Meticulous Maynard's Chain Guide

Projects
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Rather than hijacking @Onelonedork’s Deformation along to the top... Normal? thread, I decided to do a proper write up for my chain guide.

I had a lot of trouble with chain skipping coming from the back-side of my chain sprockets so I knew I needed to do something to fix that. Can’t take all the credit here, my idea is built upon the shoulders of giants. I saw @Blsteinhauer88’s Easy chain guide for chain skip and knew that would be a good starting place for my own chain guide.

I had quite a bit of fun drawing up mine in Fusion360. The model and nest files are included in the github repository below. I knew I wanted something clean that was also adjustable. I came up with this:

Maslow_Guide_1
Maslow_Guide_1.jpg3264×2448 858 KB

MaslowChainGuide2
MaslowChainGuide2.jpg3264×2448 780 KB

Link to a360 file (opens in browser, no CAD needed): http://a360.co/2APifTS

It’s two layers of 12mm (~1/2") plywood. I designed the pattern to be reversible, that way I could make one program for both the right and the left motors. I ran two screws through the back of the bigger part to secure the smaller part. You could also glue and staple it if that works for you. The most important part of the assembly is the smaller piece is roughly centered on the larger piece. Maybe I could make a revised version that uses a V-carve bit to engrave it’s position? The only problem with that is then I would have to make two separate programs.

The NC file is programmed to use the 1/4" 1 flute bit available from the Maslow store. The feeds and speeds can be changed either in the NC program using find/replace for other 1/4" bits, or by opening the nest file and changing the tool used for the operations for other sized bits.

As far as mounting to the frame, I made up a mounting bracket from 1 1/2" x 1/8" steel angle. I drilled two holes in one leg that match up with the motor mount. This way my bracket sandwiches between the motor bracket and the mounting bracket I made for the frame. In the other leg, I drilled and tapped two 1/4"-20 holes 42mm (~1 5/8") on center for the guide screws.

That being said, it would be quite easy to simply attach the guides to the wooden stock frame. There may need to be a riser or something in the system to make sure it aligns with the chain sprocket. As much as I really like my steel frame, it requires me to do a little more thinking as to how to attach modifications.

Link to github repository:
https://github.com/MaslowCNC/CommunityGarden/tree/master/Maslow%20Chain%20Guide

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So much nicer looking than mine! I’m goning to replace mine with yours. You hit my vision spot on. Nice work :+1:t2:! Hardly a “giant” here, too many brains bigger than mine ! :joy:

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I am jealous! Nice and clean design. My sewing machine bobbins look like crap now, after I’ve seen this.

mlsw-bbn
mlsw-bbn.jpg901×621 119 KB

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@MeticulousMaynard, I’ve put in a PR to add your pictures to the Readme. They are good shots, show exactly what the project is about. :smile:

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No @Gero, not crap, but simple. Simple is good, too. :smile:

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I am still jealous but to suborn to copy this wonderful design. Now I have to use metal bobbins, somehow manage to press bearing in them and create an adjustable arm.
I love how inspiring this Forum is and how openly designs are shared. Thank you @MeticulousMaynard for sharing.

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those bobins are cute though Gero

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delete (moved to my own thread)

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As this is Meticulous Maynard’s Chain Guide, I would suggest a new topic :slight_smile:
There I would then ask on what side of your drawing the sled is. Chain jumps happened for me when the sled was moving to the top of the sheet, on the side with the shortest chain to the sled. This side has the longest loose chain and the rubber bands can’t compensate for the chains trying to go vertical. Because the frame and the motors are tilted, the loose chain is coming in from a more vertical angle and when you feed that chain out, the side of the chain will try to ride on the tip of the tooth of the sprocket. With a noticeable ‘Bang’ the chain will either skip a link or fall into its meant position. If you have chain jumps starting from the sled side of the chain, your sprockets and sled-chain-mounting-points are not parallel to the work piece. With the pantographs you add or remove mounting spacers, with the brackets you go one hole up or down. One more reason for chain jumps could also be flexing top beams, as both sprockets get turned out of alignment. I apologize if you knew already, hope it still it can help someone else.

