Flexible steel sheets

Updated 4 months ago ​by Martin Lexa

The MK52 magnetic heatbed is designed to hold a double sided, Ultem PEI coated, flexible and removable spring steel sheet designed specifically so that you could easily remove your printed objects from the print surface.

Let's take a close look at what makes these sheets unique and what are the differences between them. We will also go through instructions on how to properly take care of your spring steel sheet to ensure it stays in a good shape for a long time.

There are multiple versions of the sheets as we were cooperating with multiple suppliers to provide the best possible quality. Your flexible steel sheet might not look like the ones you see on these photos, and there is no need to worry about it.

General information

The removable spring steel sheet is held in place by 27 neodymium magnets placed in the heatbed from the bottom side. On the top side, there are two pins at the rear of the heatbed that will align perfectly with cut out notches in the spring steel sheets.

Please ignore the two holes in the steel sheet opposite to the notch, they are there only to make the manufacturing of the steel sheet easier.
Before putting the steel sheet on the heatbed, make sure the heatbed is clean and free of any filament debris.
Never print directly on the heatbed. Always use either the smooth or the textured spring steel sheet.

To remove the printed object from the print surface, always wait until the steel sheet cools down to room temperature. Then you can take it off by bending the sheet inwards and outwards.

Using spatula should not be necessary anymore, use it only if the cool printed object cannot be disengaged from the print surface by any kind of bending of the sheet.

Textured vs. smooth spring steel sheet difference

We offer two types of spring steel sheets, the powder coated one and the smooth one. Both sheets are covered by Ultem PEI (polyetherimide), the only difference is that the powder-coated spring steel sheet is covered by PEI dust baked directly to its surface, whereas the smooth PEI layer is glued to the metal sheet as a sticker. It is possible to use both of them for printing with any type of material, if used properly.

Prints with a small area touching the print surface or with sharp corners are less likely to detach when printing on the smooth spring steel sheet. Some users also like the smooth and shiny bottom side of their prints. 

On the other hand, the powder-coated steel sheets are better for printing objects with materials such as PETG, CPE or Flexfill (TPU) which tend to adhere too much to a smooth surface but can be easily removed from the textured one. The textured pattern on the bottom side of your print also hides all potential imperfections of your first layer.

Please note, that both steel sheets have to be considered as a consumable item. If the sheets got damaged during the transport, before the first use, the warranty applies.
When using the sheets, they are naturally and inevitably subjected to wear and tear, which cannot be covered by the warranty. Misuse, such as printing with PETG without using any separating layer or while setting the Live Z too low, is not covered either.

Powder coated spring steel sheet

The surface of this sheet is covered with a special polymer (Ultem) to ensure perfect adhesion. For more information, check the instructional video below or this blog post.

  • Great for extensive printing of PETG, CPE, FLEX/TPU, ABS, as well as any other type of filament
  • Thinner than its smooth counterpart
  • Before launching the print, degrease the sheet by wiping it with isopropyl alcohol (IPA) 90% or more
Never clean the textured sheet with acetone and never apply ABS juice on it, it is causing the powder coating to crack and wear down.
Do not try to cool the sheet in a refrigerator or a freezer.

Smooth PEI sticker spring steel sheet

Both sides of this sheet are covered by a sticker made from smoothed PEI plastic. This is the same time-tested surface type that was used on the older MK2S printers.

  • Great for printing PLA, HIPS, PP, ASA, composite materials (metal/wood), as well as any other type of filament
  • Thicker than the textured sheet
  • Sometimes does not need any kind of surface preparation, but the safest way is to use isopropyl alcohol (IPA) 90% or more. It is possible to use the bundled gluestick or your tested window cleaner. When it comes to acetone or ABS juice, do not overuse it. Extended use makes the PEI surface brittle and fragile.


As the sheets are made from steel, they are prone to rust. Please do not leave them for long in a humid environment.
Prints don’t stick

If your print surface is perfectly clean, if all grease has been removed by wiping it with a paper towel soaked in isopropyl alcohol 90% and if the first layer height is set up perfectly, yet your print still does not adhere reliably to the print surface, read this article.

Bubbles underneath the PEI

Over time, you might see some small bubbles underneath the PEI. Don't panic, it is nothing serious. These bubbles usually does not affect the print quality and will disappear after a few days or weeks. Here are 2 tips which will make the bubbles to disappear faster:

  1. Swap the side of the steel sheet you were printing on. This will speed up the "recovery" of the PEI surface. 
  2. Bubbles appear around the spot where you print the most (center of the sheet), most often underneath the corners of your printed parts. When slicing the models, place them across the whole surface of the print surface and not just at one spot.
Dent in the PEI

Sometimes, there might be a small dimple or dent in the smooth PEI layer when you first unpack the steel sheet. Don't worry, just flip the sheet over and use the other side. Thanks to the heat of the heatbed, the dent will disappear by itself after some time (a couple of days, usually).


Find out more troubleshooting tips here: Community Forum | Assembly Manuals | Youtube channel | info@prusa3d.com

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