Using a VFD to power a cnc mill?
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  1. #1
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    Default Using a VFD to power a cnc mill?

    I have a chance to buy a 205 Cintimill for a few hundred bucks. I want to make sure it works before buying it but the guy (nor me) has 3 phase power.

    Im wondering if I can use a VFD to power the entire endmill. Not just the spindle. I have read that you can and you can't. I dont want to ruin the guys machine. Does anyone know for sure if using a vfd will damage the machine?

    On another note, can I simply run aingle phase power to the machine and see everything work except the spindle/feed servos?

    Im fairly confident the 2nd method will work just fine. If the motors are bad I have the skills to replace those but would like to test them if I can. I dont want to let this deal pass me by. Im also wondering as I would need to do something similar to power it at my shop.

    On yet another note, would a phase shifter work instead of a vfd? Again I have read mixed results with those but I can get one of those delivered tomorrow (I am going to check the mill out sunday).

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    No, you cannot run the whole machine off of a VFD. VFDs are only for running motors, and usually only a single motor unless they are all the same.

    It may be possible to power up the controller and drive electronics off single phase - depends on the machine.



    Quote Originally Posted by MacroPc View Post
    I have a chance to buy a 205 Cintimill for a few hundred bucks. I want to make sure it works before buying it but the guy (nor me) has 3 phase power.

    Im wondering if I can use a VFD to power the entire endmill. Not just the spindle. I have read that you can and you can't. I dont want to ruin the guys machine. Does anyone know for sure if using a vfd will damage the machine?

    On another note, can I simply run aingle phase power to the machine and see everything work except the spindle/feed servos?

    Im fairly confident the 2nd method will work just fine. If the motors are bad I have the skills to replace those but would like to test them if I can. I dont want to let this deal pass me by. Im also wondering as I would need to do something similar to power it at my shop.

    On yet another note, would a phase shifter work instead of a vfd? Again I have read mixed results with those but I can get one of those delivered tomorrow (I am going to check the mill out sunday).

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    Thats what I thought, thanks for answering. How about a static phase shifter? Will one of these work?

    I was able to check out the machine yesterday. Im going to buy it and pick it up this coming weekend. What I noticed is that the motors are powered off their own 220v 3ph supply and the sensors/screen are powered off another 110v supply. So what Im thinking, since its "semi-auto" (its not an actual cnc mill, its either manual or the table is operated by levers that engage the gears to have the 1hp motor feed the table), I could potentially wire in a VFD to each motor and use that as the power supplies for each motor. Not exactly what I want to do but that is an option.

    It has a 1hp 3ph motor for the feed and a 5hp 3ph motor for the spindle. I would like to be able to power then both using the one power cord the machine already has so Im looking into building a rotary phase converter with a 10hp VFD (PWM) capable motor I recently picked up. Im still researching the proper, correct method of building it but in the meantime am curious about a simpler, faster fix to get it running.

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    That machine is a beast. Well made by cinci. 3 phase motors seldom die. Myself, since you are buying cheap, I'd look for other issues, going to be very hard to get running on a site without 3 phase.

    once home, two VFDs and 220 single phase will get this old girl running nicely.

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    Thats what Im going to use if I cant find other means. I have future plans using 3 phase motors so Im looking into a rotary phase converter. I think im going to order this kit:

    10Hp Rotary phase converter kit 230vac

    I have 2 3ph 10hp motors, one is pwm/vfd capable other needs a bearing replaced. Still works but has a knocking noise. One day ill replace the bearings in it. I have a few 5hp and smaller motors as well. My hydraulic press I built has a 5hp 3ph (vfd/pwm) capable motor with a 10hp vfd on it now.

    So as a short term fix i dont mind using VFDs but eventually (especially since were are looking to buy a new house (with a pole barn that has 3 phase installed (i hope))), but Id like to be able to run different machines off one power supply without having to rewire a VFD for each different peice of equipment.

    When I went to look at the mill yesterday I ran single phase 220v to it and nothing blew up. Also checked the screen and sensors, everything I could test works. So if something in the wiring doesnt work from the wall to the motor I can use a VFD to bypass all that if needed. Of course thats not ideal - I would like it working as intended.

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    I decided to order that 10hp rotary phase converter kit from phaseconverterusa.com. I have a few extra 10hp motors around so thats not a big deal and it was only $116 with free shipping.

    Still curious about phase shifters tho, if they could also work for powering a machine (output true AC, is the issue).

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    Quote Originally Posted by MacroPc View Post
    I decided to order that 10hp rotary phase converter kit from phaseconverterusa.com. I have a few extra 10hp motors around so thats not a big deal and it was only $116 with free shipping.

    Still curious about phase shifters tho, if they could also work for powering a machine (output true AC, is the issue).
    What you are calling a phase shifter - do you mean a static phase converter?

    You should be good with a rotary phase converter. I run my mill, lathe, and VMC off of a 15 HP rotary. No issues. Just make sure you power the CNC control electronics on that mill off of one of the 2 legs coming from your main, and not the generated leg from the rotary. The generated, or wild leg, will tend to vary in voltage depending on the load on the phase converter and can damage electronics.

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    A static phase shifter, not converter. They are on amazon. What I read on one of the phase converter websites is that a phase shifter only "generstes" the 3rd leg until the motor is running then drops it completely. The site says its good for drill presses, lathes, milling machines ect... Machines/motors that once started doesnt need the 3rd leg (or full power for that matter, as these only provide about 2/3rds power). So I think that it would be fine for my mill but not for other equipment I plan on aquiring/building in the future.

    I ordered the kit so thats the route im going with. Ive read a few reviews about people not getting their orders for weeks. Similarly, I have not received any tracking numbers or even a confirmation email. I called them this morning and he told me he has everything and it will be shipped today so I should get it by friday or saturday. We will see. Im not good with people dicking me around, wasting my time or lying to me.

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    Yea what you are talking about is basically the same thing that is used to start the idler motor for your rotary phase converter. It uses some start capacitors to shift the phase on one of the legs enough to trick the motor into thinking it is getting 3 legs and start. You are way better off with the rotary phase converter - it will suit your needs. Once you build your RPC with that kit it will all make sense.

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    Quote Originally Posted by RH68 View Post
    No, you cannot run the whole machine off of a VFD. VFDs are only for running motors, and usually only a single motor unless they are all the same.

    It may be possible to power up the controller and drive electronics off single phase - depends on the machine.

    There are folks who run an entire shop off of one VFD. It's a big one, in general, and essentially acts like a Phase Perfect, the frequency does not get changed.

    The key is it being large enough that all the loads are considerably smaller than the rating of the VFD.

    Most CNC are set up to rectify the incoming power and then use a variety of VFD to power the spindle from the DC bus, with various other servos running feeds etc the same way.

    A large VFD or a suitably rated Phase Perfect can run such a machine just fine, with the VFD used only to convert to 3 phase.

    You may not need to, and it is kind of the long way around the barn. Some such machines can run from just single phase, but not at full power, since that would overstress the rectifiers, etc. Don't just assume that is possible, though, some may use all 3 phases.


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