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tjarvstrand

Printing a custom brim

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Hi,

 

I have a small print with which I'm having some problems with the build plate adhesion. I don't however want to use the standard Cura brim because I'm printing many of this part and I'm too lazy to deal with the post processing.

 

There's only a specific part of the print which tends to come loose so I thought I would add my own brim which only touches on the outer edges of my print. It basically a hollow square where the hollow is a bounding square of my print. Cura, however completely ignores the brim, even though it shows up in the UI. I've tried making the 0.1mm and 0.2mm thick in the model but no luck. What am I doing wrong?

costar_style_stabilizer2.stl

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I don't know what you are doing wrong but it sliced for me using 0.2mm layers:

 

Screenshot_2018-05-30_22-23-06.thumb.png.d330019772a2f954224187f0a396f13a.png

 

However, I wouldn't do this myself as I think it will make a really bad mess to the edge of the part trying to remove that brim.

 

What I would do is use a wide skirt with a really small gap (say, 0.1mm) so that it looks like brim but only just touches the side of the part. I use this technique for PLA parts that I don't want to warp and don't want to clean up! YMMV

 

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Leaving aside the question of "Is this good?" and getting back to the question of "How to make this work?"...

 

At least on the initial layer, Cura will completely ignore model portions that are too thin relative to the layer height. When I loaded up Cura with this model, my Initial Layer Height happened to be set to 0.27mm, and the brim was skipped by the slicer. When I lowered Initial Layer Height to 0.2mm, the brim was sliced as expected.

So try either slightly increasing your brim's height in the model or slightly lowering your Initial Layer Height.

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30 minutes ago, tjarvstrand said:

Hm, I'm not sure I follow what you mean. What is the problem? The end result in your image would in practice be more or less the same as in my initial stl right?

 

Yeah, you're right, the end result is very similar to what you started with. Glad it's working.

 

I find that with PLA some sharp corners do tend to curl up and adding a skirt that's almost a brim is a great help. My theory being that it's something to do with the temperature gradient on lower layers and having the brim helps keep the temperature uniform across the bottom of the part (this could be complete rubbish but that doesn't stop it being effective 😀)

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On 5/31/2018 at 7:15 PM, smartavionics said:

...

I find that with PLA some sharp corners do tend to curl up and adding a skirt that's almost a brim is a great help. My theory being that it's something to do with the temperature gradient on lower layers and having the brim helps keep the temperature uniform across the bottom of the part (this could be complete rubbish but that doesn't stop it being effective 😀)

I guess that might make sense indeed? A theory is as good as it produces results.

 

I found that the cooling fans do reduce bed temp by 10 to 15°C in the area where they are blowing; measured with an IR-thermometer gun.

 

So maybe such a brim or wide skirt prevents the glass from cooling down too much and thus improves bonding? And/or maybe it deflects a little bit of the airflow away from the bottom layer? So that the first layer is sitting in the shadow of the wind?

 

Anyway, I am gonna keep this theory in mind and try it on some of my next models with lots of tiny holes and sharp corners.

 

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