Xnaron Magnetic U-joint option for Rostocks

by nyl0cke, published

Xnaron Magnetic U-joint option for Rostocks by nyl0cke Sep 19, 2013

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This is a mod of the ever popular Mod for the Rostock MAXes by Xnaron. I designed a LM8UU carriage for the Rostock Mini/Rostock and any other system that works the same as these 2 printers. I have also included all of the important files for the original mod, including the original cheapskate mounts for the MAX, as well as rod adapters for the default Rostock Mini carbon fiber arms. The carriages I created have built in belt retainers that work great, as well as bolt tightened clamps for the linear bearings.

http://forum.seemecnc.com/viewtopic.php?f=54&t=1704&sid=512048173d7806425ee0b8a411e75957 - The original thread

(post about the jig)
This will happen if you don't get all of the arms the exact same length. Build a jig to make them like this http:[email protected]/8771948345/ and http:[email protected]/8771958335/

This is a WIP, I designed this in one day and printed version 1. It seems to work, but I will update and post new files if I find any problems while using this mod.

Speed tests:


The default setup is for 3/8 inch carbon fiber or aluminum rods, which can be substituted for 3/8 Crossbow bolts, 3/8 inch chrome steel balls, and 3/8 inch N52 Neodymium magnets. The chrome steel balls are meant to be JB welded or TIG/MIG welded to the heads of 6mm M3 capshead bolts. Be careful if you MIG or TIG weld them, you can easily melt the M3 bolt from the heat, all that is needed is a few tacks.

For the Rostock or Rostock mini, print 2 of the boom ends, an effector, and 3 of my magnetic carriages, as well as 12 rod adapters if you have .199" OD Carbon fiber tubes for your arms (I would recommend ABS). Assemble everything according to the instructions in the SeeMeCNC forum thread, and make sure you use the jig mentioned in the description to get consistent length arms, or they can become disconnected mid print

For the Rostock MAX print all of the same things, except for my carriages and the rod adapters, unless you want to use .199" CF arms on your MAX. Instead of the carriages, print the Cheapskate 90 degree ballends. The assembly is pretty much the same.

It is a good idea to read some of the forum thread to get an Idea of what to do an not to do while assembling, though before screwing the balls onto anything, you should tap the hole with either an M3 tap or by forcing an M3 bolt into it. Make sure not to strip the threads you create in the plastic, this is what keeps the ballbolts secured. Also, try to avoid putting torsion strain on the JB weld, It probably will break, AKA, dont twist the balls on by hand, especially if they are resisting threading into the hole. use a small pair of needle nose pliers instead.

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Today I use the original geometry of the arms.
do you mean that I should measure between the centers of the balls?
so if I have 150mm arms and 10mm bullets so should the measure be 160mm on the delta.
what about the offset?

thanks in advance

This blog http://minow.blogspot.com/index.html#4918805519571907051 is what most people use to calibrate home-brew deltas where the arms aren't professionally made on a jig. I would follow that for calibration.

As far as a starting point for the values, I don't know. Your arms are different in length than the default for your printer (default is 184mm). I don't know what other geometry differences there might be. You could try 84.5 since that is the default for your printer, but thats a guess.

hi, how will you measure #define DELTA_DIAGONAL_ROD
has a rostock mini pro
thanks in advance

The diagonal rod length is however long your rods end up being, from the center of each joint to the other. That horizontal offset is determined by the geometry of your printer. This one I can't quite help you out on, since I don't know the exact geometry of your printer. Assuming you're using the regular configuration on the Rostock Mini Pro, you should be able to find more info here http://reprap.org/wiki/Rostock_Mini_Pro

Downloading the official firmware here, https://onedrive.live.com/?cid=61d9a16368c58a74&id=61D9A16368C58A74%21136&ithint=file,.rar&authkey=!AHSZo-IZYPLl-NY
Seems that the default config for it is 84.5 for the delta horizontal radius and 184 for the arms.

in this picture
you are showing a plished ball-stud. I are having trouble to find this.
I have invented (patent pending) a new Parallel robot design which will give you unmatched workspace and dexterity compared to the Linear DELTA. I admire your work, and would be interested in having you challenge the design. If interested we should link up directly.
([email protected] , Founder CEO Preben Hjornet).

magnetic carriage size 8mm? compatibility LM8UU???

Yes, its made for the default Rostock specs, so 8mm, LM8UU compatible.

If built correctly, you shouldn't have to change anything theoretically, though I doubt you can avoid having to adjust the rod length.

When you exchange the printed joints to this new system, did you need to modify Carriage Offset and Effector Horizontal Offset in firmware or just tweaked the Delta Diagonal Rod setting?

Are the magnets 3/8" Dia. X 3/8" Long. You do not say how long they are.

Sorry, yes they are.

I designed it in Inventor Pro, so sorry, but I can't really

Nice work! By any chance could you publish the scad for the magcarriage?