The changing pivot point of the chain on the sprocket depending on the chain angle, is an error that is already, or can be compensated by the soft- or firmware, I think. I agree the a small idler can reduce the amount of error and would make room to experiment with different sprocket sizes.

Edit:

This is answered here: PDF of the formular

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woops, i’ll move it to

:slight_smile:

EDIT:
this one can also be deleted, or keep the link as it is the same kind of topic just a slightly differnet goal?

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you don’t need to change the pivot point to experiment with different sprocket
sizes, Sprocket size, and the effects of the chain angle to the sprocket are
already accounted for in the current math (or if Bar hasn’t merged it yet, it
soon will be)

With the math already accounting for the effect, adding a different effect will
just complicate the math, not simplify it.

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but if you go with a different sprocket size then the math accounting for the chain angle will also need to know the radius, if you used a idoler as your pivot point then that can remain the same and only affect the travel per revolution

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the math needs to know the radius, because that changes how much chain is fed
out in one revolution of the sprocket.

adding a different size pivot somewhere else just adds complexity, it doesn’t
remove any.

And if the pivot point is small enough, it can start to catch in the links of
the chain (at the very least, there is a difference between a regular link and a
master link going over the pivot) because the pivot works against the outside of
the link, while the sprocket works against the rollers on each link.

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I agree with Pyrosrock, though i don’t have a machine to show why i think he is right,

Anyone who want’s to lock horns on this?

I see dlang’s point but when you measure the chain length form center of bobbin then is 100% the same as center of sprocket just a smaller diameter and less error

What does @Bar think about this?

I’ll try to draw this tomorrow once i get my head around how i need to explain how i see it
maybe @pyrosrock has a simple explanation???

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This has been well covered and discussed amongst a number of threads.
All i have been saying is that

  • Yes the chain leaves the sprocket at different places depending on the direction
  • The larger the sprocket size the bigger the difference
  • If we have the maths to calculate and compensate this great!
  • If people are talking about trying different size sprockets then that would have to be taken into consideration with that maths if they are used as the pivot points.
  • or if you used the known size sprocket as a idler pivot point, then you can play with motor configuration, drive sprocket size or more wraparound serpentine work without effecting the pivot point, thus without introducing another variable
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This has been well covered and discussed amongst a number of threads.
All i have been saying is that

  • Yes the chain leaves the sprocket at different places depending on the direction
  • The larger the sprocket size the bigger the difference
  • If we have the maths to calculate and compensate this great!

we do

  • If people are talking about trying different size sprockets then that would
    have to be taken into consideration with that maths if they are used as the
    pivot points.

already done

  • or if you used the known size sprocket as a idler pivot point, then you can
    play with motor configuration, drive sprocket size or more wraparound
    serpentine work without effecting the pivot point, thus without introducing
    another variable

my point is that you are introducing another variable (the idler size) to the
existing system. No that variable won’t change if you change the other
variables, the idler doesn’t change, but adding the idler adds complexity
without elinminating any error on the stock systems

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This thread went places. I was refraining from replying because I didn’t have anything to add to the conversation but here goes.

@Gero: I really like that bobbin idler pulley you’ve used. Simple is great! I feel that my solution is quite a bit over-engineered for what we need.

Does this mean that the firmware now calculates the sprocket size? Or that it simply offsets of attachment point of the chain? (or those basically the same thing?)

If so, I have some feedrate tests to do…

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Does this mean that the firmware now calculates the sprocket size? Or that it
simply offsets of attachment point of the chain? (or those basically the same
thing?)

I believe that it was pointed out that the firmware is properly calculating
sprocket size. (at one point, this was hard-coded, but I was told in a former
thread that it’s now calculated)

I know that (at least for standard kinematics) this includes the pivot point
and the length of chain that is wrapped around the sprocket.

Bar has said that he has the code to do this fully with triangular kinematics,
but I’m not 100% sure it’s been merged, but if it hasn’t, that’s a small change
from where we are.

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The firmware uses link size and number of sprocket teeth to calculate the sprocket circumference.

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Excellent! I’m going to have to update my firmware/gc and give @dlang’s 25 tooth sprockets a try. This weekend I’ll have to test feedrates further! :smiley:

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