MAYURBHANJ SCHOOL OF ENGINEERING

SUB- Manufacturing Technology

TOPIC- Milling Machine

SEM- 4^th

BRANCH-Mechanical

By- Er. S KAR

CONTENTS

• INTRODUCTION
• OBJECTIVES
• TYPES OF MILLING
• TYPES OF MILLING OPERATIONS
• PARTS OF RAM TYPE VERTICAL MILLING MACHINE
• ADVANTAGES OF CLIMB MILLING
• DISADVANTAGES OF CLIMB MILLING

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Milling Machines�INTRODUCTION

• Used to produce one or more machined surfaces accurately on work piece
• One or more rotary milling cutters
• Work piece held on work table or holding device and brought into contact with cutter
• Vertical milling machine most common
• Horizontal milling machine handles operations normally performed by other tools

Objectives

• List four main uses of a vertical milling machine
• Describe how angular surfaces can be machined
• List three types of vertical milling machines
• State the purposes of the main parts of a knee and column machine

Vertical Milling Machine

• Developed in 1860's
• Combines vertical spindle of drill press with longitudinal and traverse movements of milling machine
• Milling process may be vertical, horizontal, angular, or helical
• Can be used for milling, drilling, boring, and reaming
• Can machine in one, two, or three planes
• X, Y, Z

Variety of Operations

• Face milling
• End milling
• Keyway cutting
• Dovetail cutting
• T-slot and circular slot cutting

• Gear cutting
• Drilling
• Boring
• Jig boring

Ram-Type Vertical Milling Machine

Parts of Ram-Type Vertical Mill

• Base made of ribbed cast iron
• May contain coolant reservoir
• Column often cast with base
• Machined face provides ways for vertical movement of knee
• Upper part machines to receive turret where overarm mounted

Parts of Ram-Type Vertical Mill

• Overarm round and may be adjusted toward or away from column
• Head attached to end of ram
• Made to swivel head in one plane
• Universal-type machines allow swivel in 2 planes
• Motor mounted on top of head
• provides drive to spindle through V-belts

Factors Affecting the Efficiency of a Milling Operation

• Cutting speed
• Too slow, time wasted
• Too fast, time lost in replacing/regrinding cutters
• Feed
• Too slow, time wasted and cutter chatter
• Too fast, cutter teeth can be broken
• Depth of cut
• Several shallow cuts wastes time

Cutting Speed

• Speed, in surface feet per minute (sf/min) or meters per minute (m/min) at which metal may be machined efficiently
• Work machined in a lathe, speed in specific number of revolutions per min (r/min) depending on its diameter to achieve proper cutting speed
• In milling machine, cutter revolves r/min depending on diameter for cutting speed

Important Factors in Determining Cutting Speed

• Type of work material
• Cutter material
• Diameter of cutter
• Surface finish required
• Depth of cut taken
• Rigidity of machine and work setup

Direction of Feed: Conventional

• Most common method �is to feed work �against rotation �direction of cutter

Direction of Feed: Climbing

• When cutter and�workpiece going�in same direction
• Cutting machine�equipped with�backlash eliminator
• Can increase cutter�life up to 50%

Advantages of Climb Milling

• Increased tool life (up to 50%)
• Chips pile up behind or to left of cutter
• Less costly fixtures required
• Forces workpiece down so simpler holding devices required
• Improved surface finishes
• Chips less likely to be carried into workpiece

Advantages of Climb Milling

• Less edge breakout
• Thickness of chip tends to get smaller as nears edge of workpiece, less chance of breaking
• Easier chip removal
• Chips fall behind cutter
• Lower power requirements
• Cutter with higher rake angle can be used so approximately 20% less power required

Disadvantages of Climb Milling

• Method cannot be used unless machine has backlash eliminator and table gibs tightened
• Cannot be used for machining castings or hot-rolled steel
• Hard outer scale will damage cutter