Powder rolling:
Metal powder is introduced between the rolls and compacted into a "green strip", which is subsequently sintered and subjected to further hot-working and/or cold working and annealing cycles. Advantages:
- Cut down the initial hot-ingot breakdown step.
- Economical - metal powder is cheaply produced during the extraction process.
- Minimise contamination in hot-rolling.
- Provide fine grain size with a minimum of preferred orientation.
Udomphol T., Rolling of Metals, p. 21
Gear Shaper:
In gear shapers, the cutters reciprocate rapidly. The teeth are cut by the reciprocating motion of the cutter. The cutter can either be "rack-type cutter" or a rotary pinion type cutter.
Advantages:
- The gears produced by the method are of very high accuracy.
- Both internal & external gears can be cut by this process.
- Non-convential types of gears can also be cut by this model.
Disadvantages:
- The production rate with gear shaper is lower than Hobbing.
- There is no cutting on the return stroke in a gear shaper.
- Worm & worm wheels can't be generated on a gear shaper.
TATA Motors Limited, p.4
Meander's Mechanism:
In atmosphere or ocean, we use to observed the encounter of two different fluid masses. At the large scale, the interaction between those masses usually forms a local narrow transitional region. In this narrow region, if the properties (such as: density, temperature, salinity, humidity...) of an either side differ rapidly in comparison with the remaining side, thus cause intensified gradients, then it is called a front.A typical case is two fluid owing different densities. In the front, there is a large pressure gradient proportionally to the difference, aligns an intense flow. Those ‘struggles’ as well as the internal movements in each fluid mass form the motion of the front. The external force, i.e. the Coriolis force, acts and activate the geostrophic adjustment. The motion of front is used to be the form of flow which is thereafter named a jet.
Hung L.Q., A Mechanism Explanation of Meanders, p.1
Degreasing (Surface):
The removal of all traces of oil and grease from the surfaces to be bonded is essential. Degreasing by one of the four methods given below should be carried out even when the surfaces to be bonded appear clean.
Degreasing methods:
Remove all traces of oil and grease as follows:
(a) Suspend in a common degreasing solvent such as acetone, MEK, Ethanol or Iso-propanol solvent unit. The unit may include a compartment to enable initial washing in the liquid solvent.
Where a vapor degreasing unit is not available:
(b) Immerse successively in two tanks each containing the same degreasing solvent. The first tank acts as a wash, the second as a rinse. When the solvent in the wash tank becomes heavily contaminated, the tank is cleaned out and refilled with fresh solvent. This tank is then used for the rinse, and the former tank for the wash.
(c) Brush or wipe the joint surfaces with a clean brush or cloth soaked in a commercial degreasing solvent. (For fine work, washing down with solvent applied by aerosol spray may be a more suitable alternative; this technique also ensures that the solvent used is clean.) Allow to stand for a minute or two to permit complete evaporation from the joint surfaces.A wide range of proprietary solvent degreasing agents with low hazard ratings are now available. These should be used according to the manufacturers’ instructions
(d) Detergent degreasing Scrub the joint surfaces in a solution of liquid detergent. Wash with clean hot water and allow to dry thoroughly – preferably in a stream of hot air from, e.g. a domestic forced-air heater.
Note: Non-ionic detergents give generally good results.
(e) Alkaline degreasing is an alternative method to the detergent degreasing. The ingredients may be selected from a wide range of compounds including sodium or potassium hydroxide, carbonates,
phosphates, borates, complexing agents and organic surfactants. They can be used hot or cold with or without applied current. There should be very thorough washing, and possibly neutralization to remove residual traces of alkaline cleaners. It is recommended to use proprietary products and follow manufacturers’ instructions for use.
(f) Ultrasonic degreasing may be employed when appropriate and is generally used for the preparation of small specimens.
Huntsman, Surface Preparation and Pretreatments, p.2-3
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