# DIY XYZ table power feeds from 1 central controller - how to?



## caveBob (Feb 20, 2015)

I'm really way ahead of myself atm with wanting to power the table feed directions. Can surely see it being highly desirous over much hand cranking, so I'm doing homework right now for future mods...

The pre-built turnkey Shars type of power feeds look very nice, but to do the X, Y, and Z (knee)... well, that's more than I want to spend on this.

What I'm thinking: power each axis with a small DC servo motor along with belts & pulleys. For the motors, something like this, but cheaper:

Dunkermotoren BG63X55 Brushless DC Servo Motor
http://www.ebay.com/itm/NEW-Dunkerm...Motors-w-PLG52-Gearhead-CNC-DIY-/221420105582

So, the question: how would I setup one controller that could be switched between any one of the three motors, only running one motor at a time? Basically want to avoid getting three separate controllers. Curious...

What range of table speeds should be my target? (will adjust available rpms & pulley sizes to accommodate)

Thanks for any ideas...


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## JimDawson (Feb 20, 2015)

For the speeds you want 0 up to about 100 IPM for rapids.

Switching a single controller between motors is probably not the best solution. Too much wiring involved, especially with a BLDC servo motor.  There are normally 8 wires between the motor and controller.  

With any system you would have to power the system completely down to switch between motors.

Stepper motors/drives (on the high end, about $450 for 3 motors, drives, and power supplies), that, along with a variable speed stepper controllers (about$20) would be a good option.  Enough power to drive the table directly with no gearing.  Cheap and very available.  Add a computer and Mach3 and you have a CNC machine!!

Small brushed DC motors with a PWM controller (about $20) would also be an inexpensive option.


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## mksj (Feb 20, 2015)

Gear head motors work well, if you can find them at the right price.  I added a power feed to the X and Z axis on my BF-30, did not want to convert it to full CNC. Used 230V 3 phase inverter gear head motors. On the Z axis I use an VFD Bodine gear head motor (34R4BFPP-E3 model 2253) 1/6hp 0-73 RPM at 135 lb-in continuous, and get ~30 IPM. I would probably also use this motor on the knee. The X axis uses a VFD Bodine gear head motor (30R4BEPP-D3 model 2216) 1/16 hp 0-175 RPM at 19 lb-in continuous. Both are a direct coupled.  The X axis is good for up to 45 IPM (I usually machine at 5-10 IPM), I use a remote control box that allows variable speed and also has high speed left/right buttons. I had to counterbalance the X axis manual crank handle as I would get significant vibrations when doing high speed movement.

I switched to the Hitachi WJ200-001SF VFD which is good up to 1/4HP, and provided quicker stopping, which was an issue on my X axis. I paid about 1/4 of list price for the motors, Hitachi had a sale on the WJ200-001SF VFDs so purchased direct. Direct drive was very simple to implement via couplings. DC gear motors could also be used. 

Having a single VFD/drive to power everything would be a pain to power down and switch each time. Also the type of switches and location would be different for each axis.


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## caveBob (Feb 21, 2015)

JimDawson said:


> For the speeds you want 0 up to about 100 IPM for rapids.
> 
> Switching a single controller between motors is probably not the best solution. Too much wiring involved, especially with a BLDC servo motor.  There are normally 8 wires between the motor and controller.
> 
> ...



Ok, got it, that makes sense having/needing separate controllers per motor, thanks.

I haven't, but probably should have first weighed the table (8x30) to give you an idea of how much mass + whatever is clamped/vised to approximate how strong of a motor I should be looking for. Found a couple vids on utube about stepper vs servo, and up to now that's been my guide:

Stepper or Servo





How to Understand the Difference Between Servo & Stepper Systems





Thanks for the info...


