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Magentic Ball Joints - alternate rod ends

Posted by lohiaprateek 
Magentic Ball Joints - alternate rod ends
May 16, 2019 06:55AM
I have been printing my own rod ends for a while and started to look at some alternates which are more professionally machined. There are the rods from Haydn which everyone loves, but I'm on a budget and shipping to India makes it slightly out of my reach.

As an alternate to Haydn's Rod, has any one tried using something like this [www.ibsmagnet.com] or [www.magnosphere.co.uk] they are essentially the same thing. Adding a little bit of lithium grease on the ball and socket should enable a smooth movement, and with roughly 1.8 kgs (18N) of holding force should be good enough for modest acceleration. I've ordered some from aliexpress, hopefully they work as intended.
Re: Magentic Ball Joints - alternate rod ends
May 16, 2019 09:51AM
I think you will find that the cost of 12 of the smallest/cheapest of those joints exceeds the cost of a set of 6 rods form Haydn. Although you might save a little on carriage.

You can buy Haydn's rods in one particular length from the UK at [www.duet3d.com]. I don't know whether the shipping would cost any less than from Haydn direct.



Large delta printer [miscsolutions.wordpress.com], Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: Magentic Ball Joints - alternate rod ends
May 16, 2019 11:21AM
If you are on a really tight budget it is not too expensive to make your own. Magnets and steel balls are quite inexpensive and all you need to make are the bits to hold them all together. make the cups out of Delrin, Nylon or bronze - DO NOT MAKE THE CUPS OUT OF STEEL - that way lies only a deeper understanding of magnetic circuits and that what is obvious really aint so.

I made mine with woven carbon fibre rod - often sold for making model aircraft. The cups and magnets are held on to the CF rods with epoxy in a 10mm OD brass tube and all parts are given a false thread to give the epoxy a bit of grip. The cups should hold the magnet very close to the ball without touching - say 0.25 to 0.5mm.

Do make a jig to get the lengths of all of the tubes as close to identical as possible.

Mike

Edited 1 time(s). Last edit at 05/16/2019 11:22AM by leadinglights.
Re: Magentic Ball Joints - alternate rod ends
May 16, 2019 11:41AM
Quote
dc42
I think you will find that the cost of 12 of the smallest/cheapest of those joints exceeds the cost of a set of 6 rods form Haydn. Although you might save a little on carriage.

You can buy Haydn's rods in one particular length from the UK at [www.duet3d.com]. I don't know whether the shipping would cost any less than from Haydn direct.

So an aliexpress seller is selling the 10mm balls with an m3 thread and magnet variant for 3.65 USD each, so 12 of them should be 43.8 USD plus 10 USD shipping and add another 5 USD for the CF rods from aliexpress which includes shipping which is 58.8 USD . I need to print small sleeves in which I could use a captive screw and and screw on the magnet which should not cost a lot. In total a fair bit cheaper than haydn's. I believe the pricing of filastruder to be the cheapest for the 215 mm rod which is about 75 USD + shipping.

Edited 1 time(s). Last edit at 05/16/2019 11:42AM by lohiaprateek.
Re: Magentic Ball Joints - alternate rod ends
May 16, 2019 11:51AM
Quote
leadinglights
If you are on a really tight budget it is not too expensive to make your own. Magnets and steel balls are quite inexpensive and all you need to make are the bits to hold them all together. make the cups out of Delrin, Nylon or bronze - DO NOT MAKE THE CUPS OUT OF STEEL - that way lies only a deeper understanding of magnetic circuits and that what is obvious really aint so.

I made mine with woven carbon fibre rod - often sold for making model aircraft. The cups and magnets are held on to the CF rods with epoxy in a 10mm OD brass tube and all parts are given a false thread to give the epoxy a bit of grip. The cups should hold the magnet very close to the ball without touching - say 0.25 to 0.5mm.

Do make a jig to get the lengths of all of the tubes as close to identical as possible.

Mike

I have been using rod ends printed in PLA and then smoothend out with a 10 mm ball nose end mill and lubed with lithium grease. I have no problem of disconnection even at printing at 3000 mm/s accelerations and 100mm movement speeds. I just wanted higher articulation in comparison to the setup I have. I'm using laser cut carriages and effector and cant angle the balls, I also don't have access to a lathe or any machining facilities and thus cant make the ends repeatable to the degree needed to make a reliable printer.
Re: Magentic Ball Joints - alternate rod ends
May 16, 2019 12:12PM
Although I do have access to machining facilities I did not need them for making the rods. Try using your ball nose milling cutter to cut a recess in the end of a delrin rod then file to fit. The most important thing is to get the length ball to ball the same on every one. It is also not usually necessary to have angled balls - see DC42s smart effector where all of the balls are straight.

Mike
Re: Magentic Ball Joints - alternate rod ends
May 17, 2019 03:15AM
Quote
leadinglights
Although I do have access to machining facilities I did not need them for making the rods. Try using your ball nose milling cutter to cut a recess in the end of a delrin rod then file to fit. The most important thing is to get the length ball to ball the same on every one. It is also not usually necessary to have angled balls - see DC42s smart effector where all of the balls are straight.

Mike

Makes sense, now let me see from where I could procure a Delrin rod locally.
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