My New G0704 Mill

Got the Belt Drive installed and tested. Runs very quiet compared to the geared drive.
I was even able to keep the speed sensor where it was mounted.
And it will go up to 3500 RPM. I'll need to make a new pulley for the motor as I had to install it upside down to get it to work. The sizes of the pulleys are backwards to what I wanted. The 2 smaller size are on the bottom now. At least it will run now so I can finish the other project tomorrow and make a new pulley this weekend. I'll need to make a guard to cover everything next.


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I changed the belt drive to one that uses the Hi / Lo gears instead of direct to the spindle.
The only problem is that in order to run the spindle the right direction, I have to set the Forward / Reverse switch to Reverse. That slows the spindle speed down to half what it will now run in Forward. 4200 compared to 2100 in reverse.
What I would like to know is if anyone knows if the stock motors can be changed to run the opposite direction?

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I didn't get any answers to my previous question so I'll ask again.
Does anyone know how to rewire the G0704 Forward/Reverse switch to get the stock motor to run the opposite way?

The reason is with the switch in reverse, the motor only runs at half the speed.
 
If its a plain Dc motor, you could probably get away with swapping the two motor leads at the output of the speed control. If its a three phase brushless, I'd have to defer to someone else more knowlegable.. One thing am not sure about with that motor is if the brushes are set at an angle or offset so it has a preferred direction. It will run in either direction, but running it in it's non-preferred direction may wear the brushes faster.
 
Reversing the motor leads should. I investigated this in the past when looking into controlling the speed via mach3 and from what I remember from the KBIC 125 manual (which is essentially the same speed controller board) the (DC) motor is connected to the PCB terminals A+ and A- and if what you have is opposite of the desired rotation, simply reverse the wiring of A+ and A- with each other. This is in essence just swapping the motor leads anyway and since the manual said this reversed the motor it should work.

That being the case you should be able to wire a simple switch to reverse the connections and then depending on which way your (added and stock) switches were be able to obtain max speed in either direction.

I got sidetracked and moved on to another mods, and it's been a while since I looked but there may also be a pot on the board to adjust the max reverse. If not then I imagine that either on the board or inline there is 5k or so resistor/resistance built in when the switch is in reverse on the G0704 circuity so it limits the speed in reverse (from what I remember it simply uses a 10k pot for the speed adjustment I think). Seems logical but this is from memory and I didn't check for or locate where the differences in signal resistance/voltage were originating and exactly how much the difference is, but it should be easy to investigate further. Remove the resistance and it should operate the same speeds in either direction.

I've had no need to mod/change my reverse speed max and haven't tried so will include a standard disclaimer... don't blame me if anything I mention screws anything up but hope this helps a little.
 
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coherent,
Thanks, I'll look at the board and see if I can find A+ and A- and trace them out to make sure.
If they do, I'll swap them and see if that works.
 
roadie33 said:
Does anyone know how to rewire the G0704 Forward/Reverse switch to get the stock motor to run the opposite way?
Click to expand...

What kind of motor is it? Brushed DC, 3 phase induction, Brushless DC, single phase induction?
 
Jim,
It is the original DC motor.
I did as coherent said and swapped the A+ with the A- and it works like it should now. Forward is forward and Reverse is reverse. I also found the Max pot and adjusted it to Max at 3200 RPM. It was doing 4500.
Not doing CNC yet, so I don't need that high of speed.
All is good now.
New Belt drive system is quieter than the other way and plus I have a Hi and Lo gear now.
Thanks Guys.
 
Sure does. Makes the end of the day seem so much better when things work out.
 
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