Magnetic and polypropylene print beds, unlike glass ones, are semi-flexible and have a little give in them. This bend makes it so that these build plates are less fragile than other types of build plates.
A bad first layer can ruin a whole print, thus first-layer adhesion is important in 3D printing.
Magnetic build plates have great adhesion, especially with PLA. However, with ABS and PETG, magnetic beds can sometimes be too adhesive, making print removal difficult.
Still, you will sometimes need to use an adhesive such as Flashforge Purple Disappearing Glue or Wanhao Masking tape to ensure that the print sticks.
While first-layer adhesion is an important aspect of a print surface, you will also want to be able to remove prints quickly and easily from the build plate. Print removal can be a tedious task if you are handling a fragile part and do not want to damage it or the build plate.
Magnetic build plates shine in this area, as you can just bend the print bed to pop the object off. Since magnetic print beds can be removed from the frame, print removal is extra easy. Once the print is off, you can just place the magnetic side right back where it was.
Cleaning of the build plate is very important. Note that if you are using an adhesive product, you’ll need to clean a lot more often because of leftover adhesive residue which can become problematic with achieving good prints.
It is recommended that you use rubbing or cleaning alcohol to clean the bed surface.
Magnetic build plates have varying temperature allowances because “magnetic” isn’t a material; how well a magnetic build plate conducts material depends on the magnetic material found on the bottom of the build plate.
There are not many reported issues concerning the loss of effectiveness over time with this type of build plate.