Stock shapes

Stock shapes, also called semi-finished materials, are extruded or cast rods, mandrels or thick-walled tubes, thick sheets or profiles. Products made from polyamide include bearings, gear wheels, bushes, pulleys, buffers, seals, scrapers and electrical insulation parts. 

Polyamide is also used in a wide range of other injection moulding applications. 

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These resins have extensive appHcations in the high performance insulation markets (traction motor, wire cable) and flexible printed circuits. Du Pont supphes Kapton film and also suppHes Verpel stock shapes made from the same resin by powder sintering methods. 

POLYBENZIMIDAZOLES. These are heterocyclic polymers that have outstanding high thermal characteristics, the highest obtainable in commercial polymers. These materials also have superior ablative and hydrolytic stability as well as high compressive and dimensional stability. Polybenzimidazoles essentially arc unaffected by solvents, acids, and bases. They are marketed in stock shapes and as finished parts. The materials are not available in resin form Hoechst Celanese markets tile products under tile tradename Celazole, ... 

Resin-based composites are usually defined as either conventional or advanced. Conventional composites usually contain glass or mineral fiber reinforcement, and sometimes carbon fiber, either alone or in combination with others. Conventional composites are usually produced in stock shapes such as sheet, rod, and tube. There are many methods of processing composite materials. These include filament winding, layup, cut fiber spraying, resin transfer molding, and pultrusion. 

To make the crossbow, first the outline of the stock is drawn on the wood and cut out with a jig saw or a coping saw. After the stock shaping is done with a rasp or flies, the top section of the barrel is cut off and set aside. Next the 2 slots, for the trigger assembly and the bow,are cut The smaller slot In front of the bow opening is for the wedges that will hold the bow In placi. 

Compression molding is the method by which massive (700 kg), cylindrical (billet), rectangular, and sheet shapes of PTFE are produced. The blocks and cylinders can be solid or annular and are by far the heaviest objects produced from any fluoropolymer. The height of a cylinder can exceed 1.5 m. These billets are cut (skived) into wide thin films (<0.5 mm thick) or sheets (7 mm thick). Sheets, blocks, and cylinders are utilized as stock shapes for machining more complex shapes. The same principles are applied to mold any shape. 

Isostatic molding is a suitable alternative to compression and automatic molding techniques for the production of PTFE parts with complex shapes in a wide range of sizes. Compression molding can supply a stock shape which can be machined to obtain the desired shape. The drawback to this option is the... 

PTFE stock shapes may require extensive machining to produce complex shapes. Coolants should be applied to remove heat if the surface speed of the tool exceeds 150 m/min. At higher speeds, low feeds are helpful in reducing heat generation. Surface speeds between 60 and 150 m/min are satisfactory for fme-fmish turning. At these speeds, feed should be run between 0.05 and 0.25 mm per revolution. At higher speeds than 150 m/min, feed must be dropped to a lower value. 1 1... 

The annealing procedure for PTFE entails heating the stock shape 10°C above its service temperature (always below 327°C, melting point of PTFE). It should be held at temperature at the rate of 25 min/cm of thickness. Stresses are relieved during this operation. At the end of the hold time, the part should be cooled slowly to room temperature. After rough cutting the part to about 300-500 pm, re-annealing will help remove stresses induced by the tool, before the final cut is made. 

Pumps Injection molding, machining stock shapes PVDF, PFA, PTFE... 

Hot Stamping - This is a process for obtaining a specific geometry in a polytetrafluoroethylene stock shape. Hot stamping is conducted using a stamp which is heated well above (>360°C) the pol5mier melt point. Pressure and time are the other variables that can be manipulated to obtain the desired pattern. 

Fig. 6.n-8 Stock shapes (sheets, rods, tubes, plaques, rings discs, and bars) and simple parts (bushings) ofVespel polyimide non-melt processable compound (courtesy, DuPont, Newark, DE, USA)... 

Parts produced by compaction and shaping with the various, previously mentioned techniques are cured by heating in specially designed furnaces. While stock shapes ... 

Uses PVDF for long-life decorative finishes on building panels, film, filter cloth, instrumentation and control equip, linings, membranes, static mixers, pipe and fittings, pumps, stock shapes, valves, elec./electronicjacketing... 

Polyimide materials can be used as unfilled base polymers or have graphite, PTFE and molybdenum disulphide added to further enhance the low frictional properties and can be used to replace metal and ceramic parts. Material is available as moulded stock shapes, e.g. rod, rings and plate, which can be machined to the final dimensionally accurate product. Some grades can be processed by compression moulding while other grades can be processed to produce a finished product by direct forming. 

Gears, bushings, wear plates, stock shapes, bearings... 

Machining reqnires skilled labor, equipment, and other production resources. However, in certain cases, it can prove to be the least costly production method. If the total nnmber of parts to be produced is small, machining of stock shapes is generally less expensive than investing in expensive and complex molding. 

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