Warco GH18 Mill with VFD, Wiring Diagrams

If you bought a GH18 milling machine from Warco in the past year or so, you may have noticed it has a box on the back of the column that sticks out about 150mm.
And operating the mill you might have noticed an a whine to the motor, and that the spindle reverses within about half a second... far too fast for a single phase capacitor start motor to do so usually.

The whine gives it away to anyone who's used a motor on a Variable Frequency Drive before, and if you can decipher that crude and innacurate wiring diagram on the side of the column, you may have noticed the 3 wires to the motor marked U, V and W coming from the 'Transducer Control'

Inside that box on the back of the column is a 1.5KW VFD, and the motor is 3 phase.

This means that in addition to the 6 fixed speeds of the gear head mill, you can also vary the motors speed.

The VFD is set up from the factory so that rotating the knob on the VFD control panel will lower the motor speed... it's set to 50Hz max stock,
The stop/start and direction buttons on the vfd panel do not do anything because it's set up to operate from the push buttons on the control box (that big yellow box that is 95% empty inside, due to not needing contactors and a timer for the single phase motor control)

So i decided to draw out the circuit diagram as it really is and in colour, as well as draw the physical wire routing between the buttons etc, all wire colours are drawn correct as on my mill, so are the markings on the wire terminals.

I've also written up what happens when the buttons are pressed, mostly to show what happens in the milling and tapping modes, but maybe to help diagnose issues in the future.

Finally i've written down all the VFD settings that are specific to this machine, the settings not mentioned are set as listed in the VFD's manual, which is available here:
**LINK**

I hope some of this may be helpful to someone in years to come when the mill is out of warranty.

tho i do wonder if warco know much about this mills drive system, they can't seem to supply me with the motor's real ratings, the plate claims it's a single phase capacitor start motor, 2 capacitors are listed with values as expected for a start and run cap. and the motor is rated at 3HP and 900 watts!!!

Sorry, i don't know how to make pictures thumbnailed on this site,

I sized the pictures to A4 size for printing, but set the DPI to 200, so they can be zoomed in on the computer. but to do that you need the pictures... right click on the pictures and copy or save, then open in your favourite photo viewer?

I have one. I seem to flex the cables every time I move the head up or down, or move the control box.

In time, I am sure this will pull something out, and this will be very useful. Thanks.

Off the cuff, I don't think the forum supports thumbnail sophistication, but what you've done works well for me. Firefox has a right-click 'View Image' option, which opens the photos full size. Other Browsers can do much the same, and I think they can all do your copy and save trick.

Thanks for sharing, detailed circuit diagrams for these machines are gold dust!

Dave

Interesting. I'm surprised that Warco keep the mechanical gearbox now that a VFD controlled three phase motor hits the right price / performance ratio for this machines market.

Many years ago I got a machine of this style from Chester which had a simple two speed belt drive from the 2 hp VFD controlled motor. It worked really, really well. Two speed belt must be cheaper than 6 gears. Quieter too. Mine had a decent western made VFD box inside the head so the whole thing ended up too expensive for its market. At the price I paid I imagine Chester lost money!

I have long considered that a re-work of the slim, compact, heads used on VMC series machines to have a VFD controlled top mounted motor, Bridgeport style, with two speed belt drive would be ideal on these big square column bench mills. Quiet with much better visibility of the work, especially when working close to small jobs, giving formidable machining capability in a small space.

Clive

oh i love the gear head idea, i get 6 speeds to choose from where i get max torque from the motor that will be running at it's normal 1420 rpm's, so getting max motor cooling too.

And the VFD allows me to fine tune those speeds if needed... watching out for the motor heating up and getting less cooling from the shaft driven fan when i lower the speed of course.

My mini lathe has the DC variable drive and 2 gears, i always seem to run that in low gear at below half speed, the motor gets fairly toasty after a while... must get round to fitting a computer style fan to the end of that motor.

I guess as this is the first mill i've owned and only having heard the bridgeport run at hackspace, i find it quiet, the cutters make the most noise.

I too find the number of cables that come and go from that yellow button box a pain, why they didnt route the power into the VFD box, then the motor power wires straight to the motor from the VFD box i don't know, why loop them into the button box then straight back out again,

Getting to the column locks i have to snake my hands through all the wire hoses.

So i am totally re-doing that, the yellow button box is 95% empty space, when it was single phase motor it would have had 2 x 4 pole contactors and a timer module in there to handle the reversing of a single phase motor when in tapping mode,

I'm putting my VFD in a much larger electrical box on the wall, mains will go into the bottom of it, through a couple of mcb's, to a 12 volt psu for the ring light and control circuits, a contactor that will switch power to the VFD, plus an outlet for the DRO to plug into, and later on a 24 volt psu for axis motors.

Then a multi core cable will come out and go to my new button box, which will be all low voltage inside, the new button box will be mounted under the front of the swarf tray (it hangs off my bench by a couple of inches.. just the swarf tray, the mill is firmly on the bench)

Then the cable from the VFD to the motor will come out the top of the electrics box, loop above the mill and go back down to the motor, the only other cable i'll need from the mill will be the one for the tapping function microswitches, and the power to my ring light that's mounted around the spindle,

i'll also have a switched outlet on the electrics box for my DRO (still in the post) and my DRO head will mount roughly where the yellow button box is on the mill now, only it'll not travel up n down with the head like the button box does now, i really don't like reaching above my head to turn the mill on and off when the heads wound all the way to the top of the column.