What methods can be used to obtain dimensional accuracy when machining parts? In the machining process of precision parts, there are many factors that affect the machining accuracy. Different processing methods can achieve different precision under different processing conditions; if the pursuit of processing precision will reduce production efficiency and increase the processing cost of precision mechanical parts. Therefore, precision machining enterprises should strive to improve efficiency and reduce production costs under the premise of ensuring quality. The machining accuracy of precision mechanical parts can be divided into dimensional accuracy, shape accuracy and position accuracy. Therefore, the level of machining accuracy is measured by dimensional tolerance, shape tolerance and position tolerance.
The method of obtaining the dimensional accuracy of the parts: test cutting method: first test cutting a small part of the machined surface, measuring the test cutting size, adjusting the position of the cutting edge of the tool relative to the workpiece to meet the processing requirements, and then test cutting measurement, test cutting measurement two or three times, when the precision machining dimensions meet the requirements, the entire surface to be machined for cutting. Machining precision mechanical parts of journal size test cutting turning, online measurement and grinding of journal size, test boring of box parts, manual fine grinding of precision measuring blocks, etc., all undergo test machining and shearing.
The accuracy achieved by the test cutting method can be very high, it does not require complex equipment, but it is time consuming and requires several adjustments, test cuts, measurements and calculations. The efficiency is low, depending on the technical water symptoms of workers and the accuracy of measuring instruments; the quality is unstable and only applicable to single-piece small batch production.
Adjustment method is to use samples or standard parts to pre-adjust the accurate relative position of machine tools, fixtures, tools and workpieces to ensure the dimensional accuracy of precision mechanical parts processing, the size of the parts remain unchanged during a batch of processing. . This is the adjustment method. Machining shaft parts on a multi-tool lathe or hexagonal automatic lathe, machining grooves on a milling machine, grinding external circles and hole systems on a centerless grinder are all adjustment methods.
If using milling machine fixture, the position of the tool is determined by the tool holder; the essence of the adjustment method is to use the fixed distance device or tool setting device or pre-set tool holder on the machine tool to make the tool reach a certain position relative to the machine tool or fixture. Accuracy, and then processing a batch of workpieces. In mass production, often use the travel limiter, prototype, prototype and other tool setting devices to adjust. The adjustment method has better machining accuracy and stability and higher productivity than the test cutting method. It does not require much operation of the machine tool, but the adjustment of the machine tool is very demanding. It is usually used for mass production and batch production.
Fixed-size method: precision parts processing using the corresponding size of the tool to ensure that the workpiece processing part of the size of the method is called fixed-size method, that is, the use of standard size tools for processing, precision machining surface size by the following formula to determine the size of the tool; that is, the use of a certain size accuracy of the tool to ensure the accuracy of the workpiece being processed. For example, using a square broach to pull out a square hole, using a drill, reamer, reamer or boring block to process the inner hole, using a combination of milling cutters on both sides of the workpiece to mill a groove, etc., are all part of the sizing tool method.