On 2008-05-22, Ignoramus12247 wrote:
On 2008-05-22, DoN. Nichols wrote:
On 2008-05-22, Ignoramus12247 wrote:
On 2008-05-22, Pete C. wrote:
It's a Bridgeport mill. No drum switch will remain and there will be no
speed pot. I'm quite comfortable with entering the speed and run stop
using the VFDs keypad. Rather similar to the Sxxxx M03 deal on a CNC.
BP drum switch is kind of hard to rewire.
Why? -- The internal wiring of the drum switch is as follows:
[ ... ]
And all you need to do is connect the one which I have marked
(L1-LINE) to the common on the VFD, and (L1-motor) to FWD, and
(L2-motor) to REV. Totally ignore all the rest of the terminals on the
switch. If you can't figure out which is which, use a multimeter to
find a terminal on the switch which is connected to another terminal
only in the FWD position and to a third terminal in the REV position.
I looked at that. What I found difficult was not the schematic, but
that there are barely enough wire length coming out of the motor, to
reach the drum terminals. I think not even enough to make wire nut
connections. Schematic wise, you are 100% on target.
Hmm ... have you opened the wiring box on the motor? mine has a
set of nine wires which can either be configured as a 240 VAC three
phase motor, or a 480 VAC three phase motor. Get some appropriate wire
or oil-tite flexible conduit, and run it directly from the motor to the
VFD -- wherever you mount that. (And I would tend to mount it on the
back of the column -- best position to keep chips from falling on it and
working their way in to short the circuitry on the VFD.) then just run
the control wiring to the drum switch, and bolt a small housing for a
speed control pot on the bottom of the drum switch or somewhere nearby.
Obviously, plug the remaining conduit hole with a goof plug to keep
chips out of the switch contacts, too.
When I first got my Bridgeport, I pulled off the wire nuts, and
crimped on ring terminals for #6 screws, then stacked the terminals to
make the desired connections, used a screw, nut and lockwasher to hold
them together, and then put heat shrink tubing over the terminals. This
way, if I ever need/want to swtich it to 480V operation, I don't have to
add flex wear to the wires by uncrewing wire nuts, trying to straighen
the leads and re-twist them, and then put wire nuts back on them.
I also find the placement of the drum switch, to be not perfectly
convenient, at least for me.
O.K. That is personal -- but you can relocte the drum switch to
a place which you do find more convenient -- and I find it easier to
work the switch and a pot with oil-covered fingers than a set of
membrane keypad switches.
Hmm ... while you are about it, get one of those red mushroom
cap panic switches to hook in series with the common lead from the VFD,
so you can stop the spindle quickly at need -- for example a badly
out-of-balance fly cutter causing the machine to dance around the shop
floor. :-)
So the only time when I reach for and switch it, is when changing from
direct to back gear.
O.K. While I believe in using the drum switch and keeping the
VFD's keypad out of the way of hot chips and the like -- and keeping the
operating habits as close to the same as possible.
Enjoy,
DoN.
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