End Mills 4. Cutting Tools 1 (Cont d) End-mills (Cont d)

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1 Outline Review of Milling Cutting Tools Milling Milling Operations Workpiece Materials Tool Selection Machining Tips Toolholders Fixtures Cutting Tools HSS tools Coated (TiN, Al O 3, TiAlN,...) versions are available, Mostly used for drilling, reaming, boring. Carbide Inserts (WC, TiC) Mostly coated, Suitable for general machining operations. Solid Carbide Tools Some are coated, Also called Hard Metal, Used in high-speed machining. Chapter 4 ME 440 Chapter 4 ME Cutting Tools 1 (Cont d) Cutting Tools 1 (Cont d) As the basic tool, most machining i centers use HSS- or carbide insert tools. Insert endmills cut many times faster than HSS: HSS endmills usually leave a better surface finish when side cutting. Solid Carbide tools combine the desired features of both HSS- and carbide insert tools. Unfortunately, they are still quite expensive! Facemills flatten large surfaces quickly and with an excellent finish. Ball endmills are used for a variety of profiling operations. Chapter 4 ME Chapter 4 ME 440 5

2 Cutting Tools 1 (Cont d) End Mills 4 HSS tools are used as drills, taps, p, and reamers. A spot drill is employed instead of a center-drill. spiral point / gun taps are for through holes spiral flute for blind holes. Slitting- and side cutters are used when deep, narrow slots must be cut. End Mill This one is unsuitable for drilling! Slot Drill Ball-Nose End-Mill Chapter 4 ME Chapter 4 Slot Drill ME Slot drill are the end- mill tools that are specially designed to drill straight down into the material. End mills are the tools that have cutting teeth at one end as well as on the periphery. Suitable for peripheral milling and facing. Cannot remove material axially if no tooth is present at the center of the flat-end. End-mills (Cont d) Mostly have two / three flutes (and rarely four!) Used to create pockets and keyway slots. Right-hand Left-hand End-mills (Cont d) Right-hand hand (helix) tools are the most common: Must rotate clockwise to cut. Left-hand tools are quite rare: Must spin counter clockwise. Chapter 4 ME Chapter 4 ME 440 9

3 Milling Operations Milling Parameters 1: facemilling : square-shoulder milling 3: profile/contour milling 4: cavity milling 5: slot milling 6: turn milling 7: thread milling 8: cutting off 9: high-feed milling 10: plunge milling 11: ramping 1: helical interpolation 13: circular interpolation 14: trochoidal milling Some important milling parameters are as follows: a e : Cutting width [mm] (or radial depth of cut), a p : Depth of cut [mm] (or axial depth of cut), f z : Feed-per-tooth [mm/tooth], f n : Feed-per-revolution [mm/rev], z n : Number of cutting edges, h ex : Maximum chip thickness [mm], h m : Average chip chickness [mm]. Chapter 4 ME Chapter 4 ME Climb-milling* Up-milling* Milling Types Modern CNC machines are equipped with ball screws to minimize the effect of backlash when changing feed directions: They allow climb milling instead of conventional (up) milling as done on most conventional machines. Climb milling has many advantages: Better surface finish for most materials Surface is not affected by revolution marks Low overall power Smoother operation Better load conditions Less tendency to chatter Longer tool life Higher cutting speeds and feeds Climb-milling is generally prefered on a CNC machining center! Chapter 4 ME Kinematics of End-Milling 3 Consider a four-flute endmill with straight edges: Helix angle: 0 4 R Motion of the cutting edges: Translation (f t) Rotation about the center (n t) Each cutting edge follows a 1 trochoidal path. R: Radius of cutter [mm] The difference between two successive (edge) trajectories n: Spindle speed [rpm] yields the ideal chip thickness. z n : No. of cutting edges: 4 f: Table feed(rate) [mm/min] Chapter 4 ME

