manufacturing v2
maximum and minimum sizes permitted for a dimension difference = the tolerance
Limit of size
M03: start spindle CW M04: start spindle ACW
M03 vs M04
Spindle off
M05
End of program, stops feed, spindle and cutting fluid
M30
coded programs that can automatically perform mathematical calculations as well as substitute those calculated values within cutting G coded programs
MACRO's
machined: high scrap loss, undesirable grain flow lines (fracture initiation), no strengthening, external and internal threads, good surface finish, can do both internal and external, low speed rolled: minimal scrap loss, desirable grain flow - better properties (improved fatigue life), strengthening, external mostly, smoother surface finish, high-speed production
Machined vs. Rolled threads
extrusion drawing (wire,bar, tube) other squeezing processes
Major bulk deformation processes (L8)
work is squeezed and shaped between dies
Principle characteristic of forging (summary)
as the ram approaches a die opening, a small portion of billet, called but, that remains cannot be forced through die opening -die must be separated from extrudate by cutting it just beyond die opening
Process of direct extrusion
upset forging cold heading roll forging swaging and radial forging
Processes related to forging
processes where the surface area of the workpiece change significantly thickness reduced
What are bulk deformation processes
involve the deformation of a material where the thickness and surface area remain relatively constant but the shape changes
What are sheet-metal forming operations?
Rolling Forging Extrusion Wire, bar (rod) and tube drawing
What are the main bulk deformation processes of importance?
uniform and there are no residual stresses
What are the material properties of hot rolling?
BD- billets, blooms and slabs SF- sheets, strips, coils
What are the starting shapes of bulk deformation processes vs sheet metal forming?
open-die forging impression-die forging flashless forging
What are the three classes of forging?
Primary processes: reduce cast material into intermediate shapes such as slabs, blooms and billets Secondary processes - further convert these shapes into finished or semi-finished products
What are the two classifications stages of the deformation process?
flat dies round dies
What are the two dies used in thread rolling?
Rolling + selected process related to rolling Forging + selected processes related to forging
What are the two main bulk deformation processes?
Flat rolling Shape rolling
What are the two types of Rolling (based on shape)?
-Two-high non-reversing mill, two high reversing mill -three-high mill -four-high mill -cluster mill
What are the typical rolling mill configurations?
early reductions called primary, roughing or breakdown passes.
What are two-high and three-high mills usually used for?
propels the materials and dictates the amount of deformation and is needed to pull the workpiece into the gap. i..e if deformation is too high, the rolls skid over its surface, and if too little, additionally passes are required.
What does friction contribute to solling processes?
due to the large surface-to-volume ratio most sheet metal forming operations are performed cold.
What does sheet material loose heat rapidly, and what does this result in?
Upset forging
What forging processes has the highest mass production?
minimum temperature at which complete recrystallization will occur ~1 hour
What is Trecry
Square or slightly oblong Range: 6"x6" to 10"x12"
What is a Bloom?
Mostly square Range: 2"x2" to 5" x5"
What is a billet?
Always oblong Mostly 2-6 inches thick, s4-60 inches wide
What is a slab?
produces: valves, couplines, gear blanks hot forged products emerge from other end rates: up to 180 parts/min -low cost input material and high production speeds expensive equipment, economical for large scale.
What is automatic hot upset forging?
manufacture of small parts from the weaker nonferrous materials, now used extensively on steel however - parts can be up to 45 kg in weight and 18cm diameter.
What is cold forging generally associated with?
includes a family of manufacturing processes in which slugs of materials are squeezed into shaped die cavities to produce finished parts of precise shape and size
What is cold forging?
widely used for making enlarged sections on the ends of rod or wire i.e. cold heading used for heads of bolts and screws, thread rolling is then used to form threads.
What is cold heading used for?
Common for intermediate shapes, where metal is solidified into a "semifinished" billet, bloom, or slab for subsequent rolling in the finishing mills
What is continuous casting?
a way of conveniently performing repetitive CNC machine operations.
canned cycle
same as high speed in addition: - parts designed so they can be gripped by same gripper of robot, avoiding need for different grippers -threaded fastener assemblies such as; nuts, bolts and screws difficult for robot, can handle snap fits, rivets, welds and adhesive fasteners
design rules for robotic assembly
Closed-die forming which fine details in the die are impressed into the top and bottom surfaces of the workpiece
coining
-much better surface finish (because of lack of scale) -better dimensional tolerances -increased mechanical strength(because of strain hardening)
cold rolling advantages over hot rolling
Tw<Trecrys Tw<0.3Tm
cold working -> cold forming temperature
wrinkling, tearing
common defects in sheet metal drawing
type of forming process hot working or cold working chemical reactivity with tool and work metals ease of application cost toxicity, odor, flammability, disposal
considerations when choosing lubrication
both form from ductile materials however continuous with built up edge has a low-medium cutting speed, where the tool chip friction causes motions of chip to adhere to rake face and BUE forms, breaking off cylindrically
continuous vs continuous with BUE
parts designed so they cannot be assembled incorrectly avoid reorientation of parts during assembly maximise part symmetry
design rules for manual assembly
Boring is when you make a hole in your work piece large, reaming - is used to slightly enlarge a hole, provide better tolerance on diameter, and improve surface finish
difference between drilling, boring and reaming
the metal removed creates part of the blank outline, whilst punching and slotting creates holes in the blank
difference between seminotching and punching (or slotting)
high initial equipment cost limited to lap joints for most RW processes low strength of discontinuous welds thickness of welded sheets limited (~6mm)
disadvantages of RW
Limitations on mechanical properties Poor dimensional accuracy and surface finish for some processes; e.g., sand casting Safety hazards to workers due to hot molten metals Environmental problems
disadvantages of casting
higher forces, powerful equipment pre-cleaning required small deformation, low ductility intermediate annealing residual stresses from work hardening directional properties
disadvantages of cold working
higher total energy lower dimensional accuracy surface oxidation shorter tool life no work hardening
disadvantages of hot working
force or power required material properties of product exit or final temp surface finish or precision nature of material flow
examples of dependent variables in forming
high FCC metals & alloys, low C steel, annealed materials low hcp metals, high C steel, alloy steels, metals previously cold worked
examples of materials with high and low workability (formability)
adaptation of shielded metal arc welding, over com electrode is continuous consumable tubing containing flux two versions -self shielded FCAW -gas-shielded FCAW
flux cored arc welding (FCAW)
F = stretching force L = length of sheet in direction perpendicular to stretching t = instantaneous stock thickness Yf = flow stress of work material
force in stretch forming
predicts future by using data in hand affects descions made in present
forecasting (PP)
undesirable - metal flow retarded, forces & power increased, tooling wears faster, surface finish degrades more severe in hot working hard to measure
friction in metal forming
electrode is consumable bare metal wire, shielding accomplished by flooding the arc with gas
gas metal arc welding (GMAW)
GMAW has better arc time due to continuous wire electrode better use of electrode and filler material higher deposition rates eliminates problems in slag removal reality automated
gas metal arc welding vs submerged arc welding
non-consumable tungsten electrode and inert gas for arc shielding
gas tungsten arc welding (GTAW)
characteristics of material being deformed speed of deformation (strain rate) friction lubrication
general parameters in forming
for low production rates performed on press brake v-dies simple and inexpensive from acute to obtuse angle air-bend and bottoming
v bending
Tw < Trecrys 0.3Tm<Tw<0.5Tw
warm working -> warm forming temperature
wavelengths of intermediate length result from:machine or work deflection, vibration and chatter or heat treatment
waviness
process in which two or more materials are permanently joined together by coalescence
welding definition
lists manufacturing operations and associated machine tools for each workpiece - useful for material handler
what a route sheet and who is it useful for?
