1、1Advanced Manufacturing Technology先进制造技术施平Part 52Contents 1.Introduction to AMT 2.Computer and communication 3.Computer-aided engineering 4.Automation 5.Modern manufacturing technologies35.Modern manufacturing technologies Basic theory and modern technology Technological change in manufacturing engi
2、neering is phenomenal and speeding Basic theories(like metal cutting theory)are the foundation of the sophisticated technologies45.Modern manufacturing technologies Precision engineering Quality improvements of products requires the enhancement of precision of production system5.1 Modern manufacturi
3、ng technologies-Precision engineering55.Modern manufacturing technologies Basic definitions Accuracy A quantitative measure of the degree of conformance to recognized national or international standards of measurement Repeatability A measure of the ability of a machine to position a tool sequentiall
4、y with respect to workpiece under similar conditions Resolution The least increment of a measuring device The least significant bit on a digital machine5.1 Modern manufacturing technologies-Precision engineering65.Modern manufacturing technologies Motion Slide Spindle Rigid element We treat individu
5、al element as rigid body Flexible structure The whole structure may be flexible due to deflections and joints5.2 Modern manufacturing technologies-Precision engineering75.Modern manufacturing technologiesRigid body motion and errorThe slide 5 constraints(Y,Z movement along Y,Z,rotation about X,Y,Z)1
6、 DOF(movement along X)We control X,while treating the other 5 DOFs as errors5.2 Modern manufacturing technologies-Precision engineering85.Modern manufacturing technologies Categories of sources of errors of a machine tool Geometric errors Caused by lack of straightness in slide-ways,static deflectio
7、n of machine tool,angular errors Dynamic errors Caused by machine tool vibration(chatter)Inherent frequency(avoid the 1st,2nd,)and resonance Stiff,light weight,well-damped machine tool has less dynamic error Work-piece effects Machine tool deflection caused by fixing and cutting forces during cuttin
8、g process Inertial effects due to motion:over-shoot on a linear motion;periodic deviations caused by dynamic unbalance due to part asymmetry about rotational axis(like the spindle axis)Thermal errors Expansion when heated,contraction when cooled Temperature control:air-condition,warming-up time befo
9、re operation5.2 Modern manufacturing technologies-Precision engineeringPerfect machine without errors does not existAll machine tools have geometric errors95.Modern manufacturing technologies Traditional finishing operations Honing Hole surface processing Radially floating,axially reciprocating move
10、ment5.3 Modern manufacturing technologies-finishing operation105.Modern manufacturing technologies Traditional finishing operations Super-finishing Pressure force very light Stone stroke very short5.3 Modern manufacturing technologies-finishing operation115.Modern manufacturing technologies Traditio
11、nal finishing operations Lapping Abrasive particles in a slurry Surface finish 0.0250.1m Polishing Non-traditional finishing operation Chemical mechanical polishing A chemical reaction occurred(example:silicon wafer polishing)Electro-polishing Electrolyte attacks the projections and peaks on the wor
12、k-piece surface to get a fine surface Polishing process using magnetic fields5.3 Modern manufacturing technologies-finishing operation125.Modern manufacturing technologiesAim of Coated tools To cope with the unique properties of new materials High srength,Toughness,Chemical propertiesCoating materia
13、l General characteristics High hardness Chemical stability and inertness to the work-piece material Low thermal conductivity Good bonding to the substrate to prevent flaking Little or no porosity commonly used coating materials TiN,titanium nitride:low friction coefficient,high hardness,resistance t
14、o high temperature,good adhesion to substrate.Performs well at higher cutting speed TiC titanium carbide:similar properties TiCN titanium carbonitride:good wear resistance when cutting carbon steel,alloy steel,cast iron Al2O3 Aluminum Oxide:low thermal conductivity,high hot hardness,wear resistance5
15、.3 Modern manufacturing technologies-coated tools135.Modern manufacturing technologies Substrate material HSS,high speed steel Cemented carbide Ceramic Super-hard material Coating process CVD,chemical vapor deposition Chemical Vapor Deposition is chemical reactions which transform gaseous molecules,
16、called precursor,into a solid material,in the form of thin film or powder,on the surface of a substrate In a typical CVD process,the wafer(substrate)is exposed to one or more volatile precursors,which react and/or decompose on the substrate surface to produce the desired deposit.Frequently,volatile
17、by-products are also produced,which are removed by gas flow through the reaction chamber5.3 Modern manufacturing technologies-coated tools145.Modern manufacturing technologiesPVD,physical vapor deposition a variety of vacuum deposition and is a general term used to describe any of a variety of metho
18、ds to deposit thin films by the condensation of a vaporized form of the material onto various surfaces.The coating method involves purely physical processes such as high temperature vacuum evaporation or plasma sputter bombardment rather than involving a chemical reaction at the surface to be coated
19、 as in chemical vapor deposition 5.3 Modern manufacturing technologies-coated toolscomputer simulation of the basic physical process underlying physical vapour deposition:a single Cu atom deposited on a Cu surface 155.Modern manufacturing technologies Lubricating coating material A coating to enhanc
20、e lubrication in cutting(especially in dry cutting)Coating material MoS2(molybdenum disulfide)Multilayer coating To get a combined property of the cutting tool CVD+PVD TiN+MoS2 Diamond-coated tool Diamond:super hard,ideal material for machining abrasive,nonferrous metals and nonmetallic composites5.
