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It was, they look really nice!

Hi All. Im also interested in the kit

My friend's neighbor has an wire EDM machine, would there be sufficient interest to trouble him and possibly make some bearings with a centered borehole halfway through? (possibly tapped). I say that hoping he'd do it for a reasonably low price. For something premade already though, someone could try These 10mm Stainless Steel Balls with M3 threads, I assume it'd be around $30 US for a set of 12.

I'd do it myself if my freetime didn't go up in a blaze of unglory. The mine I work a had a fire last week that will eat my time for awhile cleaning up my hoist motor and controls. I really hope it takes less than 3 months....*sigh*

Most SS alloys are not magnetic, there is no spec on what material is used on these. The common SS bearings are usually not magnetic.

As for bored bearings - in reality, threaded holes are not really necessary. If the hole will allow the insertion of a threaded post (I use 8-32 x 1" long studs that come threaded ready to go - with a bit of press fit, then things will be fine. This is not a high stress joint and the post simply eliminates any chance for failure that *may* occur with cap screws glued to the bearings. As added safety, the posts can be loc-tited into the holes. This is a lot simpler and faster (i.e. cheaper to make) than tapped holes.

Good point on the SS, stupid nickel making austenitic SS. Then again it could be awesome and be ferromagnetic, you never know, those brits are weird *cough* Unless whoever is reading this is british in which case you misread that because I wrote 'awesome'.

My thought process on the threaded holes was that I knew some EDM can do threaded holes with a setting change, I wasn't thinking of actually putting effort into it

I tried pressing some 8-32 studs into #25 holes drilled in ball bearings, but I wasn't really happy with how it sheared the threads off the studs. I ended up with a slightly bent stud and some sharp curly bits sticking out.

(did I just say that out loud?)

- dan

Yeah, if someone was selling some 1/2" magnetic steel balls with 8-32 threaded holes , I'd certainly be interested in buying. I've already blown away more time and money than I wanted to trying to do this myself.

- dan

I know I'm going to regret saying this, but...

With your hardened balls, something like a #21 or #22 drill would be good. You don't want the hole so small as to shear the threads off the stud. A light press fit with locktite will be just right.

cheers,
Michael

I keep thinking...magnet, ball, then magnet..... Kinda like how the rod ends are made now to contact the ball, then do the same thing to the effector..
Thoughts??

I thought about that also, but I don't think two cups could be small enough for enough freedom of movement while being large enough to stay seated.

- dan

dbarrans wrote:I thought about that also, but I don't think two cups could be small enough for enough freedom of movement while being large enough to stay seated.

- dan

but the draw strenght magnet to magnet vs magnet to steel......???

dbarrans wrote:Yeah, if someone was selling some 1/2" magnetic steel balls with 8-32 threaded holes , I'd certainly be interested in buying. I've already blown away more time and money than I wanted to trying to do this myself.

- dan

Dan, what kind of problems have you experienced? The epoxy approach failed?

so today while wandering the local home depo i found some small disc magnets with an 1/8" hole in them, thinking to myself this just may work..
the hole in the magnet keeps the ball centered and the grip is very strong even at a 45' angle. I think I might just have to have a go at making something up with this arrangement....
[img]http://i1102.photobucket.com/albums/g446/davidflowers1/Mobile%20Uploads/utf-8BSU1BRzA1ODkuanBn.jpg[/img]

What is the diameter on those magnets?

.375" diameter...

I just took a micrometer to them, they are .372" dia. Im sitting here playing with them now, I think this will work out great!! I put a piece of paper between the ball and magnets and its smoother than a greased pigs rear. I just have to figure out the hole in the magnet and how deep the ball sits into it then start designing a new effector and and carriage mounts.

Would you have the packaging they came in and would you be willing to give me the SKU number, usually found under the bar code.

Eaglezsoar, only for you would I go and root thru the trash after cleaning the cat boxes...

