Updated: Nov 3, 2018
After few prints your present PEI bed might start looking like the picture below.
At this point, the adhesive does not hold the PEI sheet to the bed no more, and your printed parts will not adhere to the bed, in addition, the parts will not be straight flat. You can try sanding the PEI but that does not resolve the issue.
If you decide to change the PEI here is a technique we used and works well.
First, you will need an exacto knife to peel off the adhesive one tiny line at a time. Be careful with the knife, and never apply pressure or force. Start by inserting the knife blade gently on the side a bit, we have done this done while the plate was heated on the printer, and moving inwards slowly.
At this point you can hold the PEI with one hand and continue cutting thin layers at a time for the remaining PEI, no pressure or force required. This can take up to 15 minutes for the whole bed.
At the end of this repeated process, the bed will look like this:
Here we can see gaps on the adhesive layer. The big gaps represent areas where there is no adhesive sticking to the metallic plate [these are the areas we see on first picture].
Now, you will need some camping fuel, again careful while using this, follow precautions as listed on the can. Gently pour some camping fuel on the bed (do this outside or in a well ventilated area). Let the adhesive soak in the fuel for 5 minutes, add a bit until saturated. You do not need a lot of camp fuel, 2 cap holders should be enough.
Using a scraper tool or spatula, you can remove the adhesive fairly easily as shown below.
Now, using a 400 sand paper, and dish washer soap, sand the bed plate under warm water.
For a finish that will look like this:
Hope this blog comes in handy for those wondering how to efficiently remove their PEI and adhesive from the bed.
At this point it is up to you to decide whether to stick another PEI sheet and go over this whole process after few prints or switch to eco-friendly, non-toxic DustnPrint.
PS: If you have removed all the PEI and you are left with both sides of the plate PEI free, please consider sticking a Kapton tape on the heated PCB bed to avoid removing of the soldermask on the PCB and any chance of shorting it when placing your plate over...