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Printing a smooth disc does not work vertically  

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Terry
(@terry)
Active Member
Printing a smooth disc does not work vertically

I'm trying to print a piece of a toy that is supposed to be a round, smooth disc. For stability, I am printing it vertically, i.e. disc is oriented 90% to the horizontal. It has the full supports turned on.

For some reason, the bottom of the disc is always rough and uneven, as in the photos below. Why?

I tried adding 5 raft layers to the supports, but it did not solve the problem. Seems to happen in both .30mm and .20mm.

What might the problem be?

This topic was modified 2 months ago by Terry
Posted : 22/02/2024 4:55 pm
Thejiral
(@thejiral)
Noble Member
RE: Printing a smooth disc does not work vertically

That is a fundamental limitation of printing with FDM printers in such an orientation. Your worries about stability are very valid ones and from that perspective your orientation is the correct one. It is very challenging to make that part look perfect but there are some options how you can improve the result:

Reduce the distance between the support and the objection. That will improve the quality of the roundness but it will also make removing the supports harder (maybe you need to use a cutter).

Print slow, very slow. let's say 10 mm/s, with maximum cooling, for everything. Maybe print two copies of the same part at once, that also helps with cooling.

The Mk3 has only one part cooling fan. So the best result in this case if you orient the part in a way that the part cooling blows onto the flat side of the disk. It looks as if you had it oriented differently, because one side looks nice but the other one rather bad.

PS: Does the part need to be perfectly and completely round? If not, an easy solution would be to cutflat a bit of the bottom, until the overhang is less than maybe 75%. If you want to maintain symmetry one could cut of the same amount from the top as well. 

Mk3s MMU2s, Voron 0.1, Voron 2.4

Posted : 22/02/2024 6:58 pm
fuchsr
(@fuchsr)
Famed Member
RE: Printing a smooth disc does not work vertically

Don't take it the wrong way but just judged by the picture, the overall print quality--not just the overhangs-- look "suboptimal ".  I'm not sure I'd be worrying much about the supports issue until I have dialed in the overall quality of the print  

 

Posted : 22/02/2024 7:16 pm
JoanTabb
(@joantabb)
Veteran Member Moderator
RE: Printing a smooth disc does not work vertically

have you tried printing it tilted back 45 degrees?

with minimum supports to stop the disc falling over

regards Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK

Posted : 22/02/2024 7:17 pm
Terry
(@terry)
Active Member
Topic starter answered:
RE: Printing a smooth disc does not work vertically

This is actually a great suggestion. I guess I'll try that; if it's symmetrical, should look fine. Doesn't technically need to be round! In fact it could even be a square or octagon or some such.

I thought of @joantabb's suggestion to tilt it 45º but the problem is that these little legs are already fragile, hence the need to print the thing in this difficult orientation of 90º. It's part of a larger toy that preschoolers play with, and joins multiple parts together. The ones I printed horizontally had very weak legs that broke right off.

The other thing I thought of was to raise the entire print a millimeter or two above the print surface, hoping the supports would just fill in below and the disk would print evenly. But I couldn't get PrusaSlicer to increase Z; no matter how much I drag it upward, it always pops back down to the plate. I also wondered about adding some kind of pseudo-support to the bottom edge of the disk inside the design tool, but that's both difficult and seems excessive.

Posted by: @thejiral

That is a fundamental limitation of printing with FDM printers in such an orientation. Your worries about stability are very valid ones and from that perspective your orientation is the correct one. It is very challenging to make that part look perfect but there are some options how you can improve the result:

Reduce the distance between the support and the objection. That will improve the quality of the roundness but it will also make removing the supports harder (maybe you need to use a cutter).

Print slow, very slow. let's say 10 mm/s, with maximum cooling, for everything. Maybe print two copies of the same part at once, that also helps with cooling.

The Mk3 has only one part cooling fan. So the best result in this case if you orient the part in a way that the part cooling blows onto the flat side of the disk. It looks as if you had it oriented differently, because one side looks nice but the other one rather bad.

 

PS: Does the part need to be perfectly and completely round? If not, an easy solution would be to cutflat a bit of the bottom, until the overhang is less than maybe 75%. If you want to maintain symmetry one could cut of the same amount from the top as well. 

 

Posted : 27/02/2024 2:51 am
Thejiral
(@thejiral)
Noble Member
RE: Printing a smooth disc does not work vertically

There is the "raft" option in Prusa Slicer if I am not mistaken which should do what you intended, put the entire print on a shallow support layer. This is not a very popular option though I think because the print quality is usually worse than with other alternative strategies. But it is a possibility.

Alternatively, if you want to rais an object entirely above the bed, you need to right click on the object and add a part to it (just a cube or literally anything, it can be absolutely tiny or flat etc). Then you have to combined objects in one assembly and you can select just the original part und are free to raise it along the z-axis because that inserted tiny object stays grounded for the entire assembly. Yeah, I know, not totally straight forward but it works fine. 

Mk3s MMU2s, Voron 0.1, Voron 2.4

Posted : 27/02/2024 7:31 am
Terry
(@terry)
Active Member
Topic starter answered:
RE: Printing a smooth disc does not work vertically

Hm, I could swear I posted an update here, with some photos... disappeared...??

Posted : 28/02/2024 5:00 pm
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