manufacturing technology-conventional milling

8/9/2019 Manufacturing Technology-Conventional Milling

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Conventional Milling

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Lesson outcomes

By the end of this lesson, students should be

able to understand:

• The concept of milling and its different

types

• Guidelines and troubleshooting for milling

operations

• Types of milling machines and their

components



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Milling - definition

Milling: a machining process whereby a

rotating cutting tool is fed against a

workpiece that can travel along various axes

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Types of milling operations

• plain milling=peripheral

milling = slab milling

•Axis of cutter rotation

parallel to workpiece surface•Cutter usually HSS

•Straight or helical teeth

•Helical teeth requires less

cutting force and torqueless vibration

•Axis of cutter rotation is

perpendicular to workpiece

surface

•Relative motion between

cutter teeth and workpieceleave feedmarks on

machined surface

•Surface roughness

dependent on insert corner

geometry and feed per tooth

• Spindle axis: vertical

• Versatile: can produce

profiles, curved

surfaces

• Cutter is called an

endmill (HSS or

carbide inserts)

• Ball nose mill, hollowend mill



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2 types of slab milling

•Max chip thickness is at the end of the

cut

•Contamination on surface doesn’taffect tool life

•Smooth process if cutter is sharp

•Tool may chatter

•Workpiece may be pulled up clamp properly

•Max chip thickness at the beginning of

cut

•Scale/oxidation on surface will damage

cutter

•Workpiece clamped down by cutting

forces less clamping requirement

• Not suitable for irregular surfaces



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Recommendations for

milling parameters



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High speed machining

• Important in machining aerospacecomponents

• Spindle speed 20,000-60,000 RPM

• High stiffness & accuracy machines



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Troubleshooting for

milling operations



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Milling Machine Types

• Column-and-knee type machines

• Bed type milling machine



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Column and knee milling machines

Horizontal spindle Vertical spindle



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• Worktable: surface on which the workpiece ismounted. Table moves longitudinally.

• Saddle: Supports the table and can move intransverse direction

• Knee: Supports saddle and provides verticalmovement

• Overarm: Adjustable to accommodate differentarbor lengths

• Head: Contains the spindle and cutter holders

Column and knee milling machine

components



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Bed type milling machine

• Knee is replaced by a bed

• Bed can movelongitudinally

• Worktable mounted on bed

• High stiffness• Used for high speed,

high production work



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Other types of milling machines

• CNC milling machines

• Machining centers

• Etc.



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Workpieces are held using:

• Plain vise

• Universal Vise

• Angle Plates• Rotary Table

Plain vise Universal viseRotar Table

Angle Plate



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Milling cutters are held

using:

• Arbor

• Collet

• Toolholder

Arbor

Collet

Toolholder



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Summary• Milling is a machining process whereby a rotating cutting tool is

fed against a workpiece that can travel along various axes• Different types of milling (slab milling, face milling, end

milling) are characterized by the cutter’s relative motion to theworkpiece, cutter type and machining output

• Calculations for cutting speed, material removal rate, power,torque and cutting times are important before performing anymilling operation

• Components should be designed with machining limitations inmind

• Troubleshooting can be performed by identifying the appropriatemachining parameter to change and modifying it in the correctamount

• Column-and-knee-type are suitable for general purpose millingwhile bed-type milling machines are more suitable for highvolume production work

manufacturing technology-conventional milling

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