Installing a glass bed is one of the most common upgrades on any 3D Printer, there is simply no better build surface out there. New owners find themselves with more questions than answers though, encountering a wide range of opinions as to what will work best. Suggestions include anything from using picture frame glass and glue sticks, to the more expensive borosilicate glass and hairspray.
The truth is, there is no one method that will be the best choice for everyone. When I switched to a glass bed from the standard Build Tak surface, I experimented with every option available. After nearly pulling out my hair in frustration, I found a plastic sheet called PEI to work unbelievably well. I will cover the most popular options for both glass and adhesives, then show you how to install the bed with a PEI surface.
Using a glass bed offers several advantages over the traditional tack surfaces found on many 3D printers. Parts will have a smooth, glossy finish on the bottom, where the printed layer lines will be nearly invisible. The glass bed can also be removed from the 3D printer as needed, a convenience for prints that may prove difficult to remove. Placing it into the freezer for a few minutes will make the plastic contract and pop off with ease. A flat piece of glass will also cover any deviations in the aluminum bed, which can warp and become deformed over time.
Choosing the Glass:
Borosilicate glass is the strongest and most durable option available. It has superior thermal shock resistance and lower thermal expansion, where it is created by replacing one of the chemicals in regular glass with boric oxide. These are fantastic qualities for 3D printing applications, where the glass will often be subjected to rapid changes in temperature on a heated bed.
Tempered glass by comparison is just normal window glass that has been post treated with chemicals. While this does improve the strength, post processing glass does not achieve the same degree of structural integrity, making it a decent albeit lesser alternative to Borosilicate glass.
Video: Borosilicate vs Pyrex Glass
As a third option, many owners opt to just use standard window glass, cut to size by a local shop. Depending on cost and availability, this may worth consideration for those on a budget. Window glass should be used with precautions though, where it can have sharp edges or shatter during temperature fluctuations.
Choosing the Adhesive:
Printing directly on to a glass bed alone will not be enough to hold prints in place, some type of adhesive component is strongly recommended. The most common choices include…
- Blue Painters Tape
- Glue Sticks
- Aquanet Hairspray
- PEI Sheet
The problem with most of these choices is that they are temporary, requiring you to reapply them on a regular basis. As the best option, PEI will provide exceptional adhesion and require almost no additional upkeep over time. I have yet to encounter a single problem with prints sticking to the bed since it was added months ago, still going strong after being used hundreds of times. When the surface quality does eventually begin to deteriorate, you can simply use an abrasive material such as sandpaper or steel wool to restore it.
We will start by attaching the PEI sheet to the glass plate using the included double sided 3M adhesive. Peel off one side of the backing sheet, exposing the adhesive layer underneath. Keeping the adhesive sheet taut to minimize air bubbles, lay your piece of glass on top.
Using a textbook, rolling pin or anything else you may have available, apply even pressure to the glass plate and press it firmly into the adhesive. When finished, we will go ahead and flip it over, where the remaining covered side of the adhesive is facing upwards. Go ahead and carefully pull off the second paper backing sheet, leaving the glass and the 3M adhesive sheet exposed.
Warning: If your 3M adhesive sheet is larger than the glass plate, place a piece of cardboard underneath to catch any excess. It is extremely difficult to remove once stuck!
The PEI sheet will have a protective blue plastic covering both sides, where you can go ahead and remove one of these now. With that side facing the glass, align the bottom of the PEI with the bottom of the glass plate. Bending the PEI at a slight angle, start by laying the sheet in small sections and pressing out any air bubbles before moving forward.
I used a paint scraper with several layers of blue painters tape to dull the sharp edges. You can also just use your fingers, a credit card or any other tool as long as it will not damage the PEI surface when doing so. The goal is to completely push out the air bubbles that formed in the adhesive before laying the next section.
After the PEI sheet has been laid on the glass and all air bubbles are removed, we need to place even pressure on top to make sure it sets. I centered a stack of heavy books and boxes of filament to firmly compress the PEI, adhesive and glass plate together. I would recommend leaving this for no less than 30 minutes, where 2-4 hours would be optimal.
From here, all that remains is removing any excess material. Flip the stack to the other side with the glass plate sitting on top. Using a box cutter, treat the glass as a guide and cut down each side, pressing firmly to cut through the plastic PEI sheet. You may need to make several passes with moderate pressure, where I recommend doing this on a disposable surface such as cardboard.
Now there are several different methods of placing the glass bed on the 3D printer. Some guides recommend using thermal adhesive pads, cut into squares and placed in each corner of the center of the glass. I personally found this method overly complicated and it seemed to delay the actual heating of the glass.
As a better solution, I recommend simply using binder clips to hold it directly to the metal, placing them around the perimeter as needed. Just take care not to damage the heating element on the bottom of the aluminum plate.