On the Lambda

Programming, Technology, and Systems Administration

On the Lambda

Dealing with a warped or bowed printer bed

January 8th, 2019 · No Comments · 3D Printing

Last time, I talked about a seesaw/lever effect when leveling a square bed with four posts. Today I’ll address dealing with a (slightly) warped printer bed. For simplicity sake, I will only examine warping on along one axis. You should be able to apply the principles here to examine the X and Y axis separately, to get the best possible results for your bed.

Bed warping is a common issue for square beds with four adjustable posts. It’s one reason you see so many people mount glass plates over top of their original bed. It’s a natural result of heating a fixed bed, which will cause it to expand, without also heating the carriage for the mount points. This stresses the metal plate, causing it to warp. Generally manufacturers try to address this by have loose screw mounts in the bed. The problem is the pressure from the adjustable springs tend to limit the ability of the bed to expand properly. Warping is also the result of heat spreading into the bed unevenly, where the bed will expand nearer the heating element first. Finally, some warping of the metal is just a natural result over time. At the tolerances we need for good print results, even a brand new bed is unlikely to be perfectly flat.

At this point, I need to make it clear I’m not talking about obvious bending or damage. The kind of warping I’m referring to is only as much 0.3 mm from one end of the bed to the other… but when we’re talking about 0.1 mm layer heights, that’s enough to cause serious problems for prints. Really, anything more than 0.5 mm and you may want to replace the bed entirely, or look into the glass addition I’ve already referred to. You can sometimes also deal with greater warps by getting the best level you can, and then using an automatic leveling system that can compensate for some surface variance with the software, where it knows the bed is higher or lower in certain areas and adjusts the print head height to account for it.

Here is an illustration of a print bed from the side, with some warping visible:

The warping is exaggerated. Any bed warped this much would be unusable.

Note how the bed bends up along the right side. Let’s say for a moment difference between the left edge and the right edge is 0.2 mm. Such a bed would be very difficult to level.

We can improve things some, though, without changing the bed at all. Consider the following illustration:

The same print bed as before.

This is the same print bed from the previous illustration. This time, we have loosened the knobs on the left side, and tightened the knobs along the right, so the entire bed rotated slightly clockwise. Now, instead of rising on the right side, it rises on both sides from the middle. The result is the left side and right side are on the same level, and the middle is now a little lower.

The point is the change between the left or right and where the warping is worst is likely to be much less than the 0.2 mm we were dealing with before before… likely close enough to get good results throughout the entire bed.

If you find yourself with a section of your print bed where you have trouble getting good adhesion, even if you’re sure you’ve leveled the bed, you may want to consider the bed may be warped, and an adjustment like this (in combination with re-setting your Z-stop) may be just the answer.


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