Metal Machining

Injection Molding: A Technology in Transition to Electrical Power



While incremental improvements will con­tinue to be wrung out of
hydraulic IMMs and molds, more significant advances in quality and
productivity will result from the transi­tion to all-electric molding
machinery. This transition has barely begun, but it is likely to follow
the same pattern it did in robots and machine tools (326).

Simply put, electric molding technology (EMT) eliminates so many
variables from the process that a machine will produce more good parts
per day at a lower cost. A rea­sonable body of experience and test data
has been developed which documents these im­provements. There are also
significant oper­ating advantages related to energy and en­vironmental
issues. Broadly speaking, three approaches to electric injection
molding ma­chinery have come to the forefront in Europe, Japan, and the
United States. Each will be de­scribed, along with its rationale.

Where are the next major quality advances for injection molding likely
to come from? Evidence from real-world applications sug­gests that EMT
has the potential to signifi­cantly raise the standard of quality.
Although EMT has a host of environmental and energy advantages in its
favor, most early adopters of the technology are committing to it for
rea­sons of quality and productivity. They simply get more parts per
shift, and better ones.

The reason is that electric machines have a window of process
capability that is inher­ently much tighter than what can be achieved
for comparable cost with hydraulic machin­ery. EMT is the enabler for
improved pro­cess repeatability, and in the long term will raise the
industry's standard for machine performance. This tighter process
capability translates into a variety of benefits, including less scrap,
lower labor costs, and improved quality.
Continue reading "Injection Molding: A Technology in Transition to Electrical Power"

Continue reading "Injection Molding Machines"

BMI and polyimide are used for high-temperature applications in aircrafts, missiles, and circuit boards. The glass transition temperature (Tg) of BMIs is in the range of 550 to 600°F, whereas some polyimides offer Tg greater than 700°F. These values are much higher than for epoxies and polyesters. The lack of use of BMIs and polyimides is attributed to their processing difficulty. They emit volatiles and moisture during imidization and curing. Therefore, proper venting is necessary during the curing of these resins; otherwise, it may cause process-related defects such as voids and delaminations. Other drawbacks of these resins include the fact that their toughness values are lower than epoxies and cyanate esters, and they have a higher moisture absorption ability Polyurethane is widely used for structural reaction injection molding (SRIM) processes and reinforced reaction injection molding (RRIM) processes.


Continue reading "Bismaleimide (BMI) and Polyimide,Polyurethane,Thermoplastic Resins"

Dielectric coatings may be used to form an additional layer of electrical interconnections beyond those already formed during wafer fabrication. Processes have been developed to alter the bonding pad topography both at the die (wafer) level and at the substrate level using polymer dielectrics. For example, a bonding pad can be reconfigured, changing its size and shape, by spin coating a photocurable BCB layer over the entire surface, exposing to uv through a mask having the image of the desired geometry, and developing it (Fig. 4.6). Dielectrics such as BCB or polyimides may also be used to redistribute peripheral bonding pads on a die to form an area array of pads to permit solder bumping for flip-chip bonding or ball grid array packages (Fig. 4.7). Likewise, internal pads on a die can be redistributed to one side to permit wire bonding of vertically stacked dice.

Continue reading "Reconfiguration and Redistribution of Die Bonding Pads"

A

0C-Al2O3 Pure alumina. Polycrystalline Al2O3 is known as corundum and
single crystals as sapphire. Its crystal structure can be described as
consisting of two sublattices: an FCC sublattice of O2– ions and a
sublattice of Al3+ ions occupying two thirds of the octahedral sites in
the first one.

OC-Fe Allotropic form of iron having BCC crystal structure and existing at temperatures below 910°C at atmospheric pressure.

OC isomorphous Ti system Ti-X alloy system in which the alloying
element X is the a-stabilizer, i.e., it raises the temperature of the p
<-> a polymorphic transformation.

OC-phase [in Ti alloys] A solid solution of alloying elements in a-Ti.

Oc'-martensite See titanium martensite.

Oc"-martensite See titanium martensite.

OC-stabilizer In physical metallurgy of Ti alloys, an alloying element
increasing the thermodynamic stability of a-phase and thereby raising
the p/(a + P) transus in the corresponding phase diagram. In physical
metallurgy of steels, it is referred to as ferrite-stabilizer.

