Compact 8 lathe servo spindle with acorn?

[frijoli]

Clay, what servo motor do you have that takes step and direction? Is it a Clearpath SDSK?
Or is it a motor and servo drive that takes step and direction?
Marty

Motor and separate drive.
Although I have access to an SDHP NEMA 34 as well.

[cnckeith]

Two basic questions.
Is it feasible to use a servo motor from the 0-10v signal and a voltage to pulse converter?
Is it possible to use one of the axis to control the spindle?
Thanks in advance.

Clay
Ps. I already Ave a spare servo, but do not have a 3 phase spindle motor or VFD available.

Clay,
It sounds like you are asking for C axis control?
If so, yes C axis control with Acorn is available in the Pro version of the Centroid Lathe CNC12 software.

There are several approaches to this advanced feature.
One cool way to add C axis to a Lathe is to have a regular spindle motor running the spindle as usual and then also create the ability to mechanically engage (and disengage) a servo motor (or stepper motor) to the spindle which then allows the spindle to be run in C axis mode. We have done exactly this on several machines in our shop and it works well. here is a web page showing one of the machines we did this on. and a video at the bottom. http://www.centroidcnc.com/cnc_c_axis_lathe.html

[frijoli]

Two basic questions.
Is it feasible to use a servo motor from the 0-10v signal and a voltage to pulse converter?
Is it possible to use one of the axis to control the spindle?
Thanks in advance.

Clay
Ps. I already Ave a spare servo, but do not have a 3 phase spindle motor or VFD available.

Clay,
It sounds like you are asking for C axis control?
If so, yes C axis control with Acorn is available in the Pro version of the Centroid Lathe CNC12 software.

There are several approaches to this advanced feature.
One cool way to add C axis to a Lathe is to have a regular spindle motor running the spindle as usual and then also create the ability to mechanically engage (and disengage) a servo motor (or stepper motor) to the spindle which then allows the spindle to be run in C axis mode. We have done exactly this on several machines in our shop and it works well. here is a web page showing one of the machines we did this on. and a video at the bottom. http://www.centroidcnc.com/cnc_c_axis_lathe.html

:O
I wasn't asking for C axis control, but you just opened up all kinds of possibilities for me. I didn't think this was feasible on the Acorn.
Does it use the encoder for position or is it open loop?

This could be awesome!

[cnckeith]

the real spindle encoder input on the Acorn board is used to keep track of the position of the spindle at all times so features like Constant Surface Speed, Rigid Tapping, and Threading work as they should. as well as True RPM display and RPM command capabilities.

[frijoli]

Clay,

One cool way to add C axis to a Lathe is to have a regular spindle motor running the spindle as usual and then also create the ability to mechanically engage (and disengage) a servo motor (or stepper motor) to the spindle which then allows the spindle to be run in C axis mode.

Keith,
Any chance you might direct me to the mechanism you used to do this? Was it commercially available?

This is really cool stuff.

Clay

[martyscncgarage]

Probably something you are going to have to make for your lathe if you pursue having a true C axis along with a conventional spindle motor, you need a clutch mechanism, similar to the AC compressor on a car, obviously it can't slip when engaged. Not an issue if you are going to directly drive the spindle with your servo motor. But if you do, you won't be able to use traditional S words for spindle speed. That works with the 0-10VDC analog output.

All that being said, with some creative imagination from the user and the machine, the Centroid CNC Acorn and software is quite capable within reason at this price point. Remember, these guys have been doing true industrial CNC Motion control for over 30 years. If it was thought of, they probably did it.

You have to decide what you want to do with your machine.

Good luck with it and have fun!
Marty

[cnckeith]

they were custom machine one off jobs.. the engagement mechanism is not for resale.
basically there are two schemes for low buck C axis that work.
One is engaging and disengaging the belt to the servo that connects to the spindle, this can be achieved in a number of different ways and is most common, you can use a manually operate a lever for the motion to engage or have automatic engagement/disengagement with a solenoid controller air cylinder or hydraulic etc..
another scheme is two wheels that engage and disengage. one wheel is on the servo/stepper motor and the other wheel is on the spindle, with a slider engagement mechanism to move the servo/stepper motor into contact with the spindle wheel. a photo is attached of this C axis wheel contact mechanism.

[frijoli]

they were custom machine one off jobs.. the engagement mechanism is not for resale.
basically there are two schemes for low buck C axis that work.
One is engaging and disengaging the belt to the servo that connects to the spindle, this can be achieved in a number of different ways and is most common, you can use a manually operate a lever for the motion to engage or have automatic engagement/disengagement with a solenoid controller air cylinder or hydraulic etc..
another scheme is two wheels that engage and disengage. one wheel is on the servo/stepper motor and the other wheel is on the spindle, with a slider engagement mechanism to move the servo/stepper motor into contact with the spindle wheel. a photo is attached of this C axis wheel contact mechanism.
DSC04265.JPG

Keith are you saying this is just a friction drive? I would not have thought that possible.

[cnckeith]

Yep.
Knurled large diameter wheel on the spindle with smaller diameter polyurethane wheel on servo motor engaged with air cylinder, motor is mounted to sliding mechanism.

[frijoli]

A servo motor is a DC brush motor. You could run it with a KB Electronics DC controller.
See my Dyna DM2400. It runs a DC brush motor and a KB Electronics motor control fitted with the SI-5 signal isolator. What you need to know is the terminal voltage of your motor and it's HP so you can size the KB Electronics DC control properly. It gets more complicated if you want to reverse the motor but doable. Different KB controller.

I have been looking at the KB website, but their data is cryptic at best. Can you elaborate on what controller I would be looking at for a reversing motor application for the spindle?