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.
fantastic stuff! how do you compensate for that extra thickness? ive been wanting to have a flex plate for the j1. tired of the coating wearing off the glass
Snapmaker allows you to set the “bed thickness” on the HMI screen but limits it to 5.5mm max because Snapmaker loves to make life difficult. All that parameter actually does is adjust your home offset in eeprom though. You can adjust it to whatever you want with M206 in a terminal, which is what I did, or you can set it in the firmware.
I added 24 more magnets (overkill I’m sure) in between the original columns pictured. Did columns of 7,5,5,7 from left to right.
The original number of magnets was fine for most prints, but on a particularly large print using PC with a tendency to warp, it overcame the pull force of the magnets on one side and lifted the flex plate upward. I have had no problems with the same print since adding magnets.
So, guided and inspired by your mod, I attempted my own. Based on your recommendations, I elected to use the 5mm graphite plate, and I used larger (1/2x1/8) SmCo magnets. I also simply cut my own flex plate from one that was oversized for a Bambu printer, using tin snips and a dremel with a diamond cutoff wheel. I knew the edges wouldn’t be 100% flat, which is why I went very carefully and cut it so that all edges fall as far outside the print area as possible. I think it all came out pretty good! Only hiccup was that I cracked a corner of the graphite when drilling a hole. I glued it back together and since it is outside the printable area, I wasn’t too concerned about it being perfectly flat on that corner.
For those possibly interested in making their own, I got my magnets from Apex Magnets since they offered the larger ones, and I used a flat-bottom forstner bit, with my drill press, to drill the holes. With the 5mm plate, there is very little extra thickness to play with, so be exacting in your drill process and measurements.
If I did it again, honestly, I might just get an adhesive magnet sheet (like those sold with flexplate kits) cut it to size, leaving room for the factory bed clips, and stick it to a replacement Snapmaker glass plate. Skip the magnets and drill-work altogether.
Either way, it was a fun project! Big thanks to DLMCW for walking me through the steps and where to source materials.
Very cool. I think there is a huge benefit to using a more thermally conductive material like graphite instead of a glass plate. The easy way to use a flex plate might be to put a magnet sticker on a glass plate but I think your print surface will be significantly cooler than the surface attached to a graphite plate. I also worry about those magnet sticker sheets losing their magnetism at high temps.
