Precision Machining


1. Introduction to Precision
Engineering and Precision
machining


What 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.


What is Precision Engineering?
• The Precision Engineering focuses on many areas:
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research,
design,
development,
manufacture and measurement of high accuracy

components and systems.

precision controls, metrology, interferometry, materials,
materials
processing,
nanotechnology,
optical
fabrication, precision optics, precision replication,
scanning microscopes, semiconductor processing,
standards and ultra-precision machining.


What is Precision Engineering?
• The precision engineering toolbox
includes:
– design methodology,
– error budgeting,
– Uncertainity analysis,
– metrology,
– calibration/error compensation,
– precision controls and actuators and
sensors.


Why Precision Engineering?
• Improve Product Performance
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Accuracy
Reliability
Improved Life
Safety

• Increase Manufacturability
– Automatic Assembly

• Lower Costs
– Circuit Integration

• Advance Science And Technology


Precision 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.



Precision 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.


Precision 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:
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structural loop components
bearing behavior

driving system
guiding elements
probing systems


Precision 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


Design 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!


Design 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


Relation between Machining Accuracy Factors


The 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


The 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


Developmental perspective of machining
precision



Four classes of achievable machining accuracy


Four classes of achievable machining accuracy


Four classes of achievable machining accuracy


Normal 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.


Normal Machining


Precision Machining
• Machining integrated circuit chips on a
CNC Milling Machine

The grinding of a silicon wafer (Integrated Circuit Chips) using a CNC milling
machine is a precision machining process. Figures shows an IC silicon chip
before and after grinding it on a MAHO CNC vertical milling machine



Precision Machining
• 006>ABA!"'=A'

The grinding of a silicon wafer (Integrated Circuit Chips) using a CNC milling
machine is a precision machining process.


High-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


High-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 die
substrate 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.