Lathe spindle speed "locked" to work diameter.

[DICKEYBIRD]

My mind is wandering this morning as I'm turning out a batch of small parts. I know, dangerous but sometimes that's when my brain spits out ideas.

As I was cranking the handle, watching the chip curling off during the gazillionth facing cut I thought "Man I wish I had a CNC lathe with spindle speed/diameter compensation" or whatever it's called when the spindle automatically speeds up to keep the SFM constant.

Then I thought if I had a variable speed setup on my lathe spindle, (treadmill motor/controller or whatever) how hard would it be to rig an encoder to the crosslide or from a DRO output into the motor controller to make an automatic speed increase as it travels across. Seems like that should be a fixed relationship and fairly easy for you guys that understand electrons and magic smoke. What say ye expurts?

Since they're ain't nuthin' new in this world, it's probably been done before, yes?

[lakeside53]

Yes.. it's been done. You can buy a module for two of the high end DRO's (Newall C80 and some of the Accurite/Anilam models). If you're interested in the issues it's worth downloading the manuals for those modules.

http://www.acu-rite.com/CMSFiles/Fil...nual_Oct09.pdf


http://www.newall.com/PDFs/downloads...p8css-user.pdf


I just turn my VFD speed control as I'm cross feeding (for now)

[Asquith]

This is how Cunliffe & Croom did it in 1914.

[Peter.]

I have a variable-speed lathe so I knock the lever up a notch at a time as I face the ends of stuff.

[DICKEYBIRD]

Originally Posted by Asquith

This is how Cunliffe & Croom did it in 1914.

Awesome pic, thanks! I wonder how the variable speed was accomplished?

[Hal]

Monarch offered that on some of their machines and call it CSCS. Constant Surface Cutting Speed.

Hal

[Asquith]

Dickeybird,

DC motor, variable resistor, chain connected to the cross slide!

[macona]

It was an option on the monarchs as well. One of those things I would like to add to my 10ee. Make sure you have something that sets max permissible speed as well.

[DICKEYBIRD]

Originally Posted by Asquith

DC motor, variable resistor, chain connected to the cross slide!

Now THERE'S a technology I can understand!

[philbur]

There are lots of machines out there with constant cutting speed. For example.

http://www.knuth.de/produkt,2032.html

Seems to me it's almost a natural consequence of having a DRO and VFD fitted.

Phil

Originally Posted by DICKEYBIRD

My mind is wandering this morning as I'm turning out a batch of small parts. I know, dangerous but sometimes that's when my brain spits out ideas.

As I was cranking the handle, watching the chip curling off during the gazillionth facing cut I thought "Man I wish I had a CNC lathe with spindle speed/diameter compensation" or whatever it's called when the spindle automatically speeds up to keep the SFM constant.

Then I thought if I had a variable speed setup on my lathe spindle, (treadmill motor/controller or whatever) how hard would it be to rig an encoder to the crosslide or from a DRO output into the motor controller to make an automatic speed increase as it travels across. Seems like that should be a fixed relationship and fairly easy for you guys that understand electrons and magic smoke. What say ye expurts?

Since they're ain't nuthin' new in this world, it's probably been done before, yes?