How to improve supported layer quality?

[bbinnard]

I have printed the top for a round box. The top's cross section looks like this:

I added supports to hold up the top's bottom curved surface and the part printed OK. I removed the support material pretty easily, but the quality of the curved surface was poor:

It's not clear to me what parameters I should try changing to improve the quality if this surface and would appreciate any guidance anyone can offer.

Thanks in advance.

[Viceman]

I had this same problem with my part and making the support pillar resolution from 4mm to 3mm improved the bottom of my part greatly. Also I noticed that changing "External fill pattern" from concentric to rectilinear made it even better.

[bbinnard]

Thanks for the suggestions - I'll give them a try and report back.

Well the results were better, but certainly not up to the quality I'd like. The best improvement was to the top surface; changing from concentric to rectilinear resulted in a much smoother surface. But the bottom concave surface still leaves much to be desired. So I think I'll simply use flat bottom surfaces from now on.

[billyd]

It's huge drawback to current 3D printing technology. If you are looking for the best quality it's probably best to split the part to create a flat surface to print on and then join them with plastic welding or adhesive. Supports are useful but only when surface quality at the support is hidden or unimportant.

[bbinnard]

So it seems, but why is this the case? Seems to me it should not be difficult to set up GCode that prints supported layers with the same quality as non-supported ones. My printer does open spans really well so I see no reason why it wouldn't be able to print high quality layers regardless of what is holding them up.

[triplanedave]

The only thing that comes to mind here is that you've got a circular pattern to the overhang. As your printer tries to span the gap between the supports, if the filament cannot adhere to the curved surface for the layer below, it will tend to pull in a straight line until it hits the next support. A few things that come to mind in looking at your photo that might help.

1. Lower your temperature. The print looks pretty shiny. Usually filaments can tolerate lower temperatures and still print OK. Reducing the temp may increase the likelihood that you can get a good quick cooling as the filament is deposited. I have gone as low as 175 before the filament cannot be melted quick enough to print. I'd suggest starting at 185 though as a low temp. Of course, it depends on the filament, but experimenting may help here.

2. Increase cooling. Again, same principle as in #1 - ensure the filament hardens as quickly as possible after leaving the nozzle.

3. Decrease layer height. Doing so will reduce the step size from layer to layer and provide more overlap with the previous layer.

HTH,

Dave

[billyd]

So it seems, but why is this the case? Seems to me it should not be difficult to set up GCode that prints supported layers with the same quality as non-supported ones. My printer does open spans really well so I see no reason why it wouldn't be able to print high quality layers regardless of what is holding them up.

I don't know but I have never heard of any slicer producing exquisite finish results in faces directly contacting supports.

I've always thought they should build a raft on the supports and then the print, but no one does that yet. Rafts generally produce better results than support do so that is a possible way to improve it. But you're still not going to get GREAT surface quality that way either.


Btw, I believe the spaghetti layer between the supports and the actual part surface is extra and meant to be shaved off. But that's a ton of work and it's easy to ruin the finish further in the process. So you can't win really.

[zemlin]

New here, but was looking for info on this same issue.

I have access to an UP Mini at the office. The little guy has a lot of limitations, but it does support right! Up builds a raft on top of the support webbing so the build on top of the support looks just as clean as the first layer on a raft from S3D. If this kind of build quality over support is typical, I will be entering an enhancement request for a raft above support.

The raft can be tricky to remove if it recessed, but normally it's not to bad to pop it out.

[CompoundCarl]

Up builds a raft on top of the support webbing so the build on top of the support looks just as clean as the first layer on a raft from S3D. If this kind of build quality over support is typical, I will be entering an enhancement request for a raft above support

Look at the dense support options in Simplify3D. That will create a raft-like surface at the top of the supports. They have a video about it on their YouTube page too

[zemlin]

Look at the dense support options in Simplify3D. That will create a raft-like surface at the top of the supports. They have a video about it on their YouTube page too

OK, I think my main issue was a lack of understanding about the difference between support infill percentage and pillar resolution (I've only had my printer for 3 days). The videos helped clarify that. I ran a test part with a 1mm pillar resolution and 3 dense support layers plus a single upper and lower separation layer. My support test part came out fairly decent on the underside.

Here are the settings I tried in an attempt to duplicate the UP supports.

Support Infill Percentage 20%
Extra Inflation Distance 1.0mm
Dense Support Layers 3
Dense Infill Percentage 80%
Print Support Every 1 layer

Horizontal Offset From Part 0.35mm
Upper Vertical Separation Layers 1
Lower Vertical Separation Layers 1

Support Pillar Resolution 1.0mm
Max Overhang Angle 50 deg

In the Support Infill Angles I was messing around with something I saw in another post (this forum? dunno) about flipping angles every 5-10 layers to help stabilize the support structure - so I have 45 degrees for 9 layers and -45 for one. Not going to claim that this had anything to do with the results - but that's what's going on in that column.

Thanks for the tips - I think I'm making progress here.