Magnetic Joints

I was going to do regular Traxxas end rods for my Kossel but then I read about all the benefits of magnetic joints and I saw this effector [www.thingiverse.com] that I really like but I am thorn in between going magnetic or just ball joints since it seems easier and cheaper to go ball joints.
Could someone please give me some suggestions? Thank you.

[forums.reprap.org]

Hercek, thank you for the link you made up my mind is too much trouble doing the traxxas I am going the magnetic route.

Good ball joints are much better (no play, light, strong) than magnetic. The problem is traxxas is not good if not carefully assembled. If you can then get e.g. MP-Jet ball joints.

Thank you Hercek, that is another option I appreciate it. In another post I saw something similar but they where all aluminum I do not remember what post was it.
I been following another thread where you posted some really good information would you mind checking my post there I hope you can illuminate me with your wisdom is here [forums.reprap.org]

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plastik
Hercek, thank you for the link you made up my mind is too much trouble doing the traxxas I am going the magnetic route.

If only that statement were true.

My advice, don't drink the Kool Aid.
For everyone who says they are great, there are a bunch who couldn't even get them to work at all. Either the glue didn't hold the screws to the balls, weren't accurate enough and the effector wouldn't stay connected or it simply couldn't keep up. If the balls touch the magnets they can cause problems, if they touch and chatter you will destroy the magnet, and if the ball is too far away, you won't have enough hold (very fine line). I spent quite a bit to get my mag joints, then spent quite a few days getting them assembled. Two broke off the bolts before I attached them, another came of during assembly. I started over and got them all attached, I ran a calibration, made one print, re-ran calibration and removed them. The second calibration broke another bolt off of the ball, and during the print job, during high speed infill I was getting chatter... The magnets weren't strong enough. Another thing I didn't like was while working on the effector it came off in my hand more times than I could count. Great for maintenance, unless the hot end happens to be hot at the time. They also weight quite a bit, at high speed, it's a LOT of weight to be flinging around, I always feared it coming off and starting a fire.

Rod ends are cheap and dead simple. You bolt them on, they work. Yes they can develop slop over time, however they cannot fall off and can handle far higher speeds. As for the slop, there's been many ways to combat that from hair ties, to springs, to rubber bands and more. I've done 0.01 layer heights (yes, 0.01 not 0.10) at 200mm/s that looked like glass, using just rod ends and hair ties, you don't need mag joints to print good. Mag joints are expensive, frustrating and a limiting way to go in my opinion.

Do mag joints work, yes.
However, here is the dumbest part I find about them. People put them on for better accuracy, but because of their limitations, they run their printer quite slow. Why use a delta if you plan on printing slow and more importantly, if you print slow, every printer will print more accurate. If I wanted to print at sub 100mm/s speeds, I could have done a cartesian with dual heads and had just as much precision and dual heads.

All good points sheepdog43, thank you. Now I am back to the MP-Jet ball joints, can someone please point me to the all aluminum ball joints? I know they are out there but I can't find the darn thread now.

Edited 1 time(s). Last edit at 10/13/2014 01:01AM by plastik.

Another alternative is to use the system I use on my Cherry Pi IIIS models. It has all the benefits of magnetic attachment, precision, ease of removing the effector, etc but none of the draw backs. It's also really inexpensive to implement. Basically you have a drilled 8mm ball bearing on the end of each delta rod and a length of Spectra line attached to a spring to hold it all together. It works great.

[forums.reprap.org] (about half way down the page)

Andy

Hi AndyCart, thank you for the info, do you know if those ball bearings are still for sale in eBay? I am guessing that it would be a bitch to drill those out, not only because of the shape but ball bearings I am going to assume they are extremely hard. Thank you.

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AndyCart
Another alternative is to use the system I use on my Cherry Pi IIIS models. It has all the benefits of magnetic attachment, precision, ease of removing the effector, etc but none of the draw backs. It's also really inexpensive to implement. Basically you have a drilled 8mm ball bearing on the end of each delta rod and a length of Spectra line attached to a spring to hold it all together. It works great.

[forums.reprap.org] (about half way down the page)

Andy

I've said it before...
Other than complexity, I really do like that system. I plan on trying it myself once I have spare time.

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plastik
Hi AndyCart, thank you for the info, do you know if those ball bearings are still for sale in eBay? I am guessing that it would be a bitch to drill those out, not only because of the shape but ball bearings I am going to assume they are extremely hard. Thank you.

I get mine from here [www.ebay.co.uk]

I did something similar. I basically drilled out a hole into some nylon spacer tubes to fit the magnets. I then glued them inside. After curing I took a 1/2" ball nose cutter and made the groove to contour with the 1/2" balls until I got them very close, but never touching. I then glued the spacers on each end of the carbon fibre rods and made a jig so that all of my rods matched. I have the 1/2" balls glued to the end effector, and the brackets at the top. And so the rods just clip in both. I have yet to see them come apart even in high speed high accelerations. the strength of the magnets is really good I have yet to see any of the rods shift around. Best of all, I made the end effector changeable by just taking off the rods and disconnecting the quick disconnect for the electrical.

[www.youtube.com]