Rigid vs Flexible Couplers for Trapezoidal Leadscrews?
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@kraegar those zyltech ones aren't actually oldham couplings at all whereas the Misumi ones are
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Ah, thanks - guess I was mis-using the term for those. They're the better of the cheaper conventional offerings, if you buy good ones.
Agreed on the points here about having enough constraint without overconstraining them. We mount the stepper rigidly on the bottom. We use a yoke to tie the leadscrew & linear rail together, and attach the bed. We do not constrain the top of the leadscrew in any way.
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I'm using the flexible aluminum couplers with a 4mm ball bearing inside to eliminate any compression, but still allows bending.
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I Have ordered 3 of the misumi Oldhams so will be interesting to see how good they are but I will also be useing thrust bearings between the bottom of the oldham and the face of the stepper motor so that there is no axial load going into the motor bearing as I feel that would lead to a fairly rapid failure.
Doug
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I might need to pick up some of the Misumi oldhams to try and compare, too.
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Did some digging and turned up this:
https://www.ruland.com/resources/technical-articles/technical-article-servo-coupling
Indeed, I was using the wrong term for the ones from Zyltech. I'll leave my error to avoid confusion. (also, helpful article)
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I'm always amazed by the complexity behind even the most seemingly simple things
Thank you to everyone who contributed to this discussion!
I learned a lot (mainly about how much I don't know...), and took my time digesting the various advice and excellent leads (thanks for the article link, @kraegar, very helpful indeed!)
@fma, you're right of course about the difficulty of offering advice without knowing the specifics, and indeed I was initially inclined to provide a detailed description within my original post. However, I eventually decided against it precisely because I wanted to keep the discussion open-ended and wide as possible, rather than narrowing it down by focusing on a particular setup or application. I hope this makes sense.
@JoergS5, many thanks for the methodological breakdown of the subject-matter into logical steps. Very helpful indeed in tackling this!
@Phaedrux, @kraegar, @Stephen6309 & @LHelge, thanks for sharing your practical knowledge and research conclusions.
@Dougal1957, @kraegar & anyone else who might engage in testing different solutions, please do come back and share your insights and discoveries. I - and I think others too - would certainly be interested to hear about your experience.
As for myself, from what I've read so far, the 'Zero Backlash Jaw Couplings' look like they could offer the best balance between accuracy of torque transmission and allowance for misalignment. These cuties aren't cheap, though, so I'm currently searching for the best deal on quality parts. I'll report back once I have them on hand and assembled.
Thanks again everyone!
SnowCrash -
@snowcrash Thank you for your nice words!
I started building a printer from scratch about 6 months ago and still learning something new about the physics of the planned printer every day. Besides the 3D printer forums, I am more and more in the CNC forums also, because they are used to take into account effects of 1/100 mm and below. Understanding the CNC issues help improving 3D printers also.
One example: thermal expansion is a widespred issue in the CNC area (and how to solve it), because mixing aluminium with steel is used often. In 3D printer construction it is often neglected, but without a reason, Because you mix materials here also, and mixing and at the same time fixing will cause bending or breaking. One example is the heat bed.
I wish you the best for improving your printer and much fun.
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Thanks, @JoergS5, a CNC is definitely on my list too
Which CNC forum/s would you most recommend? (I promised myself I won't go into the CNC project before the printer is done, but no harm in just looking, right?)
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@snowcrash don't do it you will get sucked in lol
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@snowcrash said in Rigid vs Flexible Couplers for Trapezoidal Leadscrews?:
As for myself, from what I've read so far, the 'Zero Backlash Jaw Couplings' look like they could offer the best balance between accuracy of torque transmission and allowance for misalignment. These cuties aren't cheap, though, so I'm currently searching for the best deal on quality parts. I'll report back once I have them on hand and assembled.
Please do so, because I would also be interested in this. I just recently rebuilt my Z axis to no longer use this kind of coupling at all but still I find this very interesting and I always keep my options to revert/change anything.
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Looking around for these zero backlash jaw couplings I came across ones where the spider has 4 segments about equal in size (each) to one of the jaws and others where the spider has 6 segments that are considerably smaller (maybe half) than the jaws.
Has anyone any opinion on these two types?
