Just a quick status update. We’ve now got the Aluminum bed and frogplate assembled onto the alpha robot. We had to redesign a clip to be stronger, to remove the last bit of Y backlash. We also have the X, Y sensor mounts redesigned. We’re off to heat the bed.
With wood, we didn’t have to heat the bed. Wood doesn’t conduct heat very well, and it allows the plastic to stick very nicely. But Aluminum — that’s another matter. It conducts heat very well, instantly cooling the plastic. As a result, the plastic does not stick well to the surface, and we end up have to re-print many times until we get the layer stuck. It’s not a good outcome. So, heating the bed is required.
But we have a huge build plate — 12″x12″, of which 10×12 is usable. This much metal needs a lot of power. We need 2 heat-plates! We’ve found an interesting heat-pad that we’re testing, normally used in the ATV industry. It’s fully wired, is already sticky, and has 2 heat channels. Perfect for our needs! We’re working now to adapt this thing and get it working on the Alpha. I assume it will take a week or two. This change increases power requirements massively — Aluminum is a very good heat-sink, and it radiates the heat to the air very effectively. This means more power is needed to keep the bed hot enough, and to keep the air above the bed hot enough.
We’re also switching to ABS. The PLA spool that we have been testing with has gotten too wet with the rain in Seattle. I also want to test with ABS to see how it reacts to some of the design components.
Another problem to solve is the bed itself warps. It’s far flatter than wood –but not precision ground perfect. This Al. plate has internal stresses, and those stresses warp the plate with heating/cooling cycles. We’re looking at using EasyMaker to grind the bed on EasyMaker. I think I know how to accomplish this, but it will take a few heat/cool cycles to get the stresses out, and time to experiment with bed grinding. It’s not needed — EasyMaker( EM ) works well enough without it. But I like the idea of perfection…