So U want Magnetic Balljoints for $40 or less? No Probs!

[Flateric]

By all means count me in.

But don't count on it's ease of execution before you test and such.

There are alot of tricky little intricacies to this setup that are not immediately obvious.

Be glad to help if I can.

Some sticky little points I have learned about the hard way.

- Complete range of motion is hard to obtain while maintaining strong attraction to the pivot joint. ESPECIALLY when at or near the limits of motion, things go all to hell here.
- The length of the rods must be EXACTLY, dead nuts on perfect similar between all of them. There is absolutely zero room here for variation. We are talking 3 decimal place accuracy or the whole carriage will go wacko, see above point.
- The cup and specifically the friction of that cup needs to be perfectly uniformed through all joints and must be essentially frictionless. Sounds easy, but not so much really.
- I found some success through making a linkage between the two rods for each arm thus doubly ensuring there paralelism with each other at all times help alot for all points above.
- Weight, subject to the strength of the above joints, but also very important to the momentum the carriage has. Specifically must be kept as low as possible for our delta design anyways.
- And some obvious design important point such as range clearances, wires need to be routed while not interrferring with any of the above mechanics. I found that a system bringing them all in from above seemed to be the least intrusive.

I'll add more if I can think of them. But I have been pounding on this issue for days. Some successes and some failures, but nothing stellar as of yet. It's not as simple as it originally appeared it should be. Even when it was apparently working, it became clear it was not really, not as well as it should anyways.

[Flateric]

My plan was to build a set for my machine and give it a test run, but it sounds like I need to re-think the upper end? Maybe the OP can post a photo of his setup for reference? I was planning on including tubes, bearing cups, and mag-balls with the bearing cups epoxied into place.

I'll upload some diagrams of what worked best for me so far anyways of the uppers. Just cannot due to time issues with another project this second. Perhaps later tonight or tomorow morning.

[harley573]

Flateric,

When do you think you'll get time to post the pics of the upper end you did? I'd sure like to see 'em if you get a chance.

[Flateric]

I completely forgot about that sorry man.

I got so frustrated with the whole thing I have taken a break from the entire problem to let it simmer on the backburner of my brain for awhile and see what I can come up with. Before going back into it fresher and not so frustrated.

I also couldn't take not getting my print "fix" for so long and reverted back to stock arms in the meantime. One thing I have concluded however is that I really bet most of us are running our belts to tight, likely our cheapskates to tight and our arms and joints not loose enough but still without any extra play. I spent an entire afternoon rebuilding all of the above being very careful to make things as freely moving as possible yet without any extra sloppiness or binding and it's as if I have an entirely different machine with my prints being damn close to Berry's and his magic bot level. I also went through and remeasured and verified all my delta values and correected in the firmware. They were not off by alot, very little in fact. But sum all of the above together at once and I can honestly say the result is tangable. I can print faster, cleaner and far more accurately than I would have thought the machine even capable of just 1 week ago.

Here is a reference image that I found clarified and really made me understand what the delta values referred to and helped me measure them accurately. Do not use the values in the image however they are from a totally different delta printer. But they show where to measure on ours.

delta definitions

I read everyone's progress with great interest on this topic. Berry used magic and love with a little voodoo and got his just perfect! (Damn him and his magic voodoo sugar plum Berry charms! Just joshing you Berry, nothing but love, you know it.)

[jetpad]

I got some steel ball bearings and some magnets to play around with this idea. Here's what I came up with so far.

I took four magnets, two M4 (I think) washers, and a 3/8 chrome ball bearing and made a sandwich out of it. The magnets and washers would be glued together and and center of the washers would act as a cup to keep the ball bearing centered. It is pretty strong and seems very stable. I think 6 of them holding the hot end platform would be plenty strong. The only thing that is stopping me from trying them is getting good rods of the same length.

Magnets
http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 0717855827

Ball Bearings
http://www.ebay.com/itm/25-3-8-Chrome-s ... 0630819004

Edit: It looks like the M4 washers limit the range of motion a little bit. I think switching to M3s would fix the problem and/or moving to a slightly bigger ball bearing.

[Polygonhell]

Here is a reference image that I found clarified and really made me understand what the delta values referred to and helped me measure them accurately. Do not use the values in the image however they are from a totally different delta printer. But they show where to measure on ours.

Fullscreen capture 1192012 90008 AM.jpg

I read everyone's progress with great interest on this topic. Berry used magic and love with a little voodoo and got his just perfect! (Damn him and his magic voodoo sugar plum Berry charms! Just joshing you Berry, nothing but love, you know it.)

The only two values that are actually use to compute the motion of the platform are DELTA_DIAGONAL_ROD and DELTA_RADIUS, all the other values are just used to compute DELTA_RADIUS from more easily measured values.