4 Kinematics of Milling g( (Cont d) Conventional Milling: Coordinates of Edge k (k=134)atinstantt: 1,,3,4) t: x f t = + sin R 60 R y π = 1 cos 60 R π ( 1) π [ n k t ] 60 [ n ( k 1) π t ] Kinematics of Milling g( (Cont d) Climb Milling: x f t = sin R 60R y π = 1 cos 60 R π ( 1) π [ n k t + ] 60 [ n ( k 1) π t + ] Chapter 4 ME Note that the height of tooth-mark (h) is higher in climb-milling: R f z h = 8 f zzn R ± π Use (-) for climb-milling; (+) for conventional. Chapter 4 ME Calculation of hm & hex Plan for Manufacturing Manufacturing engineers face with a number of difficult questions in metal cutting: How to select the cutting tools? Tool type (material) and geometry (diameter, length, number of cutting edges, helix angle,...) How to determine machining parameters so as to obtain the desired part quality while minimizing the overall cost? Machining plan: Type of milling, axial- and radial depth of cuts, feedrates, spindle speeds How about machining conditions? Wet or dry machining? If wet, what type of coolant? Is the CNC machine tool capable of performing the specified operations? Force, power calculations. Chapter 4 ME Chapter 4 ME

5 ISO Workpiece Material Classification The properties of workpiece material (like yield strength, hardness,...) play a key role in the selection of machining parameters. ISO classifies workpiece materials into six categories: P (Plain carbon steels) M (Stainless steels) K (Cast irons) N (Non-ferrous metals/materials) Typically Aluminum alloys S(S (Super alloys) Heat resistant alloys H (Hardened steels) Chapter 4 ME P-Class ISO Class Material Type Examples Plain carbon steel 1000 series, 1100 series Free-machining carbon steel 1100 series, 100 series Alloy and tool steels s ( HB, 1300, 000, 3000, 4000, < 47 HRC) 5000, 6000, 7000, 8000, P 9000 series Ferritic, martensitic, and 400, 500, 17-4 PH, 15-5 PH precipitation hardening (PH) stainless steels Cast steels Chapter 4 ME M-Class K-Class ISO Class Material Type Examples M Austenitic stainless steels 00 series, 300 series, (<8 HRC) Duplex, ASTM XM series Free machining steels Alloy cast irons and malleable irons 300 series ASTM A48 class ISO Class Material Type Examples K Gray cast irons Long-chipping i malleable irons Short-chipping malleable irons (10-30 HB) ASTM A48 class 0-45, SAE J431 series Nodular / ductile, ferritic / pearlitic, pearlitic / martensitic, ASTM A536 series, SAE J434 series, ASTM A47 series, SAE J148 series Chapter 4 ME Chapter 4 ME 440 1

6 N-Class S-Class ISO Class Material Type Examples Free-machining and low silicon aluminum alloys (<1.% Si) Alcan, Alcoa 510, Duralumin, A, AA 000 series, AA 3000 series N High-silicon aluminum alloys (>1.% Si) Non-ferrous metals Oh Other materials Duralcan, AA A380 series, AA A390 series, AA A413 series Zirconium, i manganese, magnesium, tin alloys, metal matrix composites (MMCs), lead alloys, zinc alloys, tungsten alloys Carbon and graphite composites, glass, plastics, wood, ceramics, nylon, rubbers, phenolics, and resins ISO Class Material Type Examples S Cobalt-based b heat-resistant t t Alloys Nickel-based heat-resistant alloys Titanium Titanium alloys AiResist, Haynes, Stellite, Jetalloy Iron-based heat-resistant t t alloys Discaloy, Incoloy 801, N-155, A- 86 Astroloy, Hastelloy, Inconel, Incoloy 901, Nimonic, Nimocast, Rene, Udimet, Waspaloy, Monel, Refractaloy Ti98.8, Ti99.9 Ti5Al.5Sn, TiAl6V4, TiAl6V4ELI Chapter 4 ME 440 Chapter 4 ME H-Class ISO Class Material Type Examples Chilled cast irons H Tool steels and hardened steels Hardened cast iron D, D3, L, L3, 440C, 6150, A, M3, M4, 5100, Ni-Hard coatings Carburized and nitrided irons, high chrome white cast iron Tool Selection Procedure Select the tool material (grade) considering: i Workpiece material Machining job (roughing, semi-finishing, finishing, super-finishing). Classify the machining operation and select proper tool geometry: Profiling Milling / Grooving Employing the cutting data (cutting speed, feedrate) of the manufacturer, determine the machining parameters. Chapter 4 ME Chapter 4 ME 440 [*] Courtesy of Sandvik 5

