Cura Brim Bug?

[cdrose 8]

Hi,

 

I've noticed a bug of sorts with the Build Plate Adhesion Type "Brim". It appears the "Brim Only on Outside" of the model doesn't work 100%.

 

Cura seems to place brim material around internal "islands" of the model so anything that loops around leaving material in the middle. To explain what I mean I've added screenshots of what happens when printing a model with text on the base such as the Benchy or the Banzai Bill model. There is brim material within the letters which "caps" them off.

 

Is there a fix for this? Can we have a feature where we can remove certain paths by clicking on them to delete?

 

Thanks

 

Edited March 11, 2018 by cdrose

[kmanstudios 1,120]

There may be something in the model that defines an inside and outside that Cura may be reading.

 

Can you post the model so that we may take a look?

[cdrose 8]

Banzai Bill

3D Benchy

[berndjm 16]

Indeed Cura makes the brim "outside" but it didn't recognice correctly what is "inside".

There are quasi "insides inside insides", tried to visualize this here:

 

If you set the brimline-count to 1 or 2 it becomes better visible how cura thinks, for example the "O"

 

Because there is part 1 inside part 2 there "must" be A the outline for part 2

and B the outline for part 1

Edited March 11, 2018 by berndjm

[kmanstudios 1,120]

@berndjm got the secret figured it out and it makes sense from how the software would see things.

[cdrose 8]

It should run a script to detect the next closest edge, if it finds one then don't place brim in there. We should be able to adjust this detection. Therefore when it traced outside the model it would reach the edge of the build plate and know that part was the outside of the model.

[kmanstudios 1,120]

I am not sure that would be wise to try to implement. Right now, it seems to be following the same rules as programs such as Illustrator use to determine inside and outside.

 

Rather, I think it would behoove the use to use the settings in Cura to use a secondary object to modify settings of the first object by eliminating the brim. I will see if I can set a thing up to demonstrate what I mean. And, see if theory and reality meet square on.

[berndjm 16]

Quote

Therefore when it traced outside the model it would reach the edge of the build plate and know that part was the outside of the model

 

I think it's not so easy to detect the "real outside" and at the same time handle cases where the currently behavior makes sense.

See this simplified use-case:

Here it could be helpful to have the brim also inside the object.

 

I think to have a adjustable threshold (is this the right word?) for the outside detection would be nice ... but how to handle than the two parts close together like in your 2nd screenshot?

[kmanstudios 1,120]

I tried to do what I thought would be possible. Again, reality and theory did not mate up nicely. Here was my train of thought:

(A)

This is a selection that would be a problem with brims. This would not be fun to trim out as it is a thin object and tiny in detail.

(B)

So I was thinking that instead of trying to make the software do something that would be really a pain to operate precisely based on the idea that @berndjm showed in the post above; When is it good/not good to have software decide what is inside or outside? My theory was to use the new feature that allows one model to modify settings of another model. This is in the 'per model settings' dialogue. I have found this to be really most useful in a variety of ways. It has easily become my favorite feature and I use it in almost everything right now.

 

But, as reality will often do, it will not work because it turns out that brim is not a per model setting. This may be easier to implement though than try to set some sort of other option.