S3D Support offsets

[ryaneb85]

What are most people running their support offsets at in S3D? It seems 1mm/1 layer is the default, but while this allows for easy cleanup, it seems to present it's own set of problems. To be more specific, if I leave the top offset as 1mm/1 layer (I can't remember the correct parameter), the bridges "sag" until coming in to contact with the support structure, which leaves a pretty ugly finish. Putting it to 0 makes the supports hard to remove and requires significantly more cleanup, which again leaves a non-perfect finish.

Am I missing a trick here?

[Jules]

Depends on the filament.

PLA gets 0.20 mm horizontal offset, 1 upper vertical separation layer and 0 lower.
PETG gets 0.30 mm offset, 1 upper and 1 lower.
PETG with PLA support gets 0.10 mm offset, 0 upper and 0 lower. (They don't stick to each other-dual.)

I prefer cross-hatched support, so i use support infill angles of 45 and -45 degrees.

And I also like to use one or two dense support layers for most prints, 65-70% infill. The dense support is usually easier to spot, and really helps with the sagging problem. Overall support is 30%.

But you know, it changes based on need. Sometimes you have to fiddle with it a little depending on the shape of the overhangs and the supports.

[ryaneb85]

Useful reply as always, Jules. Thanks for the help.

I've been playing with PLA. So you don't get any sagging with 1 vertical separation layer, cross-hatched and a couple of dense support layers? I can't comprehend how this acts as a support, as it's still technically printing in thin air.... right?! The same applies if you have 1 lower layer, doesn't the support print in thin air? It seems I haven't played around enough - real life has an annoying habit of getting in the way...

[Jules]

Useful reply as always, Jules. Thanks for the help.

I've been playing with PLA. So you don't get any sagging with 1 vertical separation layer, cross-hatched and a couple of dense support layers? I can't comprehend how this acts as a support, as it's still technically printing in thin air.... right?! The same applies if you have 1 lower layer, doesn't the support print in thin air? It seems I haven't played around enough - real life has an annoying habit of getting in the way...

Well, it still sags a bit, but one layer generally isn't enough to cause too much sagging, and you need some kind of break between them.

What helps me most is the cross-hatched support - it's less likely to have gaps that the filament above it might fall into, if it happens to be printing parallel to that gap. (And the dense support layers help.)

Still not perfect though - you're right. (And PLA is a heck of a lot better than PETG. )

[insta]

Useful reply as always, Jules. Thanks for the help.

I've been playing with PLA. So you don't get any sagging with 1 vertical separation layer, cross-hatched and a couple of dense support layers? I can't comprehend how this acts as a support, as it's still technically printing in thin air.... right?! The same applies if you have 1 lower layer, doesn't the support print in thin air? It seems I haven't played around enough - real life has an annoying habit of getting in the way...

The one-layer airgap (I run 2 upper for PLA @ 0.2mm layers) basically gives the plastic a chance to swell back into its normal round extruded shape. This presents a very small area for it to stick to the plastic above or below it, so ... it doesn't. The upper layers have their own roundyness at the same time, so the support-to-part interaction behaves more like two steel pipes in the shape of a cross -- plenty of holding up, but very little friction between them.

[Jules]

The one-layer airgap (I run 2 upper for PLA @ 0.2mm layers) basically gives the plastic a chance to swell back into its normal round extruded shape. This presents a very small area for it to stick to the plastic above or below it, so ... it doesn't. The upper layers have their own roundyness at the same time, so the support-to-part interaction behaves more like two steel pipes in the shape of a cross -- plenty of holding up, but very little friction between them.

This is interesting, I wonder if having a "second" upper layer gap on mine wouldn't give the PLA more time to finish cooling and swelling before the cover layer gets laid down....keep it from bonding so tightly and make the support easier to remove?

How's the underside of the overhangs on your PLA prints, when you do it that way insta? (Maybe denser support, but more upper gap layers.....)

Coo! Just had a brain drizzle! You could lower the printing temp a couple of degrees at the junction layers, then resume higher printing temp once the base layer gets laid down. The delay while the nozzle comes to temp gives it even more time to cool. (As long as it's not parked over the print while it changes temp. ) Okay, definitely needs more thought.

[insta]

It happens that most of my support-needing PLA prints are things like enclosures that have large, flat runs. The underside has a good finish but occasionally a loose thread.

[Jules]

It happens that most of my support-needing PLA prints are things like enclosures that have large, flat runs. The underside has a good finish but occasionally a loose thread.

Shoot! Mine tend to be angular overhangs and more organic shapes. Those are a bear. (Probably still worth trying out though.)

[ryaneb85]

looks like I have a lot of tinkering to do!