Tooling for CNC

cnc tooling Group 2(DMCH 2007) 1

CNC ToolingComputer numerical control tooling presentation:-

Prepared by:-Shyam Kumar sonu.Rahul Raman.Bijay Kumar shah. md .Sallaudin .Durga nand chaudhary.Binoy tamang.


Introduction

•CNC tooling


Topic contents

Cutting tool material. Tooling for hole operation. Types of drilling process. Milling cutters. Types of milling cutters. Special inserted cutters. Types of inserted cutters &selection. Identification system and grading system. Cutting speed and feeds. Milling & drilling feed rates.


Properties of tool material

Toughness Wear resistance.Hot hardness.Recovery hardness.Thermal conductivity.co-efficient of thermal expansion.Hardenability .Weldability.Grindability .Dimension stability.


Tooling For CNCCutting tool Materials

Cutting tools are available in three basic types

Cutting tool material

High speed steel TUNGUSTEN carbide Ceramic


Tooling For CNC

High speed steel(HSS)•HSS tool have the following advantages over carbide •HSS cost less than carbide and ceramic tooling.•HSS is less brittle and not as likely to break to during interrupted cuts .•The tool can resharpened easily.

•HSS tool having following disadvantage •HSS does not hold up as well as carbide or ceramic at high temperature generated during machining.•HSS does not cut hard materials well.


Tooling for cnc

Tungsten carbide (carbide)• Carbide tools come in one of three types.

Carbide tools

Solid carbide tools

Brazed carbide tools

Inserted carbide tooling


Tooling for cncTungsten carbide.• Solid carbide tools are made from a solid piece of carbide.• Brazed carbide tools use a carbide tip brazed in a steel shank.• Inserted carbide tooling utilize indexable inserts made of carbide

which are held in steel tool holders.

Tungsten carbide has the following advantages over HSS.

• Carbide holds well up at elevated temperatures.• Carbide can cut hard materials well.• Solid carbide tools absorb workpiece vibrations and reduce the

amount of “chatter” generated during machining.• When inserted cutters are used the inserts can be easily changed or

indexed, rather than replacing the whole tool.


Tooling for numerical control

Tungsten carbideTungsten carbide has the following disadvantage over

HSS.• Carbide cost more than high speed steel tools.• Carbide is more brittle than HSS and had a tendency

to chip during interrupted cuts.• Carbide is harder to resharpen and requires

diamond grinding wheels.


Tooling for numerical controlCeramic tooling• Had made great advances in the past several years.• Once very expensive-some ceramic insert cost now less than carbide. Ceramic has the following advantage:• Ceramic is sometime less expensive than carbide when used in insert

tooling.• Ceramic will cut harder materials at a faster rate.• Ceramic has superior heat hardness. Ceramic has the following disadvantages:• Ceramic is more brittle than HSS or carbide.• Ceramic must run within its given surface speed parameters. Notes :- If run too slowly, the inserts will breakdown quickly . Many

machines do not have the spindle RPM range needed to use ceramics.


Tooling for numerical controlFields of application. High speed steels used on:-• Aluminium alloys. Carbide is used on:-• High silicon aluminium.• Steels .• Stainless steels.• Exotic metals. Ceramics inserts used on:-• Hard steels.• Exotics metals. Notes :-Inserted carbide tooling is becoming the preferred for any cnc

application. Notes :-some insert carbide are coated with special substances(e.g. Titanium

nitride) increasing tool life up to 20 time –using recommended cutting speed and feed rates.


Tooling for hole operationTooling for hole operations.• There are four basic hole operations that are performed on nc

machinery.

Drilling Reaming Boring tapping

Tooling for hole operations.


TOOLING for hole operation


Tooling for hole operationsDrilling• Drills are available in different styles for different materials.• Twist drills remains one of the most common tools for making holes.• Drills have a tendency to walk as drill, resulting in a hole that it is

not truly straight.• Centre drills are often used to predrilled a pilot hole to help twist

drill to start straight.• Drills also produce triangular shaped holes.


Tooling for hole operations

Drilling • If the hole tolerance is closer than 0.003 inch a secondary hole

operation should to use to size the hole such as boring or reaming.• Large holes are sometimes produced by spade drills.• The flat blade in spade drills allow good chip flow and economical

replacement of the drill tip.


Tooling for hole operations• Drill point angle must be considered when selecting a drill.• The harder the material to be cut the greater the drill point angle

needs to be maintain satisfactory tool life.• Mild steel is usually cut with a 118-degree included angle drill point.• Stainless steel often use 135- degree drill point.

