1. Natural Adhesives (Connector)
Previous Answer
This term
is used to include vegetable and animal based adhesives and natural gums. These
include organic materials such as casein, blood, albumin, hide, bone, fish,
starch, resin, shellac, asphalt, chitosan, and inorganic adhesives like sodium
silicate. Their use, except for the inorganic adhesives, is mostly limited to
paper , paperboard, foil, and light wood. They are inexpensive, easy yo apply,
and have a long shelf life. These adhesives develop tack quickly, but have low
strength properties. Most are water soluble and use water as a solvent. They
are supplied as liquids or dry powders to be mixed with water. Some are dispersions
in organic solvents.
( Sina
Ebnesajjad, Adhesives Technology Handbook, page 49)
New Answer (better)
Natural
adhesives are derived from natural sources (e.g., plants and animals), including
gums, starch, dextrin, soy flour, andcollagen.This categoryof adhesive is
generally limited to low-stress applications, such as cardboard cartons,
furniture, and bookbinding; or where large surface areas are involved (e.g.,
plywood). Inorganic adhesives are based principally on sodium silicate
andmagnesium oxychloride. Although relatively low in cost, they are also low in
strength—a serious limitation in a structural adhesive.
(Groover M.P., Fundamentals
of Modern Manufacturing: Materials, Processes, and Systems 4th
Edition, pp. 760)
Vegetable or plant-based adhesives – Tapioca paste is
one basis for such adhesives and is used for gluing paper including envelopes,
labels and postage stamps that are made to adhere by wetting the adhesive
surface. Other vegetable glues are made from agar, a colloid derived from
marine plants, gum arabic, from the acacia tree and from algin, derived from
seaweed. Mucilage is a vegetable glue made from water-soluble gums. Starchbased
adhesives made from corn, potatoes, and rice, are used for mounting wallpaper
and in the manufacture of corrugated cartons.
(Bralla, J. G., Handbook
Manufacturing Processes, How Products, Components and Materials Are Made,
pp. 761-762)
2. Electro
chemical grinding (Manufacturing method)
Previous Answer
Electro
chemical grinding (ECG) is a combination of ECM and the grinding process. The
metal is removed both by anodic dissolution as in ECM and abrasion as by a
grinding wheel.
In this
process, both the grinding wheel and the work piece have to be conductors of
electricity. The grinding wheels employed are in general metal (phosphor
bronze) bonded diamond wheels or metal bonded alumina wheels in ECM, in electro
chemical grinding also, the work piece is connected to the positive terminal
and wheel to the negative terminal of power supply.
(Fundamentals
of metal cutting and machine tools, B. L. Juneja,Nitin Seth, p.296)
New Answer (better)
Electrochemical
grinding (ECG) is similar to electrochemical machining but replaces the
relatively stationary tool with a rotating conductive grinding wheel. The wheel
normally consists of aluminum oxide abrasive bonded to a metal wheel, which
acts as the cathode of the electrolytic circuit. Electrolytic fluid circulates
in the area where the abrasive contacts the work. A combination of electrolytic
and mechanical action removes material from the workpiece but the electrolytic action
predominates, accounting for about 90 percent of metal removal. Anodic
dissolution of the workpiece metal leaves surface metal oxides. In conventional
ECM, the flushing action of the electrolyte removes these oxides. In
electrochemical grinding, the abrasive mainly functions to remove the oxide film,
exposing a new metal surface to the electrolyte. The abrasive also separates
the metal wheel from the work, preserving a fine (0.001 in or 0.025 mm) gap
between the two. It also carries the electrolyte solution to the gap.
The process
has the advantage of relatively high metal removal rates for hard metals,
freedom from heat damage to the workpiece, and the ability to grind fragile
parts. Plunge, surface, cylindrical, and internal grinding are all feasible
with the process. However, capital costs are high and the electrolyte can be
corrosive to the equipment and workpiece. The process is commonly used in
sharpening carbide cutting tools, avoiding the high wear rates of expensive
diamond-abrasive wheels that would otherwise be required. It is also used for
grinding surgical needles, honeycomb structures, and other fragile parts. ECG
is illustrated by Fig. 312a.
(Bralla, J. G., Handbook
Manufacturing Processes, How Products, Components and Materials Are Made,
pp. 122)
3. Induction
Hardening (Manufacturing Method)
Previous Answer
Induction
hardening is based on the generation of magnetic fields by an alternating
current. When a metal component is placed inside the coil, eddy currents are
induced in surface regions of the object, which in turn generate heat because
of the resistance of the metal. The depth of heating depends on the strength of
the magnetic field, the magnetic properties of the material, and the proximity
of coils to the object. Cooling may be carried out in air or by quenching in
oil or water if a deep hardened zone is required. Hardened regions up to about
5mm can be produced by the two processes ;the shallower, darker regions were
produced by laser hardening. Induction hardening is easily incorporated into a
production environment, has a relatively low cost, and is particularly suitable
for rotationally symmetric components such as gear wheels and shafts, especially
when high volumes of identical components are to be treated. Codes of practice
have been written that specify the required hardness and geometry of the
treated region, enabling the process be automated by using preset values.
(John C.
