Talk about error compensation

Error compensation is a compulsory course for many precision industrial equipment, which is often the decisive factor to double the value of the product, and the importance of error compensation. This is also the short board of domestic equipment, domestic manufacturers often claim their own equipment precision to reach the level of foreign products, users in the early days can also really experience the nominal accuracy, but after a period of use, the accuracy has become worse, and with the passage of time and the season, equipment precision stability in constant change, although objectively speaking , the user of domestic equipment has congenital discrimination, maintenance and maintenance of equipment is not so equal, but the accuracy of domestic and foreign equipment, the gap is real, where is the difference? Material, assembly, quality testing and so on, but the error compensation is absolutely important, but also the domestic equipment manufacturers do not pay enough attention, and is low investment high return.

Error compensation is a knowledge, but also connected to the atmosphere, especially software compensation, the most cost-effective, to machine tool error compensation as an example, machine tool manufacturing will inevitably have mechanical errors, such as the straightness of the axes, pitch, offset pendulum, and so on, domestic and foreign manufacturers in the machine factory or delivery will provide error compensation correction services, and provide error compensation interface, allowing users to regularly detect the accuracy of calibration machine, but this step does not solve the high-precision machine tool with temperature and humidity and other environmental impact caused by deformation or error, and this is precisely the high-precision stability of the machine tool must solve the problem. To solve this problem, we need to comb the error compensation process and take the height accuracy of the nose point of the three-axis machine tool as an example.

Determination of Error source

Is the height change of the nose point of the three-axis machine tool telescopic? Absolutely not, the actual point to the table is the relative height of the offset, the offset may be the tool expansion, z-axis stretching, table and even the expansion of the bed, so first locate the error source, know where the difference in order to correctly analyze the cause of error, positioning error source can be set up by the ground laser tracker segmented detection bed, workbench , z-axis and tool expansion, can collect data at different time and different working conditions, and finally determine the error source.

Determination of the conditions of error generation

Assuming that the physical scaling of the z-axis affects the height of the nose point, then try to analyze the z-axis of the main material is cast iron, one meter cast iron per change of one degree Celsius, the length of about 12um, then whether the determining factor of its scaling is the temperature, whether the ambient temperature and the installation of the spindle temperature rise resulting in Z-axis Or to rely on the detection, in the z-axis temperature rise feature points to install the sensor, here the emphasis on the accuracy of the detection sensor must be higher than the detection accuracy requirements of an order of magnitude (in this case, assuming that the z-axis effective length of one meter, the need for compensation after the accuracy of 10um, then the temperature change is 10um, Temperature sensor precision to a magnitude of 0.1 degrees, of course, the repeatability of the sensor can meet the requirements can also, the reasons for their own experience), assuming that the results confirmed that the z-axis expansion is completely affected by the ambient temperature and the spindle temperature rise and determine the best detection point, then error compensation can be made.

Calculation of error compensation

Determine the error source and the conditions of the error, you can determine the causal relationship between the two, then there is one step-the quantitative relationship is the error compensation calculation, the traditional method has a linear table, function fitting, etc. if there are multiple singularities in the middle or the fitting effect is poor can try neural network, It can be tried in cases where the causal relationship is determined and the normal fit effect is poor.

Summarize

Error compensation is a goal is unclear and the effect is not clear process, need a lot of experience accumulation and experimental tracking, time-consuming laborious, if the method is not good results, especially in the domestic impetuous big environment, the technical personnel can not sink heart to do this thankless thing, This requires the equipment vendors to pay enough attention to allocate sufficient resources, under the strong gas to solve the problem, the value of products can be improved. such as material procurement, production assembly and quality inspection and other engineering problems are often in the physical strength, patience, spell experience accumulation, spell management, and foreign gap is often the case. Qi Baishi once had a famous saying:"Learn me to live, as if I Die", do not know plagiarism, price war, have to sink the heart to learn to absorb digestive distillation, ah, I now hear the leap-forward development on the trouble, step big too easy to pull the egg.

Talk about error compensation