21、3 Modern manufacturing technologies-coated tools165.Modern manufacturing technologies Factors lead to tool failures Extreme heat(cutting edge temperature exceeds 1000)Degrades binders and other tool constituents Triggers detrimental chemical reactions between tool and work-piece High pressure Abrasi
22、on Shock thermal shock mechanical shockBasic failure mechanisms Crater wear Thermal deformation and cracking Nose wear Built-up edge Fracture Flank wear5.4 Modern manufacturing technologies-failure mechanism of cutting tools175.Modern manufacturing technologies High speed machine High spindle speed
23、and feed speed Spindle speed exceeds 10,000 rpm Benefit of HSM Improved performance and product quality(such as finer finish)Reduced production time,lower cost Factors hinders high speed Weight of mobile component Overshoot,tip-up of machine Center of gravity Lower center of gravity can reduce probl
24、em like tip-up of machine Rigidity,stability Key to HSM Axis drive Linear motor is more rigid than ballscrew,gearbox,etc.Accuracy Machine configuration Machine programming,training and maintenance5.5 Modern manufacturing technologies-high speed machining185.Modern manufacturing technologies Hardness
25、 of material Defined by its resistance to permanent deformation Its the combination of elastic and plastic property that determine a materials resistance to permanent deformation 555HRC65HRC Tensile strength up to 2400MPa Hard turning Small depth of cut and feed though,much faster than grinding rigi
26、d machine tool,and harder tools(Ceramic or CBN,or cubic Boron Nitride)makes hard turning possible Problems to be redress Workpiece microstructure influenced(residual stress and over-hardened)Tool wear and workpiece surface quality Hard milling Takes over the work of machining 4564 HRC tool steel by
27、EDM(electrical discharge machining)Machine tool(similar requirement to HSM)and cutting tool(coated tool with TiCN,TiAlN,with good wear,heat resistance,hardness)5.6 Modern manufacturing technologies-hard part machining195.Modern manufacturing technologies Presentations topics(Each group 48 students)P
28、recision machining Dry or near-dry machining Creep-feed grinding Machining of engineering ceramics5.6 Modern manufacturing technologies205.Modern manufacturing technologies Cryogenic processing Heat treatment a method used to alter the physical,and sometimes chemical properties of a material.The mos
29、t common application is metallurgical.also used in the manufacture of many other materials,such as glass.215.Modern manufacturing technologies Heat treatment Heat treatment involves the use of heating or chilling,normally to extreme temperatures,to achieve a desired result such as hardening or softe
30、ning of a material.Intentionally:heat treatment applies to processes where the heating and cooling are done for the specific purpose of altering properties Incidentally:heating and cooling often occur during other manufacturing processes such as hot forming or welding.225.Modern manufacturing techno
31、logies Common Heat treatment Annealing:退火 a technique used to recover cold work（冷作）and relax stresses within a metal Quenching（Hardening and tempering)To harden by quenching,a metal(usually steel or cast iron)must be heated into the austenitic crystal phase and then quickly cooled.235.Modern manufac
32、turing technologies Common Heat treatment Tempering.Untempered martensite,while very hard,is too brittle to be useful for most applications.Most applications require that quenched parts be tempered(heat treated at a low temperature,often 150 C)to impart some toughness.245.Modern manufacturing techno
33、logies Common Heat treatment Selective hardening allow different areas of a single object to receive different heat treatments.also called differential hardening.Commonly used in high quality knives and swords treatment.The Chinese“jian”is one of the earliest known examples255.Modern manufacturing t
34、echnologies Cryogenic processing Cryogenics The branches of physics and engineering that involve the study of very low temperatures,how to produce them,and how materials behave at those temperatures.265.Modern manufacturing technologies Cryogenic processing Cryogenic processing Cryogenic processing
35、is not a substitute for heat treatment,but rather an extension of the heating-quenching-tempering cycle.275.Modern manufacturing technologies Feature of manufacturing in aerospace industry Low volume High reliability,precision requirements Material with high strength,light weight,difficult to machin
36、e Stainless steel(for high wear area)Titanium,high-nickel steel alloy(Good property at elevated temperature,for critical load-bearing component,like engine)Aluminum(for structural component)Alloy steel(for high strength,high impact application,like landing gear)Challenges of machining of titanium al
37、loy Work hardening:Ti alloy can be work hardened Sharp cutting edge,small feed and depth of each cut,Use rigid machine tool,avoiding chatter to get good finish Deflection:Ti has a low modulus of elasticity Reactivity:Ti is more reactive to toolManufacturing for aerospace industry285.Modern manufactu
38、ring technologies Large part handling Difficulties Flex and warp Manufacturing and assembly a radar cover of a surveillance plane Expansion and contraction Keep in constant temperature environment Put a compensation factor into cutting program5.7 Modern manufacturing technologies-Manufacturing for a
39、erospace industryRadar cover295.Modern manufacturing technologies Large workpiece and assembly measurement GPS,global positioning system GPS is the only fully functional Global Navigation Satellite System(GNSS).The GPS uses a constellation of between 24 and 32 Medium Earth Orbit satellites that tran
40、smit precise microwave signals,that enable GPS receivers to determine their location,speed,direction,and time.(19,300km high)Indoor GPS 3 or more infrared transmitters Detector,or receiver5.7 Modern manufacturing technologies-Manufacturing for aerospace industry305.Modern manufacturing technologies
41、EDM and laser EDM can make irregular holes and 0.1mm small holes,with aspect ratio 10:1 Laser welding 8m5m Laser hole-making 1.3m Nanotechnology refers to a field of applied science whose theme is the control of matter on an atomic and molecular scale.Generally nanotechnology is approximately 100 nanometers or smaller and involves developing materials or devices within that size5.8 Modern manufacturing technologies-Micro-ManufacturingLaser applicationVideo nanotech
