Publish Time: 2022-07-08 Origin: Site
In automobile manufacturing, in order to ensure the high-speed production and quality assurance of each component, batch testing is carried out with the help of high-precision measuring instruments. The CMM is the most widely used measuring instrument in the automotive industry, which can meet most of the measurement needs with high precision and high efficiency. In addition, for some small parts or parts that cannot be measured by contact, the image measuring instrument is used for testing. The image measuring instrument can quickly and accurately measure the contour, flatness, hole depth, R angle, plane size, etc. of auto parts. It has the functions of taking pictures, making reports, and generating CAD drawings.
1. Select a measuring machine suitable for the stroke of the product workpiece. For the unit of use of three coordinates, it is very important to judge the model (device size) of the device. If the measured itinerary is too small, it will not achieve the purpose of measurement, and if the measured itinerary is purchased too large, it will waste resources. Generally speaking, we choose the equipment model according to the maximum size of the workpiece we most often detect. For example, if a workpiece is 400×500×300mm, then we only need to choose 500×600×400mm for the model of the equipment. If at this time, you want to measure a slightly larger workpiece, there is also a solution. You can still measure with a device with a 500×600×400mm stroke, you just need to adjust the measurement method. Here are two methods recommended for you: one is to use splicing to find a common reference on the workpiece for measurement; the other is to use the diagonal line of the equipment to increase the measurement range. Therefore, the size of the stroke must be considered when purchasing a CMM.
2. Select the measuring machine with the appropriate product accuracy index. We need to select the appropriate measuring equipment for inspection according to the processing accuracy of our products, generally follow the economical and applicable type, and refer to the "3 times principle". The three-coordinate is a detection equipment for length measurement, so its detection accuracy is related to the length. For example, the accuracy of some equipment is marked as 2.8+L/300μm, L is the detection length of the workpiece, and 300 is the parameter provided by the manufacturer. , the longer the length, the greater the precision. Therefore, it is very important for us to choose the appropriate equipment for detection accuracy. For example, if the machining accuracy of a workpiece is ±0.01mm, then we should choose a reasonable accuracy index of 0.0033mm to meet the requirements.
3. To choose the appropriate type of measuring machine. With the continuous development of the current measurement industry, automatic or even automatic type (automatic type means that the probe is a self-selected angle probe) should be a mainstream development direction. Of course, this can be selected according to your own practicability. If the detection accuracy is not high and the frequency of use is not high, it is recommended to choose the manual type. If the amount of measurement products is large and the accuracy requirements are relatively high, it is recommended to choose the automatic type or even the full type. Automatic three-coordinate. The automatic measuring machine is chosen because it has these advantages over the manual type: programmable measurement and batch measurement, contour error measurement, runout error measurement, and high repeatability accuracy. If a manual measuring machine is used to measure the profile error, the measurement result will have a large error. The correct profile error should be the theoretical value of the given element and the theoretical vector, and the stylus is measured along the vector direction, so as to obtain the difference between the theoretical element and the actual element in the vector direction, while the manual three-coordinate It is simply impossible to have the stylus measure the element in the direction of the vector, so the resulting profile values will vary widely.
4. Choose the appropriate software when choosing a measuring machine. This is also very important. The following aspects can be focused on:
(1) The share of software in the measurement industry, that is, the mainstream orientation of the measurement industry;
(2) The choice of software functions and whether the calculation method of the software is reliable, and what determines it;
(3) Whether the tolerance report meets the requirements. The power of software functions directly affects the efficiency and reliability of our measurements. For example, are there arrays? If it is an electronic product measurement, and the software does not have an array function, the measurement efficiency will be very slow; is it fast enough to import a 3D model? At present, many measurement softwares are quite slow to import digital models, especially large digital models (above 20M), and some of them cannot be imported at all if they have 100M, which is basically fatal to the measurement of mold industry, automobile inspection tools, plastic products, etc.; Is tolerance evaluation convenient? Is it fully functional? Sometimes when we measure the degree of location, there will be the largest entity, the smallest entity, and the principle of independence. Can it be evaluated, is it convenient or not? Is software model programming, offline programming fast? A series of problems are all that we need to demonstrate and consider when choosing software.
5. Comprehensively consider the three-coordinate production enterprises. Is the service in place? Is the company big enough? Can the production environment meet the conditions for precision equipment production? How is your reputation in the measurement industry? Whether it can provide better guarantee for the later service of purchasing equipment.
6. The operation efficiency of the equipment and the stability of the machine are the selection of the repeatability of the equipment. These are mainly determined by material, structure, control system and so on. At present, the materials used in the market mainly include: granite, aviation aluminum, ceramics, etc. Among them, the manual type and some domestic types are basically made of granite, the imported and high-end ones are basically aviation aluminum, and ceramics are basically used in ultra-high-precision equipment, such as aerospace and so on. What is the main difference between these three materials? First of all, marble is inert and has poor thermal conductivity. Once the temperature changes, extrusion and bending deformation will occur. Aviation aluminum has better thermal conductivity. The temperature change is generally a linear change, controllable, and the material is light. quick. And ceramics are the best of them all. However, the cost is also relatively expensive, generally not used in economical equipment. There are also differences in structure and shape, currently there are squares, equilateral triangles, right-angled triangles, etc. It mainly determines the torsion and inertia of the equipment. Everyone knows that the center of gravity of the triangle is the lowest, and the equilateral triangle is the lowest, so the inertia of the equipment is small and the repeatability is natural.