BigFoot: The Openbeam Openrail Cartesian Printer

by oryhara, published

BigFoot: The Openbeam Openrail Cartesian Printer by oryhara Feb 2, 2013


Update: Frame assembly completed. All printed parts and motors are mounted. Wiring remains to be done, as well as tuning. The design has evolved greatly from the pictures. Maybe i'll update it later. No one should ever try to build this however, as it was annoying.

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.

Thanks. I am curious about your design with openbeam but am likely to alter anything I get anyway. :-)

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This is a work in progress, so don't print any of it. When I've finished iteration through the design far enough to complete construction of one, I'll post a BOM and build instructions. Until then, look at the design files and provide useful suggestions.

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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Anonymous on Apr 29, 2013 said:

How is this build going?

oryhara on Apr 29, 2013 said:

slowly. Working on other things at present. A few aspects of this design have changed in development, and the new design files are not uploaded.
I have all the motors and electronics, what remains is to put it all together. I simply have not had the time. My workshop is currently repairing a UAV, but this is next in the queue.