Core XYZ?

While waiting for the parts to my Mini Kossel to arrive, I started thinking about other printer designs that fulfill a similar function. As everyone knows, the purpose of a delta printer is to print fast and look cool (yes, people also say that they are mechanically simpler, more easily scalable, etc. when they don't want to use "looking cool" as a justification for purchasing one). Anyway, I became aware of the corexy system a couple of days ago. And while it appears simple, fast, and cool-looking, it is constrained to two dimensions with the only partial exception that I have seen being that corexz [www.youtube.com]. Seeing a gossamer, filament-powered system on top of a heavy-looking print bed cantilevered off of a lead screw seems somehow wrong to me, so I endeavored to design a system to add an extra dimension to the corexy in order to maneuver the hot end in all three dimensions while the motors and print bed stay stationary. Below are the two systems I came up with over lunch.

The Corexyz (mentally superimpose the three systems in the column on the left of the attached photo of my sketchpad):
Take your standard issue corexy. Fold it upward 90 degrees one third of the way up. Fold it back 90 degrees at the two thirds point. Add the y-axis system on the bottom. Voila. In the xz plane it works just like a corexy. All three motors, however, must power movement in the y axis. The printer would look like a scaled-down cnc router with a moving gantry. It uses a total of 22 pulleys, and if we are to assume a cube-shaped print area of side s, each cable would be about 6s long. I would anticipate six linear motion shafts and 12 bearings. Pulleys are small circles in the drawing, tensioning and/or connection points in the line are dots, and spools are the small cylinders.

The Corex+y+z (mentally superimpose the three systems in the column to the right. Trying to draw it all together gave me a nasty headache that I would hate to inflict on unsuspecting forum members):
This one accomplishes the same in a different manner. I envision a very attractive printer built between two acrylic walls powered by a column of dual-shaft steppers. Anyway, the y axis moves two linear motion shafts back and forth by pulling on their tops and bottoms. The z axis yanks line from the top half of the printer to the bottom half and vice versa to lift and lower the x axis. The x and z lines must constantly recirculate as the effector moves in a different direction. This one has a total of 34 pulleys. The Y-strings are about 4.8s. The Zs are 5s. And the X-line is 7s. Anticipate eight >s-length linear motion shafts and 16 linear bearings.

Is anyone working on anything similar?
Does anyone have any thoughts/critiques for either or both systems?
Am I missing something crucial/barking up the wrong tree?
What is the answer to the great question of life, the universe, and everything?

Some issues I would anticipate finding if I were to build one of these systems:
Friction - This many pulleys can't be good. If a gantry pulley bound, one would quickly end up with PLA spaghetti.
Mechanical advantage - In the Corex+y+z, the x and z lines move with twice the power/half the speed of the y-axis (to be corrected by either the spool or the programming).
Stretching and sagging - The cables in the corexyz are 50% longer than in an s by s corexy system.
Abrasion - The whole crisscrossing thing on the y axis of the Corex+y+z.

I use core XY in my large format machine. It's really really fast. Had to redesign a entire new print head to take advantage of the speeds. I am getting 500mm sec speeds.

It's actually fast enough for putting a Big laser on it for engraving.

It was the easiest to set up printer I have done. I use same pulleys and belts from prototype to big machine. Never had to change any step settings for X,Y axis. I got ball screws on the Z axis but it's a really coarse thread 4mm travel one turn. I use .9 degree steppers on the Z so it's 100 steps per mm meani g we can easily go down to .05mm.

First print put of it we did 20mm test cubes. Cme put as good as we can hope for with FDM.

Edited 1 time(s). Last edit at 09/13/2014 04:33AM by metzindustries.

You don't have to cris cross the belts, you can mount one above the other. The pulleys are just ball bearings with lasered metal,discs to keep from comi g off and a bolt for the shaft. Works fine.

I definitely like the CoreXYZ better than the x+y+z though I would flip it on its side so that the axis you currently have in the Y is instead in the Z.

Either system would benefit from flipping onto its side, in fact, allowing a more traditional z-axis for the higher precision and stability that the z-axis needs (and removing that bothersome y-axis that you have on both of these)

Any advance on this design? updates please

Isn't the Delta style basically a perfected CoreXYZ type?
The CoreXY utilises 2 motors working simultaneously to cover a plane.
Similarly Delta utilises 3 motors working simultaneously to cover a volume.

---

ShapeForger

Quote
krakadu
Isn't the Delta style basically a perfected CoreXYZ type?
The CoreXY utilises 2 motors working simultaneously to cover a plane.
Similarly Delta utilises 3 motors working simultaneously to cover a volume.

I would say the point would be to cover a rectangular prism volume while still being natively Cartesian. I love deltas but there are many reasons you might not want to use one.

---

ConceptFORGE
Wally, GUS Simpson, LISA Simpson, THOR Simpson, Sextupteron, CoreXZ