porosity - small voids by entrapped gases during solidification shrinkage voids - cavities formed by shrinkage upon solidifcation
what are cavities in welds
non metallic material entrapped in weld metal slag inclusions and metal oxides
what are solid inclusions in welds
relatively inexpensive and portable equipment - suitable to low quantity production and repair jobs easily adapted into thermal cutting
what are the advantages of OFW
good mechanical properties of product favourable grain flow little waste no handling of molten material no solidifcation problems cast structure improves, cast defects eliminated
what are the advantages of forming
young's modulus yield strength sheet thickness bend radius and bend angle
what does springback in bending depend on?
product function, assembly, quality, reliability
what does surface finish and dimensional precision effect
quantity and timing of specific products
what does the master production shcedule show
shaped punch is forced through the sheet into a shaped die and a blank or hole is made in one operation
what happens to the shaped punch in both blanking and punching
that part becomes a candidate for elimination
what happens when the answer to all three guidelines for ideal product estimation are negative?
designing a product in such a way that it can be assembled easily as assembly costs are typically 25-50% of total costs.
what is DFA?
mathematical description of materials behaviour as a function of operating conditions
what is a constituitive relationship
the assembly condition between two mating parts and is controlled by the limits of size of the two features concerned hole: internal feature shaft: external feature
what is a fit in interchangeable manufacture
degree to which indicated value confirms to an acceptable standard value
what is accuracy
discharge of electric current across a gap in a circuit - sustained by an ionised column of gas (plasma) through which current flows
what is an electric arc
describes what machining operations are done to the parts at particular machines -useful for the machinist and assembly personnel
what is an operational planning sheet and who is it useful for?
heat (metal or glass) and allow it to cool slowly, in order to remove internal stresses and toughen it.
what is annealing
wipe bending
what is another word for edge bending
at high temperatures metals are chemically reactive to oxygen, hydrogen and nitrogen in air hence the arc must be shielded by surrounding air in AW process
what is arc shielding and why is it important in arc welding?
fusion welding process, coalescence of metals achieved by heat from an electric arc between an electrode and and the work.
what is arc welding
mold (steel or iron) rotated at high speed where the centrifugal force distributes the molten metal to mold cavity
what is centrifugal casting
ease of fabrication desirable properties (corrosion resistance)
what is choice of material dictated by
clearance = internal feature size - external feature size i.e. for a shaft clearance = size of gear hole -size of shaft
what is clearance defined as in interchangable manufacture
size and shape tolerances material properties of material number of pieces machine tools
what is considered in the process selection criteria
stepped hole, in which a larger diameter follows a smaller diameter into a hole.
what is counterboring
molten metal forced into dies under high pressure, tool steel dies, die blocks open - two types: hot chamber, cold chamber
what is die casting
when axes of deformation are not linear or not independent
what is drawing? SMF
material's ability to undergo significant plastic deformation before rupture
what is ductility
added to the molten pool to facilitate the process and provide bulk and added strength to the welded joint
what is filler metal and its purpose?
coalescence by solid state fusion between two surfaces held together under pressure and at an elevated temp similar materials - solid state diffusion dissimilar materials - lower MT between
what is forge welding
when multiple bends are made with a single die i.e. roll forming
what is forming? SMF
coalescence by heat and friction between two surfaces. simultaneously applying compressive force and relative motion (rotation usually) between faying surfaces one of two work pieces held stationary, other rotated about axis of symmetry
what is friction welding (FRW)
resistance of a material to deformation, indentation, or penetration by means such as abrasion, drilling, impact, scratching, and/or wear,
what is hardness
hot -forming relatively thick walled parts of simple geometries, usually cylindrical -material thickness may change significantly cold -thin sheet metal -parts of wide varieties of shapes
what is hot vs cold drawing used for in SMD
uses wax pattern that is subsequently coated with refractory material then melted away prior to pouring.
what is investment casting
loading and scheduling: assigning start and due dates for processes components processes through the factory. process planning: determines sequence of individual manufacturing processes and operations needed for product
what is involved in shop floor level production control?
allocating jobs to work centres
what is machine loading
metalworking process of fashioning metal parts and objects through mechanical deformation; the workpiece is reshaped without adding or removing material, and its mass remains unchanged.
what is metal forming
machining operation where work is fed past a rotating tool with multiple cutting edges - peripheral milling -face milling
what is milling and the two main types?
performed by a high temperature flame from combustion of acetylene and oxygen
what is oxyacetylene welding
melting accomplished by an oxyfuel gas i.e. acetylene top temp ~ 3500 deg C
what is oxyfuel gas welding (OFW)
permanent deformation, non-coverable after unloading, permanent atomic displacements
what is plastic deformation
how closely the indicated value matches the true value a measurement of random error
what is precision
the smallest tolerance that can be maintained economically by a particular process. tolerance selected should be larger than this.
what is process capability?
slightly enlarging a hole to provide a better tolerance on diameter
what is reaming
melting achieved by heat from resistance to an electrical current between faying surfaces held together under pressure
what is resistance welding
smallest graduation of instrument
what is resolution
allocating jobs to the entire shop
what is shop loading
no yield point phenomenon control of the interstitials
what is significant in recent developments in extra deep drawing steel?
the increase in the included angle (decrease of the bend) of a bend part relative to the included angle of a forming tool (punch) after the tool is removed also called unbending
what is springback in metal bending?
producing large sheet metal parts in small quantities i.e. large panels for aircrafts, cars and trucks
what is stretch forming used for
providing internal screw threads on an existing hole
what is tapping
minimise cost and investment maximise utilisation of plant and equipment
what is the aim of aggregate planning?
harder materials require a larger part angle whilst softer materials require a sharper point angle. most common part angle is 118 deg
what is the application of the part angle in twist drills?
rapid nucleation occurs when molten metal comes in contact with cold walls narrow band of randomly oriented crystals on surface of casting
what is the chill zone
distance between the punch cutting edge and die cutting edge c= at, a = allowance range between 4% to 8% of stock thickness
what is the clearance in shearing and its typical range
rapid growth perpendicular to casting surface long and thin highly directional
what is the columnar zone
applies stresses that exceed yield strength of the metal - metal takes shape dependent on the geometry of die.