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## caveBob (Feb 21, 2015)

mksj said:


> Gear head motors work well, if you can find them at the right price.  I added a power feed to the X and Z axis on my BF-30, did not want to convert it to full CNC. Used 230V 3 phase inverter gear head motors. On the Z axis I use an VFD Bodine gear head motor (34R4BFPP-E3 model 2253) 1/6hp 0-73 RPM at 135 lb-in continuous, and get ~30 IPM. I would probably also use this motor on the knee. The X axis uses a VFD Bodine gear head motor (30R4BEPP-D3 model 2216) 1/16 hp 0-175 RPM at 19 lb-in continuous. Both are a direct coupled.  The X axis is good for up to 45 IPM (I usually machine at 5-10 IPM), I use a remote control box that allows variable speed and also has high speed left/right buttons. I had to counterbalance the X axis manual crank handle as I would get significant vibrations when doing high speed movement.
> 
> I switched to the Hitachi WJ200-001SF VFD which is good up to 1/4HP, and provided quicker stopping, which was an issue on my X axis. I paid about 1/4 of list price for the motors, Hitachi had a sale on the WJ200-001SF VFDs so purchased direct. Direct drive was very simple to implement via couplings. DC gear motors could also be used.
> 
> Having a single VFD/drive to power everything would be a pain to power down and switch each time. Also the type of switches and location would be different for each axis.



Man, that's a nice stout looking setup you've put together! Did you make the couplings or are the off the shelf stuff? Looks very nice...

I really need to solve my available power situation... before even attempting to think about running multiple VFDs. ATM, I only have 15A service total now in the shop, and from that, running overhead lights as well.

1hp motor w/VFD I have now for the mill will draw most of my available power not leaving much... Argh... but thanks for the info...


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## JimDawson (Feb 21, 2015)

Don't get too hung up on trying to just calculate the mass of the system.  That only effects the acceleration, once moving, the mass is no longer a factor until you decel to a stop.  When figuring the required torque for a mill, the more important factors are the sliding friction of the table, the friction of the lead screw, and the torque required to plow the tool bit through the work, unless you are working with very large, very high speed CNC equipment.  Something in the 400 in-oz range in a DC motor or around double that in a stepper would be more than enough torque to run any mill the average hobbyist would have.  I think my mill has about 400 in-oz motors and in most cases I'm only using a fraction of that.

One way to calculate the torque needed is to wrap a string abound the handwheel, and use a spring scale to see how much pull it takes to turn the handle.  Then a little math will give you the required torque in a standard unit.  Or you could use an in-lb torque wrench to do the same thing.


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## caveBob (Feb 21, 2015)

Thanks Jim, appreciate it!


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## mksj (Feb 21, 2015)

Zero-Max coupler for the Z axis and generic aluminum eBay shaft coupler for the X axis. Both were bored to spec, and are threaded to the leadscrew then clamped. I do not use the key way on the motor side (just clamped) in case you crash, it will allow some movement. Used a steel coupler for the Z-axis so the thread would not strip under the higher torque/load. If CNC, would be different set-up. You are limited by both power and voltage, if you do not have 240V I would not go with AC inverter motors. The motor size requirement is not that large as Jim pointed out. You can achieve a wide flat torque curve using sensorless vector mode on the VFD with an inverter motor. Just about anything should work well. Put all the drives in one box and then run control wiring to switches as needed. I use inexpensive computer RS232 cables on this build. The total current of for motors used (AC or DC) in this application is very low. Do not really see the need for a servo motor in this application because you would not be using feedback for position control, they usually cost more along with a driver. The torque curve and speed range vary by drive type. A driving factor, other than price, is if there is a future intent to go CNC, and this would require significant modifications and investment. You should also consider having electronic travel stops.

The one problem I did encounter was the mass of system in motion, the drive unit was not able stop the table movement quickly with my initial VFD. So some form of electronic braking was required, i.e. better VFD. As previously mentioned, the X axis crank handled required a lead counterweight so it was balanced.


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## joshuadoom (Feb 21, 2015)

24 volt dc power supply, pwm for speed control, and a used electric wheelchair gear motor. Decent torque and easy to wire.  Not sure what you are planning on milling though..

As far as the direction control you could either use a double pole switch with 3 positions (left on, center off, right on) or push/hold button for each direction..

You could even make a hand held controller box for directional controls and mount the power supply pwm in a convenient location, longer wire runs that way though..


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