Round on model supports  

RE: Round on model supports

If you will post your .stl file (you will need to zip it to attach here) I will sure give it a try.

My first hunch is to use a box or cylindrical support blocker on the bottom part, along with the 'everywhere' support option, but I would want to try it to get the feel of how it would work.

RE: Round on model supports

Thank you. File zipped and inserted. Had tried to upload the file originally but no-go. wheel cap v102

RE: Round on model supports

I do not see the attachment, sorry.

RE: Round on model supports

Try 2. Now I see a link posted. Must have deleted both after inserting duplicates at first.

RE: Round on model supports

Ok, let me finish up a couple of quick things and I'll give it a try.

RE: Round on model supports

From your image and what I can see in the 3mf file, I think what you're seeing is an artifact of how PrusaSlicer generates supports. Regardless of whether you use a support enforcer on top, or supports everywhere and a blocker on the bottom, it only creates support interfaces where you'd want them, under the overhanging lip and the flat area below. However, it also creates these walls on the outside that are not actually connected to the model (so they should come off clean) but act as the base for the first layers of the bottom and top support interfaces, which you can clearly see in the preview when you zoom in to where the (dark green) support interfaces start. 

I'm curious if anyone has an answer to this. I have just got used to PS producing what looks like an excess of supports (compared to say Cura) because I found that with the z distance set to 0.25 they come off super easy (unlike Cura).

RE: Round on model supports

I'm getting pretty much the same thing you are.  I want to play around with it a bit more.

And, OBTW, I recently did an item sliced with Cura with the Z distance at .25, and it broke away cleanly.

RE: Round on model supports

I agree the excess support material does cleanly break away so that is not an issue (printed it). My concern is the wasted print time and the logic breakdown in having it to begin with. This model intentionally has the upper overhang shallower than the horizontal base below it in an attempt to help the slicer know it does not need any material going all the way down to the print bed. 

Videos of random face models show on model only supports without going to the print bed and this in my mind is a much simpler scenario with a nice clean flat spot to start with. 

RE: Round on model supports

Ok, the best I can seem to do is to set supports to everywhere and do a cylinder support blocker ending just below the lip.  I carefully inspected the support and although it appears to get quite close to the object just below the lip, it does seem to have some daylight in there.

If this were not such a long to print print, I would try it to be sure.

Since the support material is sparse, it should not add that much material to the job, and the time may still be long.

I've recently been using the following parameters for almost all supports.  I think it was Bobstro who originally posted these.

0.25mm z distance.
75% xy distance.
3mm support spacing.
4 interface layers.
0.2mm interface layer spacing.

RE: Round on model supports

@mike-bemis

I am not disagreeing with you. I like PrusaSlicer but the way it generates supports clearly leaves a lot of opportunity for improvement. I have plenty of examples from my own designs where I can't explain for the life of me why it generates so much support.

RE: Round on model supports

Posted by: @fuchsr

@mike-bemis

I am not disagreeing with you. I like PrusaSlicer but the way it generates supports clearly leaves a lot of opportunity for improvement. I have plenty of examples from my own designs where I can't explain for the life of me why it generates so much support.

One of my do-it-list items is to study the code for PrusaSlicer (and for the firmware) to get a better handle on why various things happen the way they do.  That, of course, is on the back-burner section of the do-it-list.  😉

RE: Round on model supports

@jsw

So it continues the material down to the print bed still if I read that correctly? I can say the default Prusa setting worked great and did not touch the model anywhere except inside the groove. No issues with material or even time at this point beyond wanting to understand how the program works in a repeatable way and compared to videos showing blockers function, it seems something is not quite right with this scenario. If you and fuchsr agree I will send to Prusa help. (Did buy the MK3s and use only prusament).

RE: Round on model supports

Just for grins, I tried slicing it with Cura, mostly defaults for supports, with an 'overhang angle' of 50 degrees, which I think is default.

It did what I believe you want, as shown below.