what is the die tool in metal forming
angle or taper on a pattern that allows for easy removal of casting from mold
what is the draft
crystals in interior of casting spherical randomly orientated crystals
what is the equiaxed zone
flux, to clean the surfaces and prevent oxidation
what is the filler material coated in and why, in oxyacetylene welding
flask - rigid frame that holds molding aggregate cope - top half of flask drag - bottom half of flask
what is the flask, cope and drag?
developed by top level management breaks down aggregate into a separate plan based on specific products then calculate detail of manpower, material and inventory requirements
what is the master production schedule
slag inclusions - instead of floating at top of weld pool, globules of slag become encased during solidification
what is the most common solid inclusion of welds
development of reliable constitutive relationships
what is the most difficult part of process modelling
oxyacetylene welding
what is the most important OFW process
to allow slug or blank to drop through die typical values: 0.25° to 1.5°
what is the purpose of angular clearance? (in blanking and punching)
increase volume and strength of weld joint
what is the purpose of filler metal in arc welding
simulations with FEM
what is the quickest, most inexpensive, and relatively accurate modelling process
two intersecting surfaces of the wedge shaped cutting tool.
what is the rake and flank face
the smaller the tolerance the higher the manufacturing cost.
what is the relationship between tolerance and cost
forge welding
what is the simplest joining method
first stage (inner core of flame) C₂H₂ + O₂ → 2CO + H₂+ Heat second stage (outer envelope) 2CO +H₂ +1.5O₂ → 2CO₂ + H₂O + Heat
what is the two stage chemical reaction of acetylene and oxygen
compressive
what is the usual stress used to plastically deform the metal
yield strength - limit of elastic behaviour, starts plastic behaviour ultimate tensile strength - maximum stress a material can undergo
what is the yield strength and ultimate tensile strength?
consequence of friction dimensions of workpiece change, tolerance control lost, poor surface finish, expensive tool replacement
what is tool wear and why is it undesirable
ability of a material to absorb energy and plastically deform without fracturing.
what is toughness
when no filler metal is added (in a fusion process)
what makes a fusion welding process an autogenous weld?
the ability to flow plastically in the solid state without deterioration of mechanical properties
what metal property does metal forming ultise
both compression and tensile deformation occur neutral axis displaced small thinning in centre stretching of bend
what occurs in metal bending
dimensioning and tolerancing -size -form -orientation -location &, -surface texture
what practice decide the interchangeability of parts? what are the specifications required?
room temperature (cold work) on various presses for operations that use plate stock - performed warm or hot
what temperature is sheet metal forming usually performed at?
low carbon steel (C<0.15% mild steel), also aluminium and copper alloys
whats the most common sheet metal used?
if R>4t
when is compensation for springback needed?
at the upper limit of DR ≤ 2.0
when is the product defect free in sheet metal drawing?
malleable materials, high ductility allows for large plastic deformation and low yield strength to allow for lower deformation forces
which mechanical properties of materials are desirable in metal forming processes and why
recovery of elastic energy (strain) after unloading -bend radius, R increases -bend angle α increases (unbending) -remedy e.g. overbend
why does springback occur in metal forming?
capable of the highest temperature (up 3480 deg)
why is acetylene the most popular fuel among OFW group
to estimate the amount of stretching so that the final part length can match the specified dimension.
why is the bend allowance used
wire: electrical wire, for fences, coat hangers, shopping carts rod stock: for nails, screws, rievets and springs bar stock: metal bars for machining, forging and other processes
wire and bar drawing products
holding work between centres chuck collect face plate
work holding devices in turning
tapping - internal threads, drilling operation threading - external threads, turning operation
tapping vs threading
times delay for programmed moion
G04
mode for programming in m
G71
G90 - absolute distance mode G91 - incremental distance mode
G90 vs G91
no more accurate than that of the input variables
the accuracy of any model can be
die casting permanent mold casting
2 types of multiple use mold
3 jaw chuck can self centre, hold a hexagonal bar stock and is quick and easy to use, however cannot hold a square bar stock or irregularly shaped work and run off/cutoff centre cannot be easily fixed 4 jaw independent chuck can centre work to high precision, hold a square/ rectangular bar stock, turn work off centre and has slightly more grip on round stock. however, cannot hold hexagonal bar stock and is slower and more fiddly to mount work.
3 jaw self centreing chuck vs 4 jaw independent chuck
arc welding (AW) oxyfuel gas welding (OFW) resistance welding (RW)
3 main types of fusion welding
point-to-point (PTP) straight cut contouring CNC
3 types of CNC control systems
communications interface diagnostics automatic tool change on machine measurement
4 main features of CNC machine
sand casting shell casting investment casting lost foam casting
4 types of expendable mold
groove fillets spot plug and slot
4 types of welds
entry - funnels lubricant into the die, prevent scoring of work & die approach- cone shaped region where drawing occurs bearing surface- determines final stock size back relief- exit zone, provided with a back relief angle, about 30 degrees die materials - cemented carbide (i.e. WC nib +steel casting), diamond, tool steels
5 main features of a draw die
facing contour turning chamfering cutoff threading
5 main types of turning
1. mold cavity produced 2. melting process 3. pouring technique 4. solidification 5. mold removal 6. cleaning, finishing and inspection
6 steps in casting
butt corner lap tee edge flange
6 types of joints
slab slotting surface contouring profile end pocket conventional face
7 main types of milling? SSSPEPC
bulk deformation processes sheet-metal forming (sheet metalworking presswork)
According to the initial form of the workpiece and the changes to the workpiece shape and size during deformation, metal forming processes are divided into:
increased strength, close tolerances, improved surface finish, high production rates - cold extrusion at room temperature also eliminates the need for heating the starting billet
Advantages of cold (impact) extrusion
Variety of shapes possible, especially in hot extrusion Limitation: part cross section must be uniform throughout length Grain structure and strength enhanced in cold and warm extrusion Close tolerances possible, especially in cold extrusion In some operations, little or no waste of material
Advantages of extrusion
material savings, ideal grain orientation, strengthening through cold working - diameter up to 8m, height up to 2m -machining often used for surface finishing
Advantages of ring rolling
application in automotive industry recently properties: good formability, low weight, good corrosion resistance
Al alloy extrusion
ball and roller bearing races, steel tires for railroad wheels, rings for pipes, pressure vessels and rotating machinery
Applications of seamless ring rolling
-reducing diameter of tube or solid rod stock -created a tapered section or points -assembling fittings over cables and wire
Applications of swaging and radial forging
restricted between 20% - 50% (higher values require higher pulling forces)
Area reduction in drawing
denotes the change in size of work r = A₀-Aƒ/A₀ often walled %CW (percent cold work) ideal conditions, max r=63%
Area reduction, r
MIG welding is a term sometimes applied when referring to which one of the following processes: A. Flux Cored Arc Welding (FCAW) B. Gas Metal Arc Welding (GMAW) C. Gas Tungsten Arc Welding (GTAW) D. Shielded Metal Arc Welding (SMAW) E. None of the above
B MIG = (metal inert gas)
metal (uniformly heated if hot rolling) passed between two rolls that rotate in opposite directions - the rolls pull material into the gap -gap between rolls, slightly smaller than the thickness of entering material - as a result - metal is squeezed by the rolls and elongates to compensate for the decrease in thickness
Basic rolling process
theoretical size of a dimension on which limits of size and design sie and based
Basic size
Bending is deforming the material around a straight axis -Little change to thickness or surface area -Permanent deformation (bend) - multiple bends can be made simultaneously, but each axis must be linear and independent of the other.
