Final Exam
Non Center Cutting End Mill
(cannot plunge straight down) has a small hole in the center on the cutter, require a pilot hole or gradual helical spiral
Center Cutting
(straight down in z direction) cutting edges continue to the center of the tool.
Test Indicators
- perpendicular deviation from spindle's contact pt Used to sense displacement that occur in a direction essentially perpendicular to the spindle's contact point. • Locate center of a circle for a machine tool's spindle • Tram in vise parallel to axes on a machine tool. • Establish parallelism or perpendicularity.
CMM Sensor Types
1) Floor Mounted 2) Bench-top 3)Portable- accuracy to range ration, affordable, easy to use software
3 Elements of CNC Programming
1)Program of Instructions (G and M Code) 2) Machine Control Unit (Controller) 3)Processing Equipment (Tools)
Milling Operations
1. face milling 2. peripheral milling 3. sawing 4. drilling
Honing
A rotating tool carrying abrasives removes metal from the interior surface of a bore or cylinder. • Purpose is to finish the surface to a particular diameter and geometric cylindricity. • Most commonly performed on internal cylinder walls using a combined rotating and reciprocating motion.
Manufacturing Operation Sheet
A unique machining set up on the CNC machine. parts with different work holdings have different operations Assignment of specific operations to machinery. • Operation sheets give detailed instruction on how to perform a specific manufacturing step. • SafestWaytoPerformOperation • StepbyStepInstructionsonSetup&MfgOperation • Operation Sheets Should Include: • PersonalProtectionEquipment(PPE) • Engineering Drawing Reference • PertinentDimensions&Tolerances • Fixtures / Workholding • Tooling / Feeds & Speeds • Setup Figure or Drawing
Broaching
Broaching is performed on a broaching machine or an arbor press and the cutting tool is called the broach. • It can produce complex shapes with internal sharp corners. Contains a series of teeth where each tooth stands slightly higher than the last (in/tooth) creating the broach's • The pull end of a broach is first fed through the part then attached to the broaching machine where it gets pulled through the part usually by a hydraulic ram. In internal broaching, a hole must exist in the work piece into which the broach can enter.
Water Jet Cutting
Capable of slicing into metal or other materials using a jet of water at high velocity and pressure. Additives in the form of suspended grit or other abrasives, such as sand and silicon carbide, can assist in this process.
Circular Interpolation
Circular Interpolation G02 and G03 Needs a feed rate value (in/min) Cutting an arc or circle
Design for Manufacturability
DFM- engineering process of proactively designing products to optimize all the manufacturing functions includes: Fabrication, Assembly, testing, procurement, shipping, delivery, service, repair marketing, design, engineering, manufacturing minimize manufacturing operations and setups, design with symmetry in mind, avoid right/left hand parts, think about tooling and jigs
Milling and Drilling RPM
Feed (in/min)= speed (rev/min)XCL(in/rev/flute)*num flutes)
Fixed Gages
Fixed gages embody the direct or reverse physical replica of the object to be dimensioned. consistent form and measurement positive dimensional information, economic
Linear Interpolation
Linear Interpolation G01 - Cutting in a straight line or contour cut - Needs a Feed Rate Value (in/min) specified - need feed
Manufacturing Routing
Manufacturing Engineers create routings to establish, the manufacturing operations, their path, and most efficient sequence. 1) standard, 2) parallel(simultaneously) 3) split routing( across work centers)
M Codes
Miscellaneous- control auxiliary options like coolant and spindle direction. tool change, end program...
Surface Speed
N = RPM (rev/min) of the work piece (lathe) or cutting tool (mill) V = Cutting Speed (ft/min) 12 = (in/ft) d = Ø of the work piece (lathe) or cutting tool (mill/drill),π = 3.141517
Rapid Moves
Point to point Position - Get to the starting location for cutting - Absolute Positioning (G90 G00 X2.25 Y1.25) Use machine rapid override controls to slow the machine down to 5% rapid. A major cause of crashes is setting the tool or fixture offset incorrectly. Pay particular attention to moves at the start of program and immediately after a tool change as the tool moves towards the part. Use single-block mode to advance through the program one line at a time until the tool is at cutting depth. Always remain at the machine with a hand on or near the feed hold button. Stop machine's feed motion at the first sign of trouble.
Grinding Cylindrical and Surface
Surface: involves grinding flat surfaces, placed on magnetic chuck Cylindrical: external cylindrical surfaces and shoulders of workpieces, aka center-type grinding, rotating grinding wheel travels down the length of the rotating cylindrical workpiece
Milling Table Feed Rate
Table feed for mills (in/min) F = Nxft xtF: Table Feed Rate (in/min) N: Cutting Tool RPM (rev/min) t: Number of Teeth on Cutting Tool (# of teeth) ft: Chip Load (in/tooth)
Gage Blocks
The essential purpose of gage blocks is to make available end standards of specific lengths by temporarily combining several individual blocks into a single block.
Turning Centers vs. Machining Centers
Turning center is a lathe and spindle is usually horizontal. Machining Center- any CNC milling and drilling machine that includes an automatic tool changer and a table that clamps the workpiece in place, the tool rotates but the work does not, spindle can be horizontal or vertical. we have vertical?
Least and Maximum Material Conditions
Used in engineering design to relate the specified dimension to the "envelope size" of the part or feature.
Center Drilling
are short and very rigid drills used to create a conical hole on the surface of the part. Because they come to a sharp point and resist bending, they are able to locate the hole precisely before a drill is used.
