Precision Engineering is defined as painstaking attention to detail and requires knowledge of a wide variety of measurement, fabrication, and control issues. Increasing the precisionthe accuracy and repeatability of a mechanism or process is critical to our countrys Competitive position in the world of high technology.
Trang 1Precision Machining
Trang 21 Introduction to Precision Engineering and Precision
machining
Trang 3What is Precision Engineering?
• Precision Engineering is defined as painstaking attention to detail and requires knowledge of a wide variety of measurement, fabrication, and control issues.
• Increasing the precision the accuracy and
repeatability of a mechanism or process is critical to our country's Competitive position
in the world of high technology.
Trang 4What is Precision Engineering?
• The Precision Engineering focuses on many areas:
– research,
– design,
– development,
– manufacture and measurement of high accuracy
components and systems.
* precision controls, metrology, interferometry, materials,
fabrication, precision optics, precision replication, scanning microscopes, semiconductor processing, standards and ultra-precision machining.
Trang 5What is Precision Engineering?
• The precision engineering toolbox
Trang 6Why Precision Engineering?
• Improve Product Performance
Trang 7Precision Engineering
• Design and Production Systems
– Lifecycle engineering, Product & process modeling, Design
theory, CAD/CAM/CAE, Rapid prototyping, Automated &
intelligent systems, Production management, MES, CIM, etc.
• Precision Machining
– Cutting, Abrasive machining, Planarization (CMP etc),
Micromachining, EDM, Energy beam machining, Injection molding, Deposition (PVD, CVD), Nanomachining, etc.
• Mechatronics
– Micromachines, Intelligent robots, Information instruments,
Precision positioning, Machine tool & tooling, Intelligent
control, Mechanism & mechanical elements, etc.
Trang 8Precision Engineering
• Metrology
– Image processing, Optronics, 3D shape measurement,
Surface & roughness measurement, Intelligent data analysis, SPM, Inprocess measurement, Surface and Microform Metrology, Nanoscale Metrology, etc.
• Humans and Environment
– Human engineering, Welfare engineering, Biomedical
precision engineering, Biomedical measurement,
Environmental machine & ecomachining, Amusement machine, Techno-history, Human skill, etc.
Trang 9Precision Engineering
• It includes the analysis and design of components
as well as machines and instruments.
• The analysis of components includes modeling,
simulation and prototype behavior Elements of research are:
– structural loop components
– bearing behavior
– driving system
– guiding elements
– probing systems
Trang 10Precision Engineering
• Important research activities are:
– structural loop design including materials
– thermal loop design
– static behavior analysis (FEM)
– dynamic analysis and simulation of machine
elements and electro-mechanical servo systems
– design and validation of precision machinery
prototypes:
• single point diamond turning machines
• high precision measuring machines
• high precision probing systems
Trang 11Design Process
Follow a design process to develop an idea in steps from
•First Step: Evaluate the resources that are available
•Second Step: Carefully study the problem and make sure you
have a clear understanding of what needs to be done and what are the constraints (rules, limits)
– Steps 1 & 2 are often interchangeable
•Third Step: Start by creating possible strategies using words,
analysis, and simple diagrams
– Imagine possible motions, data flows, and energy flows from start to finish
or from finish back to start!
– Continually ask “Who?”, “What?”, “Why?”, “Where”, “How?”
– Simple exploratory analysis and experiments can be most enlightening! – Whatever you think of, others will too, so think about how to defeat that
about which you think!
Trang 12Design Process
• Fourth Step: Create concepts to implement the best strategies,
using words, analysis, and sketches
– Use same methods as for strategies, but now start to sketch
ideas
– Often simple experiments or analysis are done to investigate
effectiveness or feasibility
– Select and detail the best concept…
• Fifth Step: Develop modules, using words, analysis, sketches,
and solid models
• Sixth step: Develop components, using words, detailed analysis,
sketches, and solid models
• Seventh Step: Detailed engineering & manufacturing review
• Eighth Step: Detailed drawings
• Ninth Step: Build, test, modify…
• Tenth Step: Fully document
Trang 13Relation between Machining Accuracy Factors
Trang 14The need for having a high precision
• For achieving a higher precision in the manufacture of a part using precision engineering, Nakazawa [1] and
McKeown [3] have summarized some objectives and these are to:
– 1 Create a highly precise movement
– 2 Reduce the dispersion of the product’s or part’s function
– 3 Eliminate fitting and promote assembly especially automatic assembly
– 4 Reduce the initial cost
– 5 Reduce the running cost
– 6 Extend the life span
– 7 Enable the design safety factor to be lowered
Trang 15The need for having a high precision
– 8 Improve interchangeability of components so that
corresponding parts made by other factories or firms can be used in their place
– 9 Improve quality control through higher machine accuracy capabilities and hence reduce
– scrap, rework, and conventional inspection
– 10 Achieve a greater wear/fatigue life of components
– 11 Make functions independent of one another
– 12 Achieve greater miniaturization and packing densities
– 13 Achieve further advances in technology and the underlying sciences
Trang 16Developmental perspective of machining
precision
Trang 17Four classes of achievable machining accuracy
Trang 20Normal Machining
• In this class of machining, the conventional engine lathe and milling machines are the most appropriate machine tools that can be used to manufacture products such as gears and screw threads to an accuracy of, for example, 50 μm.