Types of drills:-• HSS drills are the most common.• Brazed carbide and solid carbide.• Carbide drill chip when drilling holes.• When drilling hard materials cobalt drills are used(HSS with cobalt).• Cobalt drills have greater heat hardness than HSS drills.• Specials drills with carbide inserts.


Tooling for hole operationsReaming :-

• Reaming is used to remove a small amount of metal from an existing hole as a finish operation.

• Reaming is a precision operation which will hold a tolerance of +\-0.0002 inch easily.

• Straight fluted reamers.


Tooling for hole operation

Reaming :-• Spiral fluted reamers • Spiral fluted reamers produce better surface finishes than straight

flutes.• Spiral flutes reamers are more difficult to resharpen than straight

fluted.• Reamers are available in three basic tool materials: HSS Brazed carbide Solid carbide.


Tooling for hole operations

Boring :- • Boring removes metal from an existing hole with a single point

boring bar. Boring heads are available in two designs.• Offset in which the boring bar is a separate tool inserted into the

head .• Cartridge which use an adjustable insert in place of a boring bar. Boring bars are available in four material types:-• High speed steels (HSS)• Solid carbide –up to ½-inch diameter.• Brazed carbide –up to ½ -inch diameter.• Inserted carbide –for large holes.


Tooling for hole operationsTapping:-• Tapping is used to produce internally threaded holes They are available in different flute design:-• Standard machine screw taps are widely used when tapping blind

holes .• Spiral pointed taps (gun taps)which are preferred for thru- hole

operations- shoot chip forward and out of the bottom of the hole .• High spiral taps are used for soft stringy material (e g aluminium).


Milling cuttersThe rotating cutter, termed the milling cutter, has almost an unlimited variety of shapes and sizes for milling regular and irregular forms. The most common milling cutter is the end mill. Other tools that are often used are shell mills, face mills, and roughing mills. When milling, care must be taken not to take a cut that is deeper than the milling cutter can handle. End mills come in various shapes and sizes, each designed to perform a specific task. The three basic shapes of standard end mills are flat, ballnose, and bullnose.


Milling cutters Milling cutters can be further classified as:-

Milling cutters

End mills Face mills


Milling cuttersThread hob:-• A special milling cutter is used to mill a thread in a workpiece.• Thread hobs make use of an NC machines helical interpolation

capabilities.


Milling cuttersEnd mills:- End mills are available in : High speed steels (HSS) Solid carbide

End mills are available in diameters:- From 0.032 inch to 0.500 inch.

Inserted end mills:- From 0.500 inch to 3 inch. Note 1:-two flute cutters with deeper gullets are well suited for roughing

operations. Note 2:-four flute end mills are more rigid because their rigid core.


Pictures of end mill cutter

Single end multiple flute end mill

Solid carbide two flute end mill

Ball nose end mill


Milling cuttersEnd mills:-•Inserted cutters are preferred for NC application.•Inserts are less expensive to replace than an entire tool.•By indexing the inserts four or six cutting edges can be used on one inserts.•When the insert is used up it is thrown away rather than resharpened.•Inserted cutter may used on many type of workpiece materials by changing the inserts from one designed for aluminium to one designed for stainless steel.


Pictures of end mill cutter


Milling cutters

End mill:-•Ball end mills using inserts.•Ball end mills are also available in HSS and solid carbide.•Ball mills are used for three ,four or five –axis contouring work where z axis is used.•They are also used to produce a radius in a part.


Milling cutters

End mills:-Inserted end mill (cyclo mill).•Cyclo mill uses a series of round inserts staggered on a helical pattern.•Cyclo mill was develop for NC use.


Milling cutters

Face mills:-• face mills are designed to remove large amounts of material from

the face of the workpiece.• Face mills are manufacture in : High speed steel(HSS) Brazed carbide Inserted carbide(the most common type of facing tool)• Face mills are available in two sizes: from 2 inch to over 8 inch in

diameter.• Note 1:-The cost of HSS and brazed carbide limit their application to special

situation.


Face mill cutters


Milling cutters

Face mills:-Large diameter face mill Large number of insert used.Cyclo mill was developed for NC use.


Milling cuttersFace mills:-• Plunge and profile

cutter.• It is designed to plunge

into the material first and then begging the cutting path.

• The design is a cross between end mill and face mill.


