Lecture 1& 2 Processes & Tooling Lecture 1& 2 Processes & Tooling Overview to Computer Aided Manufacturing - ENGR-2963 - Fall 2008 Class Manager - Sam

Lecture 1& 2Lecture 1& 2Processes & ToolingProcesses & Tooling

Overview to Computer Aided Manufacturing - ENGR-2963 - Fall 2008

Class Manager - Sam Chiappone

Intro to CAMChiapponeRensselaer Polytechnic

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Featured Processes For This Class

Milling Turning Drilling


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Milling Processes

Milling is one of the basic machining processes. Milling is a very versatile process capable of producing simple two dimensional flat shapes to complex three dimensional interlaced surface configurations.


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The Process

The milling process:– Typically uses a multi-tooth

cutter

– Work is fed into the rotating cutter

– Capable of high MRR

– Well suited for mass production applications

– Cutting tools for this process are called milling cutters


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Classifications Milling operations are classified into two major

categories:– Peripheral (side)

» Generally in a plane parallel to the axis of the cutter

» Cross section of the milled surface corresponds to the contour of the cutter

– Face» Generally at right angles to the axis of rotation of the cutter

» Milled surface is flat and has no relationship to the contour of the cutter

» Combined cutting action of the side and face of the milling cutter


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Related Operations

– Thread milling - milling treads using the capability of a three axis contouring CNC machine.


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Operating Parameters

Rpm– CS converted into Rpm based on cutter diameter

Feed rate– Feed per tooth

– Table feed rate


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Feed direction -- Conventional vs. Climb– Conventional milling

» Most common method of feed

» Feed work against the rotation of the cutter


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Operating Parameters Feed direction - Conventional vs. Climb

– Climb milling» Load of the cutter tends to “pull” the work into the cutter

» This results in a small feed force and about 20% less Hp than conventional milling

» Downward motion increases the load on the table ways

» This method can “pull” the work into the cutter and scrap the work and/or damage the fixture and tool.

» Machine must be very ridged to safely utilize climb milling(CNC machines)

» USE CAUTION!


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Operating Parameters Conventional vs. Climb Milling


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– Depth of cut

– Horsepower


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Milling machines Two Major Classifications - Knee & Column and Bed

– Knee & Column (Bridgeport type)» Basic job shop type mill

» Column mounted to the base which is the major support frame.

» Construction provides controlled motion of the worktable in three mutual perpendicular directions.

» Knee moves vertically on the ways in the front of the machine

» Table moves longitudinally on the ways on the saddle

» Saddle moves transversely on the ways on the knee

» Quill moves parallel in Z axis or, if head is rotated, X axis

» Versatile general purpose machine


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Milling Machines

– Bed» Used extensively in production milling operations

» Rigid construction capable of heavy cuts

» Table is mounted directly to the bed

» Spindle head moves vertically to set depth of cut

» Head locks into position for cut

» Base of machine functions as a coolant reservoir


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Machines

Conventional

ComputerNumerical

Control


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Milling Machines


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Milling Machines


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Milling Machines


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CNC Machines CNC

» Horizontal, Vertical,and Planner (up to 5 axis)


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Process Accuracy

Accuracy of milling machines» Factors to consider

Fixture Rigidity of machine tool Accuracy of the spindle Cutter condition Coolant

– Type

– Delivery method Material condition


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Process Accuracy

+/- .0005” - Optimum situation +/- .001”-.002” - Typical +/- .001” - Flatness


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Milling Cutters & Holding Systems

Cutter Types– 2 to 4 Lip Cutters

Face Mills Ball End Mills Collect Holding Systems Direct Mount Holders Face Mill Holders


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Milling Cutters


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Workholding Devices for CNC Milling Machines

Vise Chucks Special fixtures Modular fixturing systems Clamp work to table


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Workholding Devices


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Turning

Turning is the process of machining external cylindrical and conical surfaces. The process uses a machine tool called a lathe.


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Turning Processes

Turning typically involves roughing procedures followed by a finishing operation.


