Y Axis Needs Stiffening

[studio@renc.igs.net]

I have a 5' wide SB and because of the extra width, the y axis is too weak to support the router. It gets bouncey, and this causes chatter in my cuts. I have bolted a piece of aluminum flat bar 1/4" x 3" to the side of each y strut. This helped, but is not the total solution.

Has anyone had the same problem and found a solution?

I was thinking about trying aluminum H beam.

Any suggestions would be appreciated.

Richard Bouchard,
Canada
studio@renc.igs.net (mailto:studio@renc.igs.net)

[joa]

My y axis is normal width (PR96) but it also does some weird things fairly often. Hopefully one of you has experienced/fixed this and can help...

Randomly while jogging the whole y axis will start shaking back and forth and throw my positioning off. Sometimes it really throws it off (by more than an inch) and other times it only does it a little bit. Rarely if ever is my X axis off.

I have tried about everything I can think of and can't narrow down when and why it does it. My carriage is very well adjusted- none of the 6 bearings "spin" freely/loosely (aren't contacting the rail IOW) though the carriage slides back and forth easily (though with some amount of friction) when I pull the stepper out of the rack (I have a R&P machine.)

I have tried all kinds of speed settings from .5 ips to 3 ips and it seems to do it on every setting. It only does it when I'm going in two directions (X +Y) though. I have had it happen and then stopped the move and then started it again and it still doesn't go away.

What I'm thinking it must be is some harmonic that causes the vibration and then causes the stepper to stall slightly each time and this throws the settings off.

Any advice on how to cure this? It's really bothering me!!

Joa

[bruce_clark]

Joa,

Is this a new SB with the gear box? If so, you
may have a loose wire on your Y axis. Did you
check out ShopBot's technical bulletin about
having something like 3/8" wire exposed in the
Wago connector?

It sounds like one of your phases is not getting
energized all the time (like the wire is arcing)
causing the motor to sometimes turn backwards.

Now, this is ONLY a guess, but if you check all
the connectors on the Y axis and the problem does
not goe away, then you might have one of the
driver boards going out on you. Again, this is
ONLY a guess.

Bruce Clark
bwclark@centurytel.net (mailto:bwclark@centurytel.net)

[cmrtom]

I was having the same problem with my Y axis. I needed to hold + - .010 completely across the axis. We eventually bolted a laser to the Z axis frame and shined it against the wall to track the drop it was awful........so we added a plate on each end of the cross tube.....then bolted it in place, next we ran a 3/8 inch steel rod through the inside of the tube. The rod was positioned at the top of the tube on each end. next we made a little bracket to slip into the inside of the tube that would hold the steel rod at the lowest point possible at the center of the Y axis. When we threaded the end of the rod and tightened it up we were able to actually tune the cross tube. By adjusting the tension we could visually watch the laser track and get the BOT into tolerance. It works great now and we are very pleased with the Y axis after this modification.