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Operating ConditionsTurning, Milling and Drilling

K. Govindarajan Product Management & Technical Services

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Operating Conditions

–Depth of Cut

– Feed Rate

–Cutting Speed

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Operating ConditionsCutting speed

Feed

doc(m/min)

(mm/rev)

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Definition Of Speed (Cutting Speed Vc)

In turning, the peripheral speed of the work; usually measured in meters/minute (m/min)

In Milling the peripheral speed of the Cutter; usually measured in meters/minute (m/min)

In Drilling the peripheral speed of the Drill; usually measured in meters/minute (m/min)

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Cutting Speed(Vc) vs. RPM

RPM - not dependant on diameter.Vc- dependant on diameter of work piece / Cutter / Drill

(305 mm)

(100 mm)

Vc(m/min)= 3.14 x Workpiece Dia x RPM1000

6Effective Diameter

Cutting Speed (Vc) vs. RPM

Vc - dependant on diameter

Vc= 3.14 x Cutter Diameter x rpm1000

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Definition Of Feed mm/rev

TURNING: The relative amount of motion of the tool into the work for each spindle revolution. Usually measured in mm/revolution (mm/rev)

MILLING: The movement of the Cutter into the workpiece. Usually measured in millimeter per minute (mm/min)] [millimeter per Tooth (mm/tooth)]

DRILLING: The Axial motion of the tool into the work for each revolution, stroke, or unit of time. Usually measured in mm per revolution (mm/rev )

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Definition Of Depth of Cut (doc)For Turning The distance between the bottom of the cut and the uncut surface of the work, measured in a direction at right angles to the machined surface of the work.*

Depth of Cut = ½ the diameter of the drill

For Drilling

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Depth Of Cut - Milling

Radial DOC Axial DOC

In Milling Depth of Cut is normally associated with Axial Depth of Cut.

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TURNING CONDITIONS

Workpiece Material 4140 Alloy SteelHardness 250 HBContinuous CutStock Remaining For Finish Pass -0.5 mm / sideWorkpiece Diameter = 97 mmLength of Cut =216 mmFinish required = 1.2 Ra (µmm)Rigid Setup

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Determine Machine RPM:Cutting speed is defined as the distance in mtrsthat is travelled by a point on the work piece peripheryin one minute.

RPM = Vc

Pi x Diameter

Vc= RPM x Cutter CircumferenceVc = RPM x 3.14D

Circumference = Pi x Diameter, WherePi = 3.14.. RPM = Vc .

CircumferenceRPM = Vc

Cutter Circumference= Vc

3.14D

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Vc 3.14D

RPM=

Because we work in (mm) more than we do in (mtr),we need to convert the “(mtr)”in Vc to (mm).Since there are 1000mm in 1 mtr.

RPM = x (1000mm)(1 m)

Vc 3.14D

Hence,

RPM = 1000 Vc3.14 x D (mm)

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GIVEN: Workpiece Diameter = 97 mmCutting Speed (Vc) = 300 m/min

--------------------------------------------------------------------

RPM = Vc x 10003.14 x Dia(mm)

300 x 10003.142 x 97

Determine Machine RPM:

=984 RPM

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Determine Metal Removal Rate (MRR)TURNING (cm3/min)

GIVEN: Cutting Speed = 300 m/minDepth of Cut = 0.5mm or 0.05 cmFeed Rate = 0.4mm/rev

------------------------------------------------------------------------MRR = Vc X DOC X FEED RATE

= Vc m x DOC mm x fr mmmin rev

= 300 m x 0.05cm x 0.04cm x100cm =60cm3/minmin rev m

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GIVEN: Machine RPM = 984 RPMLength of Cut = 216 mmFeed Rate = 0.4 mm/ rev

------------------------------------------------------------------------Cut Time = Length Of Cut = 216 mm

Feed Rate x RPM 0.4 mm x 990 revrev min

= 216 min0.4 x 984

= 0.549 min= 32.94 seconds

Determine Cutting Time (min.):

Lets say we made a mistake, our workpiece is 9.7mmnot 97mm, If the maximum RPM on our lathe is 5,000 RPM

We proved that RPM = Vc x 10003.14 x Dia

Vc = 3.14 x Dia x RPM1000

= 3.142 X 9.7 X 50001000

= 152m/min

Determine Machine Vc:

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Turning Formulas (metric)

To Find Formula

Vc 3.14 D N 1000

RPM Vc x 1000 3.14 D

f r (mm/rev) mm/minRPM

fmm/min mm/rev x RPM

Cut time Length of cutmm/rev x rpm

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Feed Rate- Milling

Feed rate in mm per minute (mm/min) is measured as the total advance of the cutter per minute.(w.r.t to table)Feed Rate (mm) per tooth (mm/tooth) is measured by the amount of metal cut by each tooth on each revolution of the cutter (fz).

