Great that you used recycled metal for Your Maslow looks very solid. The rust is patina. I like your counter weight system and 3D printing the sprockets is cool. Did you make your sled linkage system? I plan on replacing the triangular linkage on my sled with the circular system that Bar has designed when it is available in the store.
Please let us know how they compare. We have theories that say the linkage
should work better than the ring, but nobody has done a head-to-head comparison.
David Lang
Will do when I have the circular.
Thatâs a linkage kit David Lang sells. I plan on buying the ring kit as soon as I can get it. The pantograph works in 90% of the work space but it binds in the lower left and right corners
Very interesting, I see some of the binding in the upper parts of the work space. I have looked closely at all of the joints and canât determine where they are sticking. My kit is the wood version.
I donât know the ratios, but that makes sense. I am intending to experiment with a third motor controlling a downward and left to right pull on the sled instead of so much weight on the sled which if works out would equalize that weight across the top a lot more.
Thank you for the insight. Getting to refine my ideas before my kit gets here thanks to all the knowledgeable and helpful community here!
the problem with a single motor pulling down is that the chains only work if the
angles donât get too extreme, and a third motor down a couple feet below the
bottom of the work area would still mean you couldnât cut most of the area of
the workpiece.
a practical machine would need to new lower motors, and they would have to put
just the right tension on the chain to pull the other chains tight (and note
that you are never going to be pulling directly against the other chain, you
will always be pulling at an angle), this makes the math pretty messy, so you
will need to either slow down the machine or get a faster processor.
Iâm not saying that it canât be done, but I am saying that the cost is a lot
more than it appears at first glance. We donât know the benefits for sure (and
wonât until someone builds one and we find the new sources of inaccuracy that it
inttroduces).
I would go with a coreXY gantry before trying a 4-motor maslow. It would
probably be cheaper as well as more accurate.
We kept having chain twisting, causing irregular cuts and the sled to lift off the bed. After we brought out the bottom connection point, replaced the tension string with rope, added pulley tothe top, added counter weight with pulley, just about ALL of our issues went away!
Now seeing the posts above we may slightly change to something a little more simple such as weight against wood as ours is in a community workshop http://www.themakerstation.com in Marietta Georgia and the easier we can make it for everyone, the better. Thanks again for sharing guys 
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Lol. He uses the same cad program as me. Check out the similarities here. Is milling possible?
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So if I understand correctly, and I probably donât, an approach similar to the core XY approach could actually be implemented on the current Maslow using the triangular kinematics by using longer chains, a couple more sprockets and a second linkage kit for the bottom? You could even toss a spring in to keep tension on the chain.
(I am thinking about this more, this seems implausible. I need to look at the actual math so I donât ask such dumb questions.)
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I donât know how you would get that to work, the bottom chains would be changing
their lengths at a different rate than the top chains.
draw up what you are thinking of, and measure the length of the different chains
with the sled at different points on the work area.
David Lang
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If using two tensioners (chains?) fed from the direction of the lower corners, the lower tensioner lengths can be calculated from the XY position of the sled and the machine dimensions in the same manner as the upper chains. Doing the calculations and motor control with a separate controller would take care of any concern about processing power.
If the tension were applied from a single connection to the sled, the angle of the connection could still be calculated from the sled position, chosen to pull at an angle chosen to bisect the angle between the upper chains as near as possible within the horizontal travel limits of the moving end of the tensioner carriage. Still a two-motor setup, but a simpler connection to the sled.
your lower chain(s) are going to have to be driven at different speeds than the
upper chains, so you are talking about adding one or two new motors. how can
this still be a 2 motor machine?
and if you are trying for only one additional motor, look at where it would have
to sit and the chain angle that it would have with the motor at different places
on the machine. Where itâs forces are needed the most (in the bottom corners), a
single additional chanin would be pulling in the wrong direction, making the
problem worse.
Both approaches would add two more motors. They only need to keep pace with the sled, and spring element in their connection would handle the inevitable lag of following the sledâs reported position. Those position reports come frequently enough that the secondary controller/motor group should be able to maintain tension well enough. The Maslow is not a high-speed machine.
Instead of using a third or fourth motor, what if a counterweight system was used to pull down on the sled? I havenât set up yet, but this has been my thought for when I do get it going
where would you attach the motor and what direction would it be pulling in the
bottom left corner? what dorection would it be pulling in the bottom right
corner?
people frequently suggest doing somthing like this, but so far, only the 3rd
motor approach of pushing from the top center seems to provide forces in the
right direction in the right places (and I think it may be possible to use a
weight instead of a motor using that design)
David Lang
My thought is to put 2 counterweights on pulleys, one coming from each bottom corner (with pulleys roughly as far apart and down from the work surface as the motors are above it) so that the sled is being pulled from 4 directions. Up by motors and down by weighted cables through pulleys.
how do you arrange the weights and the pulleyâs on the bottom so that they pull
towards the closest corner, not away from it?
David Lang
