ULTRA PRECISION MACHINING

1. A PRESENTATION ON
ULTRAPRECISION MACHINING
Submitted by: Submitted to:
ANKIT SINGLA Mr. VINAY & Ms. SEEMA
MAHTO
(1/15/FET/BME/1/010)
Department of Mechanical Engineering
Faculty of Engineering & Technology
Manav Rachna International Institute of Research & Studies
Faridabad (Haryana)
Academic Session: July 2018 - Dec 2018

2. MACHINE TOOL
A machine tool is a machine for shaping or machining metal or other
materials, usually by cutting, boring, grinding, shearing, or other
forms of deformation.
Machine tools employ some sort of tool that does the cutting or
shaping.
All machine tools have some means of constraining the workpiece
and provide a guided movement to the parts of the machine.
Thus, the relative movement between the workpiece and the cutting
tool is controlled or constrained by the machine to at least some
extent, rather than being entirely "offhand" or "freehand".

3. TRENDS IN RECENT
MACHINE TOOL
TECHNOLOGIES
At present, the machine tool industry worldwide is enjoying
unprecedented demand, and the industry’s output is apparently
even failing to satisfy current demands.
Trends in the research and development commitments of the
machine tool industry include:
High Speed, High Efficiency Machine Tools
Combined Multifunctional Machine Tools
Advance and Intelligent Control Machine Tools
Ultraprecision Machine Tools

4. HIGH SPEED, HIGH
EFFICIENCY MACHINE TOOLS
It is well known that demands are mounting for greater maximum main
spindle speeds and feed speeds – that,
Machine tools of higher speed and higher efficiency are much needed.
But, what is ‘high speed” machining really? Is it simply running at
maximum feed rates and taking multiple shallow passes?
This strategy is often less efficient than taking few passes at slightly
greater depths!
Achieving the shortest cutting time is related to feed rate, but the
relationship is not necessarily “fastest feed rates = most efficient”

5. Cutting at maximum feed rate, with very light cuts, small step-down and
step-over can actually require many, often inefficient, passes and can
defeat the goal of reducing time.
Cutting at a greater depth is more efficient. But the cutter may encounter
an overloaded condition causing breakage or exceeding the horsepower on
the machine.
High-efficiency machining, cutting a part in the least amount of
time, is the real goal.
The key to achieving high-efficiency machining is to vary the
feed rates to achieve the result each cutting condition encountered.
Feed rate optimization softwares like VERICUT are employed to
achieve better cutting efficiency with greater axial depths at the high
feed rates and protect the cutter, etc.

6. FEED RATE OPTIMIZATION
SOFTWARE
The software detects conditions where the chip load is too great and
adjusts the feedrate to a more reasonable level. It then returns the
machine to the higher feedrate when the chip load permits.
VERICUT knows exactly how much material will be removed in
each segment of the cut and slows the feed rates down where the
load is too great. This prevents breaking cutters and keeps the
machine from exceeding horsepower limitations. The same high
feed rates are maintained where possible, but with greater cutting
efficiency and less time than when stepping down only .

7. COMBINED
MULTIFUNCTIONAL
MACHINE TOOLS
In addition to high-speed, high-efficiency, cutting capable machine
tools, research on machine tools is currently focused on combined
multifunctional machine tools, including 5-axis machining centers and
combined multifunctional turning centers.
Combined multifunctional machine tools have advantages that include:
They are capable of machining complex forms that require
simultaneous control of five axes.
 Loss in machining accuracy from dismounting and remounting the
workpiece is prevented because once a workpiece has been mounted
to the chuck, all machining processes are executed without need for
rechucking the workpiece.
As the needs for function-intensive parts and components increase,
advanced combined multifunctional machine tools are capable of
machining these workpieces at higher precision and higher efficiency.

8. Many different 5-axis machining centers have been developed. In
particular, in addition to orthogonal 3-axis vertical and horizontal
machining centers, many simultaneous 5-axis control machining
center products that have work tables with two additional axes for
rotation and oscillation are used widely.
Most recently, some machining centers have a work table driven
by a DD motor and a high-speed, high-power rotary table capable
of high-speed indexing, and they feature the functions of vertical
turning centers.
Combined multifunctional machining tools may evolve
into novel machine tools that incorporate features of both
turning centers and milling machines.

9. ADVANCE & INTELLIGENT
CONTROL MACHINE TOOLS
The increasing sophistication of
machine tools is supported by
progress in not only hardware but
also in software.
Recently, many advanced
(intelligent) control techniques
are available that reflect an
understanding of machine tool
characteristics and machining
processes.

