Turning, micro-milling, micro-drilling,
micro EDM, micro- WEDM, micro ECM, etc. ultra-precision machining,
electrolytic in-process dressing and grinding. What is
Micro-Machining
Micro machining is one of the key technologies of micro
engineering. Micro engineering can be defined as the branch of
engineering that deals with development and manufacture of
products, whose functional features or at least one dimensionisin
the order of microns However,there is no universally
agreeddistinctionbetween macro andmicro-scalemachining. Micro
machining processes are categorized according to the machining
phenomena and characteristics
contemporarylevelofconventionaltechnologies,personperspective
machining method, type of product or material. micro in
micro-machining indicates micrometer and represents the range from
1 m to 999 m. Scientific Technical Committee of the Physical and
Chemical Machining Processes of CIRP, 1 to 500 m was adopted as the
range for micro machining The term micromachining is now associated
with the qualities of precision and ultra-precision machining. Need
of Micro-Machining Processes
The last two decades have shown an ever-increasing interest in
higher precision and miniaturization in a wide range of
manufacturing activities. These growing trends have led to new
requirements in machining, especially in micromachining. Types of
Micromachining Process
There are two basic groups of micromachining process: mask based
and tool based micromachining. The mask based technology has the
limitations of fabricating 3D structures as it is applied only to
two dimensional shapes processes using tools, especially those
using solid tools, can specify the outlines of various 3D shapes
owing to the clear border at the tool surface and the easily
defined tool path Types of Micromachining Process The manufacturing
technologies connected with micro products of silicon are
relatively highly developed compared to that of metals, polymers
and ceramics From a geometrical point of view, micro products can
be organized in to three groups: Two-dimensional structures (2D),
such as optical gratings. Two-dimensional structures with a third
dimension (21/2 D), for example fluid sensors. Real
three-dimensional structures(3D), such as components for hearing
aids Micro engineering deals with development and manufacture of
products, whose functional features or at least one dimension are
in the order of m. The products are usually characterized by a high
degree of integration of functionalities and components.
Micro-cutting process uses physical cutting tools in high precision
CNC machines to fabricate parts with micrometers features and
sub-micrometer tolerances. An advantage of this process is the
ability to use any machinable material, quick process planning and
material removal, and three-dimensional geometry only limited by
the machine tools used. Disadvantages are that forces are placed on
micro cutting tools causing deflection and possible breaking.
Deflection reduces process precision and tool breakage results in
repeated set up, slower production, and poorer tolerances Turning
microparts can be difficult work
Turning microparts can be difficult work. Not only are tolerances
and finish requirements generally tighter and finer for parts with
" and smaller diameters, secondary operations are often required
for medical and aerospace parts. In addition to turning, this
raises concerns about how to hold, mill, cross-drill, deburr and
inspect the parts. Even finding the parts in the chip tray after
cutoff can be a challenge. It is a conventional material removal
process that has been miniaturized. During machining, instructions
to the miniature machine controller were supplied as numerical
control (NC) codes which were generated by SLICER and TAPER TURNER
for straight and taper microturning process. Optical Microscope
Scanning Electron Microscope Ultrasonic Cleaning Unit Many shops
have turned to Swiss-style, sliding-headstock lathes for this type
of work. Swiss-style machines are generally equipped with
higher-speed spindles than conventional CNC lathes, which is half
the battle when turning microparts. Machinerys Handbook states that
turning a 1?8"-dia. 304 stainless steel part at 200 sfm means
revving a spindle to 6,400 rpm. For softer materials, such as
aluminum or brass, speed requirements are even higher. And the
problems youll encounter with insufficient spindle speed are many,
including poor surface finish and built-up edge, which leads to
tool chipping. Most conventional CNC lathes max out in the
neighborhood of 3,000 to 5,000 rpm, while Swiss-style machines hit
main spindle speeds of 10,000 rpm or higher. When it comes to
microparts, most conventional CNC lathes just cant cut it. But
theres more to this picture. Swiss-style machines are designed for
small work and have few part-length-to-diameter limitations.
Instead of using an indexing turret, as do conventional lathes, the
tool indexing mechanism on a Swiss-style machine generally works
off a sliding principle, making critical centerline adjustments
easier. Swiss-style tooling and workholding is also smaller, which
makes everything more small parts friendly. A C-axis, subspindle
and live tooling is pretty much the norm on a Swiss-style machine,
which means you can often drop small parts complete, avoiding
secondary operations and increasing accuracy and profitability. In
short, Swiss-style machining is the way to go for many micropart
turning jobs. I will do machining down to 3mm on my CNC lathes and
screw machines when the part configuration lends itself to those
machines, said Peter McGuire, president of Lovejoy Chaplet Corp., a
machine shop in Hoosick Falls, N.Y. I will then switch to
Swiss-style machines for anything smaller than 3mm. The parts
become too flexible and are, therefore, much easier to machine on a
Swiss-style machine. Oh, great, youre thinking. You just quoted a
job for 10,000 tiny 303 stainless injector nozzles, and now you
have to tell the boss he has to invest in an expensive new machine,
even though one job wont justify the capital outlay for it. Dont
panic. If youve got a lathe, youve got options for that
10,000-piece injector nozzle order, the one you quoted high because
you really didnt want it anyway. Even if all you have for turning
is an old 8"-chuck machine, painted ugly gray-green and limited to
a top speed of 3,500 rpm, you still have options. For starters, get
rid of that big, clunky 8" 3-jaw chuck. More than likely, the jaw
travel is going to be larger than the parts youre working on,
making it impossible to grab a small part. And spinning a chunk of
metal at top speed all day long is no fun. The noise coming off
that thing is like an F-16 on takeoff. Scary! Its better to mount a
5C or smaller collet because collets are easier to use for small
wo
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