Sensors, Switches & Transducers
Transducers (pressure sensors, load cells, accelerometers, solenoids) require parts to be joined leak tight and mechanically sound. These devices require welds such as thin film diaphragms to sensor bodies, welding of end caps and connectors, and final welding of sensor sub-assemblies.
Many of these elements require parts to have a hermetic seal and mechanically strong joints. A low heat input weld process must avoid damage and distortion yet often join thin metal diaphragms to thicker sections. In many cases welds must also be performed in close proximity to delicate glass to metal seals.
Modern Plasma and TIG equipment and welding techniques have improved to where these processes can address applications like these which were formerly catered to by more expensive processes such as laser or electron beam welding. Precision arc welding systems are now the optimum solution. This has helped to reduce or eliminate the formerly high capital costs, running costs and service costs associated with the manufacture of these transducer products.
Seals, Diaphragms & Bellows
Metal bellows are used to connect two assemblies together, providing a leak tight seal that allows for flexure. Welded metal bellows are created by welding thin pairs of metal plates on their inside diameters and then assembling these sets of pairs together on a mandrel for welding on their outside diameter.
Due to the number of convolutions required for a bellows, two factors become imperative: weld quality and weld speed. Bellows are normally welded with a micro-arc process such as TIG or Plasma, each process offering specific advantages of their own.
The TIG/micro-TIG arc is generally "softer" that a corresponding Plasma arc. As such, many bellows welding organizations prefer the TIG process for welding the outer diameters of the bellows because it is more forgiving if heat sink tooling is not in intimate contact with the bellows material.
The Plasma process often offers increases in weld speed and also allows for longer times before electrode maintenance is required. The Plasma arc welding process also offers the additional feature of deflection nozzles which allow the arc to exit the nozzle at 45 or 90 degrees to the axis of the torch. This can assist in gaining access to small internal weld joints.
Metal seals have been manufactured by welding two thin stamped disks together to create a spring seal of exceptional quality and functionality. This can replace the close tolerance machining previously required for these elements, increasing performance while simultaneously reducing cost to manufacture.
Tool, Die, & Mold Repair
Heat is the enemy of dimensional stability for parts that have already undergone heat treatment to enhance the performance of their wear surfaces. A whole repair industry has sprung up to assist companies wishing to re-use components with slight nicks and dents from misuse or wear.
The ability of modern micro-arc power supplies to gently start a low amperage arc and make repairs has provided users with a unique alternative to conventional repair and heat treatment. This avoids the distortion and/or metallurgical damage that can result from the heat of normal welding.
Both micro-TIG and micro-Plasma welding processes are used for tool, die and mold repair. For outside edges the Plasma process offers great arc stability and requires less skill to control the weld puddle. To reach inside corners and crevices the TIG process allows the tungsten welding electrode to be extended in order to improve access.
Plasma & Micro-Plasma Powderfeed Welding
Plasma and micro-Plasma powderfeed welding systems may be used for repair or hard surfacing of components in a variety of sizes. Plasma transferred arc (PTA) powderfeed systems melt the base metal and add powder to the weld puddle through the weld torch. These systems can be used for manual or automatic build-up of edges, tool, die and mold repair, cladding or any part requiring material buildup.
Powderfeed welding has a true metallurgical bond to the base material. The weld puddle can be smaller and the powderfeed rates better controlled to offer excellent weld characteristics. The welding skill level required for powderfeed welding is significantly less than with manual wirefeed. Powders can be made in any alloy to be used on a variety of materials. Weld current amperages range from 0.05 amps (micro-PTAwelding) to over 300 amps (PTA welding).
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