How To Motorize Your Mill's Z Axis

[RobWilson]

henryarnold


Very nicely done indeed


Rob

[henryarnold]

(06-16-2012, 06:29 PM)stevec Wrote:

(06-16-2012, 12:03 PM)henryarnold Wrote: I decided not to supply an example schematic because of safety issues with the way it might be assembled. The schematic I was going to publish used 120 VAC as an input and could pose a shock hazard if not assembled correctly. This issue is why all of our 2 prong power tools are double insulated.

Gimme a break!

Steve,
I was trying to help others by showing one possible way to motorize a mill's Z axis. Since you seem to have a problem with me not posting the schematic, I will go ahead and post the schematic with an warning about why it could be dangerous. Maybe some of the members would like to make suggestions for improvement or a better motor controller all together.

   
The reason that this DC power supply can be dangerous is that the hot lead from your AC wall outlet comes directly into the circuit and through one of 2 diodes to the motor. If the motor internally shorts and is not properly grounded, the motor frame or even the mill could be electrified. I've seen this happen with a refrigerator where touching the handle gives you a shock. The ways to assure this doesn't happen are to make absolutely sure that the motor chassis is tied to ground, use an isolating transformer or motor controller, or insulate anything that touches the motor so that a short can't electrify the chassis (like hand power tools). My concern is that someone using this circuit while failing to ground the motor, could get hurt if the motor was faulty. The other problem is that even if you do everything correctly, your outlet's ground may be faulty leaving a potential hazard. The best solution is to buy either a motor controller or isolated DC supply.

One of the things that has been refreshing about this forum is the patience members show towards each other. We are all trying to learn and have fun with metalworking. I hope the forum keeps this atmosphere.

[stevec]

Henry, I'm sorry, I didn't mean to goad you into posting the schematic.
As you may have noticed I posted a pic of my perm. mag. DC gearmotor for my mill drill. I actually have no need for the schematic.

I was just funin' ya about being cautious (not one of my talents, to my dismay I might add).

I am a little curious as to whether or not you are powering your 180vdc gearmotor from a 120 vac line.
Or have I misinterpreted.

(06-16-2012, 12:03 PM)henryarnold Wrote: The schematic I was going to publish used 120 VAC as an input

[DanH]

Rather than building my own circuit I just found a used KB DC motor controller on e-bay for $39 shipped. I also have a rocker switch on the way so I am ready to get this project started. I am also using gas springs but I am mounting them direct to the castings rather than seperate brackets. I have one side on and will do the other next. Even one gas spring made it easier to crank the head up so the second one will leave it balanced quite well in the middle of the travel. No help at the upper limit but so far I haven't needed it for tool clearance.

Dan

[krv3000]

a good job

[DaveH]

Henry,

A very nice job with the gas springs and the motor for the Z axis. Very professional looking

DaveH

[doubleboost]

Henry
Very nice
Neat and tidy
Be a bit easier on the arms than winding by hand
John

[RobWilson]

Hi Henry

Now that the Z is powered ,, could it be used in say a boring operation instead of using the quill ?


Rob

[henryarnold]

(06-17-2012, 12:44 PM)stevec Wrote: Henry, I'm sorry, I didn't mean to goad you into posting the schematic.
As you may have noticed I posted a pic of my perm. mag. DC gearmotor for my mill drill. I actually have no need for the schematic.

I was just funin' ya about being cautious (not one of my talents, to my dismay I might add).

I am a little curious as to whether or not you are powering your 180vdc gearmotor from a 120 vac line.
Or have I misinterpreted.

(06-16-2012, 12:03 PM)henryarnold Wrote: The schematic I was going to publish used 120 VAC as an input

SteveC,
No problem. The schematic does raise some interesting issues. I suggest someone else's suggestion of using a KB motor controller. They are inexpensive on EBay and they solve the problem of isolation. In regards to your question about the voltage. Our 120V outlets are 120V RMS but are 170V peak. If you full wave rectify and filter the sine wave power, you get a higher voltage depending on the load. In any case its enough to power a 180V motor. You probably won't find a 120 VDC motor. They seem to come in either 90V or 180V versions. Of course an AC motor could work fine if you can find one that is reversible. Reversible AC gear motors are not as common as DC motors.
Henry Arnold

[henryarnold]

(06-17-2012, 01:22 PM)DanH Wrote: Rather than building my own circuit I just found a used KB DC motor controller on e-bay for $39 shipped. I also have a rocker switch on the way so I am ready to get this project started. I am also using gas springs but I am mounting them direct to the castings rather than separate brackets. I have one side on and will do the other next. Even one gas spring made it easier to crank the head up so the second one will leave it balanced quite well in the middle of the travel. No help at the upper limit but so far I haven't needed it for tool clearance.

Dan

Dan,
Mounting the gas spring ball mounts to the casting would work great on the lower mounts. I should have done this. On the upper mounts, the hole will come very close to the yoke dovetail (at least on my mill). I was concerned that it might be weak. I look forward to seeing how you improve on the concept.
Henry