10. Let us think of a control technique for controlling thermal deformation,
which is the most critical factor adversely affecting the machining
accuracy of machine tools.
A much advanced control technique is now commercially used in which
the magnitude of the current thermal deformation is estimated in real-time
based on information about the machine tool and temperatures at various
spots on the tool.
Using this information, the motion of the machine tool is controlled so
that higher machining accuracy is ensured under any operating condition.

11. ULTRAPRECISION
MACHINE TOOLS
Other than high speed and high efficiency, the most critical requirement
for machine tools is high precision.
Recently, various ultraprecision machine tools have been developed
that are significantly more evolved than earlier high-precision machine
tools.
Previously, the industrial fields that required ultraprecision machine
tools were limited and the market scale for ultraprecision machine tools
was relatively small.
In contrast, needs have been increasingly mounting for ultraprecision
and micro-machined parts and components, such as dies for optical
parts and components.
In response to this trend, development is in progress for various
ultraprecision machine tools.

12. ULTRAPRECISION
MACHINING:
THE DEFINITION
“High Precision” in traditional machining refers to tolerances of
microns in the single-digits.
Ultraprecision machining refers to the ultimate ability of a
manufacturing process wherein processing of a material at its lowest
scale that is, at the atomic scale, is achieved.
Ultraprecision machining can be defined in general terms as the
removal of material from a substrate utilizing a machine tool that
operates at a resolution of 10 nm (0.4 μin.) or less. The machining
process may take the form of single-point diamond turning or free-
form machining.

13. APPLICATION OF UPM
Present day ultra-high-precision machining techniques are mainly applied in
Aerospace industries
Aeronautics industries
precision instruments and meters
Computer industries
 optical industries

14. WHY UPM?
For example, the planarity of magnetic disks used in computers is
required to be between 0.1 and 0.5 micrometer and the surface coarseness
be between Ra 0.003 and 0.05 micrometer.
For X-ray astronomical telescopes used in studying celestial bodies their
largest diameter is more than 1 m and their length longer than 0.6 m;
however, the requirements on dimensional precision are 1 micrometer
and surface coarseness Ra 0.05 micrometer.
 For optical parts used for ultraviolet rays and X-rays, surface coarseness
is required to be Ra 0.001 micrometer. The spherical roundness of inner
and outer supports for gas lubricated gyroscopes used in conventional
inertial instruments or meters is between 0.2 and 0.6 micrometer; the
dimensional precision is 0.6 micrometer; and the surface coarseness is
between Ra 0.012 and 0.05 micrometer.

15. In the absence of ultra-high-precision machining techniques, the
above-mentioned steady precision requirements are beyond reach,
therefore these products could never be realized.

16. TRENDS IN UPM
1. Form accuracy, finished surface roughness:
 Microns → nanometres
2. Form (in the case of optical parts)
 Spherical surfaces → aspherical surfaces → non-axisymmetric
 Surfaces → free-curved surfaces
3. Workpiece materials
 Soft metals (aluminium, copper, etc.)
 Hard metals (nickel, hardened steel, etc.)
 Resin materials, anisotropic materials (lithium niobate, fluorite, etc.)
 Brittle materials (tungsten carbide, ceramic materials, etc.)
 Other materials (plastics, etc.)

17. THE PROCESS
It is known that the lattice distances between two atoms are of the order of
0.2–0.4 nm. Therefore, the ultraprecision machining refers to processing or
removal actions of a manufacturing process in the vicinity of 1 nm.
The process is also referred as “atomic bit” processing. To remove or process
atomic bits, extremely large energy density is required, which is equivalent
to the atomic bonding energy.
The conventional cutting tools neither have high strength to sustain high
specific cutting energy nor have hardness to sustain the tool wear.
Therefore, ultraprecision machining refers to use of single crystal diamond
(SCD) tools for ultrafine cutting or very fine abrasives for lapping or
polishing.

18. When combined with an ultraprecision vibration-free machine, a
compact rigid tool holder and stable well-balanced fixture, a
single-crystal natural diamond cutting tool will remove material
from the substrates cleanly and efficiently. Because of the
extreme level of sharpness on the diamond tool’s cutting edge,
very small forces are generated during the machining process.
The end result is a surface that exhibits optical qualities in both
surface finish and form accuracy.

19. WHY DIAMOND TOOL?
When machining components to optical quality requirements, the slightest
amount of tool wear can adversely affect the quality of the machined surface.
Because of their extreme hardness and resistance to wear, diamond tools
maintain their high cutting-edge quality throughout the machining cycle better
than others.
Unlike carbide or CBN (cubic boron nitride) tools, which have random grain
structures, single-crystal diamond tools have a very clear and well-defined
grain structure. When mounting the tool in its shank, tool manufacturers orient
the tool so as to make optimal use of the hardest point of the diamond.
This orientation provides for the longest possible tool life, while also
maximizing the tool’s resistance to wear. Because of the single-crystal grain
structure,diamond tools can be sharpened to the level of atomic spacing,
approximately 3 to 5 Å.

