MAE design EXAM 2-5 Notes PDF

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Reviews for test 2, test 3, test 4, and test 5...

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EXAM 2 17.02-04 17.02 ● Screw threads are a helix or conical spiral formed on the external surface of a shaft or on the internal surface of a cylindrical hole. ● Axis—A longitudinal centerline of the thread. ● Root—The bottom of the cut on external threads. ● Crest—The top of the external threads. ● Major diameter—The largest diameter of a screw thread. The distance is measured from crest to crest through the axis on an external thread. ● Minor diameter—The smallest diameter of a screw thread. The dimension is measured from root to root through the axis on an external thread. ● Pitch diameter—An imaginary diameter measured from a point halfway between the major and minor diameters through the axis to a corresponding point on the opposite side. ● Pitch—The distance from a point on a screw thread to a corresponding point on the next thread as measured parallel to the axis. ● Depth of thread—The distance between the crest and the root of a thread as measured perpendicular to the axis. ● Angle of thread—The included angle between the sides of the thread. ● Body—That portion of a screw shaft that is left unthreaded. ● Chamfer—An angular relief at the last thread to help the thread engage more easily with a mating part. Chamfers are commonly applied to the first thread to help start a thread in its mating part. ● Classes of threads—A designation of the amount of tolerance and allowance specified for a thread. ● Fit—Identifies a range of thread tightness or looseness. ● Thread series—Groups of common major diameter and pitch characteristics determined by the number of threads per inch. ● Lead—The distance a screw thread advances axially in one full turn. ● Single Thread: Lead=Pitch ● Double Thread: Lead=2xPitch ● Triple Thread: Lead=3xPitch ● The SPEED of assembly, NOT power, is the characteristic of multiple threads ● American National Thread: 60 degree V-Thread (Standard) used in USA, Canada, and UK. ● Square Thread: Best thread for transmitting power. Difficult to manufacture-replaced by ACME thread (ex: screw jacks, vice screw) ● Buttress Thread: designed for applications with high stress in one direction (ex: breech assemblies of large guns, airplane propeller hubs, columns for hydraulic presses) ● Rolled Threads (knuckle): usually rolled from sheet metal (ex: light bulbs, light sockets, bottle tops)

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17.03 Tap-Cuts internal threads Tap set made up off: taper tap (start), plug tap, bottom tap (when threads are needed at bottom of a blind hole) Die-Cuts external threads Internal Thread: requires drilled hole first, approx same diameter as the minor diameter ○ Through Hole: Goes completely through an object ○ Blind Holes: Doesn’t go through object 17.03 Not necessary to model thread b/c thread forms have been standardized. Indicated shape of thread with a note

17.06-12 17.06 ● Bolt-threaded fastener that passes through the parts using a NUT to tighten or hold the parts together ○ Tightened or released by torque ○ Identified by thread note, length and head type ○ Length- measured from bottom of head ● Nuts- available in hexagonal or square shapes and may be slotted to secure with pin or key ○ Acorn nuts: capped for appearance ○ Self-locking nuts: use neoprene gaskets to keep nut tight when movement or vibration is a problem ● Machine Screws- threaded fasteners used for general assembly of machine parts ○ Identified by thread, length, and head type ○ Available in coarse (UNC) and fine (UNF) threads ○ Sizes range from 0.060 to 0.50 inches in diameter and lengths of ⅛ to 3 inches ● Cap screw-fine finished machine screw, used without a nut ● Stud- fastener with different threads at each end. It’s screwed into a threaded hole and holds other parts with a nut on its free end. (Fine threads at one end and coarse threads at other) ● Minimum full thread length for a screw or stud is at least the bolt diameter in steel ○ Cast Iron, Brass or Bronze: at least 1.5 times the diameter ○ Aluminum, Zinc, or Plastic: 2 times the diameter ● Must be a slight allowance for incomplete threads due to TOOL RUNOUT ● Tool Runout-the distance a tool may go beyond the required full thread length ○ An allowance of three pitch lengths ● Set Screw- used to prevent motion between mating parts ○ Usually made of steel and hardened (stronger than the average fastener) ● Self-Tapping Screws- used to hold two or more mating parts when one of the parts becomes a fastening device. ○ Clearance hole required through first part while last part receives a pilot hole

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Self-Tapping screw then forms its own threads by cutting or displacing material as it enters the pilot hole

