@Brandon_Heller got me thinking about making a backpack printer. The foldable printers are neat but I thought it would be better if the printer just WAS thin. I got a little carried away with the mock up. It is nearly complete. The shortest collapsed dimension is 72mm. The other dimensions are similar to a fullsized laptop and will most definitely fit in my backpack.
The Z is the main attraction. There are 4 scissor lifts that are coordinated by a loop of string and are actuated by a NEMA14 with TR5*2 lead screw. I did the math and even in the worst position there is still 5lbf on tap for pushing the XY stage up. Assuming I can get the hot end to zero out when the printer is fully collapsed there shouldn’t be a problem with the firmware.
The XY is a CoreXY arrangement.
The bowden tube and the string for the XY aren’t pictured.
I would like some ideas on…
How to make the exterior smoother and slimmer?
How to deal with the bowden tube during transport? (I have thought about allowing the hot end to fold down or allowing the tube to be removed.)
How to level the bed/top?
How to zero the Z?
That only works if you use multiple motors for the Z axis. In this case it only uses one motor and one rod. This will be nearly impossible to adjust.
You should use 2 motors and 2 rods. No string at all. Then you can adjust the height left and right. For the y axis you can put a adjustable nut on the z lift system wich you can adjust seperately. Hope this makes sense…
@Mano_Biletsky_Open_M unless you perform a bed measurement using a z-probe attached to the carriage and use the collected info for performing dynamic z-adjustment for each xy move?
@Miguel_Sanchez You can measure, but then what? How would you adjust the frame to level the bed or the x carriage?
Dynamic adjustment can only be done when there are at least 2 motors per axis.
Normally the z axis has 2 motors(or at least the ability to manually shift some nuts) and the y axis is done on the bed itself. With dynamically adjusting, you need the… … …never mind! It just hit me! You’re right…
What might be a problem though, is the angle of the nozzle. That cannot be adjusted and can give stripy prints (toplayers) or skew corners.
@Nicholas_Seward you could print some nice rounded corner bumpers to get rid of the sharp edges.
@Mano_Biletsky_Open_M@Miguel_Sanchez I don’t really have room for another motor and I want the adjustment to stay permanent. With the one threaded rod and the loop of string they are all synchronized. I could have a screw or something that would allow adjustments for each corner. I am considering a touch probe and software leveling but that might be more complex than a cheap portable bot needs to be. I probably will just use a spring loaded bed with thumbscrew adjustment.
A probe does not have to be expensive. In theory, you could use a plastic tube with a (fitting) metal rod (3mm or so). On one side glue a metal contact above the plastic tube, and solder a wire to it. Then solder a (thin) wire 15mm above the end of the rod. Stick the rod in the tube and test if it can touch the metal contact. Put a little rubber ring on the rod above the plastic tube so it can’t fall through.
@Mano_Biletsky_Open_M No doubt. However, this isn’t going to be a <100um layer printer so doing thumb screw leveling every so often would be pretty reasonable. Cost is not the issues. The issue is removing points of failure for a portable printer. In fact, I am quite sure there will be no limit switches on the whole bot.
An inductive proximity sensor can be bought for less than $3 on eBay. @Mano_Biletsky_Open_M you can raise or lower the z-axis as you move to any (x,y) coordinate to make sure the nozzle stays at a constant distance from the bed at all times. Of course if bed is already leveled to the xy plane such a correction won’t be needed.
I’m a little late, but it might be good for this to print upside-down with the print bed mounted on the Z axis. This way the movements of the carriage don’t have to be shaking around on the Z axis. Putting some folding legs would allow clearance for the bowden tube.
Alternately, just have the platform move in the x-y plane and mount a stationary print head on this folding z-axis. Much more stable and fewer arms needed.
