Tooling For Cnc

CNC Tooling Computer numerical control tooling presentation:Prepared by:ØShyam Kumar sonu. ØRahul Raman. ØBijay Kumar shah. Ømd .Sallaudin . ØDurga nand chaudhary. ØBinoy tamang. cnc tooling Group 2(DMCH 2007)

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Introduction

•CNC tooling cnc tooling Group 2(DMCH 2007)

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Topic contents q q q q q q q q q q

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. cnc tooling Group 2(DMCH 2007)

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Properties of tool material Ø Toughness Ø Wear resistance. Ø Hot hardness. Ø Recovery hardness. Ø Thermal conductivity. Ø co-efficient of thermal expansion. Ø Hardenability . Ø Weldability. Ø Grindability . Ø Dimension stability. cnc tooling Group 2(DMCH 2007)

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Tooling For CNC Cutting tool Materials Cutting tools are available in three basic types Cutting tool material

High speed steel

TUNGUSTEN carbide

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Ceramic

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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 disadvantage

having

following

•HSS does not hold up as well as carbide or tooling Group 2(DMCH 2007) 6 ceramic at high cnc temperature generated during

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

Solid carbide tools

Brazed carbide tools cnc tooling Group 2(DMCH 2007)

Inserted carbide tooling 7

Tooling for cnc ØTungsten 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.

Ø 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. cnc tooling Group 2(DMCH 2007) 8 • When inserted cutters are used the inserts can be

Tooling for numerical control ØTungsten carbide Tungsten 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. cnc tooling Group 2(DMCH 2007)

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Tooling for numerical control

ØCeramic 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 cnc slowly, the inserts will breakdown tooling Group 2(DMCH 2007) 10

Tooling for numerical control

ØFields 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. cnc tooling Group 2(DMCH 2007) 11

Tooling for hole operation ØTooling for hole operations. • There are four basic hole operations that are performed on nc machinery. Tooling for hole operations.

Drilling

Reaming

Boring

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tapping

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TOOLING for hole operation

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Tooling for hole operations ØDrilling • 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.

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Tooling for hole operations ØDrilling • 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.

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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.

ØTypes 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). cnc tooling Group 2(DMCH 2007) 16

Tooling for hole operations ØReaming :• 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.

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Tooling for hole operation ØReaming :• 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: ü HSS ü Brazed carbide ü Solid carbide. cnc tooling Group 2(DMCH 2007)

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Tooling for hole operations ØBoring :• 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 –upcncto ½-inch diameter. tooling Group 2(DMCH 2007)

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Tooling for hole operations ØTapping:• 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).

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Milling cutters The 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 cnc tooling Group 2(DMCH 2007) designed to perform a

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Milling cutters Ø Milling cutters can be further classified as:Milling cutters

End mills

Face mills

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Milling cutters ØThread 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.

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Milling cutters Ø End mills:End mills are available in : q High speed steels (HSS) q Solid carbide

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

Inserted end mills:q From 0.500 inch to 3 inch. q Note 1:-two flute cutters with deeper gullets are well suited for roughing operations. q Note 2:-four flute end mills are more rigid because their rigid core.

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Pictures of end mill cutter

Single end multiple flute end mill

Solid carbide two flute end mill

Ball nose end mill cnc tooling Group 2(DMCH 2007)

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Milling cutters End 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 cnc tooling Group designed for aluminium to2(DMCH one2007)

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Pictures of end mill cutter

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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

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

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Milling cutters ØFace 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. cnc tooling Group 2(DMCH 2007)

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Face mill cutters

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Milling cutters Face mills:qLarge diameter face mill qLarge number of insert used. qCyclo mill was cnc tooling Group 2(DMCH 2007)

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Milling cutters Ø Face 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. cnc tooling Group 2(DMCH 2007)

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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 cnc tooling Group 2(DMCH 2007)

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Special inserted cutters

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INSERTED TOOLS

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Examples

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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.

Ø An NC tooling system featuring:• • • • •

Tool adapters Interchangeable extensions. Tool bodies. Boring heads. Arbors. cnc tooling Group 2(DMCH 2007)

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Special inserted cutters • 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 Common inserts insert. shapes

Triangula r

80 degree diamond

55 degree diamond

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Round 39

Special inserted cutters Ø 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. cnc tooling Group 2(DMCH 2007)

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Special inserted cutters • Identification system:Prefix

shape

W R 15

S

Clearance

Toleran ce

R

C

Type

Radius & chamfer

Size

6

3

Thicknes s cnc tooling Group 2(DMCH 2007)

H

4

Chamfe r size

Edge conditi on

T

R

Hand 41

Speed &feeds • Feed Rate – Inches per minute (IPM) • Spindle Speed – (RPM) • The relationship between these 2 variables is critical to achieving optimal tool life

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Basic rule Make chips NOT dust!! Larger chip loads = less heat generation = longer tool life cnc tooling Group 2(DMCH 2007)

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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

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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.

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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 cnc tooling Group 2(DMCH 2007)

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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

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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) cnc tooling Group 2(DMCH 2007)

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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

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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!!

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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 *3.1416 Where CS=cutting speed in surface feet per minute. D=diameter in inches of the tool cnc tooling Group 2(DMCH 2007)

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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\12 On 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\4 Several 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. cnc tooling Group 2(DMCH 2007)

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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 *IPR where; IPM= the required feed rate inches per min. RPM= the programmed spindle speed revolution per min. cnc tooling Group 2(DMCH 2007)

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Speed and feed rates • Milling feed rates:To calculate the feed rates for milling cut,the following formula is used:F=R*T*RPM Where; F= the milling feed rate expressed in inches per minute . R=the chip load per tooth. cnc tooling Group 2(DMCH 2007)

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Thank you....... cnc tooling Group 2(DMCH 2007)

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