CNC machining has become more and more widely used in today's machinery manufacturing and processing industry. In particular, economical CNC machine tools are widely used in some enterprises, especially small and medium-sized enterprises, due to their wide range of processing, high efficiency, stable quality, and low prices. The application and development. However, in popularization and application, problems such as long preparation time, large processing errors, accidents or the like are often caused due to improper use or process design, which brings many inconveniences and psychological pressure to operators. In fact, the economical CNC machining method is very convenient and safe to use if used well. The following describes the corresponding methods for several common problems in processing. 1 Use proper tool setting method After the tool is installed, the tool must first be set to determine the starting point before executing the machining program. The countersink is often a headache for the operator (economical CNC without self-test device), time and labor, especially when multi-tool processing, it is necessary to measure the tool compensation value. In general, the common tool setting methods are: Jog mode Press and hold the jog key on the control panel, touch the tool tip on the surface of the workpiece (in both X and Z directions to jog twice), and clear the counter. , and then back to the initial position to be set (X, Z design initial value), and then cleared to get the initial position of the knife. The initial position of each knife is determined in turn, and after the trial machining, it is adjusted to an accurate design position (starting point). This method does not require any auxiliary tools. It can be operated at any time, but it takes a long time. In particular, the tool must be readjusted every time the tool is ground. This method is suitable for simple process or initial installation and debugging. The self-test device is adopted for the tool setting tool that is equipped with the tool setting method. However, the operation is complicated and it still takes a certain amount of preparation time. Suitable for multi-knife measurement. With the use of numerically-controlled tools, the tool positioning after initial positioning, after a certain period of time, wear occurs and needs to be sharpened, and the position of the tool tip changes when the ordinary tool is sharpened and refitting. The characteristics of CNC cutters are the high precision of the cutters, and the repositioning precision of the blades after indexing is about 0.02mm, which greatly reduces the time for the cutters. At the same time, the blade surface is coated with a wear-resistant layer (SiC, TiC, etc.), making it durable. The degree is greatly improved (3 to 5 times), but the cost is higher.
Schematic diagram of counter knife block
The use of self-made knife block method with plastic, plexiglass, etc. made of simple block (see the right figure) can easily achieve repeated positioning tool after grinding, but the positioning accuracy is poor, usually 0.2 ~ 0.5mm, but still It is a quick positioning method. It is very convenient to adjust again. 2 Elimination of easy-to-create shape errors in the machining of spheres When processing spherical surfaces, especially spheres and surfaces that have been processed through quadrants, improper adjustments can easily produce shoulders, backlashes, etc. The main reasons are as follows: System clearance causes a certain gap between the screw and the nut in the transmission of the equipment. With the increase of the equipment operating time, the gap gradually increases due to wear, so the reverse movement When the corresponding gap compensation is performed, it is the main factor to overcome the occurrence of shoulders on the machined surface. Gap measurement is usually made with a dial indicator method, and the error is controlled within 0.01 to 0.02 mm. It should be pointed out here that the table seat and the table bar should not be extended too long, because the measurement due to a long cantilever, the table seat is easily moved by force, resulting in inaccurate counts, the compensation value is not true. The uneven machining allowance results in whether or not the machining allowance of the surface to be machined is even before the design surface of the part is realized. This is also an important reason for whether the forming surface can meet the design requirements, because the uneven machining allowance can easily cause “replay” errors. . Therefore, for the parts with higher surface shape requirements, the machining allowance should be as uniform as possible or through the method of multiple processing of a profile before the molding to achieve the design requirements. Improper tool selection causes the tool to remove material through the main cutting edge during cutting. However, after the arc has been processed through the quadrant, after the arc and the tool's secondary cutting edge (line of intersection between the secondary back and the base surface) are tangent, the secondary cutting edge may be involved in the cutting (that is, shovel back). Therefore, when selecting or grinding tools, we must consider the wedge angle of the tool. 3 Reasonable design of the processing technology The use of numerical control processing equipment for processing, high efficiency, good quality, but if the process design is not properly arranged, it can not reflect its advantages. From the point of view of some manufacturers processing, there are some problems as follows: The reason that the process is too scattered to produce this problem is due to the fear of complication (referring to preparation time), simple programming, simplified operation and processing, use of a knife to process easily adjust the knife, used to Ordinary processing. As a result, the product quality (position tolerance) is not easy to guarantee and the production efficiency cannot be exerted well. Therefore, craftsmen and operators should be fully familiar with the knowledge of CNC machining, and try more to master the relevant knowledge, and adopt the method of process concentration as much as possible, and use it several times, which will naturally reflect its advantages. After the process was centralized, the unit processing time increased. We placed two devices face-to-face, enabling one person to operate two devices. The efficiency was greatly improved and the quality was well guaranteed. The order of processing is unreasonable. Some operators take into account some problems in preparation and often arrange the processing sequence extremely unreasonably. CNC machining is usually performed according to the requirements of the general machining process. For example, after the first rough and fine (for tool change), first and then outside, reasonable choice of cutting parameters, etc., so that the quality and efficiency can be improved. The G00 (G26, G27, G29) quick positioning command G00 instruction is used with caution for the convenience of programming and use. However, if it is improperly set up and used, it often results in overshoot due to excessive speed setting, adverse effects such as overshoot, loss of precision, and damage to the rail surface of the device. The zero return route does not pay attention, and it is easy to produce safety accidents that hit workpieces and equipment. Therefore, when considering the use of the G00 instruction, you should consider it comprehensively and it is not free. In the numerical control processing, in particular, it should also pay attention to strengthen the program retrieval and trial run. After the program is entered into the control system, the operator shall use the SCH key and the ↑, ↓, ←, → move keys to perform indefinite and definite search, and if necessary modify the program to ensure the accuracy of the program. At the same time, before the official execution of the program is processed, it must undergo a trial run (open the amplifier) to confirm whether the processing route is consistent with the design route. The above are some common problems and solutions when using CNC machining equipment. In the actual work may encounter some other problems, but as long as the engineering and technical personnel and operators to brainstorm, carefully grasp the knowledge and skills in CNC, CNC equipment can be a good business for the maximum effectiveness.
