Tooling for CNC
Transcript of Tooling for CNC
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CNC ToolingComputer numerical control tooling presentation:-
Prepared by:-Shyam Kumar sonu.Rahul Raman.Bijay Kumar shah. md .Sallaudin .Durga nand chaudhary.Binoy tamang.
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Introduction
•CNC tooling
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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.
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Properties of tool material
Toughness Wear resistance.Hot hardness.Recovery hardness.Thermal conductivity.co-efficient of thermal expansion.Hardenability .Weldability.Grindability .Dimension stability.
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Tooling For CNCCutting tool Materials
Cutting tools are available in three basic types
Cutting tool material
High speed steel TUNGUSTEN carbide 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 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.
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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
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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.
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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.
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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.
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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.
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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.
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TOOLING for hole operation
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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.
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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.
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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.
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.
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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.
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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.
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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.
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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).
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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.
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Milling cutters Milling cutters can be further classified as:-
Milling cutters
End mills Face mills
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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.
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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.
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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
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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.
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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 radius in a part.
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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.
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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.
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Face mill cutters
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Milling cutters
Face mills:-Large diameter face mill Large number of insert used.Cyclo mill was developed for NC use.
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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.
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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 tooling developments .
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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.An NC tooling system featuring:-• Tool adapters• Interchangeable extensions.• Tool bodies.• Boring heads.• Arbors.
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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 insert.
Common inserts shapes
Triangular 80 degree diamond
55 degree diamond
Round
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Special inserted cutters
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.
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Special inserted cutters
• 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
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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
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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 rate and work upward .
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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)
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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• .OO5 to .010 inch
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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 *3.1416Where CS=cutting speed in surface feet per minute. D=diameter in inches of the tool (work piece diameter for lathe)
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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\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.
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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 *IPRwhere; IPM= the required feed rate inches per min. RPM= the programmed spindle speed
revolution per min. IPR= the drill feed rate.
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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*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.
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Thank you.......