There are many factors affecting machining accuracy in the process of precision parts machining, and different machining methods can achieve different accuracy under different machining conditions; if you pursue machining accuracy, it will reduce production efficiency and increase the cost of precision parts machining. Therefore, precision machining enterprises should try to achieve the purpose of improving efficiency and reducing 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 cut a small part of the machined surface, measure the size of the test cut, adjust the position of the cutting edge of the tool relative to the workpiece according to the processing requirements, then test cut and measure again, after two or three test cuts and measurements, when the precision machining dimensions meet the requirements, and then cut the entire surface to be machined. Precision mechanical parts processing journal size trial cutting turning, journal size online measurement and grinding, box parts hole system trial boring processing, precision measuring block manual fine grinding, etc., all through the trial machining shear method.
The accuracy achieved by the trial cut method may 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 used for single-piece small batch production.
Adjustment method is to adjust the accurate relative position of machine tools, fixtures, tools and workpieces with sample or standard parts in advance to ensure the dimensional accuracy of precision mechanical parts processing, and the dimensions remain unchanged during the processing of a batch of parts... 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 the milling machine jig is used, 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 on the machine tool or the pre-set tool holder to make the tool reach a certain position relative to the machine tool or jig. Accuracy, processing another batch of workpieces. In mass production, the tool setting device is often adjusted using the travel limiter, sample machine, prototype, etc. The adjustment method has better machining accuracy and stability and higher production efficiency than the test cutting method. It does not require high requirements for machine tool operation, but high requirements for machine tool adjustment. It is commonly used in mass production and mass 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.