German ROTEX coupling ROTEX model ROTEX price

ROTEX couplings utilize their structural characteristics to enable continuous rotation of the connected shafts and reliably transmit torque and motion, even when the two shafts are not on the same axis and an angular misalignment exists. The most significant feature of universal couplings is their large angular compensation capability, compact structure, and high transmission efficiency. The angle between the two shaft axes varies with different structural types of universal couplings, generally ranging from 5° to 45°.

ROTEX coupling introduction

It 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 commonly used materials for the metal tube. Nickel tubes are produced using an electro-deposition process. 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 a nickel bellows. This method allows for precise control of the bellows wall thickness and can achieve thinner walls than those produced by other methods. These thin-walled bellows give the coupling high sensitivity and rapid response, making it ideal for applications in extremely small and precision instruments.

ROTEX coupling features and applications

1) Bellows couplings are backlash-free and highly sensitive. 2) High elasticity provides better equipment protection. 3) Capable of absorbing vibration while compensating for radial, angular, and axial misalignments. 4) Resistant to oil contamination and corrosion. 5) Torsionally rigid, with identical rotational characteristics in both clockwise and counter-clockwise directions. 6) Commonly used in industrial machinery such as CNC machine tools and indexing tables. The elastic element of a bellows coupling is a precision metal bellows, available in flexible and rigid series. The flexible series offers greater elasticity and is often used in micro-applications such as encoders and sensors, while the rigid series is mainly applied in servo motors and CNC machine tools (machining centers).

ROTEX coupling troubleshooting

Based on the coupling structure, power is transmitted from the coupling to the power output shaft (gearbox shaft) via a clamping hub assembly, and to the power input shaft via a clamping collar. Power is transmitted between the clamping end and the clamping hub end of the coupling through the bellows, which are bonded to the clamping hub and clamping collar. The fault location is at the junction of the clamping collar and the bellows. Two pre-deformation grooves are machined radially into the clamping collar. The groove width is approximately 2mm. On the side with the clamping screw, the groove is open through the diameter but does not penetrate fully in the depth direction at the junction with the bellows, resulting in a beveled cross-section. The other groove is not open radially, but its longitudinal section at the junction with the bellows also does not penetrate fully, resulting in a beveled cross-section. During clamping, the clamping screws are tightened to the specified torque using a torque wrench. The deformation of the clamping collar eliminates the clearance between the bore and the shaft to achieve clamping. As shown in the cross-sectional view, due to the presence of the two pre-deformation grooves, the cross-section at this location is weaker, and deformation occurs primarily at these grooves. The pre-deformation groove on the side with the clamping screw has the smallest cross-sectional area and is the weakest point. Permanent figure-eight deformation marks at its end indicate that the stress in this area during clamping is high, exceeding the yield limit of the super-hard aluminum. According to the stress distribution diagram, once the bevel gear box and main gearbox are assembled and clamped, the stress value at the bonded interface of the pre-deformation groove on the clamping screw side is 164Mpa, and the deformation magnitude is 0.027mm. During launcher operation, the coupling is subjected to alternating composite stresses, causing even greater stress and deformation at this location. If minor defects such as voids, inclusions, or flaws exist at the bonded interface during manufacturing, micro-cracks will first form at the defective areas within the region of highest stress on the coupling's bonded interface when the alternating stress exceeds the bond strength, creating a fatigue source. Due to stress concentration at the crack tip, the crack gradually propagates as the number of stress cycles increases and the duration of constant stress extends. As the crack spreads, the bonded interface is progressively weakened. When the crack reaches a certain size, fatigue failure occurs. The coupling functioned normally during initial testing, but as usage time increased, the cracks gradually propagated. Even under low loads, the coupling eventually failed. The presence of stress at the bonded joint is a potential hidden cause of failure. To avoid generating high stress when the coupling clamping collar is tightened, annular grooves are typically cut into the clamping collar for stress relief.

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