Machining accuracy INDEX

The melt index itself is not a material property like temperature or viscosity, but a machine dependent index. This is because the die is short relative to its length (8 mm long and 2.1 mm in diameter), with an L/D < 4. Typical L/D values for capillary rheometers are greater than 15. As a result, the melt index results are heavily influenced by entrance and exit effects at the die (see the section on the Bagley correction) that cannot be exactly duplicated on anything other than another melt indexer. While it is possible to calculate a viscosity from the flow data generated by the melt indexer, the entrance and exit effects also negatively influence its accuracy. 

Since direct plant costs are always estimated for some date in the future, it is necessary to determine the effect of increases in price. Use is therefore made of price indexes which are published for chemical plants in the individual countries (see Table 6.1-2). The direct plant costs make no allowance for the cost of engineers (usually 10-20 %) or for contingencies (ca. 5-10%). This method of estimation has the disadvantage that while the machine and equipment costs can be determined fairly precisely, the average value of these items is multiplied by a comparatively inexact overall factor. The accuracy can be considerably increased by breaking the overall factor down into individual factors. 

Rotary motion systems in ultraprecision machine tool include a spindle system, a rotary table system, a tilting motion system, and an indexing table system. Aerostatic porous bearings are widely used in ultraprecision machine tools from the viewpoints of thermal stability, dynamic stability, and accurate motion accuracy. 

The first machine to use 30-cm tape fabricated weapon bay doors for the B1 bomber. A government contract hmited the expenditure by the prime contractor (Rockwell), but without any sacrifice in accuracy. Requirements were met by a manually operated machine with automatic width indexing, with other motions initiated by the operator. 

Precise Motion Transmission. Many applications use gears as a means for precise transmission of motion. Usually, more precise accuracy grades are required for these gears. Examples of such apphcations are navigational tracking, telescopes, printing presses, and index devices for machine tools. 

Accurate machine vision color measurement is a non-trivial task and every step in a color quantification process can affect the accuracy of the measurement. Major areas of the color machine vision system (CMVS) development task consists of acquisition of color images, low-level image processing to compensate for aberrations caused by qitical impurity and noisy electronic devices in a system, color quality index selection/develqiment, and defming relationships between instrumental and sensory evaluation results. Successes or failures in developing each of these CMVS building blocks will affect the overall system performance. 

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