OC-Ti Allotropic form of titanium having a hexagonal crystal structure
and existing at temperatures below 882°C at atmospheric pressure. The
axial ratio of its lattice c/a = 1.58, i.e., a little smaller than in
an ideal HCP structure.

OC Ti alloy Titanium alloy in which a-phase is the only phase
constituent after air-cooling from the p-field in the phase diagram
concerned. Alloys with a small fraction of §-phase (~5 vol%) are
usually related to the same group and are called near-a alloys. All the
a alloys contain a-stabilizers.

(oc + p) brass Brass with two phase constituents: a copper-based
substitutional solid solution (a-phase) and an electron compound
(P-phase).

(oc + p) Ti alloy Alloy whose phase constituents are a- and P-phases
after air-cooling from the (a + P)-field in the phase diagram
concerned. Slow cooling of these alloys from the (3-field results in a
microstructure comprising grain-boundary allotriomorphs of the a-phase
(known as “primary” a) and packets of similarly oriented a-platelets
with the P-phase layers between the platelets.

Aj/Aej temperature In the Fe-Fe3C diagram, the temperature of an
eutectoid reaction corresponding to the PSK line in the diagram. Since
the reaction, on cooling, starts at a certain undercooling (see
nucleation), the temper-ature of its commencement, Ar1, is lower than
A1. The start temperature of the same reaction on heating, Ac 1, is
greater than A1 due to superheating. The difference between Ac1 and Ar1
is named thermal, or transformation, hysteresis.

Continue reading "Engineering Dictionary"

The field of nanocomposites has recently attracted considerable attention as researchers strive to enhance composite properties and extend their utility by using nanoscale reinforcements instead of the more conven­tional particulate-filled composites.[13] While smaller reinforcements have a better reinforcing effect than larger ones, applying the ball-milling technique for composite fabrications must have the following merits:
since ball milling is processed at room temperature, the disadvantages of the liquid metallurgy method for produc­ing undesirable materials can be avoided
moreover, the ball-milling process can produce homoge­neous nanocomposite powders instead of the more con­ventional coarse particulate-filled composites


Continue reading "FABRICATION OF SiCp/Al COMPOSITES BY MECHANICAL SOLID STATE MIXING"

INCONEL MA 6000 combines precipitation strengthening (gamma prime, γ´, precipitates) from its Al, Ti, and Ta content for intermediate temperature strength with oxide dispersion strengthening from the Y2O3 addition for strength and stability at very high temperatures. It contains about 25% of γ´ precipitates.


Continue reading "INCONEL MA 6000"

In 1980, Weber[5] prepared a large amount of mechanically alloyed ODS superalloy (INCONEL MA 754). It is essentially a Ni-20% Cr alloy strengthened by about 1 vol % Y2O3. The Ni, Cr, and Y2O3 powders were milled until a homogeneous Ni-20% Cr alloy was formed in which the Y2O3 particles were uniformly distributed. The fabricated alloy powder was then consolidated by hot extrusion which was followed by hot rolling. A recrystallization step, often directional, followed consolidation that re­sulted in elongated, high-aspect-ratio grains that were very stable owing to the inert oxide pinning. After the directional crystallization, the grains had typical dimensions of ~ 500 to 700 µm parallel to the working direction and ~ 15 µm perpendicular to this direction. The typical BFI of the fabricated MA 754 is displayed in Fig. 2.1, which shows the oxide distribution in the metallic matrix. Benjamin et al.[6] have suggested that fine particles are a uniform dispersion of stable yttrium aluminates formed by the reaction between the added Y2O3, excess oxygen in the powder, and the aluminum added to getter oxygen. In Fig. 2.1, the larger particles are titanium carbonitrides.



