Extrusion Guns

Bolton Emerson Egon John Brown Kroeneit Nordson 

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Figure 34 Different patterns available with extrusion guns.

The pump type (ratio and flow rate) to be used is decided according to the length of hoses between the pump and the extrusion guns, the viscosity of the product and the required flow rate. 

Manual units all operations reqnire handling by an operator. Common examples are the well-known mannal extrusion guns, manually operated peristaltic pumps, hand-held pinch valves and the hot-melt guns. 

Application of cold extrusion process to manuf of artillery shells is discussed in Refs 8, 9. 10. 12, 13 14 and its application to manuf of gun-barrels is briefly discussed as the Auto-frettage or Self-hooping in Vol 1, p A510-R of this Encycl... 

The viscosity of nonflowable products is determined by an extrusion test. A Semco 440 nozzle or its equivalent is attached to a standard adhesive/sealant cartridge filled with the material to be tested. The cartridge is then placed in an air-operated sealant gun set for a pressure of 90 to 95 psi. The weight of material that is extruded in 10 s is measured, and the extrusion rate is reported in grams per minute (g/min). Care must be taken to clear trapped air from the cartridge and nozzle. 

Most systems function with paste but Young et al. (10) described the use of a process whereby the extrusion was with a hot-melt system, the extrudate cut in a pelletizer (Randcastle RCP-2,0, Randcastle Inc. Cedar Grove. New Jersey, U.S.A.) into cylindrical pellets, which were then spheronized on a conventional spheronizer (Caleva Model 120, AC Compacting LLc, North Brunswick, New Jersey, U.S.A.) heated with a heat gun to 65-70 C while dusting with microcrystalline cellulose (MCC) to prevent agglomeration. The picture of the pellets shown to illustrate the product appears round but the process times of 45 and 80 minutes are considerably longer than those involved with the paste systems. 

Discs use large conical-type deflectors usually mounted in the vertical downward position so that powder is deflected in a horizontal position in a 360°radius. An omega (Q) loop conveyor system normally surrounds the powder disc that is usually mounted on an oscillator or reciprocator for vertical up-and-down motion. The powder can be charged by a corona edge or by tribocharging guns. Typical applications for the powder disc are vertical extrusions or wire goods. 

Extrusion welding Is done with guns that utilize resin pellets or reels of small diameter welding rod. Extrusion welding with pellets Is used on essentially horizontal surfaces. 

High-pressure extrusion i.e. jetting—widely used for hot melt systems where a jet is fired by a pressurised gun. 

With extrusion welding, the support is prepared (beveled or preferably double beveled) and preheated using a hot air gun to reach a surface temperature of 250°C-260°C. The molten extrusion (maximum length— 20 cm) is pressed into the bevel using stainless steel or PTFE coated tools. 

Spray deposition The spray deposition process, which was developed by Osprey Ltd during the late 1970s for producing monolithic alloys [365], has been adapted by several manufacturers to produce particulate-reinforced MMC billets with a residual porosity of 5% [366]. The porosity is eliminated by a secondary processing, such as extrusion or rolling. A spray gun is used to produce an atomized stream of aluminum alloy, into which heated SiC particles are injected. An optimum particle size is... 

Adhesives are often classified by their mode of application. Depending on viscosity, adhesives can be coated, sprayed, or brushed. Adhesive pastes and mastics are applicable by extrusion and may be applied by syringe, caulking gun, or pneumatic pumping equipment. 

Caulking gun n. A device for applying caulking compound by extrusion. In a hand gun. 

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