20. MACHINE TOOL FOR UPM
The machinery developed for such applications typically required only one linear
axis of motion, to generate a cylindrical or plano form. The machines often
utilized an air bearing work holding spindle, and linear slide, mounted to a granite
base. Machinery soon evolved into multi-axis systems, with major advances seen
in CNC control, and position feedback technology.
Today’s single point diamond turning machines have evolved to utilize a host of
new technologies. When combined in a regimented manner, these allow surfaces
to be single point diamond turned in all the aforementioned materials, to a surface
texture often as low as 2nm RMS, and with figure accuracies, low in absolute
error, and exhibiting very low slope characteristics.

21. METHOS & MEANS OF
IMPLEMENTING UPM
There are principles of maternal parentage and creativity in attaining workpiece
machining precision.
The so-called principle of maternal parentage states that errors of machine tool
transmission chain and geometry with respect to workpiece machining will be
transmitted to the workpiece in some form. Hence, workpiece precision will imitate
machine tool precision with lower precision in the workpieces.
The so-called creativity principle states that lower-precision machine tools can use a
special implement and technical means in order to machine workpieces with one
level higher precision (direct precision enhancement), or alternatively lower-
precision-level machine tool equipment can produce a new generation of machine
tools with precision level higher than the workpiece precision by using special
fixtures and technical means for batch production of higher-precision parts (indirect
precision enhancement).
By correctly applying two creativity machining principles of direct and indirect
precision enhancement, precision machining can be raised to ultra-high-precision
machining.

22. Generally, in batch production always the principle of maternal
parentage is applied to attain workpiece precision and to ensure
stable machining quality.
Only in the case of trial manufacture of limited quantities of
workpieces can the machining principle of direct precision
enhancement be used to attain high workpiece precision.
Nonetheless, the error compensation technique is involved in
developments of modern science and technology as well as progress
in software scientific technology. In other words, machine tools of
lower-precision-levels are used and computer-controlled systems are
employed to apply overall error compensation according to the on-
line measurement error of a workpiece.
Therefore, the machining precision of the machine tool can undergo
major improvements, thus implementing a higher precision level of
workpiece machining.

23. FOCUSED ION BEAM FOR
UPM OF CYLINDRICAL
COMPONENTS
Focused ion beam (FIB) sputtering is used to shape a variety of cutting tools with
dimensions in the 15–100 micrometre range and cutting edge radii of curvature of 40
nm. The shape of each micro tool is controlled to a pre-specified geometry that
includes rake and relief features.
The FIB technique allows observation of the tool during fabrication, and, thus,
reproducible features are generated with sub-micron precision. Tools are made from
tungsten carbide, high-speed tool steel, and single crystal diamond. Application of
FIB-shaped tools in ultra-precision microgrooving tests shows that the cross-section of
a machined groove is an excellent replication of the microtool face.

24. THE PROCESS
In general, it is a high vacuum apparatus that accelerates and directs ions at a target
material. Material is removed by physical sputtering, and the secondary electrons
emitted during this process are collected to form an image of the sample. A tool
blank is mounted on an X–Y stage having sub-micron motion resolution, and full
360◦ rotational motion is available to the tool blank with 0.37◦ increments. The
beam used to shape tools is 20 keV ionized gallium with a spot size of 0.5
micrometre, and 2 nA total current (as measured in a Faraday cup). The sputter
pattern is generated on a bit plane image of the tool end, and can have virtually any
shape. This pattern is recorded and transferred to the ion beam deflection system,
resulting in a shape in the tool that replicates the pattern. Once all the required facets
are ion milled for a given starting rotational position, a tool is rotated to a different
orientation, and the process is repeated.

25. CONCLUSION
Advances in Computer Aided Design, and in particular, Finite Element Analysis, have
allowed the mechanical design of machining systems to benefit from specifically selected
materials and new structural configurations. This, combined with certain basic rules for oil
bearing slide design, and finely tuned assembly techniques, results in machining systems that
are more precise, thermally stable, flexible, more reliable, faster, and less expensive than the
machines of yesteryear. The use of ultra-precision machining techniques, originally developed
for commercial applications, then fuelled by demand in defense related products, is once again
being predominantly exploited by commercial industry. Everyday products such as
televisions, video players and cameras, contact lenses, binoculars, security systems, compact
disc players, personal computers, and many more, rely on advanced manufacturing techniques
to produce high performance optics cost effectively. In the future, machine developments will
continue to be driven by market requirements. Advances in computing technology, and
photonics, will likely yield further advances in control and feedback technology that will
allow ultra-precision machining technologies to continue to advance in line with market
requirements.

26. THANK
YOU!