If your BuildTak surface is damaged and needs to be replaced, you need to head over to BuildTak for a replacement. https://www.buildtak.com/ They sell 16" x 16" sheets, a perfect size for the gMax. Or you could try one the following coatings/surfaces many have experimented with and reported success. Before installing any surface, make sure the glass is clean. These are experimental options that you will come across while searching the internet for heated bed surfaces. Most, but not all, of the following methods have been tested on the gMax with varying degrees of success. It is highly recommended that you stay away from any coating that is flammable. The heated bed puts off a lot of heat and draws a significant amount of electrical current.
PEI
PEI is a costly option but well worth it. A PEI surface will work with every common material. Use an adhesive to stick the PEI sheet to the glass. This will not work when cold. See Dunginhawk's response below for details.
PVA (Elmers glue)
You can mix water with Elmers glue and coat the mixture to your borosillicate glass. Mix 8 parts water with 1 part Elmers glue. Apply it cold, let it dry. Before your first print heat the bed to 60C and let the coating cure for about 30 minutes.
Glue stick
Yes glue stick. The same stuff our kids use for arts and crafts. Evenly apply the glue stick to the borosilicate and give it some time to dry. Heat the bed to 60C and let the coating cure for about 30 minutes.
Uncoated Glass
Uncoated glass will work for smaller PLA parts. The trick to success with bare glass is to keep it clean. But if all you are printing is PLA than a heated bed is not necessary. The only thing a heated bed is doing is wasting electricity and decreasing the effectiveness of the extruder's cooling fan. You should use the acrylic bed if the only material you use is PLA. In short an uncoated bed is not an option that makes sense.
There is an advantage to a clean glass bed. That is the reflection of the hotend is so clear and easy to see that you can use it to help manually level a bed.
Commercial Coatings
There are many commercial coatings specifically designed for 3D printing. Give them a try. I have yet to hear of a mixture that does not work well. Some are sprayed on like hairspray while others are applied with an applicator brush.
3M Blue Tape
Many people have reported great success with blue painters tape. This is probably the most common bed surface. It is cheap and easily accessible. You probably already have some laying around. Be careful not to leave any gaps or overlaps. These will show up in the model. Painters tape will not work well with ABS. It is my opinion that an unheated acrylic bed is more practical than heated glass with 3M tape.
Kapton Tape
Kapton tape is specifically designed for high temperature applications. Similar to painters tape, be careful not to leave any gaps or overlaps. These will show up in the model. Kapton tape should work well with ABS but is twice the price of blue painters tape.
Feel free to leave any comments or questions. Please share with us your experiences with different coatings and bed surfaces. Refer to Richard Horne's blog on bed surfaces. It is a wealth of information. http://richrap.blogspot.com/2015/01/stick-with-it-3d-printing-print-bed.html
PEI
PEI is a costly option but well worth it. A PEI surface will work with every common material. Use an adhesive to stick the PEI sheet to the glass. This will not work when cold. See Dunginhawk's response below for details.
PVA (Elmers glue)
You can mix water with Elmers glue and coat the mixture to your borosillicate glass. Mix 8 parts water with 1 part Elmers glue. Apply it cold, let it dry. Before your first print heat the bed to 60C and let the coating cure for about 30 minutes.
Glue stick
Yes glue stick. The same stuff our kids use for arts and crafts. Evenly apply the glue stick to the borosilicate and give it some time to dry. Heat the bed to 60C and let the coating cure for about 30 minutes.
Uncoated Glass
Uncoated glass will work for smaller PLA parts. The trick to success with bare glass is to keep it clean. But if all you are printing is PLA than a heated bed is not necessary. The only thing a heated bed is doing is wasting electricity and decreasing the effectiveness of the extruder's cooling fan. You should use the acrylic bed if the only material you use is PLA. In short an uncoated bed is not an option that makes sense.
There is an advantage to a clean glass bed. That is the reflection of the hotend is so clear and easy to see that you can use it to help manually level a bed.
Commercial Coatings
There are many commercial coatings specifically designed for 3D printing. Give them a try. I have yet to hear of a mixture that does not work well. Some are sprayed on like hairspray while others are applied with an applicator brush.
3M Blue Tape
Many people have reported great success with blue painters tape. This is probably the most common bed surface. It is cheap and easily accessible. You probably already have some laying around. Be careful not to leave any gaps or overlaps. These will show up in the model. Painters tape will not work well with ABS. It is my opinion that an unheated acrylic bed is more practical than heated glass with 3M tape.
Kapton Tape
Kapton tape is specifically designed for high temperature applications. Similar to painters tape, be careful not to leave any gaps or overlaps. These will show up in the model. Kapton tape should work well with ABS but is twice the price of blue painters tape.
Feel free to leave any comments or questions. Please share with us your experiences with different coatings and bed surfaces. Refer to Richard Horne's blog on bed surfaces. It is a wealth of information. http://richrap.blogspot.com/2015/01/stick-with-it-3d-printing-print-bed.html