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Turning Operations

Turning operations performed on a lathe include:– Straight turning

– Taper turning

– End facing

– Facing


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Turning Operations

– Shoulder Facing

– Contour Turing

– Grooving

– Form turning

– Parting-off


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Turning Operations

– Threading» Internal / External

– Knurling

– Drilling

– Reaming

– Milling-CNC turning centers


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Process Calculations

Rpm calculation– RPM

– CS


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Process Calculations Feed is typically a given distance per revolution.

This value is dependent on the operation, depth of cut, cutting speed, tool material, surface finish----etc. Units are--- in. per rev (in./rev)


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Machine Classification

Size designation– Swing - maximum diameter that can be rotated on the

lathe» 2x’s distance from spindle center line to ways

Maximum distance between centers


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Conventional and CNC Lathes

Engine– Most frequently used lathe– Heavy duty – Power drive for most tool movements– Size range 12”x24” to 24”x48” - can be larger

CNC– Computer controlled– Wide variety of process capability– Multiple axis– Indexing and contouring head– On- line and off- line programming available


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Other Types of Lathes

Tracer– Hydraulic attachment used to copy the shape of a part

from a master.


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Types of Lathes

1

2


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Types of Lathes

Combination Conventional / CNC


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Cutting Tools for Lathes

External– Right hand turning

– Left hand turning

– Round nose turning

– Cut-off

– Left hand facing


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Cutting tools for Lathes External (con’t)

– Broad nose finishing

– Right hand facing

– Threading

– Form

Internal– Boring

– Threading

– Grooving

– Form


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Typical Carbide Insert & Holder


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Workholding on a Lathe

Between centers– Live-tailstock

– Dead-headstock

– Face plate

– Drive dog


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Chuck– 3,4, or 6 jaw

– Soft jaws


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Collect system


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Others– Face driver system

– Sub-spindle system


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Drilling & Related Hole Making Processes

Basic hole making processes account for approximately 50-70% of all the metal removal processes utilized today.

Holes– Casting

» Sand, die, molding

– Punching– Machining,

» Drilling, milling, EDM, AWJ, etc.

– Burning


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Processes Standard hole making processes include:

– Drilling - Drilling is the process of producing or enlarging a hole. This is accomplished by rotating the tool and/or workpiece.

– Reaming - Enlarging an existing hole with a multi-edged tool (reamer) for dimensional accuracy and/or surface finish

– Spot facing - Smoothing, squaring, and/or flattening a surface


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Processes

– Counter sinking - operation or producing a tapered feature at the end of a hole. Most popular application is a feature for a flathead screw (82 degrees) to sit flush with a surface.

– Counter boring - Enlarging of an existing hole at one end. This enlarged hole is concentric with the existing hole and is flat at the bottom. One application of this process is a feature to set the head of a bolt below a surface.


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Process Parameters

Cutting speed Rpm Feed (in/rev ---- in/min) (Rpm x in/rev)


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Process Parameters


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Drill Variations


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Reamers


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Machine Tools

Machine tools used in this process include; drill presses, lathes, milling machines, and special purpose machines. One of the most popular is the drill press.


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Drill Presses

Upright Drill Press– Larger than the sensitive

– Can be equipped with a gearbox and variable speed head

– Hand and automatic feed mechanism

– Automatic coolant system

– Table can move on a rack and pinion system


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Drill Presses

Gang Drilling Machine– Equipped with more than one

spindle

– Multi-head arrangement

– Single table

– Used for production set-up

– Multiple operations at one location (drill, ream, tap, c’sink, c’borte etc.)


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Drill Presses

CNC Turret (Conventional)– 2 axis motion

– Computer controlled

– Series of operations

– Turret indexes to different tools

» Individual speeds / feeds


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Tool Holding Devices

Drill chucks– Key type or keyless

Drill Sleeves Collet

Lecture 2 – Tooling & Tools Lecture 2 – Tooling & Tools

Overview to Computer Aided Manufacturing - ENGR-2963 - Fall 2008

Class Manager - Sam Chiappone


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Process Basics

Components Speed & Feed Calculations Carbide Insert Specifications


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Process Basics

Tools– Refers to devices used to cut or deform the metal.