Bending (SMF)
quantitative measure - design efficiency, compares total assembly time for a product with the total for an ideal product
Boothroyd/ Dewhurst DFA Methodology
the plastic deformation of a surface due to sliding contact with another object.
Burnishing
-multiple backing rolls allow for small diameter work rolls -hot rolling of wide plate and sheets
Cluster Mill
a cold forging processes, and a form of upset forging
Cold heading
1) feeding + 2) gripping stock (3-4) upsetting
Cold heading sequence
heat sink - large number of fins maximise surface area, complex dies are more expensive and higher forces are required.
Complex cross sections example
From coiled wire rod (hot-rolled ferrous, extruded nonferrous,~6- 9mm) to wire Multiple draw dies separated by capstans Maximum deformation before annealing is needed
Continuous drawing machines
"Stick" welding is a term sometimes applied when referring to which one of the following processes: A. Flux Cored Arc Welding (FCAW) B. Gas Metal Arc Welding (GMAW) C. Gas Tungsten Arc Welding (GTAW) D. Shielded Metal Arc Welding (SMAW) E. None of the above
D
AC machines - cheap, restricted to ferrous materials DC machines - all materials, better arc control
DC vs AC current in arc welding
-smaller work rolls mean less length contact for a given reduction -therefore, lower force and energy are required to produce shape change -reduced stiffness, possibility of "three-point bending" hence backing rolls are needed
Four high rolling mill
a deformation processes in which the work is compressed between two dies using either impact or gradual pressure to form the part
Definition of forging
shaping of solid materials controlled by plastic deformation
Definition of metal forming
size shown on drawing
Design size
GO blocks check size at max material position NO-GO - checks size at lest material condition
Difference between GO and NO-GO gauge blocks
both shape workpiece by hammering dies swaging: dies rotate radial: workpiece rotates
Difference between swaging and radial forging?
also called forward extrusion starting billet usually round, can be rectangle
Direct extrusion
hard - 10:1 to 35:1 soft - 10:1 to 100:1
ER for hard alloys and soft alloys
point to point positioning
G00
G01 - linear interpolation G02 - circular interpolation CW G03 - circular interpolation ACW
G01, G02 vs G03
compression process in which the work material is pushed to flow through a die opening to produce a desired cross-sectional shape
Extrusion
ER = cross-sectional area of starting billet(mm²)/final cross sectional area of extruded section (mm²)
Extrusion (Reduction) ratio
= perimeter of shape/weight per meter - used to determine a part's extrusion performance - a higher difficulty factor makes the part more difficult to extrude, consequently affecting press production -weight per meter importance for profitable press opersation
Extrusion difficulty factor
Uniform cross section High billet-chamber friction Non-uniform deformation across the billet High cost of equipment
Extrusion disadvantages (summary)
horizontal (most common, especially hot extrusion) or vertical (cold) hydraulically driven (const force, up to 120MN) mechanical drives variable (conventional) or hydrostatic pressure (billet surrounded by liquid under pressure)
Extrusion press
the higher the mechanical properties of an alloy means lower extrusion rates greater friction between the billet and liner wall results in a longer time required to start billet extruding lighter section - smaller press
Factors affecting extrusion
Ab =0.457
Find the bend allowance
reciprocate relative to each other important process for external threads on bolts and screws
Flat dies in thread rolling
work is squeezed and shaped between dies
Forging principle
compressive forces used, increased malleability at Tw (increase ductility, yield strength reduction) - large deformations possible -significant change in shape (surface area to volume ratio small)
Hot bulk deformation
by passing work through rolls that have the reverse of desired shape, usually requiring gradual deformation through several rolls.
How is shape rolling accomplished?
cold working process that is used to plastically form recesses cavities in a workpiece - often more economical than die sinking (machining the cavity) especially for multiple impressions
Hubbing
hollow product from solid slug solid bottom, length increased, constant diameter
Impact backward extrusion
hollow product from hollow slug length increased diameters changed; stepped.
Impact combination extrusion
also called high-speed cold extrusion used to produce discrete parts in finished or near finished forms advantages of cold work
Impact extrusion
low-shape strength materials; lead, tin, zinc, aluminium - collapsible toothpaste tubes now applied to the forming of brass and mild steel parts
Impact extrusion processes initially used to shape products such as
diameter reduced; constant, length increased, solid or hollow product
Impact forward extrusion
Advantages -higher production rates -less waste (scrap) -greater strength, fatigue and impact resistance -favourable grain resistance Limitations -not capable of close tolerances -final machining often required to achieve accuracies, surface finish and special features
Impression-die forging vs. Machining from solid stock
also called reverse, backward, or inverted extrusion; a hollow ram pushes the die back though a stationary, confined billet
Indirect extrusion
Advantages -higher deformations, lower forces -longer billet length -lower extrusion temperatures and higher speeds Limitations -low rigidity of hollow ram -difficulty in supporting extruded product as it exits die -restriction to the cross-sectional size of solid extrudate -removal of the residual billet
Indirect extrusion vs. Direct
computer based inventory management system assists production managers in scheduling and placing orders for items of dependent demand
Materials Requirement Planning (MRP)
size which an item is designated as a matter of convenience
Nominal size
notching - cutting out a portion of metal from the side of the sheet or strip semi notching - removes a portion of metal from the interior of sheet
Notching and seminotching
finished sheet and plate stock with good surface finish and dimensional accuracy - can significantly change mechanical properties such as strength and ductility due to strain hardening
Product of cold rolling
high production rates excellent dimensional tolerances and surface finish reduced amount of machining (material savings) provides additional strength; enhancing toughness and fatigue life Since cold forging is a chipless process, the material is used more efficiently and waste is reduced
Properties of cold forging
similar to blanking except cut piece is scrap, called a slug also known as piercing
Punching
similar to swagging, in its action against the work, creates similar part shapes difference: in radial forging, the dies do not rotate around the workpiece; instead, work is rotated as it feeds into the hammering die
Radial forging
permanent mechanical joining of sheets or plates -head formed on shank end of rivet eg. riveted bridges, ranks, ships, airplanes.
Riveting
cylindrical or semi-cylindrical rolls several grooves used until desired shape and size produced no flash (usually) favourable grain orientation products: axles, tapered levers, leaf springs
Roll Froging properties
three point bending of loads and elastic deformation, workpiece defects: non-uniform thickness, wavy edge, centre cracking.
