Slic3r adding support above print  

RE: Slic3r adding support above print

Are you sure your part imported correctly? It seems the support generation is OK, but PrusaSlicer is very much confused about what the shape of the top of your part is. It'd be interesting to see how it slices with supports disabled.

RE: Slic3r adding support above print

It looks as I expect, I’m pretty sure it imported OK.   I’ll post a closer look tonight.  There are no overhangs in the top section, so I wouldn’t expect any support up there.

I’ll admit that I left the top edge sharp, because I don’t care much about exact height or strength.  I’ll try flattening the profile to maintain a couple of  top perimeters.

RE: Slic3r adding support above print

Nag post:  When dropping images into the text box: please change the Link To from None to Media File as shown here

RE: Slic3r adding support above print

Looks like a thin wall issue: try enabling detect thin walls.  That said, why use support at all? The part doesn't appear to need them.

RE: Slic3r adding support above print

There are legs hidden under the supports in the picture, the part won't stand alone.

I tried "detect thin walls" but it had no effect.  I flattened the top edge, but it's still only 0.17mm wide, and that didn't make any improvement either.  It will take a bit more work in Fusion 360 to make the top wider, so I might fold that in with other updates after the next pass.  I'll use the old Slic3rPE for my next prototype.  I'll say again that the old Slic3rPE works fine.

Here is the top edge without supports.  Note the final 8 layers that you see are single runs.

Here's the same view with supports:

Now with supports, but showing the first single perimeter layer (eighth from the top in previous pictures).  Everything below this layer has at least two top perimeters.  You'll see this is also where the first interface layer was placed.

RE: Slic3r adding support above print

This isn't a long-term solution, but I tried "Support on build plate only".  It generated something usable (probably).  It's got an unsupported bridge section above the back leg, but print quality isn't critical there.

RE: Slic3r adding support above print

To upload a zip: simply drag it from the desktop to the text window, just like images. Then use the same "Insert into post" ...

RE: Slic3r adding support above print

That was great - setting XY compensation to 0.1mm cleaned it up just as well as 0.5mm.

Interesting, I forgot that this section above the back foot was also knife-edged.  It doesn't respond to   Old Slic3r didn't have a problem, only new Slic3r (v2.0.0+).

RE: Slic3r adding support above print

Edit for previous post: "It doesn't respond to XY compensation" - well it responds, but does not go away.

I tried attaching the .stl, but it didn't like .stl files.  So I zipped it.  Note the file you've been looking at is TripleSlot0.stl.  I've also included TripleTube0.stl, which is the mate, just for context.  It has no fine edges, and I haven't had any problems with that one.

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RE: Slic3r adding support above print

Ouch ... yeah, a challenge.  Printing the entire part with supports is going to leave some marks.   Does the back surface need to be smooth and pretty?

RE: Slic3r adding support above print

Any chance you can put a chamfer on the one step from the base to the blades inside and outside the ring ?  I'm thinking it would make printing much easier. Even more so if that lip could be removed.

RE: Slic3r adding support above print

In any case, as is, I'd probably try first printing i this way: Leg up. XY Comp at 0.150 mm .  Bed will need to be very clean for adhesion, soap and water wash and hot rinse before printing.  Supports are only needed for the leg and the lip around the part. A lot of waste support, but will have less affect of appearance than if printed leg down.

RE: Slic3r adding support above print

Wait--- just saw the is an odd overhang inside the part when printed this way ... that central rib ... and with single walls removing support from inside will be painful. Double ouch...

RE: Slic3r adding support above print

All said - printing leg up still might result in a better part, even with having to gut the support from inside.

RE: Slic3r adding support above print

Thanks for the close look.  I've tried both orientations, slot up is best.  I could make the back leg separately and attach it somehow, but I like the unibody approach.  The back leg is a conduit for the wiring, and so acts like a small drip loop to let rain shed rather than pooling around the wire.  The whole assembly will be filled with epoxy potting compound including the leg.

I think the odd overhang you referred to is the cavity for wiring which also provides a flow channel for the potting compound.  In my orientation, there is a bit of support along the sides of the cavity, but a wire still fits down the middle.  Flipped, I'd have to dig out the slot and enough room for the wire.  Epoxy still flows either way.

To answer your other question, the bottom finish is not critical since it faces the back of the sign and is not illuminated.  Even so I can get a pretty good finish trimming it with an Exacto knife.  All of the upward facing surfaces are critical however.  The slot and shoulders keep the LED strips in the correct geometry relative to the tube (TripleTube0.stl).  Plus the upward facing flange around the slot is critical for fit with the tube.

The tube part is printed with curved surface up, since it is illuminated and outer finish is important there.  That means the mating surfaces need to be cleaned carefully.  But they face the bed, so with 75% separation between the object and its support, it just peals away leaving the mating surfaces clean.  The entire tube ends up filled with support, getting that out is the most labor intensive finishing step.

With the XY compensation (or old Slic3rPE), it's all good.  In the future I'll pay a bit more attention to wall thickness.  So I'll only torture the slicer when it is truly necessary.

RE: Slic3r adding support above print

Moving on, character 4 was even more interesting.  Without XY Compensation the entire footprint is carpeted with support.  Shown below with XY Compensation of 0mm, 0.1mm and 0.2mm.   0.2mm looks OK, but maybe I'll stick with the old Slic3r for this project.  Again thanks for the help.

RE: Slic3r adding support above print

You might want to play with the default support values Prusa has plugged in - I find them to be non-optimal in 99% of my prints.  0 works amazingly well (auto) and sometimes reduce to 15 and even as low as 7 to get what I am looking for.  And there are times on stubborn parts I need to increase support to 75 degrees to avoid support towers that are only 2mm by 2mm but 150 mm tall (aka: instant fails).  I've even seen Slic3r build support towers one pass by 2mm x 100mm.  A simple build rule added to the support algorithms would prevent a huge problem at print.

By the way: really cool project. 

RE: Slic3r adding support above print

By the way, I tried slicing your part and if you cut about a 0.5mm off the sharp top of the part, PrusaSlicer starts to behave normally. It's the sharp edge that throws the support algorithms off. Also, I'm quite surprised you get better quality printing it this way, printing it upside down should work perfectly fine with minimal supports.