13 threads.

[LePaul]

That's good to note...how much shrinkage should we account for if I model a hole that needs to be (manually) tapped?

Or...can account for X amount of shrinkage if we model the object with a 4-40 thread hole already?

[Roboduck]

That's going to depend a lot on your printer and settings. I usually model the threads at nominal because they tend to print a little undersized.

[Anders Olsson]

I've successfully printed threads as small as #0-80 although larger threads print much better.

That is really impressive!
I haven't tried printing threads with less than 0.75 mm pitch yet.

I normally print M5 (UNF #10-32) threads with 0.1 mm layer height.
From my experience, I would not go thicker than 0.1 mm layer height for M5 threads (which has 0.8 mm pitch).
It appears that you need at least that number of layers to get a decent looking thread for that size screws.

For the sample holders I print for our neutron experiments, plastic treads and screws really is an advantage since many metals tend to activate when put into a neutron beam, and threading holes in plastic is always a bit risky.

[Blizz]

Sorry I'm a bit late, lots of stuffs that need taking care of.

Managed to make a picture of the nozzle. This is after about 7 hours CF and 3 hours PLA: