Cura: Support brim towards the outside

[slikk66]

Often times I have a model I'd like to not print with a brim on it, but then there are teeny tiny support structures (<3mm round for example) that never stick unless I add brim to the entire print. Is a "brim for support only" option possible?

[ChrisTerBeke]

Related to https://github.com/Ultimaker/Cura/issues/3818.

[jackha]

Devs: see CURA-5487

[agibson2]

I was posting this same idea on the forum today and someone pointed me to this. This feature would be very helpful very often for me. I have prints where the object has a bit of detail on the bottom where cutting away the brim is very tricky or near impossible. I do need the brim for supports though quite often. This feature would solve that issue.

jackha, Is CURA-5487 something that regular github users can see? A search for 5487 doesn't turn up anything.

[fieldOfView]

CURA-5487 is a reference to an internal ticket, not publicly accessible.

[Ghostkeeper]

I'm closing this as a duplicate of #1950.

[seltix5]

Hello all,
I have the support brim enable and it does nothing if I don't enable the brim in the build plate adhesion type... Is that normal?
I have Cura 4.3.0
Thanks!

[Ghostkeeper]

Mind that the support brim goes towards the inside of the support. So you won't see it unless you look from the underside of the print or scroll down the layers to the first layer.

[seltix5]

hello,
in my case I dont see any diference, I dont know if it may be because the support area is small but in that case the normal outside brim wold be a big help :D

[Ghostkeeper]

The brim there looks fine. I see a few extra contours inside the support.

It's indeed small, but that's what the normal brim is for as well. What you really seem to be looking for is a way to print the brim only for small shapes or something like that?

[seltix5]

hello,

i was locking for a "normal" outside brim.
with the support brim disabled there is a very small diference but it wont result in a real diference when printing :

I was hopping for a outside brim like the one from the "build plate adhesion type" but only for support structures to increase adhesion for this small type of support structures :

[TheNitek]

I can confirm this. Support Brim only works correctly if Brim is enabled as "Build plate adhesion type". I would love to use the Support Brim independently.

[Ghostkeeper]

But you can! Here's a screenshot showing a skirt is used instead of adhesion, but still a brim for the support:

The support brim can be enabled even if the adhesion type is not set to brim. Doesn't that work for you?

[seltix5]

hello @Ghostkeeper ,
yes, for something like your example where you have a big space under the area you need to support the inside brim will work because there is space available for the brim to expand, but for models where it cant expand the inside brim will do nothing.
For example, the model I printscreen before (https://www.thingiverse.com/thing:600732), the arm needs support, but that area is so small there is no space to a inside brim, without a plate adhesion brim the support will just fall. For this cases a support outside brim wold be perfect since the model itself does not need brim.

[TheNitek]

I like to use support brim in combination with tree support, but when using a Skirt there is next to no support brim. That's not how I'd expect this to behave

[Ghostkeeper]

Of course, if you have a piece of support that is surrounded by something else, it will not have a brim either then if it's going outside. There will always be special cases:

But there is something to be said about the support brim going towards the outside instead of towards the inside because of user expectations. We get this bug report once in a while, that people think the brim is missing but it's actually just on the inside.

There is also a similar technique to our current support brim: You can also set the initial layer support pattern to concentric and the initial layer support density to 100% to achieve a sort of brim, so arguably there are two features with the same function there.

On the other hand, part of the reason why we chose this solution is because it simplifies the behaviour a lot. If the brim for support needs to go to the outside, you need to have brim lines with interruptions where the brim is interrupted by the model. This is not conductive to adhesion or priming. It also simplifies the algorithm for collision checking between models (in the front-end) a lot.

[seltix5]

hello,
this is not a bug report, it is more like a feature request since it is not possible to do it.
As the original title and message of this issue :

Often times I have a model I'd like to not print with a brim on it, but then there are teeny tiny support structures (<3mm round for example) that never stick unless I add brim to the entire print. Is a "brim for support only" option possible?

Your 2 examples are not related to the problem since the problem in question is to print small supports. In booth your examples the support is big enough to support himself. To print small supports the problem is not if there is something surrounding the support or not, the problem is the fact the area occupied by the support is so small it will probably move because of bad adhesion to the plate. In this specific cases the inside brim cant help because the support area is too small.

I give you this example (https://www.thingiverse.com/thing:600732), if you try to print this without plate adhesion brim chances are the support will fall. The only option here is to enable the plate adhesion brim just to increase the support adhesion to the plate.

English is not my first language, i feel i may not be explaining the problem correctly.

I cant say I image the work to implement something like this, but since the plate adhesion brim already adds good brim to model and supports, wold not be possible to do this but only for supports?

[Ghostkeeper]

I could make the second example smaller and you'd have the same problem but less stable support. Whether the brim is necessary or not is irrelevant here. It was just to show a case where a brim on the OUTSIDE wouldn't fit either.

I cant say I image the work to implement something like this, but since the plate adhesion brim already adds good brim to model and supports, wold not be possible to do this but only for supports?

You'll notice that we're not creating any brim right now in any location where a brim could be touching something that doesn't have a brim. The reason for that is that the brim then needs to be interrupted.

This is the case for:

• Prime tower brim. Here we make the prime tower collision area bigger so that they can't collide.
• Support. Here we grow the brim towards the inside so that it can't collide.
• Brim on outside only. This prevents brims from forming in holes in the print. If there is a piece inside a hole, that piece should still get a brim but then the hole will also get a brim so that both sides have a brim again, which prevents a brim from touching something that doesn't have a brim.

To implement this, we'd have to implement cutting out pieces from the brim.

[seltix5]

and woldnt be possible to use same technic used with prime tower here? and only expand the brim until reaches the desired value or a colision area.

[Ghostkeeper]

The semantics we're using for the prime tower is to increase the disallowed area around the prime tower so that you can't place anything nearby that would cause the brim to collide. If you're also using a normal brim for the main print, that one goes around the prime tower brim.

This is not feasible for support since the support must be generated pretty close to the model, otherwise it wouldn't support the model any more.

[Ghostkeeper]

We've decided to defer the support brim going towards the outside. It would be good to have but the algorithmics involved don't make it worth our time for now.

[seltix5]

thanks for all the explanations, it is in the maybe todo list is already something good :)

[ivanmalvin]

Just wanted to add my two cents that I also feel an outer brim on supports would be extremely useful in many situations. I read this thread and understand it might not be easy to implement, but I hope it gets added.

It's pretty common that I have a model with a nice flat base, so it doesn't need a brim, but the supports often get small enough (or tall enough) that they have a good chance of failing from not having enough surface area adhering to the bed. Sometimes I resort to using an outer brim on everything, but the cleanup of the brim tends to ruin the appearance when you try to fit two separately printed parts together.

I do use the support (inner) brim option, which definitely helps, but it doesn't help when supports are small/narrow so there's little to no inner brim added from that.

[seltix5]

that's exactly my problem =)

[Neohkp]

You can set the distance from the brim to 1 or 2mm, this makes no sense, but it works ;-) You have a supportbrim but no objectbrim.

[seltix5]

cool, nice workaround! thanks for sharing