The ZeMA testbed was developed for condition monitoring, lifetime prognoses and end-of-line tests of electromechanical cylinders (EMCs) with a spindle drive.
The ZeMA testbed was developed for condition monitoring, lifetime prognoses and end-of-line tests of electromechanical cylinders (EMCs) with a spindle drive. Long-term high load and speed driving tests are carried out at the testbed until an EMC failure occurs. Based on this, relevant sensors and characteristic signal patterns can be identified for condition monitoring as well as residual lifetime estimation of the EMCs.
The test set-up consists of the tested EMC and a pneumatic cylinder to simulate a variable load on the EMC in axial direction. To accelerate the wear progression, a force in lateral direction can also be applied with a fluidic muscle on the EMC. The actuators are coupled with a joint construction to allow lateral displacements. The servo motor and the EMC are coupled through a torque measurement box.
After the first test, the joint construction was replaced by a rigid connection. So, no lateral force is actually applied on the EMC.
The following table gives an overview of the various process sensors used in the testbed.
Electromechanical cylinders are widely used in applications that require a high repetition accuracy of ~10 µm and high forces. Due to their capability to combine high loads and precision, both assembly / handling systems and tool machines are typical applications of EMCs. The spindle drive as a passive mechanical component of an electromechanical cylinder converts the rotary movement of the driving servo motor into linear stroke. The wear and failure relevant parts of the EMC are the plain bearing (1), the ball bearing (2) and especially the ball screw drive (3).
The first test started in 2017. A working cycle during the test consists of a forward stroke, a waiting time and a return stroke, always using maximum acceleration. The entire working cycle lasts 2.8s. The combination of a high axial load, a high traverse velocity and a high acceleration results in a fast wear progression.
The deviation of the setpoint from the actual value of the control parameters of the motor controller is used as failure criteria, i.e. the test is completed when the EMC can no longer follow the drive commands due to increased friction.
This test bed was developed in the frame of the project MoSeS-Pro funded by the German ministry for Education and Research. Support by Festo AG for designing and realizing the test bed in gratefully acknowledged.