Intro: Polyetherimide Print Bed and Insulating Print Bed
Three big problems I had when I started 3D printing were print bed adhesion, print bed heat up time and maintaining high temps on my extruded for ABS. I found a couple solutions that really work well.
The first was solved by getting a Polyetherimide sheet for the heated bed... Something like this below.
This product needs a sheet of double sided transfer tape, something like below...
The next two problems I managed to solve with one fix. It seems that the print bed was using enough power that it was robbing the extruder heater. Insulating the underside of the print bed works wonders for solving both these problems without the cost of a larger power supply.
Step 1: Materials and Tools Needed
1) 12 x 8 or 8 x 8 Polyetherimide sheet
2) 12 x 12 3m double sided adhesive sheet
3) Heavy duty or commercial paper towels, or any material that can act as an insulator and handle the heat.
4) 3M painters tape thick stuff, chances are, you already have some of this from printing.
5) 4 x Small Binder Clips
6) Exacto knife or similar
Step 2: Remove the Print Bed
Remove the leveling screws and springs. My print bed is an aluminum sheet. Some are glass so be careful handling them.
Step 3: Cutting the PEI and 3M Adhesive Sheet
Score the PEI (Polyetherimide) sheet with your razor knife then snap it along the score lines. You likely noticed the thin protective layer of plastic on both sides of the PEI sheet, peel this off. I scored and snapped the corners off where the leveling screws will be.
Peel off one side of the protective sheet covering the 3M sheet exposing one side of the adhesive. Lay the sheet on a flat surface, adhesive side up. Take the PEI sheet and carefully bend it placing one edge down on the adhesive, slowly and carefully rolling the bend into the adhesive. The goal is no air bubbles between the adhesive and the PEI sheet. If you do get some, use a credit card to smooth them out and pop them with razor knife. Use the razor knife to cut away the excess adhesive sheet from the PEI.
Step 4: Applying the PEI Sheet to the Print Bed
Lay the print bed on a flat surface. Remove the second protective covering from the adhesive sheet. You are going to bend the PEI sheet adhesive side down carefully align it and slowly roll it pressing it bit by bit onto the print bed. Make sure to press out any air pockets, as you roll it on. This step is critical as any air pockets between the bed and PEI will make the print surface uneven. This is a one shot deal, if you mess it up you have two choices, pay for more stuff and redo it or deal with a slightly warped print surface.
Step 5: Insulation
Cut out several layers of insulating material (I used commercial grade paper towels) the size of your print bed. Make two piles several layers thick each. using the blue painters tape, tape the edges of the top layers and fold the tape around the edge to the bottom layer. When you are done you'll have two pads with taped edges.
Step 6: Re-assembly
Ok reassemble the print bed like you normally would with one of the insulation pads under the bed heater. Place the print bed PEI side up on the heater. Install the leveling screws and use the binder clips to hold the taped edges of the insulation against the bed heater. This helps keeps heat from escaping from under the print bed. The second pad is used to place on top of the print bed for pre-heating the bed.
Step 7: Final Thoughts
Make sure you run your print bed for a few hours and monitor it closely after installing the insulation... If you smell any odd burning smells check the insulation for spots or brown discoloration, indicating it's breaking down from the heat. If you have any of these you need to find another material to use.
Using the PEI solved my problems with PLA and ABS prints warping off the bed, even long thin prints adhere great, I still print a small skirt even though I'm pretty sure I don't need it. As you can see from the terminator I'm printing from ABS there is zero warping in the corners.
I didn't tape the insulation under my print bed but next time I need to take it apart I plan to. Insulating the bed increased my preheat times and eliminated the problem I was having with the print head not maintaining its temperature during prints. Using the insulation pad on top of the print bed also helps a lot with slow preheating.
I got a few bubbles under my PEI but nothing too major. So far it is by far the best print surface I have used since I started. Cleaning is very easy, just pour a bit of rubbing alcohol on the bed and wipe it down with a cloth or paper towel...leftover print plastic is easily removed with a small window razor scraper. I often use the same scraper to pop the corners of my prints then use a small screwdriver to lever the prints free from the bed.
I wish I could have taken more pictures of the process but I did it about three months prior.