Super magnets p/n 07090 qty 12 sku 9542107090
[img]http://i1102.photobucket.com/albums/g446/davidflowers1/Mobile%20Uploads/utf-8BSU1BRzA1OTAuanBn.jpg[/img]

Ohhh, so the magnets are pretty thin. From your first picture I thought they were tall, cylindrical. But I'm guessing you had it attached to another metal cylinder (or you stacked the magnets).

dpmacri wrote:Ohhh, so the magnets are pretty thin. From your first picture I thought they were tall, cylindrical. But I'm guessing you had it attached to another metal cylinder (or you stacked the magnets).

Yes I backed them with another .375" x .375" magnet. the discs by themselves are too weak, but with the extra magnet backing them thier very strong. This is only a test and the magnets arent the most powerful of the class, but I think they are plenty strong enough...

any one know where to find the actual dimensions on the rostock, not just stl files? Might save me some time measuring things up....

DavidF wrote:

dpmacri wrote:Ohhh, so the magnets are pretty thin. From your first picture I thought they were tall, cylindrical. But I'm guessing you had it attached to another metal cylinder (or you stacked the magnets).

Yes I backed them with another .375" x .375" magnet. the discs by themselves are too weak, but with the extra magnet backing them thier very strong. This is only a test and the magnets arent the most powerful of the class, but I think they are plenty strong enough...

any one know where to find the actual dimensions on the rostock, not just stl files? Might save me some time measuring things up....

Thank you for rooting through your cat litter coated trash.
I'm not sure if this is what you are looking for but the arms on the Max is 269mm so the magnetic arms would be 269mm from the center of the balls.

Eaglezsoar wrote:

DavidF wrote:

dpmacri wrote:Ohhh, so the magnets are pretty thin. From your first picture I thought they were tall, cylindrical. But I'm guessing you had it attached to another metal cylinder (or you stacked the magnets).

Yes I backed them with another .375" x .375" magnet. the discs by themselves are too weak, but with the extra magnet backing them thier very strong. This is only a test and the magnets arent the most powerful of the class, but I think they are plenty strong enough...

any one know where to find the actual dimensions on the rostock, not just stl files? Might save me some time measuring things up....

Thank you for rooting through your cat litter coated trash.
I'm not sure if this is what you are looking for but the arms on the Max is 269mm so the magnetic arms would be 269mm from the center of the balls.

Most of the measurements I can get from the programming (delta rod length, effector offset, carriage offset, ect) mostly im looking for the distance from the ply to the c/l of the axis on the carriage. distance between the diag rods would be nice also, but i dont see where that would effect anything if made wider or narrower. still I would rather have over all dimensions so I can really get things dialed in... Im not 100% sure of how the programming interperts the dimensions, but im working on it...

What about using counter sunk magnets such as these, or long ring magnets like these?

The cylinder magnets would probably work, but I think the hole size needs to stay 1/8" otherwise the balls would sit too deep and you would not get the full motion required...

Just a reminder that you don't have to keep the ball center to ball center distance exactly 269mm. Changing it in the firmware is easy. My arms are over 12 inches long and I haven't had any problems with them since I've upgraded to the long magnetic arms.

I think you guys are worrying too much about the balls detaching from the effector plate; I've been using magnetic arms since last July and I haven't had a single ball come off yet. Mine are just glued into ~4mm cap screws with loctite. Drilling and tapping chrome steel isn't a viable option for most people, and it would be extremely expensive compared to glue. Keep in mind that the ball joints will never take more than a kilogram of force under normal printing conditions, and glue is more than strong enough.

If I could I would machine my ball joint cups out of PTFE (teflon) round rod. Acetal and Nylon are good alternatives since they have low friction too. I printed my nylon cups with a 0.25mm nozzle and they are very good contact surfaces.

Just one thing about those magnets, they aren't rated for an N number anywhere on the package. The magnets that most of us have been using are grade N52, which is on the higher end. Underpowered magnets will detach during the print if the acceleration is too high.