For protecting the hot bed, and giving an accurate, flat printing surface that the parts will stick to properly, all of which yields a better quality print, especially for printing with ABS.:
We recommend Borosilicate glass, more commonly known as Pyrex and Schott glass. Your glass measuring cups in your kitchen, as well as glass baking ware are made from Pyrex/Borosilicate glass.
You want a Borosilicate glass sheet, measuring 200mm x 214mm x 3.5mm thick (7-7/8 in x 8-7/16 in x 1/8 in thick or 7.87″ x 8.43″ x .13″ thick). An 8″ x 8″ borosilicate glass sheet will also fit between the screw heads that hold the heat bed in place.
Borosilicate glass is rated for higher temperatures than normal sheet glass making it a better material for use as a heated bed. Standard glass can crack from rapid cooling or heating, borosilicate glass will stand up to rapid temperature changes. It is also beefier than standard glass. This same glass sells on Lulzbot and other sites for $25 each. Borosilicate Glass all contain Boron as a component material. This type of glass is characterized by its resistance to heat, chemicals and specific coefficients of thermal expansion.
At this time, 123dprinter does not sell borosilicate glass as we cannot source it any cheaper than you can. We recommend buying from this ebay seller.
An alternative to the ebay seller above is to purchase from McMaster-Carr. An 8 inch x 8 inch piece of Borosilicate glass will fit on the heat bed, between the heads of the supporting screws. pn 8476K181 is 8″ x 8″ x .13″
123dPrinter Mendelbot MM-1.5.1 design
Open Source 3D printer design information: Reprap Org
Our MM-1.5.1 design is based on the RepRap MendelMax. We utilize refinements to the printed parts of the original MendelMax as we have found that it makes the printer easier to use and yields better quality printed parts. Here is a partial list of what we use:
We use the Greg’s Greg’s “Wade reloaded” extruder because it makes your life easier when you need to reset the filament feed, or if you want to change your filament color mid-print. This extruder allows you to open it easily to gain access to the hobbed area of the hobbed feed bolt that pulls the filament and pushes it down into the hot end.
X-Axis Ends by Jonas Kuehling
Reinforced X-Axis Carriage by Jonas Kuehling
Compact Y-Axis Rod Mount for 8mm Smooth Rod by Jmil
Y-Axis Idler by DanFineArt
20mm x 20mm Aluminum T-Slot Extrusions and Bosch-Rexroth T-Slot nuts
We use aluminum extrusions are already cut to exact length in our MendelBot MM-1.5.1 kit and printer. This differs from the original Mendel or Prusa because those earlier versions of the 3d printer utlized threaded rods. This made assembly much more difficult as parts needed a lot of time consuming and difficult alignment after assembly (translation: they were extremely fiddley and frusterating to build and position the parts correctly). Using aluminum extrusions, while a tad more expensive, yeilds a MUCH easier to assemble, more rigid, and much nicer looking frame. Increased rigidity and stiffness of the frame is always a good thing, as it yeilds much higher quality prints.
• Installs anywhere along the profile’s T-slot and rotates into position
• Ridges “bite” into profile to lock the T-nut into position, and provide ESD protection and resistance to vibration
• Large contact surface improves gripping strength
• Tapered neck simplifies assembly; T-nut is self-aligning in T-slot
• M5 threaded nuts have 2 ridges
• Zinc-plated 8.8 steel