17.07 Rivets-permanent fasteners that take the from of cylindrical pins ○ Most mode of wrought iron or soft steel for general applications ■ Copper, aluminum, alloy for special applications ○ During instal, holes are punched or drilled in parts to be fastened, rivet is inserted, and the end of rivet is deformed using a special hammer or press ○ Shop rivets- installed in factory ○ Field rivets- installed on the job ○ Five Major Rivets: ■ Truss Head ■ Button Head ■ Pan Head ■ Countersunk Head ■ Flat Head ○ Two Basic Rivet Joints: ■ Lap Joint-parts overlap and held together by one or more rows of rivets ■ Butt Joint-pars butted and held together by a cover plate or butt strap that is riveted to both parts ○ Holes can be punched, punched and reamed, or drilled ○ Countersunk- Weakest Rivet 17.08 Washer- serve as cushions or bearing surfaces, to prevent leakage, or to relieve friction 17.09 Pins-cylindrical fasteners used to maintain some desired position or orientation between parts. ○ Can be used as an axis ○ Dowel pins-keep parts fixed ■ Tapered more precise then straight Grooved Fasteners-used to solve metal to metal pinning needs ○ Great holding power, resistant to shock, vibration, and fatigue Spring Pin- manufactured by cold-forming strip metal in a progressive roll-forming operation 17.10 Retaining rings-provide removable shoulders for positioning or limiting the movement of parts in an assembly ○ Made of materials that have good spring properties ○ Internal Axial Rings-Compressed for insertion or removal into a bore ○ External Axial Rings-Expanded so the rings can be slipped over the end of a

shaft, stud, or similar part

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17.11 Key-removable part that provides a means of transferring torque and preventing slippage between rotating parts where they are joined along a shaft ○ Five Major Keys: ■ Square Key ■ Flat Key ■ Gib Head Key ■ Pratt & Whitney Key ■ Woodruff Key ○ Three classifications of fit: ■ Class 1-Clearance fit obtained by using bar stock key and keyseat tolerances. Free fit ■ Class 2-Possible interference or clearance fit obtained by using bar stock key and keyseat tolerances. Tight fit ■ Class 3-Interference fit obtained by interference fit tolerances. Very tight fit ○ Key width is about ¼ the nominal diameter of the shaft Keyseat-rectangular groove machined into the shaft Keyway-rectangular groove machined into the hub to receive the key 17.12 Snap Fits ○ Reduce number of parts in assembly ○ Quick and easy to assemble ○ Reduce assembly and inventory cost ○ Two Categories: ■ Cantilever (Snap Legs) ■ Cylindrical Joints

9.02-03 9.02 ● Fabrication process dependent upon production volume 9.03 ● Fixtures- mechanical devices, such as clamps and brackets, which are used to hold and align the workpiece as it is being shaped ● Tool Bit- fixed or movable, replaceable cutting implement with one or more sharpened edges used for removing material from a workpiece ● Standard Commercial Shapes ○ Rounds, bars, tubes, channels, tees, angles ● Workpiece is usually cut to a rough size from a standard commercial shape by SAWING ○ Quick but surface finish quality is poor ● Axially symmetrical features can be made on a machine tool called a LATHE, on which

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the workpiece is rapidly rotated about a single axis. With a cutting tool moving in the radial and/or axial direction removing material ○ Process of shaping the workpiece in this manner is TURNING ○ Removal of material on inside is known as BORING Drilling: Round holes, stationary ○ Drill Bit ○ Drill Press ○ Through Holes-all the way through ○ Blind Holes-part way ○ Tap-creates screw threads ○ Tapped Hole-a hole with screw threads ○ Accuracy can be improved by REAMING, where a special drill bit with a very precise diameter that is just slightly larger than an existing hole is used to open the hole slowly to the final desired diameter. Milling- performed with milling machines ○ Extremely versatile ○ Spindle-can hold and rapidly spin a variety of different cutting tools ○ End Mill-like a drill bit but can cut and remove material from the workpiece in the axial and transverse directions ■ Ball and Round mills- round inside and outside edges ■ Angle end mills- bevel edges ■ Fly cutters-remove small amounts of material to make a surface flat ○ Stage- Workpiece is mounted here. Can move in both the axial and transverse directions (called three-axis mill) ○ Manually Controlled- human operated ○ Numerically Controlled- programmed EDM (Electric Discharge Machining)- uses a charged electrode through which a highlevel electric current is passed to the workpiece through a dielectric fluid. Shaped by erosion caused by the electric current. ○ Most common EDM- Wire EDM ○ EDM only work with with electrically conductive materials ○ Slow Broaching- rapidly sliding a tool called a BROACH through the workpiece forms a hole or slot Rapid Prototyping- use various methods to create parts of complex geometries quickly by selective hardening of a bed of powdered raw material or a pool of liquid raw material at room temp. ○ Constructive Process ○ Used to create parts for casting and molding ○ Sterolithography (SLA) - solid spots are formed in a pool of liquid polymer by focusing laser beams at a single spot in the pool, curing and hardening the liquid at that spot. Moving the lasers can form a solid part of complex geometry. ■ Poor surface finish and strength ○ Fused Deposition (FD)- thin stream of molten plastic is deposited from a nozzle

