ball-cap rod-end concept pros and cons

There seems to be some assumption that rod-ends don't have any play, which is completely contrary to my experience. One of the reasons I went to mag-ball was the play in the rod-ends.

I can't detect any wiggle in my shop built mag joints which have PTFE cups inside aluminum housings. They were also considerably less expensive than any even mediocre quality rod end.

Whether you use mag joints or ball ends, you still need to bolt one end to the effector. The potential for misalignment is the same for both. My effector was made on a CNC machine and distances between all of the balls are within a few microns of being equal (including the balls on the carriages).

Which rod ends have sufficient range of motion for a delta?

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dc42
My effector has zero wiggle. Yes, ZERO.

I find this hard to believe, and I know from plenty of experience this is not the case, as I can just walked over to your effector and haydens arms and yup, there is movement compared to rod ends, sure if you act like a pussy and put f-all force on it sure you can pretend and say no movement but I can walk over to any of the rod end machines and move the machine around by the effector without any movement in the joints or effector itself.
Are haydens arm kits the best mag joints currently easily obtainable?
- Probably, they are certainly the best quality “set” I have purchased if you like super thick arms
Has the DC effector and hayden mag arms come off while printing in the past
- YES, multiple times. I started designing a safety switch but then chose just to sell them to other uneducated people and remove the problems I was having permanently
Can I cause the effector head to move (not the motors) easily by hand?
- YES, night and day difference compared to Ball end or Rod end, a blind test of someone who knows nothing about 3d printing could tell you there is a difference, and which one is “stiffer”
Does the mag joints print better than ball ends or rod ends
- NO, general surface finish is still pretty good but print consistency/repeatability is down, admittedly it can make it really quick to swap over to another nozzle.

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dc42
I'm sorry, but IMHO that's utter rubbish! The holes in the effector are slightly undersize (2.9mm), not oversize. The ball studs are a close fit in them with nothing like 1mm side to side play before tightening, maybe 0.1mm. And what exactly do you mean by "only constraining about 15% of the ball with the cup"? Is that by surface area, angle, or what? Any way I measure it, it's far more than 15%. The ball ends are more than adequately constrained, bearing in mind that the forces applied during printing are predominantly longitudinal.

Good old DC42 getting all shirty as soon as someone is not making positive reviews of his products, come on dude your shameless promotion of your products in this forum gets a little old. What is the OP asking about, was it mag joints? No of course not, but the second someone makes a comment about a joint you jump in and promote your affiliated product, hardly contributing to the discussion, rather just shameless self-promotion with a link to an article of someone else’s on your own forum, the trifecta of shameless self-promotion. We have had this discussion and proof before champion, we both know I have several your effectors (or did, only one now, got rid of the rest) and we both know I have done side by side comparisons on the same deltas and the simple truth is the mag balls don’t stack up to Ball ends the op is asking about let alone rod ends (except for the odd person who changes the effector every other day.

Now I am willing to accept that some effector holes/ball end threads were tighter than others and maybe the older batches were not as tight or as well QC’d as they are currently, but this does not change my experience across multiple sets of your product.

As for joint constraint, this is clearly something you don’t understand so your commentary to date is dogmatic at best (you measured something you just said you don’t know what I mean???). A joint “constraint” is the area of movement that the joint can’t deflect, for all mag ball joints this is less than 20% because any angle you can pull the joint apart or have the ball deflect out of the joint is “unconstrained”, haydens arm sets are actually lower than the 15% but better than some being sold.
The fact of the matter is when you make a joint able to be easily pulled apart and put back together as part of daily use you have to sacrifice constraint and strength in order to achieve this. In a Mag joint this “taking apart of the joint” is super simple and as a result there is the tax to pay for this and so the constraint is super low. With a Ball end the joint is constrained a lot more (can be as high as 75% but are generally around 55%) and as a result there is more effort to take the joint apart and you will find if you do this often the joint will wear prematurely. A Rod end can’t be taken apart and put back together, or should I say is not generally designed to, and as a result they are 100% constrained at every angle of operation.

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dc42
You have obviously never used Haydn Huntley's magnetic joints. Please stop assuming that your experience with inferior magnetic joints applies to all magnetic joints.

Again, we both know this is not the case, the childish response of “you never owned one” is pretty lame and seems to be your go to when some questions your products. How many delta’s have you tried mag joints on, only the one from what I can see so what experience are you proving especially considering the mag joints are promoted by you and sold with your products? I think you need to stop assuming we are using low quality products and stop taking your experience with $0.10 traxis joints and projecting that across the board of rod ends.

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dc42
Suggestions for improving our products are always welcome, provided they are based on actual experience and not theorising.

