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Large print, should i use a brim?  

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nathan0876
(@nathan0876)
Estimable Member
Large print, should i use a brim?

Im printing a large print(110m filament used, 36 hours print time according to slicer) tonight.

Im printing it in Petg, it has very very little contact with the build plate and is almost going to max the Z height when done. This seems like a good print to use a brim on but, its also only 1cm narrower than the build plate so at most i could use a 4-5mm brim.

For a quick example first layer will look like this and only goes straight up from there no protrusions or anything:

| | |
| | |
|________|________|

those walls are only 5mm thick, and then its like almost 20cm tall. so not much contact on build plate and very tall.

Am i going to run into any issues or you guys think ill be ok, a little nervous because with the print time im obviously going to have to sleep through some of it so if it detaches it will be ugly. Im probably going to wash the build plate very well and not use any kind of separator like windex like i have been for petg just to be safe and have max adhesion, id rather it be a total bitch to get off than have it detach mid print..

edit: apparently this forum hates ascii drawings, pretend those three upright walls are above the uprights at the bottom not stuffed into the left side, looks fine when im in this edit window but not so much in the actual post.

Posted : 03/08/2018 7:58 pm
RetireeJay
(@retireejay)
Reputable Member
Re: Large print, should i use a brim?

Assuming you have control over the design of the part, you could add your own "brim" as wide as you want on the inside of the shape. (I take it that it looks like an E). In fact, you could make the whole bottom of the print one layer thick filling in all the gaps between the uprights.
But I highly recommend not printing PETG directly on bare, clean PEI. You will probably break the print and/or ruin the PEI getting the print off.

One little trick I've discovered when a print doesn't want to release: If you can get a corner or an edge to pull away by bending the steel sheet, then stick a toothpick or a piece of zip tie between the part and the sheet. As you continue to flex the steel sheet both up and down, this gives you a lever that helps pull the part off.

Posted : 03/08/2018 8:25 pm
nathan0876
(@nathan0876)
Estimable Member
Topic starter answered:
Re: Large print, should i use a brim?


Assuming you have control over the design of the part, you could add your own "brim" as wide as you want on the inside of the shape. (I take it that it looks like an E). In fact, you could make the whole bottom of the print one layer thick filling in all the gaps between the uprights.
But I highly recommend not printing PETG directly on bare, clean PEI. You will probably break the print and/or ruin the PEI getting the print off.

One little trick I've discovered when a print doesn't want to release: If you can get a corner or an edge to pull away by bending the steel sheet, then stick a toothpick or a piece of zip tie between the part and the sheet. As you continue to flex the steel sheet both up and down, this gives you a lever that helps pull the part off.

I did design it yeah, and you are right i could totally fill in one layer on the bottom inside, thats a great idea.

Posted : 03/08/2018 8:43 pm
bobstro
(@bobstro)
Illustrious Member
Re: Large print, should i use a brim?


I did design it yeah, and you are right i could totally fill in one layer on the bottom inside, thats a great idea.
I assumed the bottom was solid so wasn't overly concerned. If it's an E laying on its back, why not lay it flat?

There's no shame in using a brim. I try not to use them, but if it's a choice between a brim and a long print failure, I use 'em.

Any print positioned so you've got a large enough bottom layer should be fine. I generally only have issues on small pieces. A brim might help with warping, though that shouldn't be a big issue for PETG.

If a print is stuck, dental floss can be used to help remove it once you get a corner up.

My notes and disclaimers on 3D printing

and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan

Posted : 03/08/2018 8:58 pm
nathan0876
(@nathan0876)
Estimable Member
Topic starter answered:
Re: Large print, should i use a brim?



I did design it yeah, and you are right i could totally fill in one layer on the bottom inside, thats a great idea.
I assumed the bottom was solid so wasn't overly concerned. If it's an E laying on its back, why not lay it flat?

There's no shame in using a brim. I try not to use them, but if it's a choice between a brim and a long print failure, I use 'em.

Any print positioned so you've got a large enough bottom layer should be fine. I generally only have issues on small pieces. A brim might help with warping, though that shouldn't be a big issue for PETG.

If a print is stuck, dental floss can be used to help remove it once you get a corner up.

I cant lay it flat on its back because what i didnt add to the sketh was the middle finger on the E really looks like this T not this |. and the end fingers from the E also have a 1cm protrusion going inwards only. This is a wall mount for boxes so i can slide boxes into it from the end and pull the contents out the front. So if i put it on its back there would be 4 1CM overhangs 20cm up unsupported, and i cant 45 degree it on the inside because the boxes that slide in are square, obviously lol.

Posted : 03/08/2018 9:20 pm
nathan0876
(@nathan0876)
Estimable Member
Topic starter answered:
Re: Large print, should i use a brim?

Turned out alright, printed with a 4mm brim and filled the inside of the bottom with one layer as well. Good thing i did because two corners separated a little from the build plate, one at the 20 hour mark and one at the 28 hour mark. Nothing major though and it finished alright. Thanks for the suggestion of filling in the bottom!

Posted : 05/08/2018 3:35 pm
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