Presentation on theme: "INT 201 Eastern Kentucky University"— Presentation transcript:
1INT 201 Eastern Kentucky University MachiningMetal Cutting ProcessINT 201Eastern Kentucky UniversityLecture References:Degarmo E.P., Black J.T., Kosher R. (2003). Materials and Processes in Manufacturing, 9th edition. WileyRepp, V. (1994). Metalwork: Technology and Practice, 9th edition. McGraw-HillGroover, M. (2004). Fundamentals of Modern Manufacturing: Materials, Processes, and Systems, 2nd edition. WileyChen, C.S. (2001) ITEC 502: Advanced Design and Manufacturing [Course]. Iowa State University
2Lesson Objectives REVIEW: Fundamentals of Machining Identify the basic parameters associated with machining (milling)Understand how these basic parameters are used to create and remove chipsUnderstand that machine parameters are directly related to type of material and the machine
3Machining Fundamentals REVIEWMachining is a process of removing unwanted material from a workpiece in the form of chips.Making and removing chipsImportance of lubricants$60 billion spent annually on metal removal operations
7Specific process/equipment Basic Machining ParametersMachining variables such as cutting speed, RPM, table feed rates, metal removal rates, and depth of cut all depend on:Work materialTool materialSpecific process/equipment
8Cutting Speed (SFPM)Cutting speed is the distance a point on the circumference of the milling cutter travels in one minuteMeasured in Surface Feet per Minute (SFPM)Calculated at the outside diameter of the cutter
9Cutting Speed (SFPM)Different cutting speeds should be used when machining different metalsWith cutting speeds too fast, cutter will overheat and dulls rapidlyWith cutting speeds too slow, time is wasted and production costs will increase
10Cutting Speed (SFPM) Factors affecting cutting speeds in milling: Material properties, cutting tool (HSS, carbide, cast alloy), cutting fluidsCutting speed recommendations for various materials and tooling combinations can be found in sources including: Tooling Mfg. & Engineering Handbooks (Machinist Handbook, etc)
11SFPM = Surface Feet Per Minute Cutting Speed FormulaSFPM = (π * D * N)/12whereSFPM = Surface Feet Per Minuteπ = Circumference constant per inch of DiameterD = Diameter of the cutter, measured in inchesN = revolutions per minute of the spindle (RPM)12 = 12 inches per foot (conversion calculation to feet)
12Cutting Speed ExampleIf a 2 inch dia., 6 tooth milling cutter is turning at 100 revolutions per minute (RPM), what is the calculated cutting speed of the cutter (SFPM)?
13Spindle Speed (RPM)The speed of the milling machine is measured at the spindle and is measured in REVOLUTIONS PER MINUTE (RPM)
14Same equation; different arrangement Finding N (RPM)Same equation; different arrangementSFPM = (π * D * N)/12
15Determining RPMWhen milling with a 3” diameter, 8 tooth milling cutter with a recommended cutting speed of 250 SFPM tooling material combination, what is the recommended RPM?
16Feed RateThe linear distance moved along any machine axis, by the cutting tool in inches per minute.Feed rate in milling is determined by multiplying:Number of teeth on the cutterChip load per toothSpeed of the cutter (N)
17Chip Load or Feed per Tooth The Chip Load is the amount of material removed by each tooth of the milling cutter during one revolutionChip load recommendations for various materials and tooling combinations can be found in machining and engineering handbooks
18Milling Feed Rate Formula F = N * Ct * TwhereF = Feed rate in inches per minuteN = Spindle RPMCt = Chip Load per tooth [feed per tooth]T = Number of teeth on cutter
19Calculating Feed RateA 6 inch dia., 12 tooth milling cutter is turning at 250 RPM. The recommended chip per tooth is 0.004”. What is the feed rate?F = N * Ct * T= 250 RPM * ”/tooth * 12 teethF = 12” per minute
20Metal Removal RateMetal Removal Rate (MRR) is the volume of material removed from the work piece in one minute.Limited to available machine powerHow much material is removed in 1 minute
21MRR Formula MRR = W * D * F MRR = Cubic inches removed per minute whereMRR = Cubic inches removed per minuteW = Width of CutD = Depth of CutF = Feed rate
23MRR ExampleWhat is the MRR of a surface 3 inches wide that is to be milled with a 6 tooth milling cutter. Each depth of cut is inches and the table feed rate is 4 inches per minute3”Feed Rate = 4”/min.125”
24MRR Example MRR = W*D*F MRR = (3”) * (0.125”) * (4” per minute) Feed Rate = 4”/min.125”MRR = W*D*FMRR = (3”) * (0.125”) * (4” per minute)MRR = 1.5 cubic inches per minute (in3/min) of material removed
25Horse Power (specific) HPs HPs = Horse power required to remove 1 cubic inch (in3/min) of material per minuteAll machined materials have a HPs ratingHPs is used to determine the HP required for machining.The standard HPs = 1Materials with HPs > 1 require more than 1 HP/minute to remove 1 in3 of materialMaterials with HPs < 1 require less than 1 HP/minute to remove 1 in3 of materialHPs can be found in machining and engineering handbooks
26HP = HPs * MRR Horse Power Formula whereHP = Horse Power required to make a desired cutHPs = specific Horse Power of materialMRR = Material Removal Rate
27HP = HPs * MRR HP = 1.8 * 3.94 HP = 7.1 HP Example How much Horse Power is required to machine a part with a desired MRR of 3.94 in3/min and a specific Horse Power (HPs) of 1.8?HP = HPs * MRRHP = 1.8 * 3.94HP = 7.1
28ReviewWhat is the maximum MRR of a material with a 1.6 HPs on a 1.2 HP machine?How much material can be removed from the same material on a 7.1 HP machine?
29Specific process/equipment ReviewMachining variables such as cutting speed, RPM, table feed rates, metal removal rates, and depth of cut all depend on:Work materialTool materialSpecific process/equipmentWHY?