slic32r: understanding supports  

Re: slic32r: understanding supports

I screwed up the IMG tags...

I'm a bit perplexed by what slic3r did for this model

I had slic3r generate supports "everywhere" with just the default settings and I get the preview

And I'm perplexed: the entire flat underside of the model is *unsupported* ????

andwhat does it mean when slic3r colors something in red. I understand gold -- the model -- and green -- supports.. But what is the pink?

Re: slic32r: understanding supports

Third time is the charm

I screwed up the IMG tags...

I'm a bit perplexed by what slic3r did for this model

I had slic3r generate supports "everywhere" with just the default settings and I get the preview

And I'm perplexed: the entire flat underside of the model is *unsupported* ????

andwhat does it mean when slic3r colors something in red. I understand gold -- the model -- and green -- supports.. But what is the pink?

Re: slic32r: understanding supports

From the looks of your pictures you have bridging enabled. With auto supports they will only be generated when the overhand exceeds the value you have set in your print settings, that's why the sloping walls near the top have no support. The small holes around the top must have an angle that exceeds the overhand value so those get support built up to them.

On the bottom the entire area isn't supported due to the bridging I mentioned at the start. The printer can do short (how short/long depends on lots of things) prints between supported areas. This is known as bridging. The circular perimeters need something under them to print but once they are there the lines between are anchored at each end and so fall under the bridging parameters from the looks of it.

If you want support under all of it you could either disable bridging or put a support enforcer modifier under there.

Re: slic32r: understanding supports

Thanks for the info!! Indeed, the print settings are "don't support bridges" but I can't see where to set the maximum bridge. IN a print that is just finishing, it 'bridged' across four inches [basically across the bottom of the model above]. I guess I'll find out in a while when the print is done to see if the bridging worked.

What are the setting for the bridges? The only thing I see is "XY sepatation between an aobject and its support" which is set to a perplexing "55%". 55% of what? and is that a reasonable value [I assume so, because it is the default that came with slic34pe]

Re: slic32r: understanding supports

My print finished and the long-span-bridges are a mess. Across the 4+ inches across the bottom of the part, it is all just unfused separate strands. It breaks apart almost as easily as actual supports [only leaving a gash in the part of course]. The only setting I could find was ieither support or don'e support bridges. I can uncheck that, but is there some way to "tune" the bridge-spanning -- say, limiting it to 20 mm or something like that? [would that allow it to space out 'supports' in a kind of lattice of supports? If not, I guess the only alternative is to completely fill the part with supports under the base.

Re: slic32r: understanding supports

I do not know what the other side of that model looks like but I'm thinking I would be printing it flipped over? That has a heck of a lot of supported areas and those generally just don't look as good for me as top layers would. Is there a reason you can't flip it?

Re: slic32r: understanding supports

I do not know what the other side of that model looks like but I'm thinking I would be printing it flipped over? That has a heck of a lot of supported areas and those generally just don't look as good for me as top layers would. Is there a reason you can't flip it?

I thought about that -- but if I flipped it wouldn't the *entire* interior be filled with support? [or, if it decided to try 'bridging' again, I'd guess that the same thing would happen as happened on the bottom.

One thing I'm contemplating [but I'm not sure about] is rotating it 45°. Instead of horizontals and verticals, it'd be virtually all 45s and should be able to be printed bridge and support free... dunno. But if i don't get that to quite work out, I think I have to turn off the 'don't support bridges' machinery or else the upper side or lower side of the bottom won't come out well

Re: slic32r: understanding supports

I did some testing and it was much as I thought. I sliced the housing upside down:

and the upper surface of the bottom would have the same bridging problem as when I printed it rightside up The "normal" thing to do would be to disalble not-supporting bridges. That makes for an interesting build:

and it wasn't easy to get slic3r to do the rotation, but here is it rotated on its edge at 45°

I need to reprint the housing [the lower surface of the bottom is really a stringy mess] and I'm not sure quite what to do I'm sorely tempted to try the 45° tilted version. The easy way out would be to z-slice the housing at the lower side of the bottom, so it would sit flat on the plate, then print that [and it'd be bridge-free] and then print the shaft bores separately and glue them on.

Re: slic32r: understanding supports

As far as I know there is'nt a setting for maximum bridge length that I've found as yet. Not even in the alpha/beta releases.

Supermerill has a version of SlicerPE on his github that has some interesting experimental features, Ive not found a maximum bridge length in his as yet but there is a seperate Bringing infill angle.