Roll benchind and rolling defects?
shaping between two rotating rolls with grooves hot round or flat bar stock is inserted between the rolls and progressively shaped in grooves.
Roll forging
rotate relative to each other to accomplish rolling action ~ 200pieces/min
Round dies in thread rolling
molds rotated around an axis of symmetry, central axis must beb machined away, lower RPM than true
Semi-Centrifugal Casting
includes shearing and forming operations performed on sheets of metal (<6mm thickness) or thin plates
Sheet metal forming
hot or cold-trolled (annealed steel) high ductility (%EL>40%) thickness up to 3 bare or galvanised pure ferrite (C<0.1%) car body panels, whitegoods
Sheet steel for deep drawing
depends on material - ductility at forming temp - strain hardening exponent controlled by tool design adjusted by operator
amount of deformation
accomplished by rotating dies that hammer a workpiece radially inward to taper it as the piece is fed into the dies
Swaging
Fales. Usually performed cold, some swagging operations are conducted on heated material though.
Swaging and radial forging is usually performed hot? T/F
turning milling drilling
Three basic types of machining
- no need for reversing -elevator needed to raise and lower material on both sides -mechanical manipulations to turn product between passes -difficult to maintain correct speed for all passes -less expensive with higher output than 2-high
Three high rolling mill
direct, indirect, impact
Three main extrusion methods
1. one must know the temperature 2. avoid application of force 3. expected precision of measuring instrument must be 5-10 x higher than that expected of the object
Three principles of measurement
difference is stock size wire drawing: small diameter rod stock, can be coiled bar: large diameter and rod stock, cannot beb coiled
Wire drawing vs bar drawing
Non-reversing: material passes in one direction, rolled material returned manually to feeding side. Rolls must be adjusted between consecutive operations Reversing: back and forth rolling, rolls must be stopped, reversed and brought back to rolling speed between each pass, multi-grooved rolls
Two high rolling mill
operation in which the cross section of a bar, rod, wire or tube is reduced by pulling it through a die opening
Wire, bbar and tube drawing
cleaning - prevent work surface damage and draw fie pointing - reduce diameter of starting end, allowing for insertion through draw die (i.e. swaging). annerealing or special heat treatments - provide optimal combination of strength and ductility of stock.
What is done to prepare work for drawing?
work is completely constrained within die; no flash starting workpiece volume = die cavity volume usually classified as precision forging
What is flashless forging?
used to reduce thickness of rectangular cross section
What is flat rolling used for?
ability of metal to flow and fill a mold - metal should flow into all regions of mold and then solidify
What is fluidity?
to establish basic form of large parts that are subsequently machined to their final shape or size.
What is forging often used for in metal industries?
Metal flows and completely fills the shaped die cavity, excess metal squeezed out to form flash (trimmed from final forging). Requires further machining for precision and tolerances. Small to moderate sizes
What is impression-die (closed die) drop-hammer forging?
Forming processes conducted at constant temperature - used for temperature-sensative materials such as Ti alloys or Ni based super alloys
What is isothermal forming?
forging for large and very large pieces, large forces, slower deformation, mechanical manipulation of workpiece
What is open die press forging?
-impact by mechanical hammer -hammer (ram) and anvil dies usually flat (simple shape) -operator positions and turns workpiece -small to large pieces (large called press forging) -simple shapes, further processing
What is open-die drop-hammer foging?
formation of a new set of strain free grains within a previously cold worked material
What is recrystallization?
most widely used casting method, sand is used as mold.
What is sand casting?
preform circular ring is first upset and pierced, thick-wall smaller diameter ring is then reduced to a thin-walled larger diameter ring hot working- for large rings cold working - smaller ringes flat or shaped rolls; circumferential grain oreintation
What is seamless ring rolling?
to deform work into a contoured cross section, rather than a flat rectangular shape.
What is shape rolling used for?
the strengthening of a metal by plastic deformation. This strengthening occurs because of dislocation movements and dislocation generation within the crystal structure of the material
What is strain hardening?
medium-to-high rates of production, rates as high at 50 parts/min can be possible
What is swaging and radial forging suitable for?
differs from ODDHF in that closed impression dies rather than open face dies are used -improvements introduced precision forging -alternative is flashless forging
What is the difference between open die drop hammer forging and impression die drop hammer forging?
the extent of error is not indicated when an object is rejected
What is the main disadvantage of GO/NO-GO gauge blocks?
use of a "crowned" roll to compensate for roll flexure, when the roll flexes in three-point bending, the crowned roll flexes into flatness -other measures to reduce bending forces: lower reductions, stronger rolls, smaller roll with backing rolls, high temps
What is the possible solution to rolling defects?
die opening -solid, semi-hollow or hollow cross section -long length or cut to short lengths -final shapes can be produced or shapes shaped produced later for further processing
What is the shape of direct extrudate determed by
compression of a cylindrical workpiece between two flat dies upset forging
What is the simplest form of open-die drop-hammer forging and what is it known as?
d=D₀-Dƒ used in circular bar and rod drawing
What is the term draft, d (in drawing)
used to form threats on cylindrical parts by rolling them between two dies. mostly performed by cold working in rolling machines with special dies that determine the size and form of the thread
What is thread rolling?
involves increasing the diameter of a material by compressing its length - hence, produces materials with no flash, eliminating further machining -performed as an open die or closed die operation.
What is upset forging?
what products to make how many of each and when completion should be scheduling the delivery and/or production of the parts and products planning the manpower, raw materials and equipment resources needed to accomplish the production plan
What logistic issues is production planning concerned with?
four-high and cluster type, due to the smaller size and higher strength
What rolling mills perform cold rolling and why?
when deformations are less severe and/or workpieces are discrete units
When is cold or warm working uses in BD?
when massive deformations of large workpieces is required
When is hot working done in BD?
aluminium, brass, copper, lead tin
Which metals and alloy sare typically used in extrusion and why?
reduces interpretation errors instantaneous readings quick conversion between scales zeroed out at any point
Why is digital measurement advantages?
annealing - to restore ductility and enable further deformation.