Special inserted cutters

• Special inserted cutters:-• A number of special tools have been developed for

use with CNC.• The NC programmer is always confronted with

new ideas to improve productivity.• Prospective and experienced programmers should

spent time looking at tooling catalogs to become acquainted with current tooling developments .




INSERTED TOOLS


Examples


Special inserted cutters• An inserted milling cutter with interchangeable tooling

extensions.• A machine tap in a tap holder with interchangeable tooling

extensions.• An inserted tool mounted in a holder with interchangeable

extensions.An NC tooling system featuring:-• Tool adapters• Interchangeable extensions.• Tool bodies.• Boring heads.• Arbors.



• Carbide inserts and their selection:• Carbide inserts are manufactured in a variety of types and grades.• The type of the insert describes the shape of the insert.

Common inserts shapes

Triangular 80 degree diamond

55 degree diamond

Round



Carbide inserts and their selection:-• The grade of insert describes the hardness of the inserts

and the application of which it was developed.

• Each type of inserts identified by a designation code.

• The identification system used on an insert will vary depending on the manufacture.



• Identification system:-

Prefix Tolerance Size Radius & chamfer

Edge condition

shape

Clearance Type Thickness

Chamfer size Hand

W R 15 S R C 36 H 4 T R


Speed &feeds

• Feed Rate – Inches per minute (IPM)

• Spindle Speed – (RPM)

• The relationship between these 2 variables is critical to achieving optimal tool life


Basic rule

Make chips NOT dust!!

Larger chip loads =

less heat generation =longer tool life


Factors effecting feed rates

• Hold Down (part movement) • Depth of Cut • Material Density • Tool Design (up shear / downs hear) • # of flutes and geometry of flute • Tool Balance + centricity


The amount of feed depends:-

• Material being cut.(hard and soft)• Rigidity of job and machine.• Depth of cut.• Power available.• Range of feed available.


Steps to finding “optimal” feed rate

1) Assess hold down and machine capabilities

2) Select tool(s) for material and application

3) Decide on depth of cut and no of passes

4) Start at lowest recommended feed rate and work upward .


Maximum rpm.

Base on diameter to tool:

¼” & under – 22 000 ¼’’ to 1’’ – 18 000 1” to 2” – 16 000

2’’ to 3.5’’ – 14 000 3.5’’ to 5” – 12 000


Important Formulas

Chip Load = Feed Rate / (RPM x # of Cutting edges)

Feed Rate = RPM x # Cutting Edges x chip load

Speed (RPM) = Feed Rate / (# of cutting edges x chip load)


Chip Load Ranges by Material

• Chip Load = Feed Rate / (RPM x # of cutting edges)

• SOLID WOOD • .008 to .025 inch

• MDF / Particle Core • .012 to .030 inch

• PLYWOOD• .010 TO .025 inch

• PLASTICS• .005 to .015 inch

• CARBON FIBRE• .OO5 to .010 inch


Ways to Improve Tool Life

• Make Chips NOT dust!!• Use highest possible feed rates • change collets regularly • Consider hogging + finish pass tools Use DIAMOND tooling!!


Speed and feed

• Cutting speed:-• The spindle rpm necessary to achieve a given

cutting speed can be calculated by the formula: rpm =CS *12\D *3.1416Where CS=cutting speed in surface feet per minute. D=diameter in inches of the tool (work piece diameter for lathe)


Speed and feed

• Cutting speed:-The cutting speed of a particular tool can be determined from the rpm ,using

the formula:- CS=D*3.14*rpm\12On the shop floor ,the formula are often simplified . The following formulas will yield results similar to

the formulas just given.

Rpm=CS*4\d or CS=rpm*d\4Several factors which include:-1 . The kind of material to be machined.2. The cutting tool material.3. The quantity of the surface finish.4. The efficient use of cutting fluid .5. The method of the holding of work.


Speed and feeds

• Drilling feed rates:-for machining centre use ,the feed rates given in the table will have to be converted to Ipm values . To accomplish this the following formula is used:-

IPM=RPM *IPRwhere; IPM= the required feed rate inches per min. RPM= the programmed spindle speed

revolution per min. IPR= the drill feed rate.


Speed and feed rates

• Milling feed rates:-To calculate the feed rates for milling cut,the

following formula is used:- F=R*T*RPMWhere; F= the milling feed rate expressed in

inches per minute . R=the chip load per tooth. RPM= the spindle speed in revolution

per minute.


Thank you.......

Tooling for CNC

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