German VMA coupling VMA model VMA price

VMA couplings transmit motion by welding or bonding a thin-walled corrugated tube (bellows) directly to the two coupling halves. This type of coupling features a simple structure, compact dimensions, ease of machining and installation, and high transmission accuracy. It is mainly used in low-power precision machinery and control mechanisms that require compact structures and high transmission accuracy. The coupling consists of two hubs and a thin-walled metal tube, connected by welding or bonding. Although many other materials are available, stainless steel and nickel are the most common materials for the metal tube. Nickel tubes are completed using electrodeposition. This method first involves machining a solid mandrel into a corrugated shape, electroplating nickel onto the mandrel, and then chemically dissolving the mandrel to obtain the nickel bellows. This method controls the precision of the bellows wall thickness and achieves thinner walls than bellows made by other methods. These thin-walled bellows give the coupling high sensitivity and rapid response, making it ideal for applications in extremely small and precise instruments.

VMA coupling structure

Couplings have two main structural forms: (1) achieves alignment of the two shafts using bolts in reamed holes and transmits torque through compression and shear on the bolt shanks; (2) achieves alignment by matching a shoulder on one coupling half with a groove on the other. The bolts connecting the two coupling halves can be ordinary bolts of grade A and grade B, with torque transmitted via the frictional moment at the mating surfaces of the two coupling halves. Flange coupling materials can be gray cast iron or carbon steel; cast steel or forged steel should be used for heavy loads or when the circumferential speed exceeds 30 m/s. Depending on the magnitude of the transmitted torque, all bolts on the flange can be reamed-hole bolts, or half can be reamed-hole bolts and the other half ordinary bolts.

VMA coupling features

1) Misalignment compensation. The misalignment compensation of a coupling refers to its ability to compensate for the relative displacement between two rotating components. Manufacturing and installation errors between connected components, temperature changes during operation, and load-induced deformation all impose requirements on misalignment compensation. This capability compensates for or alleviates additional loads on shafts, bearings, couplings, and other components caused by relative displacement between rotating components. 2) Damping. For applications with frequent loaded starts or varying working loads, the coupling must include elastic elements that provide buffering and vibration damping to protect the prime mover and driven machine from damage. 3) Safety and reliability, with sufficient strength and service life. 4) Simple structure, easy assembly, disassembly, and maintenance.

VMA coupling selection

Selection of coupling type: When selecting a coupling type, consider the following items. 1) The magnitude and nature of the torque to be transmitted, requirements for buffering and vibration damping, and the possibility of resonance. 2) The degree of relative axial displacement caused by manufacturing and assembly errors, shaft loading, thermal expansion deformation, and relative motion between components. 3) Permissible outer dimensions and installation methods, including the necessary operating space for assembly, adjustment, and maintenance. For large couplings, disassembly and assembly should be possible without axial movement of the shaft. In addition, consider working environment, service life, lubrication, sealing, and economic factors, and refer to the characteristics of various couplings to select a suitable type.

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