Ender 3 cracking magnetic bed

Question

My first magnetic bed mat for my Ender 3 Pro is cracking underneath. On the top side there is a bubble in the middle which prevents any viable print. The layers are probably separating.

I am new to printing but have read many articles on hiccups to expect, fixes etc. I do understand these magnetic mats can break down. They're pretty cheap on Amazon (something like \$12 for a 2-pack). Not a huge deal. I've printed only about 1100g worth of filament over 30 prints. Despite their cheap price I don't feel I got a proper amount of mileage out of the mat.

I keep my bed at 60 °C and 215 °C for the filament. I'm pretty sure 60 °C is below the maximum temperature for this kind of bed. I am struggling to find articles on this issue.

What can I do to prolong the life of these mats? I have removed the mat (with its print) while the bed was still hot to remove items just as much as removing cold items. Am I supposed to wait until it's cold? The cracks I only assume are from flexing the mat. I'm not trying to fold it here. I do pull on the item as I'm curving the mat to break it free. I can't explain the bubble.

The bed deteriorated after my first large print which took 27 hours. Prior, longest print I had was about 5 hours, most prints 1-1.5 hours. Is this a factor?

Answer 1

My personal technique for removing prints (particularly larger prints) is not to flex the mat at all. Instead, I wait until it's cool and then work the spatula under an edge and move it under the model to basically peel it from the mat.

Smaller prints usually pop right off if I start with this technique from one end.

Surface area on the bed (for a single part) is most important to how much work is involved. For example, a raft or brim will greatly increase the surface area. The spatula is long enough that usually I can reach everywhere under the model so eventually it will pop free. I might have to work around the model a bit before it reaches this point.

Answer 2

I had quite a few Ender 3's with magnetic beds and I did start to notice the cracks on the underside with use. To stop the cracks from appearing so soon you should avoid excessive bending of the mat. Any time where you are bending the mat near 90°s or so is when you will start to cause those stress forces that cause the crackling you see.

However, I would like to point out that the bed is still quite usable and should not need to be replaced until it no longer adheres to the build plate firmly. I would also point out that most Ender 3's that I've dealt with needed to be upgraded to glass beds for superior flatness and consistent bed adhesion. I recommend upgrading if you do decide to spend money on ned beds.