Originally shared by Nicholas Seward
I have been wanting an infinite build volume printer that I can print directly on trade show tables. I consider this a cross between the Printrbelt http://youtu.be/UYAYLEVVLT8 and RepRap Tuga http://youtu.be/VRkYpnTxO_M . I have no clue what to call it yet. The build volume specs on this first mockup are X325 Z100 Y(a lot) on a normal conference table and X600 Z100 Y(even more) on the floor.
Thoughts/Notes:
*I hope I can get away with driving the wheels only on the left side. (It wouldn’t be hard to physically or electronically slave the right wheels if it is needed.)
*I had to bastardize the Scott Russell linkage to make it more foldable and increase build volume. I really wish X and Y were decoupled but the math isn’t too bad.
*The BlackBelt printer just released a version of CURA so slicing is mostly done. Support structures have to be done manually for now but I always design to avoid support.
*I want to make the angle adjustable but a clean solution hasn’t come to me yet. The problem if you need to rotate around the line where the print can print on the table. That requires trunnions or some fancy linkage. That said…the E3D nozzle geometry dictates that you can’t be at more than a 20 degree tilt for .2mm layers.
*The belt printers seem to have the nozzle print right at the edge of the belt support plate. This lets them get a better interface angle between the belt and the nozzle. I don’t have that luxury which means I have to keep the angle pretty shallow. I think I might need to round off the tip off the nozzle a tiny bit.
*I am thinking about bed leveling before I print each layer or every once in a while. Tables are usually very warped but they have very large radius of curvatures so you only need to gather leveling points every 5mm or so. The incremental bed leveling I have implemented for RepRap HELIOS should do the trick. I will need to tweak the weighting algorithm so that additional points will slowly bend it back into shape instead of causing a sharp shift. (Inverse time weighting?)
*The right wheel block can slide to fit the surface but it limits the build volume. I have 4 rails and can just attach the wheels to a second pair. Using more than 2 rails just seemed crazy. I can still get 600mm on the X if I just move to the floor. How often does one really need a part with two dimensions over 325mm?
*All but the 3 arm pieces can be printed on a 120x120x120 printer without support. The arms could be printed in pieces but you probably don’t want to do that. The arms need to be rock solid.
*I am looking into making this battery powered. Without a heated bed, it is very doable. If I put a bunch of 18650 cells in the carbon fiber tubes then I can get about 1/2 a kilowatt-hour. I can get a full kilowatt-hour with 4 rods. I suspect that I could get 10-20 hours of printing off of that.
*I might need a sensor to keep this from rolling off the table.
*The 20mm carbon fiber rods seem to have worse tolerances than the 10mm rods I have used in the past. I am waiting on the IGUS bushing to get a feel for how fiddly this will be.
*The steppers are so nicely packed that any box for the electronics seems out of place. I have a Smoothie and a MKS but they are both way too bulky for this. I will go with an Azteeg X5 mini or a Cohesion3D mini just to keep the size in check.
*Everything can fit in a 125x125 square travel tube. I guess I need to expand the Z just a bit more so it can print its own travel tube.
*I am looking at using a strip heater to warm the table right before it gets printed on. I am thinking for PLA we would heat the table to 80 and try to get the strip as close to the interface line as possible. I wonder if anyone will let me try this on their glass table. 
It would be nice to not use tape. (I don’t think I will cause any thermal fractures.)
*All homing will be done with a bump (accelerometer) sensor located on the effector. This will even be used for bed probing.
*What do I name this? My filename is TableBot. I sometimes jokingly call it RepRap Chugga Chugga. Maybe RepRap Ninja because of the swiping arm and the BlackBelt printer. I don’t know.
Let me know what you guys think. I usually do a dump like this right before most builds and you guys are great at refining and enriching.
