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What are the steps in the design of automotive inspection tools?

2021-06-25 Page view : 223 views

1 Detailed planning and modeling of workpieces and inspections-automotive inspection tools
  First, analyze the workpiece with reference to the part drawing, start to draw up the planning plan of the inspection tool, determine the reference plane, height condition 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 modeling of inspection is the key, which directly affects whether the inspection tools can accurately inspect the quality of the workpiece.

  Because the car body cover is mainly characterized by free surface, “reverse seeking of objects” is the current general method of modeling. Reverse seeking is a method of constructing prototype models with detailed shapes and structures based on existing prototypes of workpieces or objects, using a laser scanner to collect data, and through data processing, three-dimensional reconstruction and other processes. We use a laser scanner to scan the surface of the standard workpiece, collect the feature information of the part appearance mainly based on point clouds, convert the point coordinates to the car body coordinates, and use the surfacer software to process the point information to obtain the characteristic curve of the surface of the workpiece. , And then generate the final free surface model; together can check the generated prototype model through the maximum and minimum distances 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 according to the appearance scanned by the scanner. This is particularly important for detailed inspection planning.
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Finish the inspection of the free surface of the workpiece by the inspection tool, usually make the detailed appearance of the inspection and the inner and outer surfaces of the workpiece adhere to a constant gap of 3 or 5mm. The CNC machining machine tool can meet the higher precision requirements according to the planned surface digital model. The reciprocating movement of the special measuring tool for the inspection tool profile cooperation can measure the error of the workpiece surface. There are two main inspection methods for the external generalization of the workpiece. When planning the corresponding inspection tools: ①The detailed appearance of the inspection extends 20mm outward along the tangential direction of the outer generalization of the workpiece; ②Extends about 20mm downward along the normal direction of the external generalization of the workpiece. In general CAD software (such as UG), offset the workpiece surface inward at an interval of 3 or 5mm (if the generated workpiece model is the outer surface, add the thickness of the workpiece when making the offset), and then move the surface along The generalized tangential or normal extension is 20mm to obtain a detailed inspection appearance, and then stretched to the reference plane at a certain interval is the inspection detailed model. Because the body cover is relatively messy, most of the above-mentioned two methods are required for the detailed inspection of the appearance of the production inspection, and it is still difficult to conclude with regard to some special shapes. Schematic diagram of the processing of messy shapes. In the figure, the appearance of the workpiece of the engine support in the figure is marked by self-intersection and interference. In order to ensure that the main generalization of the workpiece is checked, I devoted myself to the inspection of the corners with the straight height difference, as shown in the figure. The detailed appearance of the inspection, after all, the detailed appearance of the inspection is summarized along the workpiece and double-lined with an interval of 3mm to facilitate the inspection of the workpiece. Of course, there will be many similar questions in the planning of inspection tools (especially the detailed inspection), and post-processing of the infiltration understanding and experience of the principles of inspection tools is required.

2 Planning and modeling of cross-section model
The inspection of the critical surface of the workpiece is usually completed through the cross-sectional template. The cross-sectional template of the inspection tool is divided into two types: rotary and piercing. When the span of the cross-sectional template exceeds 300mm, in order to ensure the inspection accuracy in the straight direction, it is usually The plan is piercing. Inspect the detailed appearance inspection is the inner and outer surface of the workpiece, and the section model is used to check the outer surface of the critical section. Usually the working surface is separated from the outer surface of the workpiece by 2-3mm. Its modeling method and inspection tool Similar in appearance. The plate material of the cross-section model is usually steel or aluminum, and some of the work surface can be made of aluminum or resin. The cross-section template of the chaotic shape will interfere with each other when it is rotated or pierced, and it can be divided into sections in the practical planning.

If it is set as a penetrating cross-section template, it will interfere with the positioning pin of the workpiece; if it is set as a single rotary type, because the workpiece itself is multi-folded, it will form an interference with the inspection or the workpiece, so it will be planned into two independent pieces. Rotating section model can satisfy all inspection requirements.

3 Positioning and clamping of workpieces-automotive inspection tools
  Accurate and reasonable positioning of the workpiece is the foundation of accurate measurement. The positioning method of the body cover on the inspection tool is mainly completed by the clamping and positioning of the positioning hole and the chuck or the clamping with a permanent magnet. Following the wide application of checking fixtures in car body making, both lever-type movable chucks and permanent magnets are available for purchase in series. The movable chucks are also equipped with brackets or brackets of different types and sizes. Most body covers have two positioning holes, main and auxiliary. The main positioning pins are usually cylindrical pins (round holes) or diamond-shaped pins (waist holes) to constrain the freedom in the X and Y directions; the auxiliary positioning pins are tapered pins. Or diamond plug pin, used to restrict the freedom of ZXYZ four directions. When planning the inspection tool, punch holes in the orientation of the positioning holes on the inspection details (subject to the insertion of the positioning pin bushings), and give the body coordinates of the positioning holes. At the same time, place the positioning spacers and movable chucks in a position with good rigidity and reasonable distribution of the workpiece to ensure the strong positioning of the workpiece. The number of clamping points should be reduced as much as possible to ensure that the movable chuck does not interfere with other parts when working. , And taking into account the convenience of the workers, the body coordinates of the exterior base on the positioning gasket are finally given.

4 Planning of the bottom plate assembly
The upper surface of the inspection section is stretched at a certain interval along the direction of the reference plane, so that the lowest point is greater than the thickness of 150mm to ensure that the inspection section has sufficient strength. Together, try to make the inspection section bottom surface, that is, the upper surface of the bottom plate assembly (base surface) ), in the integer orientation of the body coordinate system. The inspection bottom plate assembly is usually composed of a base plate, channel steel (when necessary, processing steel at the base), positioning blocks and universal wheels. After the base plate is fixed by the inspection section, other components can be selected according to the actual conditions of the standard type.

5 hole inspection
  In the body stamping parts, many major holes and flanges need to be inspected independently. In the planning of inspection tools, a 1mm thick boss is usually added to the surface of the inspection details. The base of the boss and the base of the workpiece hole are on the same axis, and the diameter is 5mm larger than the hole diameter. The double scribing method is used on the boss. When the accuracy requirement of the tested hole is relatively high, use the method of positioning hole to check with plug gauge and bushing. In the large body cover, because of the messy shape, huge volume, high production cost, single inspection target, poor flexibility, it is difficult to quickly obtain a lot of accurate information, and it has gradually been adopted by leading automated inspection methods (such as On-line inspection system), but with regard to the inspection of small stamping parts produced in large quantities, the current automobile manufacturers in my country still mainly rely on this type of inspection tool.

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