F = fz x Z x RPM(mm/min)

fz = F (mm/min)(mm/tooth) Z x RPM

f = F . (mm/rev) RPM

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Workpiece Material Gray Cast Iron Class 20

Hardness 250 BHN

Radial Width of Cut = 100 mm

Axial Depth of Cut = 2.5 mm

Diameter of Cutter = 160 mm

Number of Inserts In Cutter = 10

0° Lead Angle Cutter

50HP Machine / Rigid Setup

MILLING CONDITIONS

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STARTING PARAMETERS

From Table

•Kyon 3500•Starting Cutting Speed 700 mtrs/min•Feed 0.15 mm/tooth•Dry

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GIVEN: Cutter Diameter = 160 mmCutting Speed = (700 mtrs/min)

Determine Machine RPM:

RPM = Cutting Speed x 1000 =Diameter x 3.14

700 x 1000 =1393 rev/min160 x 3.14

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GIVEN: Number of Inserts In Cutter = 10Machine RPM = 1393Chip Load = 0.15 mm/tooth

Determine Feed Rate (mm/min):Milling

F = fz x No. of Teeth x RPM

= 0.15 X 10 X 1393

= 2090 mm/min

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GIVEN: Axial Depth of Cut = 2.5 mmFeed Rate = 2090 mm/minRadial Width of Cut = 100 mm

MRR = RWOC x ADOC x Feed Rate

Determine Metal Removal Rate (cm3/min):

100 x 2.5 x 20901000

= 522.5 cm3/min

=

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To Find Given Formula

Vc D, rpm Vc = 3.14 x D x RPM1000

RPM D, Vc RPM = Vc x 1000

3.14 x D

f F f = F / RPM

F fz, Z, RPM F = fz x Z x RPM

fz F, Z, RPM fz = F .Z x RPM

fz Z, f Fz = F / Z

Formulas

LegendVc Cutting Speed

f Feed per revolution

F Feed per minute

fz Feed per tooth

Z No. of effective tooth or inserts in cutter

3.14 3.1416

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Workpiece Material 303 Austenitic Stainless SteelHardness 200 BHNDiameter of Drill = 32mmDepth of Hole = 76mmHorizontal ApplicationHigh Pressure Coolant AvailableHole Tolerance Required ±0.1

DRILLING CONDITIONS

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KSEM DRILLFrom Table

Starting Speed 70m/min

Feed 0.3mm/rev

STARTING PARAMETERS

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GIVEN: Diameter of Drill =32 mmCutting Speed = 70 M/Min.

------------------------------------------------------------RPM = (Cutting speed x 1000) / (3.1415 x Diameter (mm) )

RPM = ( 70 X 1000) / ( 3.1415 X 32) = 696

Determine Machine RPM:

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GIVEN: Feed Rate = 0.3mm / rev.Machine RPM = 696 RPM

---------------------------------------------------------Feed rate ( MM/Min) = RPM X Feed (mm/rev) Feed rate ( MM/Min.)= 696 x 0.3

RESULT: 209 mm / min.

Determine Feed Rate (mm / min.)

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GIVEN: Diameter 32mm (D )

Feed mm/min. = 209mm / min.

------------------------------------------------------------------------MRR = Pi (D²) x Feed mm/min.

4 1000

= (3.14) (32mm.)² x 209mm/min.4 1000= 168 cm³ / min.

Determine Metal Removal Rate(cm³ / min.):

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BASIC FORMULAS

To find Formula

Cutting Speed Vc

3.14 x d x rpm 1000 (m/min)

rpm 1000 x Vc3.14 x d

mm per rev mm per minrpm

mm per min mm per rev x rpm

Cut time Drill hole depth mm per min ( min)

MRR π d2

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