Relates only to turning centers

Commonly taught in basic CNC courses:

G96 – constant surface speed mode

Use when machined diameters changeSpecify speed in sfm or mpmImproves part finish and tool life

O0001N005 T0101N010 G96 S500 M03N015 G00 X3.2 Z0.005

Example:

Constant surface speed mode

Commonly taught in basic CNC courses:

G96 – constant surface speed mode

Use when machined diameters changeSpecify speed in sfm or mpmImproves part finish and tool life

Not always taught in basic courses:

Eliminating spindle dead time

Commonly taught in basic CNC courses:

G96 – constant surface speed mode

Use when machined diameters changeSpecify speed in sfm or mpmImproves part finish and tool life

Not always taught in basic courses:

Eliminating spindle dead time

G96 – constant surface speed

Constant Surface Speed Is A Very Helpful Programming Feature

G96 – constant surface speed

• Easy To Program• Improves Workpiece Finish• Prolongs Tool Life

Constant Surface Speed Is A Very Helpful Programming Feature

G96 – constant surface speed

However, Constant Surface Speed Can Be A Cycle Time Waster If

Not Properly Programmed

G96 – constant surface speed

No Turning Center Can Instantaneously Change Spindle Speed

G96 – constant surface speed

The Time It Takes To Change Speeds Is Based On Many Factors

G96 – constant surface speed

The Time It Takes To Change Speeds Is Based On Many Factors

• Machine Size• Work Holding Device• Spindle Parameters• Bar Feeder

G96 – constant surface speed

An Example: 30 HP, 10 in Chuck

0-1000...3 Seconds0-2000...6 Seconds0-3000...9 Seconds0-4000...12 Seconds

Test your turning centers to find out what spindle response time is for each!

G96 – constant surface speed

Current RPM: 0

O0001N005 T0101N010 G96 S600 M03N015 G00 X1. Z0N020 G01 X-.04 F.010N025 G00 X.875 Z.1N030 G01 Z-.5

Time Required: 0

Based upon the machine just shown, consider this program:

G96 – constant surface speed

Current RPM: 0

O0001N005 T0101N010 G96 S600 M03N015 G00 X1. Z0N020 G01 X-.04 F.010N025 G00 X.875 Z.1N030 G01 Z-.5

Time Required: 0

Program number

G96 – constant surface speed

Current RPM: 0

O0001N005 T0101N010 G96 S600 M03N015 G00 X1. Z0N020 G01 X-.04 F.010N025 G00 X.875 Z.1N030 G01 Z-.5

Time Required: 0

8.0 Diameter

Index turret – note 8.0” diameter tool change position

G96 – constant surface speed

Current RPM: 286

O0001N005 T0101N010 G96 S600 M03N015 G00 X1. Z0N020 G01 X-.04 F.010N025 G00 X.875 Z.1N030 G01 Z-.5

Time Required: 1 Second

8.0 Diameter

Start spindle – speed will be 286 rpm – this will take about one second

G96 – constant surface speed

Current RPM: 2292

O0001N005 T0101N010 G96 S600 M03N015 G00 X1. Z0N020 G01 X-.04 F.010N025 G00 X.875 Z.1N030 G01 Z-.5

Time Required: 6 Seconds

4 in Movement Will Be Internal

To Spindle Accel (0.5 Seconds)

Rapid to first position – speed will increase to 2,292 rpm, taking 6 seconds!

G96 – constant surface speed

Current RPM: 4000

O0001N005 T0101N010 G96 S600 M03N015 G00 X1. Z0N020 G01 X-.04 F.010N025 G00 X.875 Z.1N030 G01 Z-.5

Time Required: NA

Machine workpiece

G96 – constant surface speed

Current RPM: 2619

O0001N005 T0101N010 G96 S600 M03N015 G00 X1. Z0N020 G01 X-.04 F.010N025 G00 X.875 Z.1N030 G01 Z-.5

Time Required: NA

Machine workpiece

G96 – constant surface speed

Current RPM: 2619

O0001N005 T0101N010 G96 S600 M03N015 G00 X1. Z0N020 G01 X-.04 F.010N025 G00 X.875 Z.1N030 G01 Z-.5

Time Required: NA

Machine workpiece

G96 – constant surface speed

Current RPM: 286

N035 G00 X8. Z3.N040 M01N045 T0202N050 G96 S700 M03N055 G00 X.75 Z.1N060 G01 Z-.505 F.005N065 X1.