Why is intermediate heating sometimes required in drawing? What is this called.
cross section is reduced by pulling through a die opening: similar to extrusion but the work is PULLED through die in drawing, whilst it is pushed through in extrusion. -usually performed as cold working
Wire and Bar(or rod) drawing
absolute: no accumulative positioning errors or tolerances between dimensions, faster programming & easier to debug incremental: errors accumulative in nature, preferred for CNC machines that take advanatge of macros and other subroutines.
absolute vs incremental positioning
least expensive, applicable to most metals, no size or shape limitation not very precise, surface and dimensional accuracy decrease, mold erosion common, labor cost.
advantages and disadvantages of sand casting
no filler metal required high production rates possible lower operator skill than AW low fumes good repeatability and reliability cost effective easy automation
advantages of RW
complex shapes; external and internal parts can have hollow sections or cavities very large or small parts near net shape different mold materials can be used different pouring methods ferrous and non-ferrous materials
advantages of casting
no heating good surface finish good dimensional control net or near net shape work hardening - increasing toughness of material directional properties
advantages of cold working (below recrystallisation temperature)
lower forces and power large change in shape isotropic properties: uniformity in all directions for low workability materials no work hardening
advantages of hot working (plastically deformed above recrystalisation temperature)
advantages reduces non productive and manufacturing time improves accuracy reduces inventory and human error disadvantages higher investment and maintenance cost, finding and/or training NC personnel
advantages vs disadvantages of CNC machining
advantages dimensional control good surface finish thin walls possible thousands of casting per die disadvantages expensive (die material & die making) non ferrous materils shapes limited by need to open die economic for large quantities
advantages vs disadvantages of die casting
advantages - environmentally clean, narrow heat affected zone, mass production disadvantages - one workpiece must have a rotatable axis of symmetry, high equipment and tooling costs, process turns grain direction 90 deg creating potential for preferential corrosion
advantages vs disadvantages of friction welding
advantages all types of metals, complex and intricate shapes possible, dimensional control (+- 0.0075 mm dimensional accuracy possible), wax recycling, good surface finish disadvantages relatively expensive, low volume, casting weight < 4.5 kg
advantages vs disadvantages of investment casting
advantages solid state process - no melting, join dissimilar material combinations, weld thin and thick materials disadvantages restricted to lap joint configuration, more difficult for high strength materials, material may deform under tooling.
advantages vs disadvantages of ultrasonic welding
induces and controls metal flow affects process success or failure
are of major significant of tool or die geometry
material strength decreases ductility increases rate of strain hardening decreases - promote ease of deformation
as temperature increases..
products assembled after customers order -key components stocked in anticipation i.e. carts, office furniture
assemble-to-order
casting and molding, machining, joining, and shearing and forming.
basic manufacturing processes
length of bend (arc length of the neutral line) determined using bend allowance Ab = bend allowance (length of neutral axis in bend) α = bend angle Kba = factor for estimate stretching t= stock thickness [mm] R= bend radius [mm]
bend allowance
F = bending force TS = tensile strength of sheet metal w = part width in direction of bend axis [mm] t = stock thickness [mm] D = die dimensions [mm]
bending force
reduce time to market whilst maintaining better quality and higher productivity
biggest challenge in manufacturing
sheet metal cutting along a closed outline to separate a part (called a blank), from surrounding stock
blanking
N20 G01 X10. Y40. F150 N21 X40. N22 G02 X60. Y 20. I0J-20. N23 G01Y-10.
centre point code
the centre of the arc is entered using I (x coordinate) and J (y coordinate)words.
centre point method CNC
- strength or resistance to deformation at deformation temperature and speed -initial strain -effects of temperature -reactions with various environments and lubricants
characteristics of material being deformed
less heating than HW lower force and power than cold working intermediate annealing often not needed more intricate geometries required usually applied to bulk deformations (forging, extrusion)
characteristics of warm working
discontinuous chip continuous chip continuous chip with BUE
chips in machining
assumed previous position in code known
circular interpolation
minimum dimension limit of hole > maximum dimension limit of shaft i.e. clearance between hole and shaft is positive
clearance fit
two or more bubbles, droplets or particles are merge together into one
coalescence
cutting speed (V), units: m/min feed rate (f): rate at which the tool advances along its cutting path, units: mm/rev, mm/min, mm/tooth depth of cut (d): thickness of the layer of material removed from workpiece surface
cutting parameters
drawing process where depth of formed product is greater than diameter otherwise called shallow drawing
deep drawing
process which objects by filling a mold cavity by gravity or pressure -expendable mold -multiple mold
definition of casting and two main types
single point cutting tool removes material from workpiece, performed by lathe
definition of turning
complex consequences of independent variables limited control by engineer
dependent variables in forming
design efficiency = 3 x NM/TM NM = estimation for theoretical minimum parts TM= operation time =handling time + insertion time -assumes assembly time for a part is 3 seconds
design efficiency
-parts easily separated from the bulk -parts easily orientable -non-geometric features avoided -reorientation during assembly avoided -all parts should fall into place automatically -chamfers, tapers etc added for self alignment of parts -top-down assembly preferred
design rules for high speed automated assembly
discontinuous forms from machining brittle work at low cutting speeds and and a large feed rate and depth of cut, high tool-chip friction continuous forms from ductile work at high cutting speeds and small feeds and depths of cut. low tool-chip fricition.
discontinuous vs. continuous chip
indicates the severity of drawing ratio Db = blank diameter Dp = punch diameter
drawing ratio
bench drill smaller, on floor. radial drill is large drill press designed for large parts
drill press vs radial drill
Vise -general purpose workholder with twojaws Fixture -workholding device that is usually custom-designed for the particular workpart Drill jig -similar to fixture but also provides a means of guiding the tool during drilling
drill work holding devices
for high production cantilever loading pressure pad required dies more complicated and costly
edge bending
products made after customers order with significant customisation i.e. customer-designed capital equipment - space vehicles
engineer-to-order
relative motion: during the operation of the product, does the part move relative to all the other parts already assembled? material difference: is the part of a different material to other parts already assembled need for assembly/disassembly: can the part be separated from all the parts already assembled because otherwise necessary assembly/disassembly if other parts would be impossible?
guidelines for estimation of ideal product
hot chamber: low melting point metals, high production rates (Mg, Zn, Sn, Pb) cold chamber: high melting point metals, lower production rates (Al, Cu, Mg)
hot chamber vs cold chamber die casting
Tw>Trecry in practice Tw >0.6Tm
hot working -> hot forming temperature
by a number of parameters: most commonly used is the arithmetic average
how can surface roughness be expressed
why in which heat is removed rate of nucleation and growth control size and shape of crystals faster cooling - finer grain size
how can the rate and type of grain be controlled?
S = shear strength of metal (MPa)≈0.7TS t = stock thickness (mm) L=length of cut edge(mm)
how can you calculate the cutting forces in blanking and planking?
jigs - guide the machine tools fixtures - holding workpiece in the proper position blocks & gauges - check accuracy of finished parts
how did the innovation of jigs,fixtures, blocks and gauges aid achievement of interchangeable parts?
pool of molten metal forms near electrode tip and as electrode is moved along the joint, weld pool solidifies in its wake
how does arc welding work
shielding gases: helium, argon, CO2 flux: substance that prevents formation of oxides and other contaminant in welding or dissolves them, facilitating removal
how is arc shielding accomplished in AW
PC = process capability (mm) S=magnitude of size dimension (mm) IT = standard tolerance grade number *** for drilling IT grade is 10 to 13
how is process capability calculated?
electrode is brought into contact with work and quickly separated by a short distance
how is the electric arc initiated
deep draw immediately after rolling 2% temper rolling (2% CW) just before drawing keep in cold storage after rolling
how to avoid stretcher strains in SMD
small - fracture lines pass each other, causing double burnishing & larger shearing force large - metal pinched between cutting edges and excessive burr (sharp corner on edge) occurs.
