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Improved chain tensioning for top beam configuration

what about adding a ledge to support the chain? then you wouldn’t need high enough tension to defeat gravity.


A ledge might cause enough slack that the sprocket on the hook side comes loose because it’s just held in there by the tension.

I can second that @mrfugu’s roller works well. I have had zero chain skips in my testing (air cuts only). I still use the original bungee setup, though.I like that it keeps the chain in place.


Just make sure not to tension the nylon roller (I trimmed mine a little bit) so that it rolls freely while the screw through it is still firmly threaded (IIRC, 4-6 full turns into the motor housing)


That is true that it would transfer the load more directly, but at under 50 pounds at the sprocket, there is really no flex (I tested the flex by hanging on the motor bracket, and it was minimal with my body weight).

That depends on how high the motor is mounted. With the stock frame it’s an issue, but some have a higher top beam.

I ended up using some longer cap head screws that I had on hand.

I like this idea, and only part I don’t like is how it hits the bottom of the beam, so would be interested in how you fixed that when you put up pictures.

This was my inelegant yet functional solution. It is the same idea as @mrfugu’s, where the chain just hangs with no elastic or extra weight. I used the sprocket on a screw to keep the excess chain from tangling or wrapping around the motor. Nothing has skipped, jumped, gotten tangled, or even seemed like it was close to doing any of those things. The chains do touch the ground when the machine gets close to the corner where the motor is, but that doesn’t seem to cause any problems.

For reference, this is on the Bar’s Bolt Together Frame.


Here is the picture of the simple guide block sorry for the delay. The chain has yet to skip off or anything after several practice cuts of the sled while I tune the z axis


Do you think the motors have to work/strain against the bungee cord much?

I went to using counterweights (jugs of water) that hang off the end of the beam with an eyelet to raise the level of the chain as it nears the sprocket. Using the plastic spacer as well to keep chain tight to sprocket. I have yet to use Maslow since these changes though because of life but thought I’d share.


I like the use of the eyelet and spacer here.


They should not, we should always have more tension on the sled side of things,
otherwise the backlash of the gearbox becomes a factor to hurt accuracy

I am a little concerned about the chain having that much side flex in it.

Seems to be working fine so far, maybe it’ll stretch the chain more over time. I cut my sled and the maslow logo out. The sled and logo are within 2mm all around but I would like a bit better before trying to make a sub cabinet.

Yeah that might not be great. I wonder if there is a allowable amount of radius a roller chain can bend? If so we could 3d print a radius that starts at the height of the sprocket and slopes gently down so chain hangs vertical.

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I don’t see how we can make a weighted chain hanging off a point that isn’t in line with gravity without some bend unless the guide is made to go all the way to the floor and guide the weight too. Or am I just being thick?

I ran my chains over the top like this photo with weights on the gear and hook bits

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It’s not skipping cogs so far

what we are primarily talking about is having the chain go horizontally across
the top beam (where it stays lined up with the angle of the sprocket and top
beam) and then have a weight drop down from the top beam stright down, where the
angle of the weight and the angle of the chain have nothing to do with each

If you are running the chain down, you need to have supports in front of the
workpiece at the bottom to anchor the tension mechanism to.

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Here is a 3d printed guide I made to smoothen the transition between the 15 degree tilt and vertical.