Time Required: 6 Seconds

Rapid to tool change position – speed slows to 286 rpm, taking six more seconds

G96 – constant surface speed

Current RPM: 286

N035 G00 X8. Z3.N040 M01N045 T0202N050 G96 S700 M03N055 G00 X.75 Z.1N060 G01 Z-.505 F.005N065 X1.

Time Required: 0

Optional stop

G96 – constant surface speed

Current RPM: 286

N035 G00 X8. Z3.N040 M01N045 T0202N050 G96 S700 M03N055 G00 X.75 Z.1N060 G01 Z-.505 F.005N065 X1.

Time Required: 0 Seconds

Index to next tool

G96 – constant surface speed

Current RPM: 334

N035 G00 X8. Z3.N040 M01N045 T0202N050 G96 S700 M03N055 G00 X.75 Z.1N060 G01 Z-.505 F.005N065 X1.

Time Required: 1 Second

Spindle is running

G96 – constant surface speed

Current RPM: 3565

N035 G00 X8. Z3.N040 M01N045 T0202N050 G96 S700 M03N055 G00 X.75 Z.1N060 G01 Z-.505 F.005N065 X1.

Time Required: 9 Seconds

Rapid to approach position, speed increases to 3,565 rpm, taking 9 seconds!

G96 – constant surface speed

Current RPM: 3565

N035 G00 X8. Z3.N040 M01N045 T0202N050 G96 S700 M03N055 G00 X.75 Z.1N060 G01 Z-.505 F.005N065 X1.

Time Required: NA

Machine workpiece

G96 – constant surface speed

Current RPM: 2674

N035 G00 X8. Z3.N040 M01N045 T0202N050 G96 S700 M03N055 G00 X.75 Z.1N060 G01 Z-.505 F.005N065 X1.

Time Required: NA

Machine workpiece

G96 – constant surface speed

Current RPM: 334

N070 G00 X8. Z3.N040 M30

Time Required: 6 Seconds

Rapid to tool change position

G96 – constant surface speed

Current RPM: 0

N070 G00 X8. Z3.N040 M30

Time Required: 1 Second

End of program

G96 – constant surface speed

In This Program, About 30 Seconds Of Time Is Required To

Accel/Decel Spindle!

G96 – constant surface speed

In This Program, About 30 Seconds Of Time Is Required To

Accel/Decel Spindle!

Additionally, Electricity Will Be Wasted And Undue Wear & Tear

On The Machine Will Occur

G96 – constant surface speed

Current RPM: 0

O0001N005 T0101N010 G00 G96 X1. Z0 S600 M03N015 G01 X-.04 F.010N020 G00 X.875 Z.1N025 G01 Z-.5N030 G97 G00 X8. Z3. S3565N035 M01

Time Required: 0

Consider this more efficient program:

G96 – constant surface speed

Current RPM: 0

O0001N005 T0101N010 G00 G96 X1. Z0 S600 M03N015 G01 X-.04 F.010N020 G00 X.875 Z.1N025 G01 Z-.5N030 G97 G00 X8. Z3. S3565N035 M01

Time Required: 0

Program number

G96 – constant surface speed

Current RPM: 0

O0001N005 T0101N010 G00 G96 X1. Z0 S600 M03N015 G01 X-.04 F.010N020 G00 X.875 Z.1N025 G01 Z-.5N030 G97 G00 X8. Z3. S3565N035 M01

Time Required: 0

Index turret

G96 – constant surface speed

Current RPM: 2316

O0001N005 T0101N010 G00 G96 X1. Z0 S600 M03N015 G01 X-.04 F.010N020 G00 X.875 Z.1N025 G01 Z-.5N030 G97 G00 X8. Z3. S3565N035 M01

Time Required: 6 Seconds

Accel Occurs During Motion

(Motion Internal)

Start spindle during approach movement, saving about one second

G96 – constant surface speed

Current RPM: 4000

O0001N005 T0101N010 G00 G96 X1. Z0 S600 M03N015 G01 X-.04 F.010N020 G00 X.875 Z.1N025 G01 Z-.5N030 G97 G00 X8. Z3. S3565N035 M01