if clearance is too small or large, what happens respectively? (in shearing)
starting material starting geometry of workpiece tool or die geometry lubrication starting temperature speed of operation amount of deformation
independent variables in forming
-easy assembly for new devices -easier repair of existing devices -minimize time and skill for assembly or repair
interchangeability of interchangeable parts allows:
consists of machining parts of a given mechanism with such tolerances that any of the parts will properly function in any of the machines
interchangeable manufacture
assembly of block 1 and block 3 can be made by selecting any part from block 1 pile and any part from block 2 pile.
interchangeable manufacture example
-identical practical purposes -made to specifications so that they will fit into any assembly of the same type -one such part can freely replace another without custom fitting (such as filing)
interchangeable parts are:
maximum dimension limit of hole ≤ maximum dimension limit of shaft i.e. clearance is negative
interference fit
experience experiment modelling
links between independent and dependent variables
power saving - up to 50% power can be used to overcome friction coolants, thermal barriers, corrosion inhibitors, parting compounds
lubricant function in forming
applied to tool-work interface to reduce friction and tool wear, key to success in many metal forming operations
lubrication in metal working
welding cracks cavaties - porosity, shrinkage voids solid inclusions residual stresses shrinkage incomplete fusion incomplete penetration improper shape or contour
main defects in welds
- in SS temperature always below MP & no filler material is added
main differentiating factors between solid state and fusion welding
made after customers order - simple or custom variation of similar parts i.e. industrial punch presses, vehicle chassis
manufacture-to-order
making goods and services available to satisfy human needs
manufacturing is the economic term for
products are manufactured before customers order i.e. televisions, power hand tools, off-the-shelf items
manufcature-to-stock
cast iron, thermosetting polymers, ceramics,
materials that are not shaped by forming and why
provides details of recommended manufacturing process steps
operation planning sheet example
coining, hubbing, riveting
other squeezing processes
supply a product that maximises customer satisfaction at a minimum cost
overall objective of manufacturing
approximate duplicate of part to be cast made of: wood,
pattern
peripheral milling - cutter axis parallel to surface being machined, cutting edges on outside periphery of cutter face milling - cutter axis perpendicular to surface being machined, cutting edges on both end and outside periphery of cutter.
peripheral milling vs face milling
yield point phenomenon due to interstitial atoms (C, N, O) around local dislocations localised plastic deformation leads to stretcher strains
problems with plain low C steel in SMD
cold heading - upsetting eg: heads on bolts and screws roll forging -shaping in grooved rolls eg: axles, levers swaging and radial forging -shaping by hammering dies eg: shaped tubes, tapers, points
processes related to forging (summary)
high pressures- although little flow of metal (5 - 6 x strength of material) lubricants cannot be applied: can become entrapped in die cavities & prevent full reproduction of surface details & finish.
properties of coining process
die size determines blank size, Db punch size determines hole size, Dh
punch and die sizes in blanking and punching
both punching type operations slotting - cuts out an elongated or rectangular hole perforating - simultaneous punching of a pattern of holes in a sheet metal (usually for decorative purposes)
slotting and perforating
radius of the arc is entered using R word.
radial method
N20 G01 X10.Y40. N21X40. N22 G02 X60. Y 20.R20. N23 G01Y-10.
radius method code
machine reference points, reference return point, program reference point, work reference point
reference coordinates
roll bending roll forming
related operations to bending in SMF
repeatability: degree of consistency when one person uses measuring device to measure the same dimension multiple times reproducibility: degree of consistency when measuring device used by different people measure same dimension
repeatability vs reproducibility
resistance spot welding - fusion of faying surfaces of a lap joint achieved at one location by opposing electrodes - widely used in mass production, car has typically ~ 10 000 spot welds resistance seam welding - rotating wheel electrodes to produce a series of overlapping spot welds along a lap joint - can produce air tight joints, good for a gasoline tanks ect
resistance spot welding vs resistance seam welding
additional void in the mold that provides additional metal to compensate for shrinkage
riser
continuous form of 3-point bending where metal sheets, plates, pipes, extrusions etc., are formed into curved surfaces using forming rolls
roll bending
progressive bending of metal strip through series of forming rolls at high speed all bends parallel to each other, uniform cross section multiple shapes possible
roll forming
used for job shop to tell the material handler where to take the containers of parts after each operation is completed
route sheet example
t= metal thickness w = width of workpiece R = bend radius α = bend angle α'=included angle where α+α' = 180⁰
schematic of metal bending
1. Continuous casting to make slab 2. Flat hot rolling to make a plate 3. Flat rolling to make a sheet 4. Stretch forming to make a panel
select a sequence of manufacturing shaping processes to make a low C steel body panels for . a truck. Include both primary and secondary processes
N = 1000V/piD N= spindle RPM D= diameter of workpiece
selection of spindle speed
mechanical cutting of materials without the formation of chips or use or burning metal - two straight cutting blades
shearing (cutting) operations
plastic deformation around a curved axis cold forming solid bottom cylindrical or rectangular containers depth much greater than thickness
sheet metal drawing
consumable electrode consisting of filler a filler metal rod, coated with chemicals that provide flux and shielding
shielded metal arc welding (SMAW)
QForm 3D, LS-DYNA for Metal Forming, ANSYS, AutoDesk, DEFORM
simulation software packages
additional operations more expensive equipment a more skilled operator low production rates
smaller tolerances require
preventative techniques: melting in vacuum, or environment with low solubility gases, minimal turbulence vacuum degassing: removes gas from liquid before boring gas flushing: passing inert gases through liquid metal
solutions to gas porosity in casting
designing casting to have directional shrinkage - prevents cavities and voids.
solutions to solidification shrinkage in casting
speed sensitive materials may shatter or crack if impacted but will deform plastically when subjected to low speed loadings, whilst others stronger when deformed at high speed speed sensitivity greatest at elevated temp related to speed of operation and productivity
speed of deformation
required force for deformation lubricant effectiveness time for heat transfer speed of deformation (strain rate)
speed of operation has a direct influence on
1. pattern (make pattern in sand) 2. gating (create channels to feed in metal and let air out) 3. fill w/ metal 4. cool (as cools, metal contracts and can crack) 5. break mold
steps in sand casting
biaxial tension + compression simple unaxial tension
stresses in deep drawing
triaxial compression
stresses in extrusion
triaxial compression
stresses in forging
biaxial tension + biaxial compression
stresses in straight bending
biaxial compression, tension
stresses in wire and tube drawing
sheet of metal is stretched and wrapped around a form block (die) - deformation carried out via tensile stresses -lower bending forces, little springback and wrinkling
stretch forming
consumable bare wire electrode arc shielding by cover of granular flux, flux introduced into joint slightly ahead of arc by gravity from a hooper
submerged metal arc welding (SAW)
consists of short wavelengths, resulting from manufacturing method
surface roughness
technically used to describe the repetitive or random deviations from the nominal surface which forms three-dimensional surface topography
surface texture
increase in temperature decreases material strength, strain hardening rate increase in temperature increases ductility and ease of deformation at an elevated temperature, any deformation operation can be accomplished with lower forces and power
temperature effect on forming
chill zone, columnar zone, equiaxed zone
three cast structures
chemical reactions: molten metal and surroundings gas porosity: gas not rejected from liquid metal trapped upon solidification solidification shrinkage: volumetric contraction upon cooling, depends on coefficient of thermal expansion and amount of superheat
three casting issues
true centrifugal semi centrifugal centrifuge
three methods of centrifugal casting
forge welding (FOW) friction welding (FRW) ultrasonic welding (USW)
three types of solid state welding
proper clearance good alignment good condition of punch and die surfaces (no wear damage)
to obtain smooth cut edges in shearing it is necessary to have:
clearance is neither always positive nor always negative
transition fit
molten metal is poured into rotating mold to produce a tubular part
true centrifugal casting
K = strength coefficient n = strain hardening exponent
true stress strain curve
reduces hot tube wall thickness and diameter - tubes with thin walls and small diameters can be made. enhanced properties from strain hardening, good surface finish an precise dimensions
tube drawing (cold)
used for most ferrous alloys e.g. stainless steel tubes. brass and copper tubes are also often cold drawn,.
