Adding a Flexible Sheet on Elegoo Mars Build Platform 2: Final Design

A month ago I experimented with a flexible build plate on Elegoo Mars – see the previous blog post. It gave promising results, so I decided to design it properly.

First of all – why flexible and removable build plate? There are three reasons:

  • you can take the sheet off, bend it at peel the prints really easily. No more spatula scraping and breaking prints from fragile materials (I am looking at you, Elegoo Standard!).
  • you can quickly change the sheets without the need for multiple build platforms (a platform costs around 30 €, a sheet around 2 €).
  • you can chapel and safely experiment with various surface finishes.

First of all, I used an ordinary galvanized steel sheet in my first experiment. It is really not suited for the task since it is soft and once you bend it stays deformed. The proper choice is the spring steel sheet – it is flat enough and you can bend it as you want. However, since it is hardened steel, you cannot machine it easily. Fortunately, there are companies laser cutting an arbitrary shape out of them on laser or water cutter. The sheets are pretty cheap to make – I made them in a small quantity and depending on the material the price for a single piece was 1-2.5€/piece including shipping. So I made the sheets 2 mm larger than the build platform with a 2mm radius on the corners. This way, there a flange you can press on to remove the sheet from the build plate.

I experimented with different thickness – 1 mm, 0.5 mm, 0.3 mm and 0.2 mm. 1 mm is practically unusable, as it is hard to bend in hand. 0.5 mm is usable, but I prefer much more 0.3 mm. 0.2 mm is my choice for extremely fragile prints.

The second part of the design are the magnets for holding the sheet. They have to be strong enough to not stick away when peeling the layer from the bottom of the vat. Also, you have to mount them on the build plate. First, I bought a self-adhesive magnetic 1mm film. It worked nicely – easy to apply and my biggest fear of the resin dissolving the adhesive showed up false.

There was however one drawback – the magnetic sheet provided enough adhesion for 1mm and 0.5mm sheets, but not enough for 0.3 and 0.2mm ones. Therefore I started to look for another solution.

I ended up with 20x20x1mm neodymium magnets, which I attached to the build platform via 3M tape. I also oriented the magnets with opposing polarity to force the magnetic flux to close though the steel sheet to get enough adhesion. And it worked – the adhesion of even the thin sheets is sufficient to peel the whole plate covered. See the photos below. There are gaps between the magnets, but I have no trouble with resin being there – the gaps seem to be small enough that the viscous resin doesn’t get deep – only about 8 mm. Which is acceptable. One thing I don’t like about it is the fact that I didn’t get the spacing quite right and it triggers my OCD. Unfortunately, the 3M adhesive is so strong, that I am afraid of breaking the magnets…

To end it, see video below of peeling the prints out of it. One disclaimer – I didn’t was the prints properly, so there is some excess resin (and yeah, I am aware of not having gloves, but small quantities of resin for short period of time does not trigger a reaction for me).

This is how easy is to peel the prints now

There is, however, one disadvantage of my current solution – the magnetic stirring bar I use for cleaning the prints sticks to the build plate. So I probably need some separator in the tank to use it again.

One observation: my hypothesis I stated in a my previous experiments about surface reflectiveness affecting the size of elephant foot seem to be correct – with the shiny, nearly mirror-like surface I get much larger elephant foot. So the next step will be to coat one the sheets in the dark surface finish – probably by cold bluing the steel sheet.

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