Trang 21Normal Machining
Trang 23Precision Machining
• 006>ABA!"'=A'
The grinding of a silicon wafer (Integrated Circuit Chips) using a CNC milling machine is a precision machining process
Trang 24High-Precision Machining
• High-precision CNC diamond turning machines are
available for diamond mirror machining of components such as [3]:
• (a) Computer magnetic memory disc substrates
• (b) Convex mirrors for high output carbon dioxide laser resonators
• (c) Spherical bearing surfaces made of beryllium, copper, etc.
• (d) Infrared lenses made of germanium for thermal
imaging systems
• (e) Scanners for laser printers
• (f) X-ray mirror substrates
Trang 25High-Precision Machining
Both lapping and polishing are considered to be high-precision machining operations Although the grinding of an IC silicon die discussed earlier falls under Taniguchi’s second class of machining-precision machining, the
machining of the PCB of the IC after completely removing the silicon diesubstrate essentially falls under high-precision machining This operation tends to expose the transistors in the layers of the PCB Figure depicts a typical high-precision machined PCB in which transistors in a layer are exposed
Trang 26High-Precision Machining
Polishing of hard and brittle materials such
as silicon wafers on a three-axis polishing
machine
An LP600 precision Lapping and Polishing Machine
Trang 27Ultra-Precision Machining
• Taniguchi [5] has referred to “ultra-precision machining”
as a process by which the highest possible dimensional accuracy is or has been achieved at a given point in
time Also, it is referred to as the achievement of
dimensional tolerances of the order of 0.01 μm and a
surface roughness of 0.001 μm (1 nm) The dimensions
of the parts or elements of the parts produced may be as small as 1 μm, and the resolution and the repeatability of the machine used must be of the order of 0.01 μm (10 nm).
Trang 28Ultra-Precision Machining
The accuracy targets for ultra-precision machining cannot be achieved by a simple extension of conventional machining processes and techniques The Figure shows the dimensions of an integrated circuit (IC) specified to 0.1 μm and indicates the requirement for ultra-precision machining accuracy capability of the order of 0.005 μm (5 nm)
Trang 29Ultra-Precision Machining
Nanoform 200 (Figure 1.25) has viable features for carrying out ultra-precision
work The machine has a high performance, ultra-precision machining system designed for the most demanding aspherical turning and grinding applications It has a swing diameter capacity of 700 mm and can be utilized for single-point diamond turning and peripheral grinding
Trang 30Ultra-Precision Machining
• The most noteworthy developments in processes capable of providing ultra-precision are as follows :
• (a) Single-point diamond and cubic boron nitride (CBN) cutting
• (b) Multi-point abrasive cutting/burnishing, for example, in diamond and CBN grinding, honing, etc.
• (c) Free abrasive (erosion) processes such as lapping, polishing, elastic-emission
machining and selective chemico-mechanical polishing
• (d) Chemical (corrosion) processes such as controlled etch machining
• (e) Energy beam processes (removal, deformation and accretion) including those given below:
– (i) Photon (laser) beam for cutting, drilling transformation hardening and hard coating
– (ii) Electron beam for lithography, welding
– (iii) Electrolytic jet machining for smoothing and profiling
– (iv) Electro-discharge (current) beam (EDM) for profiling
– (v) Electrochemical (current) (ECM) for profiling
– (vi) Inert ion beam for milling (erosion) micro profiling
– (vii) Reactive ion beam (etching)
– (viii) Epitaxial crystal growth by molecular-bit accretion for manufacturing new super-lattice crystals, etc.
Trang 31Review questions
• 1.1 Explain with sketches the difference between accuracy and precision.
• 1.2 (a) Discuss the achievable machining accuracy for normal, precision, high-precision and ultra-precision machining
• (b) Highlight some mechanical, electronic, and optical components, their tolerances and their machining aspects
• (c) Describe with sketches one component from each one of the above categories
• 1.3 Figure on page 16 shows the development of overall machining
precision starting from the early 1900s State the machining accuracy achieved in 2000 for:
• (a) Normal machining
• (b) Precision machining
• (c) High-precision machining
• (d) Ultra-precision machining