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@snowcrash said in Rigid vs Flexible Couplers for Trapezoidal Leadscrews?:
Thanks, @JoergS5, a CNC is definitely on my list too
Which CNC forum/s would you most recommend? (I promised myself I won't go into the CNC project before the printer is done, but no harm in just looking, right?)
The largest seems to be CNCzone.com/forums, one of the technical best I found is practicalmachinist.com/vb
Sometimes I find interesting threads on reddit.com also.
To get ideas I check openbuilds.com
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Hi all,
@dougal1957 said in Rigid vs Flexible Couplers for Trapezoidal Leadscrews?:
@snowcrash don't do it you will get sucked in lol
Too late...
Thanks for the links, @JoergS5!
Some really nice machines out there
One of the biggest challenges I'm facing atm as I'm working on the prototype is that I often need small custom metal parts and it's incredibly difficult to find anyone to make small quantities at a reasonable price.
So if there's anyone who's based in the UK and already has a CNC and would be willing to help out (I'd of course cover all the costs of material and fabrication) - please ping me!
Back to the present topic, my search for suitable couplings led me to realize that I haven't provided enough support for the leadscrews to begin with. Apparently, without sufficient lead-screw support, there's little even high-quality couplings can do, so tackling this issue has become the top priority.
Once it's sorted (I hope
) , I'll proceed to the matter of couplings and report back.@wilriker said in Rigid vs Flexible Couplers for Trapezoidal Leadscrews?:
Looking around for these zero backlash jaw couplings I came across ones where the spider has 4 segments about equal in size (each) to one of the jaws and others where the spider has 6 segments that are considerably smaller (maybe half) than the jaws.
Has anyone any opinion on these two types?
Sorry, @wilriker, I only came across spiders with 4 segments in my research and unfortunately don't know enough to offer any help on this.
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I Received my Oldham couplings from Misumi and jeez they are nice and they are also very compact (About half the size of the std couplings that we normally use) I also realise that using them directly could transfer quite a lot of side thrust into the stepper motor bearing's so I intend to fit some Thrust bearings between the coupling and the stepper body to account for the side thrust.
Doug
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@dougal1957 said in Rigid vs Flexible Couplers for Trapezoidal Leadscrews?:
I Received my Oldham couplings from Misumi and jeez they are nice and they are also very compact (About half the size of the std couplings that we normally use) I also realise that using them directly could transfer quite a lot of side thrust into the stepper motor bearing's so I intend to fit some Thrust bearings between the coupling and the stepper body to account for the side thrust.
Doug
Thanks for the update, @Dougal1957. But I'm a bit confused by how you describe your planned setup: if the thrust bearings goes between the coupling and the stepper motor, does that mean it will actually be going around the motor's shaft? If you could perhpas post some pics once you've got it installed, it'd be awesome as I'd love to see it and learn how you went about it
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@snowcrash here you go I do need to locate a slightly smaller bearing and make a spacer up for between the bearing and the coupling the one shown is a 10mm bore one and I am looking for a 6 or 8 mm one the reason for the over size is I dont want the bottom race to be in contact with the shaft at all.
HTH
Doug
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Thanks, @dougal1957! That certainly helps.
Good looking coupling too
So is the bearing going to be attached to the stepper (or something else) in some way or just stay this way?
Also, if you get a chance at some point to post a few pics of the whole assembly once it's done and perhaps say a word or two about how it works, I'd very much appreciate it as it'll help me learn more about this subject which is totally new to me (and, unlike theoretical discussions, practical implementations - especially ones for 3D printers - are quite hard to come by).
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@snowcrash there will be a printed spacer between the bearing and the coupler just to centralise the upper bearing race and the motor shaft may need to be shorted as the shaft only need to be inserted into the coupling by around 5mm else it will restrict the ability of the coupling to manage any misalignment.
I will indeed post some pics once it is assembled.
Doug
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@kraegar said in Rigid vs Flexible Couplers for Trapezoidal Leadscrews?:
Oldham - Best of the "common" couplers, quiet with the least artifacts transmitted. Cheap ones separate easily.
When you say the cheap ones separate easily, do you mean from the ones with better quality or the parts of the coupling itself?
