Study On The Electric Clamping Power Of Testing Machine And Its Electric Holding Device

Currently, manual, pneumatic and hydraulic driven chucking have been fullydeveloped in the area of testing machine fixture technology. However, the electric clampingdevice remains to be a fresh field. As a new clamping method, electric chucking has a lot ofunique advantages which are the most needed characteristic of each science and technologyproduct such as energy access convenient, easy automatic control, low pollution and lownoise. Therefore, it is an inevitable trend that testing machine fixture drive areelectrification.This article started from the most common wedge tensile clamp, analysed thecharacteristics of the fixture structure and clamping force, explored the feasibility of electricdrive, raised the theory of electric clamping, developed a practical electric clamping deviceand verified by experiments.Firstly, established the mechanical model of wedge clamp device to research the forcesituation of clamp splices and the influence of wedge angle on clamp force, Selected therepresentative15°as the research angel. Proposed a method to calculate the initialclamping thrust.Secondly, researched the clamping state of the fixture, found the clamping torquerequired is small throughout most of the time in the process of the whole clamping, only asmall period of time the large torque is needed to accomplish clamping while thedisplacement of the clamp splices is nearly zero. Considering the operation feature of themotor, the locked-rotor characteristic which means the motor can provide several times ofrated torque in locked-rotor state will be available, Since torque motor allows running stop up and will not burn out, we can provide great driving force for clamping device with asmall motor to save the cost.Thirdly, set up the structure system of electric fixture, designed two sets o f electricclamping structure scheme and chose the large load one for detailed design. By chain-drivento transfer the output torque of the motor, by the sliding lead screw nut to transform therotation movement of the motor shaft to straight movement, by the eccentric mechanism toensure the nut no rotation and drive the clamp splices a straight moving. Confirm theavailability of each parts by means of size calculation and check analysis and thencommence production and install the whole clamping device. Design the ordinary controlcircuitry and the electronic semiconductor control circuitry for the motor and make sure itcan run normally.Finally, mental tensile test was tried on a testing machine using the self-designedelectric clamping. Found that it can complete the clamping test of the maximum design load,the sample can exit smoothly at the end of the test with orderliness indentation on surface,which suggested that there was no skidding and peeling during the clamping process. Thesuccessful test proved that the designed electric fixture is up to standard, the theory of theelectric clamp proposed is feasible.This topic creatively put forward a new driving mode of testing machine chucking, andproved the feasibility and reliability of electric-driven through the practical example. Itprovides a new direction for testing machine clamp driving.