R&P upgrade

[jimt]

Just wondering who's done the upgrade from cable to R&P drive and what kind of improvement it made. I'm planning on changing over to R&P but wouold like some feedback from those who've done it already.

Thanks

Jim

[bruce_clark]

Jim,

Yes, I have done the cable to rack upgrade. It
really has changed the machine! First off,
accuracy has doubled, feed is much more positive.
Matter of fact, under high speed jogs/cuts, I can
actually SEE the railings twist! The only
downside I have noticed is you loose about 2
inches of Y travel because the new X axis motors
are in the path of the Y carriage.

As for the actual change over, it takes about
4 hours (including some trips to the hardware
store ect). If you are interseted, I took a lot
of photos when I did my upgrade, that I would be
more than happy to email you (about 1mb including
pitfalls ect that I needed to change).

I have been VERY happy and I use my SB to do
things that I have not done before (for example
engrave "engraver's plastic" with a speed reducer
on the router).

Bruce Clark
bwclark@centuryinter.net

[jimt]

Bruce,

Did you get the new gear head motors or the thrust boxes using the existing motors? I have the 125 oz-in motors that I guess will work but are not as powerful as the newer gearhead type. I thought I would probably lose osme travel in the y axis and was thinking about alternate motor mounts that would acutally hang the x axis motors upside down from the present position and let the thrust box go where the motor goes now. If I offset them to the side of the carriage opposite the router, they should clear OK. Are you using two drivers for the x axis? Also, Ted had mentioned an upgrade to 2-1/2"? high rails for the y carriage to make them stiffer. Have you done this? Seem like it should be done before adding the R&P drive.

Thanks for the info

Jim

[bruce_clark]

Jim,

My machine has larger Y axis rails (but I don't
know if they are 2-1/2"). It was the last
iteration of improvements before they switched
over to the rack and pinion drive.

As for loss of travel versus fooling around a lot
for two aditional inches, is not really worth it
to me (it still cuts 4' X 8'). The only thing I
"worry" about is that if you over shoot the "zero"
on the Y axis, the X axis motor becomes the "stop"
(through, I found by putting a rubber "foot", like
they use to control the tension on the pinion gear,
on the rack, the carriage will not only stop but
will bounce right back to "zero".

As for the driving gearboxes, they are the new
Vexta gearbox and larger motors. Two on the X
axis and one on the Y. I also put a larger motor
on the Z axis (running about ~300 oz/in on the Z).
Also, the machine is running at 28V (ShopBot PS
upgrade).

I have been very happy with the upgrade and think
it REALLY has made a difference.

Bruce Clark
bwclark@centuryinter.net