First we will prep the PEI to be attached to the borosilicate glass bed. Open a precut package of PEI sheets for Mini and attach to the oven rack via binder clips (see picture). These need to be hung so that the natural curvature of the PEI allows heat to rise to the top of the oven for an even bake (see images). Once the oven rack is full we will bake the PEI for a set amount of time depending on weather conditions. Check the humidity to determine the bake time.
0%-69% - 1 hour and 30 minutes
70%-85% - 1 hour and 45 minutes
85%-100% - 2 hours max
NOTE: Do not exceed 2 hours when baking the PEI it can cause the adhesive to run and create bare patches lacking adhesive, as well as introduce microbubbles that will cause "silvering" during post bake
Once the PEI has finished baking we are ready to apply it to a borosilicate glass bed. To start we will inspect the glass bed for chips and trapped air bubbles (see images). Do not use glass with trapped air bubbles. Some minor chips can be cleaned up with a glass file, but if they are too bad do not use the glass. Now we will spray the glass with some AP115 Silane Glass Treatment. This allows the adhesive to flow/spread across the surface of the glass for optimal adhesion. Use 3-4 squirts covering the entire surface area of the glass and wipe til dry with a clean paper towel.
Now that the borosilicate glass is prepped we are ready to apply the PEI sheet to the glass. First grab a sheet of baked PEI from the oven and do an initial inspection of the PEI. Look for small microbubbles or patches that no longer have adhesive. If you find some PEI with patches of adhesive missing, you may be able to still use some of the PEI on a mini heat bed, avoiding the missing patch of adhesive. Do not use if there are microbubbles present throughout the sheet or the PEI will "silver" in post bake.
Now we will attach the PEI to the glass. Pull the adhesive backing about halfway off the PEI sheet. Attach the PEI to the edge of the glass with the PEI sticking nearly straight up, about 90 degrees from the surface of the glass (see images). Next, feed the glass with the PEI attached to the edge into the roller to ensure no air bubbles are trapped during the lamination process. Keep the PEI at about a 45 degree angle to the glass when feeding through the rollers and peel the backing as the roller pulls the glass and PEI through (see images). Try and keep the backing on as long as possible. Dont peel too much because if the PEI falls and touches the glass you will end up with trapped bubbles. Feed all the way through the laminator and you will have a piece of glass with PEI attached and no trapped air bubbles.
Now we need to trim the excess PEI off the glass bed. Using the adjustable razor blade and cutting mat, push two blade sections out of the razor to allow enough clearance from the edge of the glass to trim the PEI (see picture). Run the blade along the edge of the glass just enough to "score" the PEI. Now fold the edge of the PEI forward and it will snap free (see picture) and you can remove the trimmed edge (see picture).
Now it is time to attach the silicon heater pad to the back of the glass and PEI assembly. Clean the backside (glass side) of the PEI and glass assembly with a little acetone and wipe clean using a clean paper towel. Inspect the backside of the heat pad for dented corners and creases. Also peel the majority of the adhesive backing off and inspect the adhesive side for bubbly adhesive, debris, and creases or missing adhesive patches.
Before applying the heat pad, crease the adhesive backing diagonally (see image). Attach the first corner and check the alignment on your second corner. If the alignment looks good on your second corner check the remaining two corners dont overhang. Once youve checked the alignment of all four corners press near the diagonal crease with two fingers to get the adhesive started (see image). Now working from the first corner use the hand roller to apply firm pressure and work toward the crease. Slowly peel the backing while using the hand roller to ensure you dont trap air bubbles. Once the backing is off and you have rolled the pad on, run the roller around the section where the wires go into the pad. Use your finger to push any remaining bubbles down.
We are now ready for the second press. Raise the top roller and put the heat bed in between the rollers, use the hand wheel to adjust the pressure. Crank the hand wheel to 60%pressure.
Now, feed the Mini bed through the laminator PEI side down on the butchers paper (see images) l. Run this all the way through the laminator making sure the connectors arent going to be crushed by the rollers (see images). Once this has gone all the way through the rollers the second press is complete.
After the post bake, while the bed is still hot, put it through the laminator rollers again the same as in step 4.
After post bake it is time to run the beds on the tester. There are two different sd cards one has a 30 min cycle and the other is a 50 min cycle. If the bed has been sitting for 2 days or longer use the 50 min test. If the bed has been sitting for less than two days use the 30 min cycle. After the test is complete inspect the beds for bubbling or silvering. If the bed passes the tester, it is ready for use in the production line or to send to the store.