I was wondering if there was anyone who actually went with a 12’ beam?
Yes, there have been a couple posts this week from people who have gone with 12’
beams.
I ordered extra chain. Should I also raise the height of the beam above the
cutting area from the stock design?
Is there any drawback to extending the beam past 10’? (aside from space
considerations, my shop has 20’ ceilings and a 16’ rollup door)
extending the beam past 10’ helps cutting in the bottom corners, but it makes it
harder to cut in the top center.
Along the top, you are limited by the force the the motors can provide, the
higher the static force needed to keep you in position, the more likely you are
to run into problems
In the bottom corners, you are limited by the force that gravity can provide,
the lower the force that gravity provides, the more likely you are to run into
grief
take a look at the spreadsheets developed in the thread
Maslow Chain Geometry Spreadsheet and play
around with the numbers. you want to maximize the force in the bottom corner
while not driving the force in the top center up too high.
we know that a yoffset of ~12" or a sled weight above 30 pounds can cause
problems, which seems to imply that a force in the top center exceeding 50
pounds is
I’m very familiar with traditional cnc equipment, but this triangular articulation is completely new to me.
I’m not expecting real precision, but the goal is to be as consistent as possible.
we are seeing people with accuracy within ~ 1mm (1/32")
but all along, our repeatability has been good.
When the forces are too high/low, and the feed rate is too high, (and the
friction between the sled and the workpiece too high) the sled doesn’t follow
the desired path (wandering on downward cuts, rounded corners in the bottom
corners, and hooked cuts along the top)
It looks as if you can get a drastic improvement by going to a 12’ beam, a 30
pound sled, and keep the top tension under control by raising the beam a foot
higher than stock
but play around with the numbers, and if you can, play around with the actual
machine. The spreadsheet is only math, and math != reality
To quote Albert Einstein:
As far as the laws of mathematics refer to reality, they are not certain; and as
far as they are certain, they do not refer to reality.
David Lang