7 Example for Tool Selection Let us consider finishing with Sandvik CoroMill Plura Endmill (Solid Carbide). Workpiece: AISI 1090 steel ISO P-class (carbon steel) Normalized structural steel Yield strength: 590 MPa Hardness: HB < 300 Dry contour milling / profiling Finishing operation Grade Selection The grade GC160 works well for semi-finishing to finishing (wet or dry). Wear resistance is especially high when dry machining. This grade also performs well when machining stainless steels wet. Chapter 4 ME Chapter 4 ME Machining Operations Tool Geometry Chapter 4 ME Chapter 4 ME 440 9

8 Tool Selection Cutting Speed For this specific finishing operation, let a e = a p = 0.5 mm. Chapter 4 ME Chapter 4 ME Spindle Speed Calculation Feedrate Recommendations Since the cutting speed (v c = 410 m/min) is determined c using the corresponding table of tool catalog, the spindle speed (n) [rpm] can be calculated as 1000 v n = π D c c = π 1 If the machine tool is not capable of reaching such speeds, it can be modified to accommodate the limitations of the machine. Recall that t the values in the tables are only recommendations! Chapter 4 ME Chapter 4 ME

9 Feedrate Calculation Since feed for milling cutters is read as f z = mm/tooth, the feed rates (f) on milling machines become f = f zznn = f = 6.1 [ m / min] Note that for solid carbide cutters, the feedrates as well as the spindle speed are very high. h In general, slow feedrates give a better finish, but sometimes this actually dulls the cutter faster than a higher feedrate. Issues in Feedrates Feedrates calculated thru the tool datasheets (catalogs) are oftentimes NOT optimal: Employ the calculated values as a starting point to optimize the perfomance the actual machining task. Data for carbide insert milling cutters should be obtained from the insert manufacturer. Unlike lathe cutters (which are fairly standard), milling cutters vary widely among manufacturers, so use your manufacturer s data. Chapter 4 ME Chapter 4 ME Summary Properties of the selected tool are as follows: Sandvik CoroMill Plura ball-nose end mill R AKN (GC160) Diameter: 1 mm 4-Flute Machining parameters are Spindle speed: rpm Feedrate: 6 m/min Recommendations for Face Milling 3 Cemented carbide Face milling Roughing Finishing Cutting speed: v c (m/min) Feed: f z (mm/tooth) Depth of cut: a p (mm) Suitable grades P0-P40 coated carbide P10-P0 coated carbide 1. Use a milling cutter with a positive-negative or positive-positive geometry.. Climb milling should generally be used. 3. Milling should generally be done without coolant. If a high surface finish is required coolant may be used. 4. Cermets can be of use when finishing under stable conditions. Chapter 4 ME Chapter 4 ME

