Advanced Manufacturing Choices

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Advanced Manufacturing Choices

• MAE 195-MAE 165
• Spring 2009, Dr. Marc Madou
• Class 2

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Table of Content

• Manufacturing types Primary, secondary and
  tertiary manufacturing
• Mechanical machining definition
• Recognized categories of mechanical machining
  turning, milling, drilling and grinding.
• CNC machining
• Precision machining
• Ultraprecision and nanotechnology
• Desk top factory (DTF)

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Manufacturing Types

• Manufacturing dominates world trade. It is the
  main wealth creating activity of all
  industrialized nations and many developing
  nations. A manufacturing industry based on
  advanced technologies with the capability of
  competing in world markets can ensure a higher
  standard of living for an industrial nation
  (McKeown, 1996).
• Where primary manufacturing processes involve
  casting and molding, secondary manufacturing
  processes constitute the main mechanical removing
  techniques involving turning, drilling and
  milling. Abrasive processes to super-finish a
  work-piece are called tertiary manufacturing
  processes. Casting/molding The act or process
  of making casts or impressions, or of shaping
  metal or plaster in a mold the act or the
  process of pouring molten metal into a mold.

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Manufacturing Types

• The difference between casting and molding is
  that in "traditional" casting processes, the mold
  is destroyed/ consumed when removing the
  work-piece from it while in molding, the mold is
  re-used multiple times(this difference is not
  often respected in naming different processes).
• Lost wax casting process see video
• Sand casting see utube

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Mechanical Machining

• In mechanical removal processes, stresses induced
  by a tool overcome the strength of the material.
• The process produces complex 3D shapes, with very
  good dimensional control, and good surface
  finishes.
• The method is wasteful of material, and expensive
  in terms of labor and capital.
• How well a part made from a given material holds
  its shape with time and stress is referred to as
  the dimensional stability of the part and the
  material.

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Mechanical Machining

• To maximize dimensional stability, the machine
  design engineer tries to minimize the ratios of
  applied and residual stress to yield strength of
  the material.
• A good rule of thumb is to keep the static stress
  below 10 to 20 of yield strength.
• Increased heat at the work-piece causes uneven
  dimensional changes in the part being machined,
  making it difficult to control its dimensional
  accuracy and tolerances. Thermal errors are often
  the dominant type of error in a precision
  machine, and thermal characteristics such as
  thermal expansion coefficient and thermal
  conductivity deserve special attention .

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Mechanical Machining

• In mechanical subtractive machining, physical
  removal of unwanted material is achieved by
  mechanical energy applied at the work piece.
• Mechanical material removing technologies are
  also categorized as single point machining or
  abrasive machining I.e., multi-point machining).
• Mechanical removal processes can be broken down
  into four commonly recognized categories
  turning, milling, drilling and grinding.

First lathe as depicted in an Egyptian bas
relief about 300 B.C. Shown here in a line
drawing. The man at left is holding the cutting
tool. The man at the right is making the
workpiece rotate back and forth by pulling on a
cord or thong.
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Mechanical Energy Based Removing

• What is milling? The use of a rotating
  multi-point cutting tool to machine flat
  surfaces, slots, or internal recesses into a
  work-piece.
• Milling is one of the more versatile machining
  processes. There are three degrees of freedom
  associated with milling. The tool can move up and
  down, left to right, and front to back. In this
  process the tool spins while the part remains
  stationary. Although milling is a more versatile
  process than turning or grinding, it is not as
  accurate and tends to leave a rougher surface
  finish than the other two processes.
• What is turning ? Turning is the machining
  operation that produces cylindrical parts. In its
  basic form, it can be defined as the machining of
  an external surface with the work-piece rotating
  and with a single-point cutting tool.

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Mechanical Energy Based Removing

• The main difference between turning and milling
  is that in turning the work-piece spins while the
  tool remains stationary. Because of this, turning
  can be used to create a great surface finish on
  cylindrical parts.
• Turning is done on a machine called a lathe. The
  lathe spins the workpiece, while the lathe
  operator can position the tool to remove the
  material. The work-piece is held in the chucks of
  the lathe.

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Mechanical Energy Based Removing

• Drilling can be defined as a rotary end cutting
  tool having one or more cutting lips, and having
  one or more helical or straight flutes for the
  passage of chips and the admission of a cutting
  fluid.

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Mechanical Energy Based Removing

• Grinding is a finishing process that is used to
  remove surplus material from the work-piece
  surface. It is usually used on almost any
  surface that has been previously rough machined
  and is among the most expensive process for it is
  generally quite slow in removing material.

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Mechanical Energy Based Removing

• By 1977, highly precise instruments such as
  servomotors, feedback devices, and computers were
  implemented, paving the way for computer
  numerical control machining, commonly called CNC
  machining, which is now standard in many types of
  machine shops. At the start, the smallest
  movement these machines could reproducibly make
  was 0.5 µm.
• The resolution of the steps a machine can make,
  of course, is a determining factor for the
  manufacturing accuracy of the work-piece.
• Numerical control is a method of automatically
  operating a manufacturing machine based on a
  code of letters, numbers, and special characters.

