PETG "tacky" when used on threaded prints any solutions?
I have an issue when using PETG and threaded prints, the finished print seems to be "sticky" when trying to thread the two parts together. Is this common? Has anyone experienced this? With the MK4S you can print to some pretty tight tolerances so when I print a nut and a bolt I leave 0.5 to 0.7 MM gap between my design dimensions. If I'm using PLA they'll thread together right off the printer but with PETG there seems to be some tackiness on the surfaces preventing smooth movement. This is also happening on flat surfaces, a lid on a box for example. Is this common or am I missing something, PETG is much more user friendly with the MK4S and I'm using it more. Now I'm experiencing these issues and I have to reach out and see if there's any solutions... anyone? The other possibility is shrinkage with my tight tolerances which I'm testing now, but from what I've read PETG has the one of the lowest shrinkage rates. If anyone has experienced these issues Please reach out share some insight, and as always thank you in advance for responding.
(Prusa slicer, and Fusion360 for design) C
RE: PETG "tacky" when used on threaded prints any solutions?
It's all about the clearances. You just need to play with the clearances until you get the fit you want.
Depending on the thread size I often run a tap into the hole after printing, and a die over the screw of I have the right size one.
Another thing to consider is the seams. Those can get in the way making it difficult to turn. I've recently printed some screws with the scarf seams and that definitely helped.
@brian-12 has the essence, you need wider tolerances for PETG than PLA. It prints hotter and has a longer cooling curve so it sags and settles fractionally more; imperceptible until two high precision parts interact.
Cheerio,
RE: PETG "tacky" when used on threaded prints any solutions?
I started modeling my threads with the coil tool instead of the thread tool because it is easier to apply the required clearance.
RE: PETG "tacky" when used on threaded prints any solutions?
Pardon my limited experience in this area, could you please explain this in a little more details? If I design a screw and a bolt in fusion360, where do I adjust the tolerances exactly? I can adjust tolerances for other parts usually pretty ok, but the screws always baffle me...
PS: thanks @Brian-12 for the tap and die idea btw, didn't think about that!! The forum is a continuous source of intelligent suggestions, amazing.
RE: PETG "tacky" when used on threaded prints any solutions?
Pardon my limited experience in this area, could you please explain this in a little more details? If I design a screw and a bolt in fusion360, where do I adjust the tolerances exactly? I can adjust tolerances for other parts usually pretty ok, but the screws always baffle me...
PS: thanks @Brian-12 for the tap and die idea btw, didn't think about that!! The forum is a continuous source of intelligent suggestions, amazing.
I don't use fusion as I have SolidWorks, but the easiest way to increase the clearance is to increase tap drill size for the threaded hole. Not sure how to do that in fusion, but in SolidWorks you can adjust the size of the tap drill in the hole command window.
RE: PETG "tacky" when used on threaded prints any solutions?
This should help
I don't use your software but @brian-12 is on the right lines again. In essence you increase (female) or decrease (male) the diameter of the thread while retaining the same pitch and profile. PLA will often work at 0.2mm tolerance or smaller whilst PETG may need 0.5mm.
Cheerio,
RE: PETG "tacky" when used on threaded prints any solutions?
thank you all for the insight, it has answered my questions. Diem has it right, by increasing tolerances when using PETG the surfaces will match much smoother. Based on my test pieces it did work quite well. A few words about Fusion 360, the web (free-private non-commercial use only) version is limited while still powerful in my opinion it has its limits. When it comes to thread sizes custom sizing is not possible, after selecting the cylinder surface to thread it uses that diameter to set thread size your options are more about thread type i.e metric, ANSI, pipe thread etc. I f you have a 40mm surface it set a 40mm thread then you choose type. I just can't justify a paid subscription. All in though a very good program for my limited design needs.
Thank you all again for the responses it has solved my issues, next up matching PLA up against PETG.
C
RE: PETG "tacky" when used on threaded prints any solutions?
same here: thanks a lot for sharing your insights on threads!