Continue reading "INCONEL MA 754"

As previously mentioned, the main process which takes place in a mill
during the MA method to produce quality powders with controlled
microstructure is the repeated welding, fracturing, and rewelding of a
mixture of powders of the diffusion couples. It is critical to
establish a balance between fracturing and cold welding in order to
mechanically alloy successfully. Two techniques are proposed by Gilman
and Benjamin[22] to reduce cold welding and promote fracturing. The
first technique is to modify the surface of the deforming particles by
addition of a suitable processing control agent (PCA) (wet milling)
that impedes the clean metal-to-metal contact necessary for cold
welding. The second technique is to modify the deformation mode of the
powder particles so that they fracture before they are able to deform
to the large compressive strains necessary for flattening and cold
welding. Cooling the mill chamber is an approach to accelerate the
fracture and establishment of steady-state processing (effect of
milling temperature).[23]
Continue reading "MECHANISM OF MECHANICAL ALLOYING"

The MA process is affected by several factors that are playing very important roles in the fabrication of homogeneous materials.[40] It is well known that the properties of the milled powders of the final product, such as the particle size distribution, the degree of disorder, or amorphization, and the final stoichiometry, depend on the milling conditions and, as such, the more complete the control and monitoring of the milling conditions, the better end-product is obtained.[2][40][41] These factors can be listed as follows:

Three main factors that determine the properties of cast iron are:  the chemical composition of the cast iron, the rate of cooling of the casting in the mold, and the type of graphite formed. Continue reading "PROPERTIES OF CAST IRONS"

Metallurgical Considerations — The AISI or SAE alloy steels contain, in addition to carbon, up to about 1 percent (up to 0.5 percent for most airframe applications) additions of various alloying elements to improve their strength, depth of hardening, toughness, or other properties of interest. Generally, alloy steels have better strength-to-weight ratios than carbon steels and are somewhat higher in cost on a weight, but not necessarily strength, basis. Their applications in airframes include landing-gear components, shafts, gears, and other parts requiring high strength, through hardening, or toughness. Some alloy steels are identified by the AISI four-digit system of numbers. The first two digits indicate the alloy group and the last two the approximate carbon content in hundredths of a percent. The alloying elements used in these steels include manganese, silicon, nickel, chromium, molybdenum, vanadium, and boron. Other steels in this section are proprietary steels which may be modifications of the AISI grades. The alloying additions in these steels may provide deeper hardening, higher strength and toughness. These steels are available in a variety of finish conditions, ranging from hot- or cold-rolled to quenched-and-tempered. They are generally heat treated before use to develop the desired properties. Some steels in this group are carburized, then heat treated to produce a combination of high surface hardness and good core toughness. Continue reading "LOW-ALLOY STEELS (AISI GRADES AND PROPRIETARY GRADES)"

Drop Hammer Forming,Mechanical Drop Hammer Forming

DROP HAMMER FORMING is a process for producing shapes by the progressive deformation of sheet metal in matched dies under the repetitive blows of a gravity-drop hammer or a power-drop hammer. The configurations most commonly formed by the process include shallow, smoothly contoured double-curvature parts; shallow-beaded parts; and parts with irregular and comparatively deep recesses. Small quantities of cup-shaped and box-shaped parts, curved sections, and contoured flanged parts are also formed. Continue reading "Drop Hammer Forming,Mechanical Drop Hammer Forming "

CAD CAM Applications in Sheet Forming, CAD CAM Applications in Sheet Forming,CAD CAM
COMPUTER-AIDED DESIGN AND MANUFACTURE (CAD/CAM) typically involves the use of graphic displays, which allow the interactive creation and modification of geometric shapes, but CAD/CAM is not limited to this technique. In its broadest definition, CAD/CAM can be the application of any software program--batch or interactive--that facilitates product design and manufacture.
There are two principal advantages of applying CAD to the design of dies for sheet metal stamping. First is the generation of computer surface data for downstream CAM applications to generate numerically controlled (NC) cutter paths and to eliminate the need for die models. Second is the reduction of downstream die tryout time and the reduction of die construction aids by producing more geometrically accurate data. These advantages can result in both time and cost savings. This article will discuss the application of CAD/CAM to the diemaking process, first in general terms and then in a specific case study. Continue reading "CAD CAM Applications in Sheet Forming, CAD CAM Applications in Sheet Forming,CAD CAM"

X-Ray Photoelectron Spectroscopy

General Uses

· Elemental analysis of surfaces of all elements except hydrogen

· Chemical state identification of surface species

· In-depth composition profiles of elemental distribution in thin films

· Composition analysis of samples when destructive effects of electron beam techniques must be avoided Continue reading "X-Ray Photoelectron Spectroscopy "

