How to scientificially determine best torque values?
I have spent an hour looking here and elsewhere. Has anyone tested to see what torque values should be used on 3d printed parts? I notice that Prusa has been repeatedly asked for torque values. Certainly their engineers must have determined these values to design their parts. But I have never seen answers.
Could anyone suggest a process? I am making this up, but maybe something like this: print ten test blocks with hole sizes like 2.3, 2.35, 2.4, 2.45, 2.5 mm. Measure the torque until stripping of these five holes in the ten test blocks. Find the hole size with the greatest stripping torque and de-rate by 20%.
Now I made all that up out of my butt. But is there a proper engineering method to determine this, or maybe my idea will work with different values, I don't know.
(Engineers: I know the formula is T=kDP, but I don't know the coefficient of friction or the desired tension in kilonewtons. So is there an empirical way to determine the torque rather than mathematically?)
We can all throw out ideas, but I'd really like to hear from a machinist or engineer on the proper or standard procedure.
Cheers, everyone.
Tom
RE: How to scientificially determine best torque values?
You should check out Thomas Sanladerer vids on YouTube as well as CNC kitchen as Im pretty sure Stefan did one on this topic too, think it was this one . For example There are various people on YouTube that have tried to approach this with a semi scientific method.
The trouble with all this of course is that theres so many possible variables, filament type, moisture content, print temps (and so inter layer adhesion), hole orientation, thread size/pitch etc.
RE:
Thanks, @Neophyl. A really helpful answer as always. I am grateful.
I will check out those two videos.
Cheers and Happy Thanksgiving!
Tom
RE: How to scientificially determine best torque values?
If anybody follows this thread, maybe this will be helpful. I measured some Prusa-designed parts. Here are the exact measurements. Everything is M3 screws.
-through hole (not threaded) 3.286 mm (the threads pass through)
-hole to be threaded 2.791 mm (the screw buts it's own threads)
-square nut pocket 5.600 mm x 2.150 mm
-hex nut pocket 5.456 mm across the flats
Not exactly the topic in the subject line, but I am going to start with their 2.781 mm hole size and see what the strip out torque is.
I will lose these numbers, so I am putting them here so I can retrieve them later. 🙂 🙂
Tom
RE: How to scientificially determine best torque values?
Testing torque for 3D-printed parts is tricky but doable. Your idea of testing hole sizes and recording max torque before stripping is solid—just ensure consistent print settings and use a torque wrench. Apply a safety factor (20-30%) to your results for practical use. For better strength, consider thread inserts or check if your filament manufacturer provides torque data.