How to stop Cura adding brim inside letter on benchy bottom

[mlitzkow 1]

I am slicing a standard 3d benchy with Cura 3.6.0 on Windows 10. Using a brim for bed adhesion and with "Brim Only on Outside" set, I find that Cura is filling in the "D" on the bottom of the boat.  Going by the color scheme shown, it appears to be creating a brim inside the "D".  This is not a printer issue.  I'm just showing the bottom layer of the gcode file Cura creates.  If I slice with build plate adhesion set to "None", there is not blue line inside the "D", so I think the blue line is part of the brim that Cura is generating for me.  I want the brim, I just don't want it inside the lettering.  Is there a different setting I can use to ask Cura not to generate a brim inside my model?

 

 

[gr5 2,097]

I see you have "brim only on outside" checked. 

 

It's working as intended.  It's only putting brim on the *outside* of the inner circle in the D.

 

Not the answer you wanted, sorry.

 

[kmanstudios 1,120]

I tried a couple of thins and did not find a way to modify that instance.

 

The only way I see to make it happen is to make a brim for your object.

[ahoeben 1,890]

How about using a skirt instead of a brim, and using the skirt settings to make the skirt wider and the distance between the skirt and the model very small?

[mlitzkow 1]

OK, I now understand why the "D" is a problem and other letters aren't.  It's because of the "island" inside the "D". When I set up for either a skirt or a brim, Cura wants to put a tiny skirt (or brim) around that island.  I want to be able to put part numbers, version numbers, maker's marks, etc. on the bottoms of my prints.  Thus the letters on the bottom of benchy are a good test for me.

 

• I tried using a skirt with Skirt Distance set to 0 instead of a brim.  That also puts a skirt around the inner part of the "D".  
• I tried support blocking, but it seems that the brim isn't considered to be a support, so it doesn't get blocked.

I've considered hacking the gcode, but that seems like a pretty complex solution. Surely there must be other users who want to print a perfect benchy - including the bottom.  Of course, maybe others can print the benchy without a brim.  I find that the bottom of the boat is rather small compared to the height of the boat, so my printer will consistently knock the boat over at around 3/4 way through the print.

 

Does anyone have any ideas on things to try before resorting to hacking the gcode?

 

[gr5 2,097]

Benchy - at the default size - is too small to need brim.  You need to watch my video.  It's a bit long but packed with information.

 

[mlitzkow 1]

GR5 - thank you for the pointer.  Somehow I had the idea that benchy would need a brim.  I print on PEI, which I think has a little less adhesion than glass.  So far I have not gotten the benchy to stick well enough with glue sticks, but the blue painters tape works well.  That eliminates the need for a brim, so the problem goes away.  Well - not exactly.  There is still a question of how to print letters on the bottom of something that would really need a brim.  Anyway, today's problem is solved.

 

Again, thank you for making the video.  I found it very helpful.

[geert_2 557]

For complicated designs, you can always design custom brims, custom supports and other custom structures in the CAD file itself. And then switch off the automatic brims and supports in Cura. Then you have full control. For example if you want brim on some areas, but not on others. Or if you want special supports with holes suitable for your pliers and tools, to make removal easier from the inside of complex models.

 

It will take some trial and error (do this on tiny test plates or so), but once you have found a concept that works well for your application, you can re-use it quickly.

 

For example in this tiny model (key chain), the orange and rose custom supports have some brim, and the green dummy tower also. The dummy tower is to provide extra cooling time, otherwise the top of the yellow model does not solidify well; it is too small. I don't want to risk a model being destroyed because a dummy tower or a support comes off, so they get brim. But the rest don't need any. Further, these supports need that extended shape, otherwise I can not grab them with pliers and wiggle them loose, and the space is too small to get in there with a knife. So I provide all this in the CAD file.

 

For reference: text caps height is 3.5mm, and text legs are 0.5mm wide.

 

[mlitzkow 1]

Wonderful - you just opened my eyes!  I have been modeling in Fusion 360 and slicing in Cura.  Somehow it never occurred to me that I could design custom supports or adhesion features in the modeling tool.  Of course, it makes perfect sense now.  Many thanks.

[PrettyCoder 2]

You can add very thin lines at the bottom of model. They will not printed but prompts Cura that it is not outer.