Auger Electron Spectroscopy

General Uses

· Compositional analysis of the 0- to 3-nm region near the surface for all elements except H and He

· Depth-compositional profiling and thin film analysis

· High lateral resolution surface chemical analysis and inhomogeneity studies to determine compositional variations in areas ≥100 nm

· Grain-boundary and other interface analyses facilitated by fracture

· Identification of phases in cross sections Continue reading "Auger Electron Spectroscopy"

X-Ray Spectrometry,X-Ray Emission

General Uses

· Nondestructive multielemental analysis of thin samples, sodium through uranium, to approximately 1 ppm or 10-9 g/cm2

· Nondestructive multielemental analysis of thick samples for medium and heavy elements

· Semiquantitative analysis of elements versus depth

· Elemental analyses of large and/or fragile objects through external beam proton milliprobe

· Elemental analyses using proton microprobes, spatial resolution to a few microns, and mass detection limits below 10-16 g Continue reading "X-Ray Spectrometry,X-Ray Emission "

THE FUTURE FOR PLASTICS This section was written for the fourth edition published in 1982 at a time when there had just been a further sharp increase in the price of petroleum. At the time I was optimistic about the future for plastics, although I did not anticipate the slump in oil prices that has taken place since then. Oil remains a finite resource and sooner or later prices will rise again. Apart from changing one word and inserting one other for technical reasons, I see no reason to otherwise change what I wrote then.

The advent of the oil crisis of 1973 led to dire predictions about the future of plastics materials, which to date have not been realised. Before attempting to predict what will happen in the next few years it is worthwhile to consider why the growth of plastics was so spectacular during the period 1945-1973. In essence the reason for the spectacular growth lay in the interaction of three factors: Continue reading "THE FUTURE FOR PLASTICS"

Polyamides and Polyimides POLYAMIDES: INTRODUCTION Whilst by far the bulk of polyamide materials are used in the form of fibres, they have also become of some importance as speciality thermoplastics of particular use in engineering applications. The fibre-forming polyamides and their immediate chemical derivatives and copolymers are often referred to as nylons. There are also available polyamides of more complex composition which are not fibre-forming and are structurally quite different. These are not normally considered as nylons (see Section 18.10). The early development of the nylons is largely due to the work of W. H. Carothers and his colleagues, who first synthesised nylon 66 in 1935 after extensive and classical researches into condensation polymerisation. Commercial production of this polymer for subsequent conversion into fibres was commenced by the Du Pont Company in December 1939. The first nylon mouldings were produced in 1941 but the polymer did not become well known in this form until about 1950. In an attempt to circumvent the Du Pont patents, German chemists investigated a wide range of synthetic fibre-forming polymers in the late 1930s. This work resulted in the successful introduction of nylon 6 (and incidentally in the evolution of the polyurethanes) and today nylons 66 and 6 account for nearly all of the polyamides produced for fibre applications. Mention may, however, be made of nylons 7 (Enanth) and 9 (Pelargone) which have been investigated as fibres in the Soviet Union. Very many other aliphatic polyamides have been prepared in the laboratory and a few have become of specialised interest as plastics materials including nylons 11, 12, 46, 69, 612, 66/610 and 66/610/6. For a variety of reasons the aromatic polyamides were slow in their development. Continue reading "Polyamides and Polyimides"

The development of small grains during the solidification of the casting is generally an advantage. When the grain size is small, the area of grain boundary is large, leading to a lower concentration of impurities in the boundaries. The practical consequences that generally follow from a finer grain size are:

1. Improved resistance to hot tearing during solidification.

2. Improved resistance to cracking when welding or when removing feeders by flame cutting (for steel castings).

3. Reduced scattering of ultrasonic waves and X-rays, allowing better non-destructive inspection.

4. Improved resistance to grain boundary corrosion.

5. Higher yield strength (because of Hall-Petch relationship).

6. Higher ductility and toughness.

7. Improved fatigue resistance (including thermal fatigue resistance).

8. Reduced porosity and reduced size of pores. This effect has been shown by computer simulation by Conley et al. (1999). The effect is the consequence of the improved intergranular feeding and better distributed gas emerging from solution. Improved mass feeding will also help as described in section

9. Improved hot workability of material cast as ingots. Continue reading "Structure, defects and properties of the finished casting"