Time Required: NA

Machine workpiece

G96 – constant surface speed

Current RPM: 2619

O0001N005 T0101N010 G00 G96 X1. Z0 S600 M03N015 G01 X-.04 F.010N020 G00 X.875 Z.1N025 G01 Z-.5N030 G97 G00 X8. Z3. S3565N035 M01

Time Required: NA

Machine workpiece

G96 – constant surface speed

Current RPM: 2619

O0001N005 T0101N010 G00 G96 X1. Z0 S600 M03N015 G01 X-.04 F.010N020 G00 X.875 Z.1N025 G01 Z-.5N030 G97 G00 X8. Z3. S3565N035 M01

Time Required: NA

Machine workpiece

G96 – constant surface speed

Current RPM: 3565

O0001N005 T0101N010 G00 G96 X1. Z0 S600 M03N015 G01 X-.04 F.010N020 G00 X.875 Z.1N025 G01 Z-.5N030 G97 G00 X8. Z3. S3565N035 M01

Time Required: 3 Seconds

Spindle ACCELs To RPM Needed For Next Tool!

Return to tool change position – but note spindle mode change – 3,565 rpm is the speed required for the next tool!

G96 – constant surface speed

Current RPM: 3565

O0001N005 T0101N010 G00 G96 X1. Z0 S600 M03N015 G01 X-.04 F.010N020 G00 X.875 Z.1N025 G01 Z-.5N030 G97 G00 X8. Z3. S3565N035 M01

Time Required: 0 Seconds

Optional stop

G96 – constant surface speed

Current RPM: 3565

N040 T0202N045 G00 G97 X.75 Z0 S3565 M03N050 G96 S700N055 G01 Z-.505 F.005N060 X1.N065 G00 X8. Z3. M05N067 M30

Time Required: 0 Seconds

Index the turret

G96 – constant surface speed

Current RPM: 3565 Time Required: 0 Seconds

No Spindle Speed Change! N040 T0202

N045 G00 G97 X.75 Z0 S3565 M03N050 G96 S700N055 G01 Z-.505 F.005N060 X1.N065 G00 X8. Z3. M05N067 M30

Approach workpiece – note still in rpm mode

G96 – constant surface speed

Current RPM: 3565 Time Required: 0 Seconds

Re-select CSS Mode (No

Change In RPM)N040 T0202N045 G00 G97 X.75 Z0 S3565 M03N050 G96 S700N055 G01 Z-.505 F.005N060 X1.N065 G00 X8. Z3. M05N067 M30

Reselect constant surface speed mode – since spindle is already running at 3,565 rpm, this command takes no time

G96 – constant surface speed

Current RPM: 3565 Time Required: NA

N040 T0202N045 G00 G97 X.75 Z0 S3565 M03N050 G96 S700N055 G01 Z-.505 F.005N060 X1.N065 G00 X8. Z3. M05N067 M30

Machine workpiece

G96 – constant surface speed

Current RPM: 2674 Time Required: NA

N040 T0202N045 G00 G97 X.75 Z0 S3565 M03N050 G96 S700N055 G01 Z-.505 F.005N060 X1.N065 G00 X8. Z3. M05N067 M30

Machine workpiece

G96 – constant surface speed

Current RPM: 0 Time Required: 7 Seconds

Motion Internal To Spindle Stop

N040 T0202N045 G00 G97 X.75 Z0 S3565 M03N050 G96 S700N055 G01 Z-.505 F.005N060 X1.N065 G00 X8. Z3. M05N067 M30

Turn spindle off during last tool’s retract to tool change position

G96 – constant surface speed

Current RPM: 0 Time Required: 0

N040 T0202N045 G00 G97 X.75 Z0 S3565 M03N050 G96 S700N055 G01 Z-.505 F.005N060 X1.N065 G00 X8. Z3. M05N067 M30

End of program

G96 – constant surface speed

This Revised Program Requires About Sixteen Seconds Of Spindle Accel/Decel

Time (compared to thirty seconds)

G96 – constant surface speed

This Revised Program Requires About Sixteen Seconds Of Spindle

Accel/Decel Time

About 14 Seconds Are Saved With Just Two Tools!

Commonly taught in basic CNC courses:

G96 – constant surface speed mode

Use when machined diameters changeSpecify speed in sfm or mpmImproves part finish and tool life

Not always taught in basic courses:

Eliminating spindle dead time