What are the steps in the design of automotive

by:Top Talent     2020-07-14
1 Detailed planning and modeling of workpiece and inspection
  

  First analyze the workpiece with reference to the part drawing, start to draw out the plan of the inspection tool, determine the reference level and height of the inspection tool, check the cross section, positioning surface, etc., and make its two-dimensional schematic diagram briefly.

  

  In the planning of automobile inspection tools, the detailed planning and modeling of inspection is the key, which directly affects whether the inspection tools can accurately check the quality of the workpieces.

  

  Because the body cover parts are characterized by free curved surfaces, 'reverse seeking' is the current general method of modeling. Reverse seeking refers to the method of constructing a prototype model with a detailed shape and structure based on the existing workpiece or prototype, collecting data with a laser scanner, and after data processing, three-dimensional reconstruction and other processes. We use a laser scanner to scan the standardized workpiece appearance, collect the feature information of the part appearance that is mainly point cloud, convert the point coordinates to the body coordinates, use the surfacer software to process the point information, and obtain the characteristic curve of the surface of the workpiece. , And then generate the final free-form surface model; together we can check the generated prototype model through the maximum and minimum interval from the point cloud to the surface. It should be noted that the model obtained at this moment is a sheet model with no thickness. It is necessary to identify the model as the internal or external appearance of the workpiece based on the appearance scanned by the scanner. This is particularly important for detailed planning of inspection.

  

The inspection of the free surface of the workpiece by the inspection tool is usually completed, and the detailed appearance and the internal and external surface of the workpiece are adhered to a constant gap of 3 or 5mm. The CNC machining machine can reach the requirements of higher accuracy according to the planned surface model. The measuring tool's special measuring tool can be reciprocated to measure the error of the workpiece surface. There are two main inspection methods for the general outline of the workpiece. When planning the corresponding inspection tool: ①The detailed inspection surface extends 20mm around the general tangential direction of the workpiece; ②Extends 20mm around the normal direction of the workpiece. In general CAD software (such as UG), offset the surface of the workpiece by 3 or 5 mm inward (if the generated workpiece model is external, add the thickness of the workpiece when making the offset), and then follow the curved surface The general tangential or normal direction extends 20mm to obtain a detailed inspection appearance, and then stretches to the reference plane at a certain interval is the detailed inspection model. Because the body cover parts are relatively messy, most of the above two methods are required for the detailed inspection of the appearance of the inspection, and this is still difficult to complete with regard to some special profiles. Figure 2 shows a schematic diagram of the processing of messy profiles. In the figure, the appearance of the workpiece of the inner engine support is significantly intersecting and interfering at two places, in order to ensure that the main summary of the workpiece is checked, dedicated to the inspection at the corner with a straight height difference, generated as shown in the figure The detailed appearance of the inspection, after all, is summarized along the workpiece and double-dashed at 3mm intervals in order to facilitate the inspection of the workpiece. Of course, many similar questions will be encountered in the planning of inspection tools (especially inspection details), all of which require post-processing on the infiltration and experience of inspection tool principles.

  

  2 Planning and modeling of section template

  

The inspection of the critical surface of the workpiece is usually completed through the cross-section model. The cross-section template of the inspection tool is divided into two types: rotary and puncture. When the span of the cross-section template exceeds 300mm, in order to ensure the inspection accuracy in the straight direction, it is usually The plan is piercing. The detailed appearance inspection is to check the internal and external appearance of the workpiece, and the cross-section model is to span the external appearance of the workpiece. It is used to check the external appearance of the critical section. Usually, the working appearance is 2-3mm apart from the external appearance of the workpiece. Appearance is similar. The material of the panel body of the cross-section model is usually metal such as steel or aluminum, and some of its working appearance can be made of aluminum or resin. The cross-section template of the chaotic shape will intervene when it is rotated or penetrated, and it can be processed in sections in practice planning, as shown in Figure 3.

  

If it is set as a piercing section template, it will interfere with the positioning pin of the workpiece; if it is set to a single rotary type, because the workpiece itself has multiple folds, the formation and inspection details or the workpiece will be interfered, and it is planned to be two independent Rotating section model can satisfy all inspection needs.

  

  3 Workpiece positioning and clamping ――Automobile inspection tool

  

  The precise and reasonable positioning of the workpiece is the foundation of accurate measurement. The positioning method of the vehicle body cover on the inspection tool is mainly completed by positioning and clamping the positioning hole or the chuck or clamping with a permanent magnet. With the wide application of inspection tools in car body production, lever-type movable chucks and permanent magnets are available in a series of products. The movable chucks are also equipped with different types and sizes of brackets or brackets. Most body cover parts have main and auxiliary positioning holes. The main positioning pin is usually a cylindrical pin (round hole) or a diamond-shaped pin (waist hole) to restrict the freedom in X and Y directions; the auxiliary positioning pin is a conical pin Or diamond-shaped plug pin, used to restrict the freedom of ZXYZ in four directions. When planning the inspection tool, punch holes in the location of the positioning hole on the inspection details (subject to the positioning pin bushing), and give the body coordinates of the positioning hole. Together, the positioning spacers and movable chucks should be placed in a position with good rigidity and reasonable distribution of the work piece, to ensure that the number of clamping points should be reduced as much as possible when planning the strong positioning of the work piece, and ensure that the movable chuck does not interfere with other parts when working. , And taking into account the convenience of the worker's operation, after all, the body coordinates of the exterior base on the positioning gasket are given.

  

   4 Planning of the bottom plate assembly

  

In the detailed inspection, the surface is stretched by a certain interval in the direction of the reference plane, so that the lowest point is greater than 150mm in thickness, to ensure that the detailed inspection has sufficient strength, and try to make the detailed bottom surface, that is, the upper surface of the bottom plate assembly (base surface) ), in the integer orientation of the body coordinate system. The detailed inspection bottom plate assembly is usually composed of a base plate, channel steel (if necessary, steel is processed at the base), a positioning block, and a universal wheel. After the base plate is fixed by the detailed inspection, other components can be selected according to the actual situation.

  

   5 hole inspection

  

  Automatic inspection of many main holes and flanging in body stamping parts. In the planning of the inspection tool, a boss with a thickness of 1mm is usually added to the inspection surface. The base of the boss is on the same axis as the hole base of the workpiece, and the diameter is 5mm larger than the aperture. The double scribe method is used on the boss Check

  

  When the accuracy requirement of the measured hole is relatively high, the method of selecting the positioning hole is checked with a plug gauge and a bush. In the large body cover parts, because of the disordered shape, huge size, high manufacturing cost, single inspection target, and poor flexibility, it is difficult to quickly obtain a lot of accurate information, and it has gradually been used by leading automated inspection methods (such as Online inspection system), but for the inspection of small stamping parts produced in large quantities, China's automobile manufacturers still rely mainly on such inspection tools.
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