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Tips/Techniques CX706 Lathe - half speed in reverse?

Tips/Techniques
slow-poke

slow-poke

Ultra Member
My CX706 lathe is wired such that (from the factory) when in reverse the spindle runs at 1/2 speed. No idea why. Anyone out there with a CX706, can you see if your's does the same thing?

The potentiometer wiring actually passes through the forward/reverse switch on the filter board.
 
That seems like a mistake.
Is it wired according to the diagram in the manual?
1733864336915.png
 
Never heard of that before. Did you buy it new? Guessing not. So someone messed with it.
 
I purchased it new.

Wiring is really haphazard and does not follow the wiring diagram in that they flipped the hot and neutral at the filter board. That being said they made a conscious effort to run the speed pot through the forward/reverse switch with 1/2 speed indicated on the wiring diagram.

Do you have a CX706 and does it run half speed in reverse?

This is how mine is actually wired.....

CX706 Wiring Diagram_Actual.png
 
Google search tells me that this is by design, most likely to preserve motor life, because the brushes wear faster in reverse and tend to over heat if run at full speed in reverse. At some point I'm going to need to do an upgrade, need to keep an eye out for another VFD and suitable motor.
 
The KBIC controllers used by BB do not have any circuitry that affects motor polarity. My guess is pins 11 and 12 on the R/F switch are adding a resistance in parallel to the speed control P1 and P2, which lower the speed control signal. I suggest disconnecting pins 11 and 12 and running the motor, it shouldn’t affect anything and will confirm whether there is a shunt resistor.

As @slow-poke mentioned, the DC motor brushes will develop a set and will run better in the forward direction.
 
DavidR8 said:
Can I interest you in a 1.5Kw brushless DC motor? :D
Click to expand...

IIRC the factory motor is 1HP and does not make a lot of power at very low RPM.

I will probably go 3P+VFD(FVC) but I'm always open to explore (brushless is appealing), details of the motor and drive?

IIRC you were planning to use this for a spindle drive on a mill?

My Google search of sensorless vector control VFD vs. Brushless DC motor torque and power comparison is not yielding any useful information, anyone knowledgeable on the topic?

I'm guessing that they probably have very similar characteristics and the quality/ complexity of the drive being the deciding factor. When you think about it there is not a huge difference between the two technolgies.
 
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slow-poke said:
IIRC the factory motor is 1HP and does not make a lot of power at very low RPM.

I will probably go 3P+VFD(FVC) but I'm always open to explore (brushless is appealing), details of the motor and drive?

IIRC you were planning to use this for a spindle drive on a mill?

My Google search of sensorless vector control VFD vs. Brushless DC motor torque and power comparison is not yielding any useful information, anyone knowledgeable on the topic?

I'm guessing that they probably have very similar characteristics and the quality/ complexity of the drive being the deciding factor. When you think about it there is not a huge difference between the two technolgies.
Click to expand...
It’s actually the motor off my mill. I’m replacing it with a servo motor and driver
 
I recently bought the CX706 also, haven't had much chance to use it yet, this is good to know. I will test it out later this week and report back. Like your wiring diagram :)
 
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