» Cutting tools - examples include end mills, carbide inserts, drills, grinding wheels, shell mills, etc.


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Process Basics

Tooling – Refers to holding devices

» Examples include- vises, fixtures, jigs…...etc.


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Process Basics

Cutting fluid– Act as a coolant and lubricant

– Reduce friction between chip and tool face

– Extend tool life

– Help to remove chips from cutting area


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Metal Removal RelatedCalculations

To efficiently use these components, different input parameters have to be calculated. They include:– RPM of cutter

» Milling or drilling operation = Rpm for cutter

» Turning operation = Rpm for part Basically the rotating component

– Feed» The distance in inches, feet, or millimeters per minute that the

work advances into the cutter.


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Input parameters (con’t)– Cutting speed(CS)-the surface feet per minute or

meters per minute, at which a metal can be machined efficiently. This variable has a direct relationship to the diameter of the cutter, in a milling or drilling operation, or the diameter of the work piece in a lathe operation.

» Example - When machining(using a milling machine) a medium grade steel, the cutter must achieve a surface speed of about 90 ft/min. The diameter of the cutter will have a direct relationship to the rpm calculation.


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Input parameters (con’t)– Depth of cut - Amount of material being removed.

– Horsepower required for cut

– Material removal rate (MRR) - volume of material being removed per unit of time

– In a milling operation, you also have to take into account the thickness of the chip each tooth will remover per revolution as it advances into the work. This value is expressed in feed per tooth.


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Metal Removal Problem

Cutting Tools

1.

2.

3.

4.


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Metal Removal Problem


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Factors Effecting Calculations

Set-up conditions Machine conditions Tooling conditions Material conditions Cutting fluid


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Tool Selection Process


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Tool Materials

Wide variety of materials and compositions are available to choose from when selecting a cutting tool


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Tool Materials

They include:– Tool steels - low end of scale. Used to make some

drills, taps, reamers, etc. Low cost equals low tool life.

– High speed steel(HSS) - can withstand cutting temperatures up to 1100F. Have improved hardness and wear resistance, used to manufacture drills, reamers, single point tool bits, milling cutters, etc. HSS cutting tools can be purchased with additional coatings such as TiN which add additional protection against wear.


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Tool Materials

– Cobalt - one step above HSS, cutting speeds are generally 25% higher.

– Carbides - Most widely used cutting tool today. Cutting speeds are three to five times faster than HSS. Basic composition is tungsten carbide with a cobalt binder. Today a wide variety of chemical compositions are available to meet different applications. In addition to tool composition, coatings are added to tool materials to incerase resistance to wear.


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Tool Materials

– Ceramics - Contain pure aluminum oxide and can cut at two to three times faster than carbides. Ceramic tools have poor thermal and shock resistance and are not recommended for interrupted cuts. Caution should be taken when selecting these tools for cutting aluminum, titanium, or other materials that may react with aluminum oxide.


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Tool Materials– Cubic Boron Nitride(CBN) - This tool material

maintains its hardness and resistance to wear at elevated temperatures and has a low chemical reactivity to the chip/tool interface. Typically used to machine hard aerospace materials. Cutting speeds and metal removal rates are up to five times faster than carbide.

– Industrial Diamonds - diamonds are used to produce smooth surface finishes such as mirrored surfaces. Can also be used in “hard turning” operations to eliminate finish grinding processes. Diamond machining is performed at high speeds and generally fine feeds. Is used to machine a variety of metals.


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Carbide Inset Selection

A.N.S.I. Insert Identification System

ANSI - B212.4-1986

M1-FineM2-MediumM3-S.SM4-Cast ironM5-General Purpose

M1-FineM2-MediumM3-S.SM4-Cast ironM5-General Purpose


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Carbide Inset Selection

Documents

Lecture 1& 2 Processes & Tooling Lecture 1& 2 Processes & Tooling Overview to Computer Aided Manufacturing - ENGR-2963 - Fall 2008 Class Manager - Sam