1 Introduction
As an important part of advanced manufacturing technology, special processing technologies increasingly affect modern processing methods and continue to broaden our manufacturing model. The low-speed wire-cut WEDM as a representative of special processing is not only widely used in the fields of medicine, aviation, electronics, electrical appliances, automobiles, home appliances, and light industry, but also has a large market capacity at home and abroad. The research value of high-tech products is self-evident.
This paper analyzes the bed components that carry the main components of the low-speed WEDM machine. It is the main carrier of the work table components and the wire-drawing box components and is the key assembly structure of the low-speed wire-wound wire EDM machine. The process is subjected to complex load conditions, and the structure of the plate and shell is complex, and vibration is easily generated due to the excitation of various vibration sources. The vibration of the bed part is an important index that affects the accuracy of the overall machine tool, and it must have enough static stiffness to ensure the assembly and use requirements. Therefore, the most important and basic modal study of the low-speed WEDM machine is the modal analysis of the bed.
2 Modal study
Firstly, the 3-D solid model of the bed was built using advanced 3D CAD software UGNX4, then the bed model was imported into Hypermesh 7.0 software, and the finite element model of the bed was established using HyperMesh's powerful finite element preprocessing function. The necessary geometrical cleaning during the pre-treatment process is indispensable (eg removal of excessive chamfers, screw holes for mounting positioning, etc.), pre-set material for the bed is cast iron, density 7.3g/cm3, mooring The loose ratio is 0.25 and the elastic modulus is 150 GPa. The UG modeling bed body and the imported finite element mesh model are shown in Figure 1.
The total number of finite element models of the entire bed mechanism divided is 523,888 units, the number of nodes is 139,267, and the degree of freedom of the total finite element model is 398,940. For bed design requirements, set the bed surface to 0 degrees of freedom relative to the ground to ensure the relative stability of the parts.
The modal analysis parameters of the finite element model are set in the real feature analysis card EIGRL of HyperMesh. Calculate the 1st to 10th order modes from 0 to 1000 Hz, and set the load step in LOADSTEP uniformly, and then submit the OptiStruct solver for optimization. The result of modal analysis is shown in Figure 2 (only the first 14 steps are listed) :
Due to the article space relationship, the modal diagrams from the first, fourth, eighth, and tenth orders are selected as shown in Figure 3, where different colors represent different frequency ranges:
3 results analysis and program improvement
From the post-processing display, it can be seen that the natural frequency of the body part of the low-speed wire EDM wire-cutting machine tool is slightly lower, and it is easy to generate large deformations at the place where the ball screw used to drive the worktable and the parts that carry the wire-drawing box are located; Because the supporting strength of the wall around the bed is not enough, local vibration deformation is easy to occur; the probability of a large amount of deformation is low, and the mode shape is complex. There are three options for formulating a solution to this problem:
1. Increase the wall thickness at the corresponding thin wall to increase its stiffness and improve its modality.
2. Damping materials are added at correspondingly larger amplitudes to improve their modality.
3. Ribs are placed at correspondingly larger amplitudes.
After the above improvement program is analyzed and calculated, the comparison between each improvement scheme and the original design's fundamental vibration frequency is shown in Figure 4.
Taking into account factors such as cost, ease of processing and aesthetic appearance, the third option is more reasonable. The addition of stiffeners inside the bed not only supports the connection between the bed body and other components, but also takes into account the bed side. Deformation of the wall. The structure of the modified bed is excellent in modal performance, and its structure is shown in Figure 5.
4 Conclusion
Through the finite element modal analysis results of the body parts of the low speed wire cutting machine tool, a variety of improved design methods of the machine tool bed are proposed, and further modal analysis and comparison are carried out to prove that the selected improved program has better stiffness. It is the successful application of HyperMesh software in the design analysis of special processing machine tools.