I think designing for the strengths and limitations of fdm printing is a bit of an art, something I have yet to master lol. I also think that part placement/angles etc is another new skill that can make so much difference to a print.

btw if you are having so much trouble rotating things do give the beta version of Slicer PE a go. The manipulation tools are so much better. I've got links to start up 3 different slicer variants at the moment, the normal release, the latest beta and Supermerrills Slic3rPE++ build.

RE: slic32r: understanding supports

RE: slic32r: understanding supports

On youtube search with this(or google), 3d printer supports

The you can make supports by hand if needed, so bridging is smaller. Tree support!

RE: slic32r: understanding supports

Peter,

I have used Meshmixer to make tree supports, removing unwanted supports.  However, tree supports are not recommended for flat surfaces.  They work, but eat up a lot of filment for my models and leave a pitted surface.  

I have created my own supports by putting horizontal slabs under each level at 0.2mm spacing, then using the conventional supports below them.  This works the best, but is tedious to implement, and I have trouble removing the slabs from the model without using a chisel and a lot of time, and some gouging on the model. Slic3r & PruserSlicer give 0.2mm spacing from the support to the model (using 0.2mm layer height - 6 hr print).  This is not enough and everything sticks.  If I try 0.4mm, the surfaces are very poor.

I will have to continue along the DIY path since there don't seem to be any good automatic solutions.  Right now I am reducing the print temp, hoping for less adhesion between the support and model.  

I just wish the auto supports would do what is claimed for them, or at least function the way they are supposed to.  PrusaSlicer needs a lot of debugging to even be usable.

RE: slic32r: understanding supports

Ben, have you played with the supported angle setting in Slic3r/Plicer?  Default is 55 degrees, but other settings can work better in most cases.

I've found 0 (automatic) works fairly well in many cases; and have found low angles can help with parts that just have low spots that need support (points that are below grade - like the v in the middle of an M doesn't touch the bed, so needs support). 

The 45 degree print angle may work, but you'll need to consider the layer height to ensure overlapping layers can adhere well and build a stong part.  Think about stacking bricks to form an overhang.  It's a good analogy for how perimeters work.

RE: slic32r: understanding supports

Posted by: bernard.c4

I'm a bit perplexed by what slic3r did for this model

 

I had slic3r generate supports "everywhere" with just the default settings and I get the preview

And I'm perplexed: the entire flat underside of the model is *unsupported* ????

Plicer will detect where a part can use bridging. Those areas are - by default - not supported.  There is a check box to disable this. What you see here is the low areas not touching the bed have support. Support is required for perimeters that would start in free space, somewhere above the bed. Like the perimeter rings around the various round raised sections of your part.

As for part placement: Bridging works fairly well, but the resulting surface quality is a bit lackluster. So it's best to have bridged surfaces hidden in use. Same with supported large flat areas.  Supports will "weld" with flat surfaces placed on them - that's just what hot plastic does.  Also a case to avoid, or use only where you can hide the surface.

If it were me, I'd invert the case and let the gasket surface sit on the bed.  Set bridge detection on (this improves the printers ability to print bridges well), and leave bridging unsupported.  This will leave round support regions for the various hole perimeters - but internal so the cosmetic down sides won't be as visible.   It eliminates the need for supports in places they just won't work well.

Then play with angle to find a good minimal set of support structure.

RE: slic32r: understanding supports

Tim,

I have found the support angle setting to be of no use when the actual angle is 90º on the dwg.  I have tried 65-89º with no change.

I have found a way to get the blocker to work and am printing now.   This still leaves the question of removing the supports without needing a hammer and chisel. Will report on the results when done. 

RE: slic32r: understanding supports

Maybe you aren't understanding what the support angle means. Works fine for me.

RE: slic32r: understanding supports

Support blockers work very well, but it's a bit hard to get folk to understand the block must envelope the area to be blocked.  And enforcers only work with support disabled.  A bit counter-intuitive, but they do work.

RE: slic32r: understanding supports

Oh -  as a light goes on - for the supported angle setting, it depends on the part. A cube at 45 degrees will have little if any variation from 1 to 44 degrees, and from 46 to 89 degrees.  Essentially, support is either on or off at the described angle.  A sphere will see a lot of range over the entire range as the circumference encompasses many angles.  

I am curious to see how you placed the part on the bed and a photo of the result.

RE: slic32r: understanding supports