Jigging operation

Figure 6.3.3. Hydrualic jig operation schematia (a) doumstroke of piston (b) upstroke of piston.

Many improvements have been made to streamline performance and to reduce machine operation labor. Some of these are tensionless jigs using variable speed electric motors with built-in drag for brakes, automatic reversing equipment, and automatic temperature and level controls. These machines are widely used for goods that are easily creased, such as fabrics consisting of filament acetate, heavy filament nylon, or cotton duck. They are also convenient for small dye lots and for sampling purposes. 

However, these requirements go further than merely controlling the devices used for measurement. They address the measurements themselves, the selection of the devices for measurement and also apply to devices which create product features, if they are used for product verification purposes. If you rely on jigs, tools, fixtures, templates, patterns, etc. to form shapes or other characteristics and have no other means of verifying the shape achieved, these devices become a means of verification. If you use software to control equipment, simulate the environment or operational conditions, or carry out tests and you rely on that software doing what it is supposed to do, without any separate means of checking the result, the quality of such software becomes critical to product verification. In fact the requirements apply to metrology as a whole rather than being limited to the equipment that is used to obtain the measurement and therefore a more appropriate title of the section would be Control of measurements . 

While the ISO 9001 requirement applies only to quality records, ISO/TS 16949 extends retention times for many other documents because you cannot demonstrate you have or had operations under control without specifications, plans, procedures, etc. You may also need to retain tools, jigs, fixtures, test software - in fact anything that is needed to repair or reproduce equipment in order to honor your long-term commitments. 

Sensitivities achieved in f.a.b. analysis are both operator- and sample-dependent. Experienced mass spectrometrists working with well purified samples use between 0.1 and 5 jig of sample when analyzing derivatives, and between 1 and 10 (ig when analyzing native compounds. The higher the molecular weight, the greater the quantity of sample needed. 

Jigs are relatively cheap with regard to construction, operation, and maintenance, and are relatively unaffected by the grade of the feed. They are basically designed for handling material that is too coarse for table feed (380 mm in diameter down to 2 mm). The cleaning of coal and the production of tin mineral concentrate can be cited as two major examples where jigging is found to be in use even today. 

The dynamics of such a mode of semi-fluidization is similar to that of jigging in ore dressing, which is a common operation in coal or ore dressing, though little used in the design of chemical reactors. Thus, at least on a periodic basis, jigging yields the same advantages as other modes of fluidization with no net fluid flow. 

As part of the U.S. Department of Energy (DOE) Heavy Metals in Contaminated Soils Treatability Project, total operating cost for the Campbell centrifugal jig is 1.07 per ton (1995 dollars). Capital costs to lease the centrifugal jig are estimated at 16,000 per month or 0.64 per ton. Costs considered in this operating cost estimate include the following ... 

Apparatus, such as that developed at RAPRA13, has been designed to reduce as far as possible operator dependence. A load cell is driven onto the jig by a pneumatic ram at the moment when a very small additional compression on the test piece is detected electrically, the ram is automatically stopped, the force reading digitally recorded and the ram reversed. The Rapra measuring head can be used with a variety of jig designs including Lucas. 

Jigging. In this operation, a pulsating stream of liquid flows through a bed of materials of different specific gravities, causing the heavy material lo work down to the bottom Of the bed and the lighter material to rise to the lop. This is a very old operation used for concentrating heavy mineral... 

A 45-millicurie 60Co source, stainless steel encapsulated, is bolted onto an adjustable plastic jig (not shown) for. insertion into the source hole in the lead block. This allows the source to be precisely positioned in the slit for max radiation transmission. With the source in position an additional shield consisting of a combination of lead bricks and concrete blocks is placed around and under the assembly on the table to maintain a permissible level of radiation for the operator... 

Barriers are essential too in all tear-seal work, to prevent electrical contact between the cutting surface and the electrode or jig the welding machines are fitted with arc-anticipating units , which will operate in the absence of a suitable barrier. 

The IR apparatus and dichroism methods used in this work have been previously described (11,12). In the differential dichroism experiment, the samples were stretched from both ends simultaneously at a true strain rate of approximately 30% per min. A motorized stretching jig was used which fits inside the instrument in the path of the common beam at a 45° angle. Wire grid polarizers were set at 45° in the reference and sample beams, and the instantaneous dichroic difference A A — AM — Aj was recorded with the instrument operating in constant, wave-number mode. 

When processing plastics some type of tooling is usually required. Tools include molds, dies, mandrels, jigs, fixtures, punch dies, perforated forms, etc. The terms for tools are virtually synonymous in the sense that they have some type of female and/or negative cavity into or through which a molten plastic moves usually under heat and pressure or they are used in secondary operations such as cutting dies, stamping sheet dies, etc. These tools fabricate or shape products. In this chapter injection molds and extrusion dies are primarily reviewed because they represent over 95% of all tools made for the plastic industry. This chapter also includes information applicable to other molds and dies used in the other processes some of the other chapters too provide information applicable to their tools. 

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