Ion, Laser Processing of Engineering
Materials, p. 224)
New Answer (better)
Induction
hardening uses induction heating to produce high temperatures at the surface,
or in those areas requiring hardening. As with other processes requiring
induction heating (See 7A2h, 7B4 and 7C2.), an electrical coil must be designed
and fabricated to produce the heating effect in the desired location. The
process is well suited for surface hardening because the depth and location of
the treatment can be controlled by establishing the optimum heating time,
current, frequency, power level and coil configuration. (Higher induction
frequencies concentrate the heating effect more at the surface and produce
shallower hardened cases; lower frequencies produce deeper hardening or even
through-hardening.) After the heating cycle, which is quite rapid, the workpiece
is immediately quenched. Round and cylindrical workpieces are most easily
processed since simple coil shapes can be utilized. Shaft and crankshaft bearing
surfaces are frequently surface hardened by induction heating. Vehicle and
machine shafts and hydraulic piston rods are typical parts treated by induction
hardening for improved wear resistance and fatigue life. When the operation is
automated, the shafts pass through the induction coils in a timed cycle and are
immediately spray quenched when they exit the coils.
(Bralla, J. G., Handbook
Manufacturing Processes, How Products, Components and Materials Are Made,
pp. 348-349)
4. Styrofoam (Material)
Previous Answer
--Polystyrene
another named styrofoam is a high volume world-wide consumed plastic. It is
used in many different formulations. Styrofoam is noted for its sparkling
clarity, hardness, low water absorption, extreme ease of processing general
purpose PS, excelent colorability, dimensional stability, and relatively low
cost. This amorphous TP often competes favorably with higher priced plastics.
--In its
basic crystal PS form it is brittle, with low heat and chemical resistance,
poor weather resistance. High impact polystyrene is made with butadiene
modifiers that provides significant improvement in impact strength and
elongation over crystal polystyrene accomponied by a loss of transparency and
little other property improvement.
(Dominick
V. Rosato,Donald V. Rosato,Matthew V. Rosato, Plastic product material and
process selection handbook, page 63)
New Answer
Styrofoam is
polystyrene expanded to 42 times the original size2. It is used, usually in
panel form, as a cold-temperature insulation. The panels are made by extrusion,
most commonly with a dual, tandem extruder system. The first extruder heats and
mixes the polystyrene with a nucleating agent, a fine powder of talc or other
material, with small amounts of other materials. The output of the first
extruder is passed under pressure to a second extruder, sometimes called a
cooling extruder, where the liquid or gaseous blowing agent is injected. The
blowing agent is usually a blend. Several key materials that may be used
include: pentane, carbon dioxide, butane, and HFC- 152aI5. The blowing agent is
kept under compression as it is mixed into the cooling resin. At the nozzle of
the second extruder, the blended material passes through a shaped die into the
open atmosphere where the blowing agent expands, changing the extrudate to a
foam. Often, an annular die is used, creating a tube of foamed polystyrene. The
tube is slit and the foamed material is flattened to thick sheet or slab form.
Slabs are further cooled and cut to standard lengths.
(Bralla, J. G., Handbook
Manufacturing Processes, How Products, Components and Materials Are Made,
pp. 761-762)
5. Crushing (Manufacturing Method)
Previous Answer
The major
equipments are mortar and pestle, heavy drop hammer, and jaw crushers. In jaw
crushing the crushing chamber is formed by one fixed jaw and one movable jaw
between stationary side support walls. The movable jaw is mounted eccentrically
at the top and is driven by a motor via a flywheel. During the crushing
process, the material is drawn down into the tapered crushing chamber as a
result of the eccentric jaw motion and is reduced in size by compression and
frictional forces. In addition, the angle between the jaws can be altered to
give optimum adjustment to the crushing of the material. The final crushed
product particle size can be adjusted to values between 15 and 1 mm by
adjusting the gap at the base of the jaws. The standards jaws and side walls
are manufactured from hardened steel. If the feed material is very abrasive or
particular impurities are to be avoided, these components are also available in
stainless steel or hard tungsten carbide. If the fixed jaw is removed, access
is given to the crushing chamber and the equipment can be cleared easily. In
addition, the connection of an exhaust device allows work to be carried out in
dust free conditions.
(Upadhyaya
G. S., Powder metallurgy technology,
p. 33)
New Answer (better)
Crushing is
most often effected by a slow application of strong force. A jaw crusher has a swinging
plate or “jaw” which is connected to a double toggle that is moved by an
eccentric on a large flywheel. Each forward movement of the jaw exerts heavy
pressure on the material between the jaws and breaks up the large pieces.
Crushed pieces fall between the jaws. Large lumps may be hit several times as
they work their way down and out of the machine. See Fig. 11D1.
Gyratory crushers use a cone-shaped pestle
that moves eccentrically in a bowl-shaped hopper. Crushed pieces fall to the
bottom and exit through the hopper. A gyratory crusher is illustrated in Fig. 1
1 D 1 - 1. These machines are widely used in the first-step crushing of rock
materials. Both jaw and gyratory crushers - of an appropriate size - may be
used for primary and secondary crushing. Gyratory crushers with wide-angle
cone-shaped pestles are often called cone crushers. Cone crushers are used more
for secondary crushing. Roll crushers, described below, are also primarily used
for secondary crushing, except with coal and other friable materials.
(Bralla, J. G., Handbook
Manufacturing Processes, How Products, Components and Materials Are Made,
pp. 454-455)
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