If you do want to try Cura, one caveat, most default Prusa speed settings on the Cura versions I've used go MUCH too fast, particularly on the first layer.  Compare the settings for speed, temperature, etc. with those in PrusaSlicer and you will probably have good results the first time.

RE: Round on model supports

@jsw

YES, that is exactly what I had expected to see and was trying to achieve in Prusa slicer given the various degree settings and support modifiers. Thank you for essentially confirming it is a software quirk. Downloading Cura. 

RE: Round on model supports

Although Prusaslicer is now my go-to slicer for the MK3S, there are a few cases where Cura does better.  One is supports, and the support options in Cura are almost overwhelming.  Please RTFM about Cura supports.  The options for supports in Cura do not correspond 1:1 to those in (Prusa)Slicer.  Also please pay attention to the speed and temperature settings in Cura.  I've had good luck by closely mirroring what they are for a similar material in PS.

Cura also is usually, but not always, more forgiving in successfully slicing iffy .stl files.

Tonight I downloaded a model building from one of the usual suspect sites, made by a designer who, speaking freely, is notorious for producing corrupt .stl files.  (This one was apparently done in sketch-up.)  Neither PrusaSlicer nor Cura would slice it to render what was expected.

My usual repair process with FreeCad was unsuccessful.  Fortunately the old free version of Netfabb fixed it enough to slice as expected in PrusaSlicer, but Cura's attempt resulted in mostly empty space.

RE: Round on model supports

@ mike-bemis

I'm a little late to this post I guess, however I thought I'd throw my hat in the ring, and show you one of the ways  I've been doing my supports in these types of over hang conditions. I hope you don't mind but I printed up a sample of the top 14mm of your model to help explain.

I'm making an assumption that you modeled the wheel cap, and with that assumption you must have the modeling skills to achieve the same results.

Basically I exported your model to .stl from slicer. imported .stl (in my 3d program of choice, doesn't what one) then created a box, in this case at 205.66mm (I was guessing cause you can always scale it later) with 128 segments, skipping the first segment I then grabbed every other segment so that I had 64 segments ready to go I moved them in the X 2.75mm because the depth of your over hang was 4mm more or less, making a zig zaggy box /\/\/\/\/\/\/\/\/\ , and then I applied a( bend modifier) to it and made it 360 degrees I centered it to your wheel cap moved it into the area that needed to be supported I made it 0.2mm shy of touching the lower area and 0.1mm shy of toughing the top. I made sure that the support was attached, or in other words, even though not touching, it would be viewed by slicer as one model. I exported as .OBJ (you could export as whatever your program of choice give you options for, as long as Slicer likes it) I imported the .OBJ I setup for PETG @ 0.2 layer height, since that's what your .3MF showed you wanted.

Now when slicer goes to slice this it wants to make everything 0.2 and it will try to either make the 0.1mm space at the top of the support into a 0.2, or it will go the other way and try to make it touch the layer you want a space between. so you turn on layer editing and gently massage the top 5 or 6 layers where you want the 0.1 to be maintained. its a small area but its easy enough to do. then re-slice and examine that area to see that its right. If it is then Cut (as I did) a sample and export the G-code and do a test print to see that its right.

(Note: If you cut the model down to 14mm for the test print you will have to go in and redo the layer edit for those same layers before exporting.

If you do it right you should be able to very easily unzip and remove the support with no farther post processing of any kind, and an almost tool free removal of the support. I say almost tool free, because the space you have there is nominally 7/32"/ 5.54mm and I couldn't get my fingers in it to grab the support, so I used the tip of my knife to grab it and then just zipped it out, on larger spaces this isn't necessary. 

Ok so I wrote all this, and it sounds like a lot. But it only took 2min and 54 seconds to produce this hand made support that's counting the time it took to export it as an .stl from slicer. it took 56min to print the test, and about 30 sec to remove the support material, but that's because I had to stand up to get my Knife out of my pocket. 😉  I've had very good success using this method.

I included some pictures maybe they will help show what I tried to explain.

Good luck I hope this helps,

Dan

This was made from the worst PETG I had on hand, and it didn't fail.