I have created a new print bed system for the J1. Here are the details if you would like to create your own:
Graphite plate replaces the glass and clips onto the PCB. Graphite has the same low thermal expansion as the glass but has much better thermal conductivity. More importantly, it’s easily machinable. I drilled 20 blind holes (pockets) and embedded samarium cobalt high temp magnets into the graphite with high temp epoxy. I then ordered a custom sized magnetic flex plate with smooth PEI on one side and smooth PEA on the other side, but you can choose from many different coating options.
I ordered an 8mm thick graphite plate and cut 3mm deep rabbets on the long edges on my router table to make it fit in the clips. I only did 8mm because I was unsure how rigid the material would be and I wanted to make sure it wouldn’t flex when clipped to the PCB which has corners that are bowed downward. Now that I know how rigid it is, I would just get a 5mm thick plate if I were to do it again.
The magnets are 1/4” diameter and 1/8” thick. I drilled my holes with a 7mm bit to make them oversized so that thermal expansion of the magnets won’t crack the graphite, and to give the epoxy more surface area to bond to. You want to be very precise with the hole depth and make it so the magnets will sit just a hair below the surface. If you try to make them perfectly flush, you’ll inevitably have at least one or two that don’t set right and create an uneven print surface. The pull force of the magnets is plenty strong enough to securely hold the flex plate without being in direct contact.
Sources:
Graphite: Ohiocarbonblank.com. UT-3 material. Precision ground Z dimension. Dimensions in imperial: 12.9” x 8.75” x (0.3149” for 8mm thick like mine or 0.197” for 5mm thick).
Cost = $59 total.
Magnets: Magnet4less.com. 20x 1/4 in x 1/8 in Disc Samarium Cobalt.
Cost = $24 total.
Epoxy: Amazon.com. JB Weld High Heat Epoxy Syringe 25 ml.
Cost = $8 total.
Custom flex plate: Energetic 3D Store on AliExpress. Message them with the size and coatings you want.
Cost = $47 total.
Grand total = $138.
