Centroid Community CNC Support Forum

Hello, I am going to use a servo motor to drive my spindle on my Taig micro mill. I am going to drive the spindle to 10,000 rpm using a 2:1 ratio. I would love to be able to use the built in encoder on the motor. The servo drive puts out the quadrature signal.

The encoder needs to be 1:1 with the spindle so there is one and only one index pulse per revolution. Rigid tapping will not work otherwise.

I guess the encoder is really only needed for that function right? Was more interested in speed feedback as I would mostly be using thread mills, not rigid tapping on the Taig

Even with a thread mill, the control needs to know the rotational position of the spindle to start the thread in the same spot. Unless you are going to single pass thread mill, you'll need a 1:1 index pulse with the spindle rotation.

Neither a spindle encoder nor an index pulse are needed for thread milling.

Thread milling simply moves the X, Y and Z axes (relatively slowly) along a spiral path, while cutting thread grooves with a rapidly-spinning tool. There is no synchronization between any particular spindle orientation and any particular part of the toolpath.

Need a good source for the diy to purchase the high rpms encoders. Not much on understanding the specs and when you call they want to sell you a $1000 plus encoder. Maybe someone would start a source page.

Tblough used a nice encoder on his Bridgeport conversion. I forget where he got it but they offer many options that would make fitment much easier. They weren’t cheap but not outrageously expensive either.

I'd like to know as well. I haven't found many that will work on a 7500+ rpm spindle. One place I have found in my searching is: https://www.rls.si/eng/products/rotary- ... l-encoders

Looks to me like a couple of theirs would work.

Yup. High RPM encoders are tough to find. You'll be limited by mechanical rpm or electronic bandwidth, or probably, both. The ones I used were limited to about 6K rpm with the 1024 ppr resolution I chose. It takes pretty expensive bearings to handle 10K rpm and a 1000 line encoder is approaching 700 kHz at top speed. Most encoders I found were limited to 3-4K rpm mechanically and 200-400 kHz.

If you are not going to rigid tap, I don't see why you can't use the motor encoder. The drive ratio is probably not exactly 2:1 so you'll need to experiment with the encoder counts per rev to get the spindle RPM correct. You'll have more than one index pulse per rev but as long as you don't try to peck tap, it should work fine for feed per rev calculations.

Dale Powell wrote: ↑Thu Dec 19, 2019 5:53 am Need a good source for the diy to purchase the high rpms encoders. Not much on understanding the specs and when you call they want to sell you a $1000 plus encoder. Maybe someone would start a source page.

I started a source page... please send me your sources to add..

https://www.centroidcnc.com/centroid_di ... _gear.html