The large size of my printer design presents an interesting challenge of how to create a 4'x4' flat surface for the build platform. Ideally this would be perfectly flat, practically thats nearly impossible without using a precision ground slab of granite. There's also considerations with respect to weight: a heavy platform will require more force to move, and once moving will carry greater inertia and require even more force to stop.
It was originally suggested that I simply use a piece of manufactured lumber such as MDF, around 1" thick so it doesnt warp over time. While this may satisfy my requirement of consistent flatness, it surely is not a lightweight solution. Instead I chose to use a sheet of 2" foam insulation, laminated in 1/8" acrylic or polycarbonate. This solution is extremely light, the foam core weighing around 4 lbs, as well as durable. The foam is rigid but lacks any tensile strength, the lamination process solves this problem and from an engineering perspective, is similar to an I-beam. In my research of of other existing FDM 3D printers, Molten ABS or PLA sticks well enough to acrylic during manufacturing and can be easily removed once it cools. It may be adventageous to later score a grid into the surface.
Hello,
ReplyDeleteYou mention molten ABS sticking to acrylic; do you think it would also stick to sanded brass plate?
quite possibly- but the surface would need to be abraded first to increase the friction and get the molten PLA/ABS to stick.
ReplyDeleteThe other consideration you should make is the temperature of the build platform. If you are using metal, you may want to also design a way to keep the platform lightly heated. 3D printheads heat the material only slightly above the temperature at which the material undergoes a phase change from solid to liquid. Because the filament is so fine, it will loose its heat very quickly once it leaves the print head. If your build platform is very cool, the temperature will drop too quickly, and the material will return to its solid state before it actually "attaches" to the print bed.
Thanks for the quick insight. Some more details:
ReplyDelete- The brass flat bar is rectangular in shape; 7" by 1.25" by 0.125" (or 0.1875").
- It is sanded with 200 grit metal sand paper to remove the oxidation. Scratches are apparent throughout. Hopefully that would provide enough grip.
- I’m thinking of using a MakerBot Replicator which has an 8.9 x 5.7 x 5.9 inches build envelope. The platform can be heated to 120 C. Is that hot enough?
- I want to deposit a fairly thin (.5 mm or about) amount of plastic as a resist for the next step in my process which is etching with copper chloride in aqueous hydrochloric acid or ferric chloride. After etching the plastic will be removed.
- I need to deposit plastic on both side of the brass flat bar.
I already noticed that heat loss at the edged is a problem with my existing, very manual, method. I could build a frame out of brass into which the plate would sit. This would conduct heat into the brass flat bar from the build platform. It is a low volume product so I can spare the time to have the brass reach uniform temperature. I could have the Replicator in an enclosure to prevent drafts.
Again, thanks for any extra insights you can provide.