that can be moved in two or three dimensions. 3-D Printing- Fuses small plastic particles, which lie on a horizontal bed, by depositing from a nozzle a thin stream of solvent that acts as an adhesive. ○ Selective Laser Sintering (SLS)- Similar to 3d printing except that a powdered metal replaces the powdered plastic. Welding- fuses pieces together ○ Introduces flaws, reduces material strength Brazing- Metal workpieces are bonded together with a metal alloy filler Grinding- uses a rapidly rotating abrasive wheel to remove material from a workpiece very slowly ○ Flat Grinding ○ Inside Cylindrical ○ Outside Cylindrical ○

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9.04-07 9.04 ● All casting processes require a MOLD of the desired part ● Mold: supported cavity shaped like the desired part into which molten raw material is poured or injected ● Split Lines: places where the mold can be disassembled ● In the case of Sand Casting, the mold is created by making a Master Pattern ● Investment Casting: form of sand casting that can be used to create relatively intricate shapes with good accuracy. Begins with fabrication of a wax master form. ● Casting and molding processes usually require the sides in the mold to be slightly tapered in the direction of the mold opening. The slight angling of the surfaces is known as DRAFT ● Extrusion: method for creating long lengths of material with a uniform cross-section shape ○ Piece of the extrusion machine that contains the orifice is called the extrusion DIE (Usually Interchangeable) ● Wire Drawing: wires and small round bars can be reduced in diameter by pulling slightly larger stock diameters through one or more nozzles with gradually reducing orifices ● Deep Drawing: thin shelled parts are created from sheets of thin, malleable metal, also known as sheet metal. A plunger shaped like the desired shell is pressed into a piece of sheet metal. ● Rolling: Malleable raw material is reduced in thickness by squeezing it through large rollers ○ Cold rolling accuracies are 3 to 5 times better than hot rolling ● Die Casting: mold is made of steel with surfaces that have been hardened to improve its durability and wear resistance. STEELS CAN’T BE DIE CASTED ● Injection Molding: similar to die casting but with plastic. Mold cavity is cut to shape not formed from a master pattern. ○ Sprue: leftover bits of material at either set of ports ○ Flash: leftover material on the part at the split-line ● Forging- deforms a workpiece by pressing it with a great deal of force between two preshaped molds, or forging dies ● Stamping- Used on sheet metals. Deforms the metal between a cavity and a closely fitting plunger ○ Stamping die: like a large version of a hole punch ● Sintering (Powder Metallurgy): (Use Metal Powder) metal powder is placed in a mold and a great deal of pressure and high temps are applied, fusing the metal together to form a solid part

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9.05 Burrs: part features that have been produced by cutting processes are prone to have sharp edges and small bits of extraneous raw material attached to them Tumbling: Medium and high level production volumes, burrs, and edges can be removed. ○ A part is surrounded in a bin filled with ceramic pellets. 9.06 When the planned production volume of the part exceeds 10,000, tooling investment required for die casting and extrusion starts to become economically justifiable 9.07 - Caution Long, Skinny Holes Long, Skinny Protrusions Sharp Inside Corners Made by Cutting Processes Sharp Outside Corners with Molding and Some Casting Processes Undercuts on Cast or Molded Parts

7.02-03 7.02 ● Components: The objects that make up a system ● Instances: The copies of a component within the system are called instances ● Subassembly: grouping of components that serve a single purpose within the overall assembly ● Associativity: can exist between parts, components, and assemblies ○ In assembly modeling, associativity means that if you change the geometry of a part, the component and all instances of it also will change by the same amount 7.03

