Test Tube Mendel

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Test Tube Mendel

Release status: experimental

Test Tube Mendel is a vinyl tubing vertex based Mendel.
[Creative Commons attribution share alike]
CAD Models
External Link

The Test Tube Mendel design is a minimal printed parts Mendel designed for rapid and cheap duplication. It is built around the vinyl-washer vertex proposed by Mrkim on thingiverse.


1. Dramatically reduce printed parts

2. Reduce total build cost

3. Push the boundaries of simplification

4. Have a good time

Print time savings vs. Prusa

Times are skeinforge estimates and not exact times. My settings that gave these times were 25% fill and hex fill pattern. I'll fill in times as I go.

Part Prusa Test Tube
Vertices 6 h 0 h
Y motor mount 0.5 h 0 h
Z motor mounts 2 h 1 h
2x Pulley 0.25 h same
3x endstop holders 0.5 h same
Z motor couplings ? same
X end idler 1.5 h 1 h
X end motor 1.75 h unk
X carriage 1 h same
8x bar clamp 1 h same
12x pla bushing 0.5 h same
4x belt clamp 0.25 h same

Design Log

6-2-2011: The vinyl washer vertex (Link broken, idea copied here) posted on thingiverse recently inspired me to work on a Mendel derivative using that idea that would have a much lower print/replication time. So far I have only built a frame to play with, and I hope to be able to reuse some of the Prusa printed parts. I consider this project still a reprap (rather than a repstrap) though others may disagree. I think the use of another vitamin (vinyl tubing) is justified by the dramatic savings in cost and time to print a duplicate.

The initial frame seems to be adequate in stiffness but will likely need an electronics mounting board attached to the frame to add lateral stiffness. I have decided that a large hose clamp will be my Y motor mount. I tried using nuts and washers to clamp the motor, but they just slid off. The hose clamp is cheap and it provides a much stronger mount than the printed part while simultaneously reducing printed part count. For those that already have a printer the cost savings might be minimal, but if you have to buy printed parts, the dollar spent on the hose clamp is more than made up by the current cost of printed parts.

Test Tube Mendel Frame
Z Motor Mount
Z Motor Mount with Motor

6-7-2011: Got a rough draft version of the Z motor mounts. Files are on thingiverse for now as I don't have a github account nor do I know the first thing about openscad. I am using a 1/4 inch cross bar a strap of some sort (twist tie, zip tie ...) and some small printed parts for the z motor mount. I am probably sacrificing some build height doing it this way, but that was a design compromise I had to deal with. All the threaded rod for the frame are the same length. My frame is currently built using 15 inch lengths. That is a very wasteful length, but it should end up with a similar build volume to the other Mendels out there. Since the frame is made from a single length, it should be easy to scale up or down. I think a 12 inch and an 18 inch version would be naturals. Both would make better use of commonly available lengths (usually 3 ft at Lowes/Home Depot).

X motor mount and idler are next. Might take me a while. I'm thinking of something similar to Prusa's but backwards and possibly upside down since my smooth rod is inside the threaded rod rather than vice versa as on the Prusa.

6-11-2011: Mrkim has posted his solution for a Z motor mount. I like it. Here it is. http://www.thingiverse.com/thing:9180. And it seems that the code name for Mrkims vinyl vertex reprap is Silvercat (1X2 Silvercat). http://mrkimrobotics.com/?page_id=5049. Can't wait to see what he does with it.

6-20-2011: Got the X end idler done. It is a three piece design, the main body and a couple of clamping plates. Files are on thingiverse. The smooth rod spacing is the same as Prusa in order to allow reuse of the X carriage and all the available extruder designs. So those print times will be identical. The pulley is just a small piece of threaded rod clamped into the idler body and the bearing is built up like in the Prusa and secured with a nut. You can't tighten the nut down too much or it will just pull the threaded rod out of the clamp, so just tighten till there's not play and then put some lock-tight on it or something.

X idler front view
X idler back view

8-3-11: Finally got some steppers for the bot. Now I won't have to keep swapping them off my Prusa build. The other end of the X and Z assembly is about done, so someday soon I'll post that stuff. Got to study for boards though so not too much to happen till the end of the month.

9-10-2011: The X motor design is basically done. I'll post files and pics soon, but I think I'll soon redesign for vertical X axis arrangement to comply with the Vertical_X_Axis_Standard.

3-7-2012: Been working on Gen7T for a while. This is not dead, but no real update for now.