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### Author Topic: Mach Turn Feed Per Revolution  (Read 18043 times)

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• 4,918
##### Re: Mach Turn Feed Per Revolution
« Reply #10 on: February 28, 2009, 05:03:48 PM »
Quote
Your explanation is even better than the books.

Typical !

Thanks Graham,
RC

#### codemangler

• 4
##### Re: Mach Turn Feed Per Revolution
« Reply #11 on: March 01, 2009, 07:00:21 AM »
... In G97 spindle mode with a feed of 1 unit per minute (G94) and a spindle speed of 1000 the feed rate is 1/1000 = .001/rev if you then drop the spindle speed to 500 rpm then the feed is still 1 unit per minute but the feed rate is .002/rev...

Graham

Graham,

On line three, I believe you have mixed apples and oranges.  FPM and IPR

In G97, G94:
.001 IPR @ 1000 RPM  => 1 IPM
.001 IPR @ 500 RPM  => 0.5 IPM  - Slower not faster.

In G97, G95:
.001 IPR @ 1000 RPM => Feed rate = .001
,001 IPR @  500 RPM => Feed rate = .001  The same, because the feed rate is locked to the RPM of the spindle.  As it should be with threading on a ANY lathe!

Wayne

Wayne

• 4,918
##### Re: Mach Turn Feed Per Revolution
« Reply #12 on: March 01, 2009, 09:19:40 AM »
Wayne,
I believe Graham is correct.

Where you said
Quote
On line three, I believe you have mixed apples and oranges.  FPM and IPR

In G97, G94:
.001 IPR @ 1000 RPM  => 1 IPM
.001 IPR @ 500 RPM  => 0.5 IPM  - Slower not faster.

The G94 is entered and constant at 1 IPM for both instances....Which makes the IPR change to .002 IPR.

RC

#### codemangler

• 4
##### Re: Mach Turn Feed Per Revolution
« Reply #13 on: March 01, 2009, 11:32:54 AM »

Yes, for a constant 1 IPM.  I was calculating constant .001 IPR.  It get confusing when modes are mixed.  Bill is having trouble with the threading operation of Mach3 Lathe.
His spindle speed is one PPR encoded and the feed per revolution is loosing position when the RPM changes slightly from thread tool  contact with the materail.  Bill should start another thread for threading...

#### Hood

• 25,835
• Carnoustie, Scotland
##### Re: Mach Turn Feed Per Revolution
« Reply #14 on: March 01, 2009, 11:48:40 AM »
However what problems is Bill having?
Hood

• 4,918
##### Re: Mach Turn Feed Per Revolution
« Reply #15 on: March 01, 2009, 01:42:43 PM »
Mangler,
So you are referring to G95 for threading.....
In the quote, it is G94. So the feedrate is constant although the spindle speed can vary, as well as the chip thickness.
RC

#### wulkan

• 15
##### Re: Mach Turn Feed Per Revolution
« Reply #16 on: March 01, 2009, 06:29:30 PM »
Hello All,

Well I tried my lathe out today and used the following program code.  What I found was is if my actual spindle speed matches the programmed spindle speed than the feedrate DRO would reflect the correct .050 per revolution.  However if the actual spindle speed was slower than the programmed spindle speed than the feedrate DRO would reflect a slower feedrate, and if the actual spindle speed was faster than the programmed spindle speed the feedrate DRO shows a faster feedrate.

I would think the feedrate DRO should show a constant feedrate regardless of spindle speed.  Perhaps actual feedrate is correct and it is just the DRO showing compensation for the programmed spindle speed difference versus actual.

Please note I am not altering the spindle speed during the cut pass. I am using the single step mode and slightly adjusting the spindle speed usually 20-25 RPM  prior to each cut pass.

The problem is I manually adjust a potentiometer for spindle speeds on my lathe so I can not program the correct spindle speed unless I stop to monitor it and than enter that speed in a program.  And it would be wrong if the spindle speed drifts.

Does anyone have an explanation of how the Feedrate DRO reflects a thread pitch and why it shows a variation according to actual spindle speed changes?

G40 G18 G80 G90 G95 G97 S400 M03
G00 X0.525
G00 Z0.1
G00 X0.5
G76 X0.4 Z-2 Q1 P0.05 J0.006 L45 H0.022 I29 C0.025 B0.0001 T0
M5
M30

Bill

#### Hood

• 25,835
• Carnoustie, Scotland
##### Re: Mach Turn Feed Per Revolution
« Reply #17 on: March 01, 2009, 06:33:03 PM »
« Last Edit: March 02, 2009, 02:12:00 AM by Hood »

#### Hood

• 25,835
• Carnoustie, Scotland
##### Re: Mach Turn Feed Per Revolution
« Reply #18 on: March 01, 2009, 06:37:00 PM »
Oh just another thought, make sure you have "Use Spindle feedback in sync mode" checked on Ports and Pins, Spindle Setup page if you want to do threading.
Hood