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Mechanical Energy Based Removing

• Point-to-point control systems cause the tool to
  move to a point on the part and execute an
  operation at that point only. The tool is not in
  continuous contact with the part while it is
  moving.
• Continuous-path controllers cause the tool to
  maintain continuous contact with the part as the
  tool cuts a contour shape.

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Mechanical Energy Based Removing

• These continuous operations include milling along
  any lines at any angle, milling arcs and lathe
  turning.

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Mechanical Energy Based Removing

• CNC machines milling machines can perform
  simultaneous linear motion along the three axis
  and are called three-axes machines.
• More complex CNC machines have the capability of
  executing additional rotary motions (4th and 5th
  axes).

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Mechanical Energy Based Removing

• Machining Centers, equipped with automatic tool
  changers, are capable of changing 90 or more
  tools. Can perform milling, drilling,boring
  turning, on many faces. Boring is the process
  of using a single-point tool to enlarge a
  preexisting hole.
• Process flow
• Develop or obtain the 3D geometric model of the
  part, using CAD.
• Decide which machining operations and cutter-path
  directions are required (computer assisted).
• Choose the tooling required (computer assisted).
• Run CAM software to generate the CNC part
  program.
• Verify and edit program.
• Download the part program to the appropriate
  machine.
• Verify the program on the actual machine and edit
  if necessary.Run the program and produce the
  part.

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Mechanical Energy Based Removing

• In an integrated CAD/CAM system, the geometry and
  tool motions are derived automatically from the
  CAD database by the NC program (Pro/E,
  Unigraphics, .)

CNC milling is a cutting process in which
material is removed from a block of material by
a rotating tool using computer numerically
controlled program or code to achieve a desired
tool path to machine very accurate parts
precisely and efficiently. 
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Precision Machining

• Mechanical engineers define precision machining
  as machining in which the relative accuracy
  (tolerance/object size) is 104 or less of a
  feature/part size
• For comparison, a relative accuracy of 103 in
  the construction of a house is considered
  excellent. It is important to realize that, while
  IC techniques and silicon micro- and
  nano-machining can achieve excellent absolute
  tolerances, relative tolerances here are rather
  poor compared to those achieved by most
  mechanical machining techniques.
• The decrease in manufacturing accuracy with
  decreasing size is rarely mentioned in
  discussions of Si micro-machines this probably
  is because Si micromachining originated from
  electrical engineering practice rather than
  mechanical engineering.

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Precision Machining

• In the 1980s advanced machine tools became
  equipped with precision metrology and control
  tools. These machines used laser interferometer
  and capacitance probe feedback controls,
  temperature control and hydrostatic bearings, and
  featured accuracies better than 0.1 micrometers.
  Precision manufacturing methods were extended for
  industrial use for cutting aluminum, which was
  used for making components for scanners,
  photocopying machines and computer memory disks.
  Also in the 1980s, cutting with very small
  diamond tools (e.g., 22 µm diameter) was
  developed in Japan.

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Ultra Precision Machining-Nanotechnology

• Taniguchi coined the term nanotechnology and in
  1974, used the term to define ultra-precision
  machining.
• Taniguchi defines ultra-precision machining as
  the process by which the highest possible
  dimensional accuracy is achieved at a given point
  in time.
• See Norio Taniguchi predicted accuracies along
  with the processes or tools used to achieve it
  (next page)

Norio Taniguchi (????) (27 May 1912 - 15 November
1999) was a professor of Tokyo Science
University.
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Precision and ultra-precision machining
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Ultra Precision Machining-Nanotechnology

• By 1993, 0.05 µm became possible, and today there
  is equipment available featuring 0.01 µm and even
  nanometer step resolution 10 (http//www.fanuc.co.
  jp/eindex.htm).
• This evolution closely follows the predictions
  sketched in the Taniguchi curves showing a
  machining accuracy for ultra-precision machining
  of sub-nanometer resolution for the year 2008
  (see previous slide) .
• Fanucs the ROBOnano Ui an ultra-precision
  micromachining station (cost 1 million) and a
  Noh mask made with this machine
  (http//www.fanuc.co.jp/en/product/robonano/index.
  htm).

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Desk top factory

• The fact that it often takes a two-ton machine
  tool to fabricate micro parts, where cutting
  forces are in the milli- to micro-Newton range is
  a clear indication that a complete machine tool
  redesign is required for the fabrication of
  micro-machines.
• One approach is the desk-top factory.

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Desk top factory

• Desktop factories (DTF) constitute a rather
  interesting new manufacturing philosophy
  involving flexible and modular table-top-sized
  automated factories that feature minimal human
  participation in the manufacturing process.
• An example of such a factory is shown below.
  Since the early nineties progress has been made
  towards making such desktop factories (DTF) a
  reality. A desktop factory as shown here has the
  potential of becoming the factory of the future
  a totally self-contained, robotic, desktop-size
  machine tool that only requires materials, power
  and water as outside inputs, and out come the
  finished machined products. The first RD desktop
  factories incorporated lathes, cleaning, gluing,
  punching and drilling stations. The workpiece is
  transported between these different machining
  functions by a cart moving from station to
  station.

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Desk top factory

• An example of a desktop factory at AIST, Japan.