Selective brims - possible?  

Re: Selective brims - possible?

I've seen what you're describing referred to as "mouse ears". I'm not aware of a slicer that will add these, but I have seen suggestions to add them to the model in CAD as snap-off parts. A discussion on the Simplify 3D board suggested the same.

As a quick test, I placed a cube on the bed in Slic3rPE, then loaded a small disc shape and resized it to 0.20mm thick and smaller XY dimensions, copied it and placed it in the corners.

I also tried a adding a modifier part with 0 top and bottom layers:

I'll print these and let you know how well they worked.

Re: Selective brims - possible?

Many thanks! Great idea. I'll give that a shot too.

Do you know if the printer prints brims differently (layer height, perhaps?) from any single layer "real part"?

Will the original external perimeters of your cube be lost on layer 1? Does that matter? Could you share a screenshot of your layer 1?

Re: Selective brims - possible?

Do you know if the printer prints brims differently (layer height, perhaps?) from any single layer "real part"?I think brims are just a single layer of whatever layer height you've selected for layer 1. Not 100% sure though.

Will the original external perimeters of your cube be lost on layer 1? Does that matter?I've just started a print of the 1st version (positioned discs) and it printed layer 1 of the discs 1st and is simply overlaying the cube perimeter and 1st layer atop the discs. With anything thicker, this might be a problem. I expect the 1st layer will look a little wonky.

Looking at the Slic3r preview for the 2nd approach, the infill butted up against the perimeters of the main part, so shouldn't cause any distortion.

Tabs done in CAD with bevels against the printed part are probably the best way to go, but these are possible options in a pinch.

Re: Selective brims - possible?

Understood.

Here's a zoom-in on my part without any brim or mouse-ears. This is prone to warping:

Here's what it looks like with Brim. This prints fine, but I have a lot of unwanted brim to remove. External perimeter of the part is maintained.

Here's what it looks like with Mouse-Ear - an overlayed part added in Slic3r. The original external perimeter is lost. I don't know if that's a problem.

Many thanks for your interest and help, though! Very interesting discussion and thoughts...

Re: Selective brims - possible?

[...] Here's what it looks like with Mouse-Ear - an overlayed part added in Slic3r. The original external perimeter is lost. I don't know if that's a problem.It may depend on how thick your part is at the tips. If you can just zip along the edge with a knife to remove the ears, it may be fine. My disc test is almost done. The ears are 1 layer thick, so should be fairly easy to remove on a robust part.

Re: Selective brims - possible?

How did you get your "modifier part with 0 top and bottom layers"? If I add a cylinder with 0 top / bottom layers (or, in fact, any number of layers), set to type "modifier", it simply doesn't show on the Preview. It does show if I set to type "part", but I'm still seemingly missing that original external perimeter. This is in Slic3r PE 1.41.1.

I wonder if I'm overthinking the whole "loss of external perimeter" thing, and shouldn't worry about it, and just try it as you have...

Re: Selective brims - possible?

How did you get your "modifier part with 0 top and bottom layers"?
Sorry, I created it as a part and modified the top and bottom layers, and infill density:

It's printing now:

Results are in with the overlaid resized part:

The ears can just be bent back and forth a few times and removed cleanly with a fingernail scrape:

The bottom layer looks pretty good:

Of course, the real test will be to try it on a part with actual warping problems!

Edit: I just noticed that I did not lose the external perimeters on the box. They over-printed the disc completely. Not sure why yours is different looking.

Re: Selective brims - possible?

Got it. Awesome. Thank you very much indeed! New technique duly added to the armoury... 😀

Re: Selective brims - possible?

Got it. Awesome. Thank you very much indeed! New technique duly added to the armoury... 😀

Yup, I've got a new page for my notebook too! Every time I figure something out, I document it online. See my signature for my current compendium of stuff.

Re: Selective brims - possible?

Quick results using the part modifier approach in Slic3r:

Snaps off easily with a bit of flexing and fingernail work:

Bit of a serrated edge on finish that needs a bit of knife or file work:

Not sure why the modifier part over-wrote the perimeter lines on the main part. Perhaps printing order affects this.

I think I'll gen up some "dimes" in Fusion 360 with 90 degree corner cut-outs with bevels for placing up against parts for these situations.

RE: Selective brims - possible?

Posted by: @bobstro

Not sure why the modifier part over-wrote the perimeter lines on the main part. Perhaps printing order affects this.

I think I'll gen up some "dimes" in Fusion 360 with 90 degree corner cut-outs with bevels for placing up against parts for these situations.

I also find it overwrote the lines.  I wondered if this would cause problems as that part of the print now has two layers of filament?

I also looked on your site in case you had more detailed notes, or found a solution, however couldn't find this anywhere.

RE: Selective brims - possible?

Just a quick note: you can trick slicer by adding very tiny specks of model to the bottom of your actual model, say 0.4 or 0.35 in diameter and 0.1 or 0.2 in height slicer will see it as the first layer however the model will still be pressed in just like if they weren't there.

RE: Selective brims - possible?

Posted by: @bobstro

Not sure why the modifier part over-wrote the perimeter lines on the main part. Perhaps printing order affects this.

I think I'll gen up some "dimes" in Fusion 360 with 90 degree corner cut-outs with bevels for placing up against parts for these situations.

I discovered something which may help.

If you right click on the bed, and do "add shape", the perimeters overlap.

If you right click on the object, and do add part, the parts are merged together.

See below, (I seem to have drawn a cok and balls...) but anyway, the circle to the left is a new shape, and on the right was "add part".

The one on the left prints overlapping perimeter lines.

However it doesn't seem to matter, and the ear is easier to remove.

Posted by: @dan-p12

Just a quick note: you can trick slicer by adding very tiny specks of model to the bottom of your actual model, say 0.4 or 0.35 in diameter and 0.1 or 0.2 in height slicer will see it as the first layer however the model will still be pressed in just like if they weren't there.

Sorry, didn't understand that at all.

RE: Selective brims - possible?

I found this old post and felt it was good enough to ressurect it with a comment.

I tried it and it was amazingly helpful. Major warping issue on one little spot on my print and brim worked, but it brimmed everything and that worked, but that was a major pain to clean up every edge!

I did notice when I add a modifier it does print over it twice which could cause issues if you make the brim too tall. It started getting messy in that area. It even printed right on the skirt. It didn't mess up my print but just thought to mention.

I have play with Add Part since it merges it all together which will slice seamlessly.

RE: Selective brims - possible?

It's even easier now. If you right-click and use Add part, the mouse ears will be part of the shape, so you avoid the double-layering. I create 30mmX0.2mm discs, position them on the build plate, and drag them to corners where some extra adhesion will help. 

RE: Selective brims - possible?

@bobstro

I believe there is a plug in for Cura that creates "mouse ears".