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Hierarchy: The organization or structure of a system Parent-Child Relationships: The associations between components and subassemblies Base Instance: Remains stationary with the other instances moving into place around it ○ After selecting base component, establish reference planes for the assembly that are connected to the base component. Serve as coordinate planes Assembly Constraints: maintain dimensional or geometric relationships with respect to each other within the assembly Start with 6 degrees of freedom (DOF) ○ 3 translational ○ 3 rotational

EXAM 3: 8.05

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The types of physical properties that are typically calculated from a 3-D part definition include the surface area, volume, mass, density and center of mass. ○ Inertial properties- Radii-of-gyration, moments-of-inertia, principal-axes of rotation, and products-of-inertia

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Measure Point: returns the coordinates of a specific point on a sketch or model, usually has to be a pickable point Measure Line Length: Returns the length of a line Measure Line Distance: returns the shortest (perp) distance between a line and another identified entity Measure Circle: Returns the center and diameter of a circle Measure Arc: returns the center and radius of an arc Measure Surface: returns the area of a specified surface and the length of the perimeter surrounding that surface

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Mass Properties depend on two things: the geometry of the part and its density

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Main advantages to be gained from assembling a system of parts is that you are able to determine whether two parts overlap or interfere with each other

7.06

8.06 8.07 2.2 2.3 2.4 ● ● ● ●

Arcs & Circles: types of geometric entities Bounding boxes: help to draw arcs/circles by defining the limits of the curved entities as tangent to the edges of the bounding box Tick mark: these establish the points of tangency for the circle along the bounding box Ellipse: same as sketching a circle except your bounding box is a rectangle instead of a square

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Construction lines should be nearly impossible to see when held at arms length Create construction lines to define prominent features of your drawing Can be used to locate the center of a square or rectangle

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3D Coordinate System: a space that can be represented by 3 perpendicular axes (xyz) Right-Handed System: if you point the fingers of your right hand down the positive x-axis and

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curl them in the direction of the positive y-axis, your thumb will point in the direction of the positive

z-axis AKA THE RIGHT HAND RULE BIH

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Axonometric: ○ Isometric- All angles equal ○ Dimetric- two of three angles equal ○ Trimetric- No angles equal ○ Isometric is the easiest and fastest to produce

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Cylindrical Surface: may be positive (such as a post) or negative (such as a hole)

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Oblique drawings are forms of pictorial drawings that enable the viewer to see the most descriptive view of the object as a front view ○ Holes and cylinders appear as circles and not ellipses Disadvantage: tend to be distorted and appear elongated

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12.03

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Two types of oblique drawings: ○ Cavalier: true length of the depth dimension is measured along the receding axes ■ Most distortion ○ Cabinet: half the true length of the depth dimension is measured along the receding axes ■ Least distortion

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Oblique drawings can be constructed using the “framing” technique

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“Boxing-in” technique can be used to create an oblique drawing of an object that has circular features

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Perspectives incorporate the concept of vanishing points to produce the 3-D shape of an object

12.03.02

12.03.03

12.04

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Three types of perspective drawings ○ One point perspectives ○ Two point perspectives-often most used ○ Three point perspectives

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Two point perspective- generated using the top (plan) orthographic view of the object and an elevation view ○ Plan view- rotated at an appropriate angle to enhance the 3d aspects of the perspective ○ Elevation view- shown as it normally would be shown in its orthographic position ○ Picture plane- defines the size and position of the perspective when viewed from the station point ○ Horizon line- where ground meets sky ○ Ground Line- defines the position of the elevation view of the object ■ Determines the vertical location of the perspective drawing

12.04.02

Video Lectures: 4.1 4.2 5.1.1 ●

Freehand Sketching: the most effective and ready means for transferring concepts, ideas, modifications, suggestions, thoughts

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Draw lines from top to bottom and left to right Focus on endpoint Rotate paper

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Use CONSTRUCTION LINES, STRAIGHT LINES Use Bounding boxes

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EXAM 3 VL: 6.1, 6.2, 6.3, 6.4 10.2-5 10.02.01 Problems with a pictorial

- it is difficult to depict an objects angles - distortion of true lengths and internal measurements - curve distortion Pictorials look realistic but difficult to create an object with precision from them 10.02.02 Multiview- depicts in one planes, many images of the same object Viewing Plane- Transparent plane fixed in space between you and the object 10.02.03 Orthogonal projection- image of an object is composed of point...