BigFoot: The Openbeam Openrail Cartesian Printer
by oryhara, published
Update: redesigned the brackets to be simpler and easier to assemble. Added mounting plate for the azteeg x3 controller I'm using. New image, step, assembly, and stls.
Bigfoot is the printer I want to make. Since no existing designs included the 3 facets I want in a printer, I am designing bigfoot as well. Those 3 characteristics are: Openbeam frame, Openrail linear motion, and at least 300x300 build platform. Bigfoot's Z axis is not limited by frame geometry. it is theoretically possible to stuck uncut 1meter openbeams on with full-length openrails and print almost 1 meter up. The height of the X axis would be subtracted from that meter, so a meter-tall object would not be able to be printed.
I'm using richrap's quick Fit X carriage, because I've had great success with it on my current printer, and even designed a QUBD dual extruder mount for it. That's the extruder I'm planning to use in this printer.
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I'd put radial bearings under the Z motor coupling before I moved the steppers to the top. However i doubt it will be a problem. The X carriage and Z axis screws are not heavy. One of the nice things about this design is the ability to arbitrarily expand it vertically, and that would be lost with top-mounted Z steppers.
One comment: you might want to have the Z motors above without the weight of things resting on them (as it does on the bottom). In similar designs, people have pointed out that resting the weight on the steppers is not what the steppers are really designed to handle.
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Version 0.2 files uploaded in a zip archive. Not done yet by any stretch, but the openbeam lengths should be correct. I've cut my openbeams to the sizes specified. Will post more details in the BOM.
0.3 uploaded. Y axis drive is designed. Based on clearance tests in the assembly, it should allow full travel while only requiring an 848 long belt. I'm planning to use complete loops of belt rather than cut them. I've also changed the frame triangle back to 75-15-90 from 73-17-90 as in version 0.2.
There should still be room for an ATX power supply within the frame under the Y carriage.
Version 0.4 files uploaded in a zip archive, as well as a new STEP file with the completed printer. This is the version I'm going to assemble initially, to sort out any issues which modelling cannot show me. Alas this design is not easy to assemble, as every bracket i designed is connected to every OB extrusion with at 3 M3 screws and nuts, and putting them all in is quite tedius. However, I believe that the tedium will pay off in terms of frame strength and rigidity.
I've run out of M3 nuts, but more are on order, so assembly progress is slowed.
0.5 is still a bit tedious to assemble, but less so than the previous versions, and looks much nicer once assembled.
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