Prevent Corner Lifting During 3D Printing – The Overkill Method

A brief explanation of why corners of large 100% infill solids lift off the print bed during 3D printing, and my way of solving the problem.

beforeaftercornersolve

Cause

I am printing a model that is essentially half of a box, meaning there is a bottom and 4 walls. The bottom and walls are thick (because it’s not actually a box) for strength and I printed it at 100% infill. When it was printed, the corners lifted during printing, causing the entire model to deform. Sometimes this can cause the entire print to fail.

what I want vs what i got.fw
problem

Why does this happen? The bottom is touching the heated bed, it is hot. The temperature is lower further away from the bed. That means the colder plastic contracts.

cold contracts.fw

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The walls didn’t shrink nearly as much, that is because:

  • We are printing layer by layer, the walls are not that warm to begin with
  • Less material means less capacity for heat
  • Less material means less material that can shrink. If the bottom was 100mm and shrunk to 99mm, then a 10mm wall would only shrink to 9.9 , so it is less noticable on a wall

Easy Solutions

To avoid this, you can simply not large print 100% infill objects. Also, use a brim on the bottom layer, which will hold down the bottom layer better. A funny looking trick is the “Micky Mouse Ears” technique, which puts down a pad on the corner of a model so the corner doesn’t lift.

However, my model was huge and thick and the even a full 20mm brim still couldn’t hold it down. My idea was, instead of using glue to keep the brim down, I make the brim super thick so that it’s stiffness is what is keeping it down. So I came up with this technique, the extra-thick-brim:

new idea.fw

new idea zoomed in.fw

The stiffness keeps the first layer down on the bed. The extra-thick-brim is wide on the bottom and narrow on top, which gives it strength while preventing itself from curling. In fact, the triangular shape might even provide a force that is the exact opposite of lifting corners.

The downside is that this obviously uses more plastic and takes more time, plus takes up bed area, and you need to cut away the excess plastic after. But at least you are almost guaranteed a successful print on the first try, so when the situation is right, you are actually saving plastic and time by not having any failures.

To save some time and plastic while still using this method, put the extra-thick-brim around two models, so the weight of one model keeps the second model’s corners down. This saves two lengths worth of extra-thick-brim.

example in action screenshot 2

WHy 0.3mm for the bottom? That’s the default bottom layer thickness in the Cura slicer, which works pretty well. Why 0.8mm for the gap? It should be wide enough to avoid Z scarring from joining the outside and inside, and fit a thin knife blade into.

Results

Through a view of the bottom, one can see that there’s still some force threatening the corner to lift, but now it is drastically reduced.

zoomedinonpossiblecornerlift

During print:

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After print:

20150726_003045
20150726_004659

5 thoughts on “Prevent Corner Lifting During 3D Printing – The Overkill Method

  1. Doug

    I have been looking for a solution for this for a long time. Great and simple idea can’t wait to try it out . My boxes have all been lifting hopefully its going to work for me too.

    Reply
  2. benmlee

    Heat the baseplate close to the softening temperature of the plastic. For ABS, softening temperature is 150C, so I use 120C for the baseplate. High temperature keeps the upper layer soft. If is soft, then it does not have enough force to lift the first layer. For large parts, I will even put a piece of cardboard in front of the table to push the air away as the table is moving. Keeps the part hot to prevent lifting.

    Reply
  3. Solice

    I just thought I’d drop a note that this article helped me out. I just happened upon it and I’m glad I did. I was at my wit’s end trying to prevent bottom curling, even on a raft. Thanks for the explanation of why it happens; that helped most of all!

    Reply

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