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kthesnake

Print Thread on UM3

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Hello,

I am a satisfied recent owner of a UM3 extended. For one of our projects, we need to print a thread (M6 in my case but it doesn't matter).

So I draw a M6 thread on a nut and a bolt and did a test print. At first it didn't work and I thought that it was because the thread pitch was too small (1 mm). Therefore, I increased the thread pitch to 1.5mm (not a standard anymore but because we are printing both bolts and nuts, this is not an issue). And again, it was not working. I told myself that it could have been because of a bad drawing so I downloaded a model from youmagine, print it and again it failed.

Now the diagnostic, I realized that the problem was that the shape of the thread was not symmetric. On Cura, the shape looks like it should be:

\

/

But when I look at the prints it is more like

_

/

My understanding is that it is because of warping... But I am not expert enough to know how to deal with that.

Any idea on how to solve this?

I am printing PLA silver with the standard settings for the highest quality.

Thanks,

K

Edited by Guest

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Perhaps your layer height is too thick to properly recreate the thread?  {assuming you are printing the thread/bolt standing upright and not on its side}  What is your layer height now? Can you post pictures and a link to the model?

Edited by Guest

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Hello,

Thanks for the reply! I tried with the smallest possible thickness (0.06mm). As the pitch is 1mm, even 0.1mm should not be a problem. Attached is a picture of a thread for a M12 (pitch > 1mm).

IMG_20170504_172948.thumb.jpg.e413dc626b02d12baa3b275b487932b7.jpg

This comes from Thingverse Yet ANOTHER Machine Vise. Several (more than 100) people have successfully printed this. You can see clearly that on the right of the picture, the thread seems really nice, while on the left this is not the case. This effect is even stronger on smaller diameters but I do not have a picture here (I could provide one Monday). For the art presented on the picture, I could "force" the nut and the bolt but only if I aligned them with respect to the printing direction (the entrance of the nut is the bottom part). If I do the opposite, it does not fit. For me this is a proof that the thread profile is not symmetrical. I also tried a squared thread profile but it did not work and the same phenomena occurred...

Thanks,

Pierre

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I printed that vise out last week.  I just have the two pad inserts left to do.  Funny, I broke one of those threads in two places after it completed printing and glued it back together.  Fragile!  Need to print another one, though, I might import it into Solidworks and see if I can add cutouts for some nuts at the ends of the threads.  Then I can insert a long, thin, threaded metal rod inside each plastic thread for better strength.  I don't recall the layer height I printed it at, but it was probably .1mm.  Mine printed out with one side of the pitch flatter than the other, too.  Seems better for pushing :)   I'll be more aware during the reprint and post a picture here when it's done.  Gonna do .06 or .05 layers and slow it waaaaaay down.

Oh, and I just viewed the threads in "thingiview" mode and zoomed way in. They seem perfectly symmetrical.

Edited by Guest

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Hello,

Thanks for the reply! I tried with the smallest possible thickness (0.06mm). As the pitch is 1mm, even 0.1mm should not be a problem. Attached is a picture of a thread for a M12 (pitch > 1mm).

IMG_20170504_172948.thumb.jpg.e413dc626b02d12baa3b275b487932b7.jpg

This comes from Thingverse Yet ANOTHER Machine Vise. Several (more than 100) people have successfully printed this. You can see clearly that on the right of the picture, the thread seems really nice, while on the left this is not the case. This effect is even stronger on smaller diameters but I do not have a picture here (I could provide one Monday). For the art presented on the picture, I could "force" the nut and the bolt but only if I aligned them with respect to the printing direction (the entrance of the nut is the bottom part). If I do the opposite, it does not fit. For me this is a proof that the thread profile is not symmetrical. I also tried a squared thread profile but it did not work and the same phenomena occurred...

Thanks,

Pierre

 

Warping caused the inconsistent profile of thread. The problem with the bolt in this vise is that the thread seems to have a ISO standard 30 degree angle. It's too steep for most printers. Only printers with strong part cooling fan could handle it. Normally if you create your own bolt, do it with 45 degrees overhang.

With average part cooling fan, to improve the overhang print, print with slow wall speed such as 10-15mm/s, in such case the fan can cool the stroke before it warps. As long as the wall speed is slow, it should work fine with 0.1 even 0.2mm layer.

Edited by Guest

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