Chip Load
chipload/feed for lathe (in/rev) Table feed for mills (in/min) F = Nxft xtF: Table Feed Rate (in/min) N: Cutting Tool RPM (rev/min) t: Number of Teeth on Cutting Tool (# of teeth) ft: Chip Load (in/tooth)
CNC Machining and Batch Production
coordinates, feeds, speeds and G&M codes
Taps
cutting tool used to form the B-internal thread
Non Traditional Manufacturing Processes
do not use mechanical energy to shear a chip off the work piece- Do not use shear stress as E source - generally have higher E requirements and slower 5 nontraditional processes Mechanical Electrical Thermal Chemical Generally have higher energy requirements and slower throughputs than the traditional machining processes we have learned about in lecture and lab. • Developed and used in manufacturing applications where traditional machining methods were impractical, incapable, or uneconomical.
Threads
drill and tap chart -uniform cross sections minor is inside major is outside . 60 degree thread angle for Unified National crest is at top root is at bottom
Fixtures
fixture offset-G54 home location- allow CNC to know distance from machine home position and part's coordinate system. Programs written in relation to the part instead of the machine coordinates. locates and holds securely for casting and forgings, establishes an X,Y,Z zero point. Device which holds the workpiece in a specific position in relation to the tangential force of a machine tool, establishes zero points from part datums
Abrasive Processes
helps get a better surface finish and dimensional accuracy abrasive on harder workpieces, better surface finish, tighter tolerance includes grinding and others
First Article Inspection
helps make sure the first part of manufacturing process is done
End Mills vs. Face Mills
in face milling the surface generated is a right angle to the cutter's axis however most of the cutting is done by peripheral portion of the teeth
Common Mill Work Holding Methods
jaw and collet chucks(lathe), Soft jaws areused in milling vise or three jaw chuck
Laser Cutting
leaves a small heat affected zone uses light energy to melt material in very small area, laser is always sharp melts and evaporates portions of the workpiece The laser itself is a single point cutting source with a very small point, (0.001" to 0.020) allowing for very small cut widths.
Jigs
locates and guides tools. locates edges, surfaces, plane shapes, holes, angles, lengths of parts
Height Gages
master gages are ten times more accurate than the product tolerance electronic gages developed in parallel with electronics industry by electronic amplification, micron inch measurements possible. pneumatic small probe, high amp. Optical Gage- primary source of light surface Plate functions as a datum reference plane Scribers can be attached to contact jaw
Optical Comparators
observation and measurement of objects with optical magnification needs light source, collimating lens, projection lens system, and viewing screen
Engineering Microscopes
optically assisted instruments for measuring the geometric dimensions and forms of small and medium size technical parts- magnify, reference angles, and stage- uses illumination
Press Fit
press fit- shaft is larger than hole, not taken out for service or anything
Reaming
reaming removes a small amount of material from the surface of a hole created by drilling or boring. 1)bring to more exact size 2) improve surface finish on existing hole Used on drill press, vertical mill, tailstock or lathe requires pilot hole slightly smaller than finished size (one to two drill bit sizes smaller than hole being reamed as little as .005" and smaller than .025" can be within 0.001" of correct size/ have fine surface finish.
Electronic Discharge Machining
removal process that uses spark discharges to erode electrically conductive materials. • Electrode - positive or negative charge • Workpiece - negative or positive charge • Non-contact - No cutting forces generated • The electrode is maintained between 0.0005" to 0.030" from the work piece surface. • Material removal is independent of work piece hardness. sinker die wire edm uses electrical energy uses thermal process
Turning Operations
set a depth of cut, changes the size of the diameter. Use right facing tool use forward- machining on the diameter- uses compound set and cross slide Setting on the dial corresponds to total change in diameter while actual depth of cut is one half the reduction of the diameter. Uses the right facing tool. To turn toward tailstock toward z direction.
Common Lathe Work Holding Methods
should locate and clamp a workpiece so all six degrees of freedom are fully constrained and the workpiece has repeatable origin every time it is inserted (mills)machine vises and parallels, jaw and collet chucks(lathe), and clamps. Soft jaws areused in milling vise or three jaw chuck
Dial Indicators
travel indicator- continuous dial or balance dial Senses measuring distance variations that are in the axial direction of the measuring spindle. parallel
Tool Length Offsets
used to establish the tool length value in the CNC program and control for each tool
G Codes
very accurate and powerful industrial robots since 1950s. prepare machine for a certain type of motion: rapid motion, linear interpolation, circular interpolation, return home, home locations, absolute positioning, incremental positioning
Material Removal Rate
volume of material per unit of time in^3/min uses horsepower required for cut for a lathe MRR =12Vfd 12 in/ft V=Cutting Speed (ft/min) f= chip load (in/rev) d= depth of cut or mill: MRR=Fwd F= table feed rate (in/min) w= width of cut (in) d= depth of cut (in )
Go, No-go Gages/ Limit Gages
• Reverse replica of the dimensions to be checked. • The acceptable size of the part is determined by its limit dimensions. • MMC & LMC • Principles of Measurements • Limit gages are made identical to design size limits. • When a part is out of tolerance two cases will occur. • The part being gaged does not fill the permissible boundaries. • The part feature exceeds the specified boundaries. GO NOT GO gages are used to determine functional adequacy of a part. • The Go limit gage contains the reverse physical replica of the dimension to be measured at its maximum permissible material condition. (MMC) • The NOT GO gage contains the reverse physical replica of the dimension to be measured at its minimal acceptable material condition. (LMC)