We both know that is not true, they are only welcome if they are positive feedback, anything that could even be construed as negative is pooed on and then you belittle the person who provided the feedback. After the jump in delta control the Duet Wifi brought (although seems to have been overtaken now by smoothy on print quality) I was happy to promote your products, but the more I see your posts on the forums the less I mention your brand when asked what I use and even less I am willing to provide feedback to make your products better, your attitude simply does not justify the time to bother supporting you, to the point I will probably now buy the next couple of duets as clones.…..

Here is a simply guide you can follow as a vendor (yes you are a vendor despite you using a “personal” persona account) on the forums you don’t control. Never promote a product you own or are affiliated with unless you are specifically asked about it. If you see a post asking about something (like Ball Ends, or even mag joints for that matter) and that something is not specifically asking about your product/affiliated product then keep your comments/advertisement about your products to yourself (so don’t chime in as second post saying “go buy these mag joints”). That is not to say you can’t join the discussion about “ball joints” but joining the discussion does not mean promote your products and shirt on everyone else who does not promote the product alongside you. If you don’t have anything to add to the discussion SPECIFICALLY about ball joints without promoting your products/forum/affiliates then don’t post, it’s pretty simple.

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frankvdh
There seems to be some assumption that rod-ends don't have any play, which is completely contrary to my experience. One of the reasons I went to mag-ball was the play in the rod-ends.

Guilty as charged, I assume you would not be using a rod end with play, rather that it would go in the bin. The reason you have play in rod ends is because you are buying $1 rod ends, a set of the “famous” haydens rod ends is $115 USD for my main delta’s, certainly more expensive than a set of “super top notch” rod ends with lifetime warranties and rolled CF tubes to match and much more expensive than a set of “decent” rod ends already made up on custom length CF arms and many times more than a set of decent Ball ends on arms…..

May I ask the brand of the rod ends you used?

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etfrench
Whether you use mag joints or ball ends, you still need to bolt one end to the effector. The potential for misalignment is the same for both. My effector was made on a CNC machine and distances between all of the balls are within a few microns of being equal (including the balls on the carriages).

The specific alignment issue I speak of is the traditional clamp style with a bolt and nut approach coming through a hole in the top of the effector like dc42’s design. By clamping through a hole, you can move the bolt around in the hole (has to fit through it right) and then when you tighten up the nuts you then twist and move the bolt in the hole causing reduced alignment. This is even worse when you use the mag ball style that has a cup you screw/bolt through the center to attach it to the effector as it is even easier to move the cup out of alignment when you tighten up the bolt/screw even if it is going into a threaded insert instead of bolt and nut. Unfortunately the Ball ends have the same mounting issues but also gain the advantages of binding like rod ends if out of alignment.

When you CNC your effector out of aluminium and all the connection mount points are machined and tapped then you basically can’t get anything out of alignment (assuming the CNC machining was accurate) irrelevant of your joint style. But then again, most people don’t have access to decent/accurate CNC machines although there is plenty cheap all aluminium effectors on the net that are great quality and cheap. The aluminium adds some additional weight but is definitely my preferred approach to a good effector setup, effectors made out of filament/plastic/PCB materials all have too much flex in them.

When you mount a rod end correctly, the ability to get everything accurately align is much easier as the rod end, mounting surface and matching rod end bolt have specific tappers to force alignment. You can simply bolt all the joints in loosely, then tighten up opposing triangles which will force alignment if there is some play in your holes or cause binding which will immediately tell you something is out of alignment (again assuming arm lengths and delta towers are accurate in measurement and alignment also).

Do you have links to quality ball ends with large enough range of motion?

My preferred brand of rod ends for 3D printers (and my other much larger toys that require a registration) is FK Bearings.

Never had one fail, usually get extras when ordering in numbers and you can get them with a range of different materials as the internal bushing dependant on your need.

@Redemptioner, I'm sorry but I didn't know that you had tried Haydn Huntley's magnetic rods and the Smart Effector. Maybe you've said so somewhere, but I can't remember everything that everyone I have replied to has said on these forums.

So the question is, why is your experience of them so different from mine? These are the possible explanations that occur to me.

1. Haydn makes his rods in two forms: with printed ends, or with the more expensive machined Delrin ends. I have only used the ones with Delrin ends. Which sort(s) have you tried?

2. Haydn was gracious enough to admit that one of the batches of ball studs he received turned out to have under-sized M3 shanks. See [forum.duet3d.com]. I think your set must be from that batch, because you said they are a loose fit in the holes in the effector. Mine are a tight fit, as we intended when we designed the effector.

3. It's important to fit the rods with alternating N and S magnetic poles around the effector. Otherwise the magnetic force is less strong, and the magnetic field reaches further below the effector and may affect the fans. Perhaps you had all the N poles at the same end?

Haydn's magnetic rods are not "my" product, I am just a very satisfied customer. The Duet3D web shop run by my JV colleagues resells them in one size only as a service to our European customers, to save them the expense of carriage from the USA and VAT collection charges.

Edited 1 time(s). Last edit at 12/04/2018 04:44AM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].