10 Square Shoulder Milling 3 Square shoulder milling with cemented carbide a e = 0.1 D a e = 0.5 D a e = 1 D Cutting speed, v c (m/min) Feed, f z (mm/tooth) Suitable grades P15-P40 P40 coated carbide 1. Climb milling should generally be used.. Choose the cutter diameter (D) and the radial depth of cut (a e ) so that at least two cutting edges are engaged simultaneously. 3. If the machine tool power is inadequate for the data given reduce the depth of cut, but do not reduce the feed. Chapter 4 ME Slot milling Depth of cut: a p = 1 D Slot-milling 3 Cutter diameter (mm) Uncoated HSS v c (m/min) f z (mm/tooth) , Coated HSS v c (m/min) f z (mm/tooth) Solid cemented carbide 5-8 Indexable insert (carbide inserts) 6-8 v c (m/min) f z (mm/tooth) v c (m/min) f z (mm/tooth) Suitable grades P15-P40 P40 coated carbide 1. Climb milling is generally recommended.. Use a cutter with chip breaker when side milling with radial depths of cut, a e > 0.3 xd. 3. When side milling with small radial depths of cut (a e) the cutting speed can be increased by up to 15%. 4. Use liberal amounts of cutting fluid. 5. It is recommended to use a TiCN coated cutter when milling with solid cemented carbide tools. The axial depth of cut should not exceed the cutter diameter when slot milling. 6. Climb milling is generally recommended. 7. When side milling with small radial depths of cut (a e) the cutting speed can be increased by up to 30%. 8. The radial run-out, at the cutting edges, must be small and not exceed mm. Chapter 4 ME Side-milling 3 For side milling, the same cutting speed as for slot milling can be used: Feeds must be adjusted to obtain a suitable average chip thickness: f z = f z (slot-milling) C f Axial depth of cut: a p = 1.5 D Chapter 4 ME Drilling 3 Drilling Drill diameter (mm) Uncoated HSS vc (m/min) f (mm/rev) Coated HSS 1- Cem.Carbide insert 3-4 Solid cem. carbide 5-7 Brazed cem. carbide 5-7 vc (m/min) 6-8 f (mm/rev) vc (m/min) 00-0 f (mm/rev) vc (m/min) f (mm/rev) vc (m/min f (mm/rev) The cutting fluid should be ample and directed d at the tool.. When drilling with short "NC drills" the feed may be increased by up to 0%. For extra long drills the feed must be decreased. 3. Use insert grades in the range of ISO P0-P30. Under unstable conditions a tougher carbide grade should be used for the centre position. 4. Use a high cutting fluid pressure and flow rate for a good chip removal. 5. If machining with solid or brazed cemented carbide drills, a rigid set-up and stable working conditions are required. 6. The use of drills with internal cooling channels is recommended. 7. Use a cutting fluid concentration of 15-0%. Chapter 4 ME

11 Problem Chatter Poor surface finish Rapid tool wear Tool breakage Tap breakage Machining Tips 3 Suggested Remedy Reduce cutting speed. Increase feed rate, sharpen tool, check rigidity of machine or set up, reduce nose radius of lathe tool, check spindle bearings, etc. reduce tool and work overhang. Sharpen tool, increase cutting speed, reduce feed rate, increase nose radius of lathe tool. Reduce surface speed. Use harder grade of tool material, use cutting fluid. Reduce depth of cut, reduce feed, increase cutting speed, use more rigid set up, sharpen tool, check alignment of tool. Tap not square, tap jamming on bottom of hole, tapping too far with taper tap, too small a tapping size, swarf jamming tap, use cutting compound. Toolholders 1 All cutting tools must be held in a holder that fits in the spindle. These include end mill holders, collet holders, face mill adapters, etc. The gage length shown in the drawing is entered in the machine control as the tool length. The machine the compensates for the length. Chapter 4 ME Chapter 4 ME Fixtures Fixtures include anything that holds the work on the machining center table. The simplest fixture is a vise! Double vise with machinable jaws are used to hold odd shaped pieces. Fixtures (Cont d) Tombstone shown has a vise on two of its faces for use on a four or five axis machining center. Chapter 4 ME Chapter 4 ME

12 Fixtures (Cont d) Fixtures for mass-production are often custom designed and manufactured at great expense. For small runs of oddshaped parts, many manufacturers have turned to modular fixturing: consists of many yprecision ground pieces that fit together to hold all sorts of parts. References Some of the materials used in these notes are adapted from the following references: 1. MFET 75: CNC Applications, Purdue Calumet.. Sandvik Coromant 007 Catalog. 3. Cutting Data Recommendations, Grane Engr., Wikipedia. Chapter 4 ME Chapter 4 ME

CARBIDE END MILLS SPECIFICATIONS

CARBIDE END MILLS SPECIFICATIONS SPECIFICATIONS COATING GUIDE Material Hardness TiN TiCN TiALN Austentic Stainless Steel < 35 HRc * X Martinistic Stainless Steel < 35 HRc * X Martinistic Stainless Steel >= 35 HRc X PH Stainless Steel