Designed supports -- recommendations for gaps and contact points?  

Tailored supports will always be better than the generic ones from slicer algorithms.

Wherever possible I try to make bridges so that the bridge itself is the bottom of the supported part:

This illustrates the principle 'though in practice you would close the shape so that little of the red support would be visible - note that the red bridge/support is also the bottom layer of the supported area.

For supporting curves or more complex shapes soluble support interfaces do the best for me; they too can be tailored by using the part itself as a negative shape to configure the support surface.

Cheerio,

RE: Designed supports -- recommendations for gaps and contact points?

Thanks! So the red bridge is in full contact with the yellow bracket it supports, but only along the two lines where they meet, right? 

Yes, using soluble supports (or not-so-adherent supports, e.g. PLA for PETG?) is high on my wish list. Wouldn't mind getting that INDX upgrade some time soon... 😉 

RE: Designed supports -- recommendations for gaps and contact points?

Posted by: @jurgen-7

I have a few slightly unwieldy parts which I need to print at 45° tilt. So they will only touch the bed at a couple of points, and will otherwise "float" on support structures. I find that PrusaSlicer miscalculates the support distance when the contact surface is at 45°: Even with a specified contact distance of 0 mm there is a pronounced gap; the supports come off (too) easily, sometimes during the print.

So I intend to design supports into my model. What are your experiences / recommendations regarding the contact area and distance? Or do you use point connections where the model and the support are fully connected? If so, how many (per surface area), and how large? This is for PETG prints with the standard 0.4 mm HF nozzle and 0.15 mm Balanced profile, if that makes a difference.

Many thanks for your suggestions! Hopefully I can reduce the number of trials and errors a bit... 

I've had a real eye opening realisation that has completely changed the way I design and print a lot of my parts....courtesy of the legend James (clough42).
This video, and the subsequent follow up video which improves on it even more:

The results are every bit as good as he says, I couldn't quite believe it at first.

I've been using custom supports and permanent marker for separation for many of my parts for the last year or 2 with great results, but this really has been a game changer for me. A bit more work to design the custom support, but more than worth it in the end IMO, especially if it's a part you're going to print repeatedly.
I only ever use Prusaslicer's supports if it's a quick and dirty part that no-one will ever need to look at.

RE: Designed supports -- recommendations for gaps and contact points?

Forgot to mention in those videos he's using Bambu Studio, but it all applies the same to Prusaslicer. In PS select classic perimeters, not Arachne, I think BS uses classic by default, PS uses Arachne by default.

In PS if you zoom in like he does, it really doesn't look like the supports are making any contact, but I think that's just how the sliced image is displayed in PS...in reality the parts are making the same, extremely slight contact...which is all they need.

RE: Designed supports -- recommendations for gaps and contact points?

the red bridge is in full contact with the yellow bracket it supports, but only along the two lines where they meet, right?

In essence, yes; sometimes not where complex curves are involved.

Cheerio,