Design and mechanical characteristics analysis of three-dimensional measuring probe for flexible hin

The probe is an essential component of a coordinate measuring machine (CMM). In recent years, researchers have been increasingly focusing on three-dimensional probes due to their versatile measurement parameters and flexible measurement methods. Both domestic and international researchers have been dedicated to the application and development of probes, including the exploration of new probe structures and probe error theory. As a result, three-dimensional probes are being used more frequently in various types of coordinate measuring equipment.

The integral probe has emerged as the main direction of development because of its mechanical performance and theoretical model being closer to ideal, as well as its high integration and precision. The integral three-dimensional probe features a flexible hinge mechanism, which has been thoroughly analyzed for its mechanical properties.

The structure design of the three-dimensional measuring head includes a guide mechanism and an overall structure design. The guide mechanism consists of three hinges - one for translation in the X direction, one for translation in the Z direction, and one for translation in the Y direction. These hinges are interconnected in a parallelogram configuration, ensuring that the probe moves in parallel during three-dimensional measurements.

The overall structure design of the 3D probe includes the translational actuators (hinges) in each direction, as well as displacement sensors for measuring the displacements of these actuators. The measuring head is connected to the guide mechanism through threads. During three-dimensional measurement, the measuring head is fixed to the coordinate measuring machine, while the workpiece to be measured is fixed on the workbench. The probe then makes contact with the part to be measured, and moves in the X, Y, and Z directions. The inductance sensors detect the probe's movement, which is then processed to obtain measurement results.

The integral three-dimensional probe mechanism is achieved through the overall cutting method. The outline and size of the flexible hinge are designed according to theoretical considerations, and the entire mechanism is processed using wire cutting. The mechanism consists of two parallelogram mechanisms in each direction, making a total of eight flexible hinges. This design allows for translation within a small displacement range, enabling three-dimensional movement of the measuring head. The composite mechanism reduces the overall volume of the probe and improves its integration. Sensors and acquisition circuit boards are integrated into the hollow parts of the mechanism to reduce external interference and improve detection accuracy.

The flexible hinge mechanism used in the three-dimensional probe is a link mechanism without mechanical assembly. It utilizes the elastic deformation of the material to achieve the desired constraint. This approach offers advantages over traditional mechanical constraints, such as having no gap or friction and being closer to an ideal constraint. The use of a parallelogram mechanism in the hinge mechanism ensures high displacement fraction, high guiding accuracy, and a compact and lightweight structure.

An analysis of the bending moment in the flexible hinge mechanism reveals the relationship between the external force and the bending moment. By analyzing the rotation angle of the hinge and the movement of the workbench, it is found that the rotation angle and the displacement are proportional to the force. The flexible hinge mechanism behaves similar to a spring, with an elastic coefficient that can be calculated based on its design parameters.

In conclusion, this article discusses the design and analysis of an integral three-dimensional probe mechanism based on a flexible hinge. The findings highlight the relationship between the external force and the rotation angle and displacement, emphasizing the proportional relationship between these factors. The research on parameter errors, the nonlinear deformation of the flexible hinge, and theoretical compensation are areas that require further exploration in the design of three-dimensional probe mechanisms. Through continuous advancements and improvements, the use of three-dimensional probes in coordinate measuring equipment will continue to expand, leading to enhanced measurement accuracy and precision.