DC motor vs AC motor for spindle

[ZipSnipe]

I noticed that a lot of these mill motors for the spindle are DC , are there any that are AC? Also can a reverse and variable switches be built for an AC motor?

[ignatz]

I'm pretty sure that you can you can use a common dimmer switch for variable speed to an AC motor... the only catch is that you have to make sure that the switch is rated for the Watts that the motor will draw. Typically in home improvement stores you can find a dimmer switch for lights and another for ceiling fans... the switch for fans might work. If not, I think that a HF router speed control would do the trick.

[wizard]

They are DC because that is cheap and easy to do and gives good results over a wide range of speeds.

AC motors have advantages. The motors themselves are low cost. The big disadvatage is that controlling them is more demanding. There are many types of AC motors, but none of them that are useful in this sort of application are easily controled. A Dimmer switch will not work on AC induction motors!!!!!!!!!!!!!

The ideal approach is a three phase AC induction motor. To run this off single phase (home power) one needs an inverter. These are generally a bit more expensive than a DC speed control. The wider the speed range that you want with a AC control the more expensive everything becomes. At the lower end though servicable conversions cna be done relatively cheaply, like maybe $250 for all new motors and controls

Thanks
dave

Originally Posted by ZipSnipe I noticed that a lot of these mill motors for the spindle are DC , are there any that are AC? Also can a reverse and variable switches be built for an AC motor?

[phantomcow2]

WEll the ultimate speed control in my opinion is AC motor and a mechanical setup. Like on a bridgeport mill. Or if you can get a geared system.
Of course this is not always easy for the home machinist, so DC motor is the way to go

[RotarySMP]

I used a three phase motor, single phase to three phase Siemens Vector inverter and four step pulley for me mill head drive. Gives a speed range from about 16 Rpm to over 6000.