tube drawing examples
v-bending edge bending
two common types of bending methods
solid state welding: application of pressure alone or a combination of heat to cause diffusion at joint, causing parts to fuse together fusion welding: heat applied to create molten material at joint, which fuses parts together upon solidification.
two main joining processes and their difference
nucleation: stale particles form from the liquid metal which occurs when there is a net release of energy grain growth: occurs when the heat of fusion is extracted from liquid
two main types of solidification process and definitions
inner diameter not controlled→small diameter, long length inner diameter controlled by plug( or mandrel)
two tube drawing methods
upset, elongation, squeeze
types of elongation in forging (summary)
open die, impression (closed) die, flashless die
types of forging dies (summary)
impact (drop hammer) gradual pressure (press)
types of forging forces (summary)
bending, shearing, drawing (includes stretching)
types of sheet metal forming
engine crankshafts and connecting rods, gears, aircraft structural components, jet engine turbine parts
typical components made by forging
automobile and truck bodies, airplanes, railway car, various applications, office furniture
typical sheet metal forming applications
coalescence by ultrasonic oscillating motion in a direction parallel to contacting surfaces of two parts held together under pressure welds almost every material but is typically limited to small lap joint welds of thin materials
ultrasonic welding (USW)
general description (eg. close running fit) minimum and maximum clearance (Cmin, Cmax) mean fit and variation (MF±VAR) specification (eg. H7f7)
usual specifications of fits
manual assembly: simple tools, economic small lots high speed automated assembly: utilizes transfer mechanisms designed specifically for assembly robot assembly: one or two general purpose robots operate at a single workstation or the robots operate at a multi-station assembly
what are the basic methods of assembly
reduced forces and power better surface finish, corrosion protection thermal barrier and heat removal from tooling increased forming efficiency
what are the benefits of lubrication
open die drop-hammer forging impression-die drop-hammer forging; flashless forging press forging upset forging; automatic hot forging, cold heading roll forging swaging
what are the common forging processes?
high forces required to deform materials machinery and tooling expensive most economical for large properties
what are the disadvanatges of forming
route sheet and operation planning sheet
what are the documents in process planning that specify the process sequence through job shop?
submerged arc welding (SAW) shielded metal arc welding (SMAW) gas metal arc welding (GMAW) gas tungsten arc welding (GTAW) flux core arc welding (FCAW)
what are the five types of arc welding?
permeability: sand porosity allows gases and steam to escape mold strength: resists breaking, easy removal of casting refractoriness: resists high temperatures without fusing grain size and shape: effects surface finish and angularity provides bonding strength
what are the four basic properties of sand
acetylene, hydrogen, propylene and propane
what are the four common fuels used in OFW
performed manually disassembly of welded joints is not convenient often have defects ultraviolet radiation emitted in AW sparks, splatters of molten metal, smoke and fumes pose heath risks
what are the limitations/ drawbacks of welding
parts to be welded two opposing electrodes means of applying pressure power supply (which a controlled current can be applied)
what are the main components in resistance welding
reduced control of heat into the weld zone performed manually hence dependent on skill of welder
what are the main limitations of OFW
shearing blanking, piercing, notching and trimming
what are the processes called when the cutting blades are straight and curved, respectively
clearance fit interference fit transition fit
what are the three classifications of fits
short range: machine loading, job assignments <2 months intermediate range: employment, output, inventory - 2 months to a year long range: what products to manufacture, facility location and size
what are the three levels in aggregate planning
bilateral tolerances: -equal (10±05) -unequal(10+0.7/-0.3) unlimited tolerances (10.5+0/-1) limit of size (9.5,10.5)
what are the three methods used for tolerance specifications?
1. demand for products and services 2. availability or need for manpower 3. inventory and material needs daily
what are the three things forecasted in PP
consumable - electrode consumed, source of filler metal in process. non consumable - filler metal must be supplied
what are the two basic types of AW electrodes
resistance spot welding (RSW) resistance seam welding (RSEW)
what are the two principle RW processes
stylus tracing, optical microscopy, light scattering, electron microscopy
what are used to examine surface roughness
interruptions in either weld or base metal adjacent to weld - significantly reduces strength caused by embrittlement or low ductility of weld and/or base metal combined with high restraint during contraction MUST be repaired
what are welding cracks and what are they caused by
provide basic needs for keeping inventory levels low and fulfilling customers expectations for on time delivery
what can a good material requirements planning (MRP) program do
material, tool geometry, lubricant, speed of operation, starting temp direct relationships to independent variables unknown
what do force and power requirements depend on
people, money, equipment, materials, suppliers, markets, management, manufacturing system, aspects of commerce
what do production systems include
computer numerical control
what does CNC stand for
1. 0.33 2. 0.50
what does Kba equal to 1. if R<2t 2. if R>=2t
v-bending - 1.33 edge bending - 0.33
what does Kbf equal to for V-bending and edge bening
greater strain hardening for a given plastic strain
what does a larger n value mean
- creates schedules identifying specific parts and materials required to produce end items - determines exact numbers needed -determines the dates when orders for those materials should be released, based on lead
what does a material requirements planning system do?
overall framework by integrating demands of marketplace through forecasting based on manufacturing capacity.
what does aggregate planning provide?
opposite to ductility, break under tensile stress a material is brittle if, when subjected to stress, it breaks without significant plastic deformation. i.e. cast iron, ceramics
what does it mean for a material to be brittle
-making good use of manufacturing resources -making customer delivery products -resolving trade-offs between buy and/or manufacture -attaining strategic objectives in the sales and operations plan
what does master production schedule provide a basis for?
-interpretation of design drawings -processes and sequences -equipment selection -tools,dies,moulds, fixtures and gages -method analysis -work standard -cutting tool and cutting conditions
what does process planning encompass?