Cutting is the use of cutting tools from the blank (or profile) to cut off part of the excess material, the blank will be processed to meet the drawing requirements of the size, shape accuracy and surface quality of parts processing process. Cutting is divided into machining and fitter two parts. Machining is a kind of cutting process which is completed by workers operating machine tools. The main processing methods include turning, milling, planing, drilling, grinding and gear processing. Fitter is generally carried out by workers hand tools cutting. The processing of products is usually divided into four stages: rough machining, semi finishing, finishing and finishing. This section only introduces turning, milling, drilling, grinding in machining and marking, sawing, filing, chiseling, tapping and threading, assembly in fitter.
With the improvement of the performance of the core processor of the CNC system, the feed speed limit of the high-speed machining center can reach 80 m / min, and the idle speed can reach about 100 m / min. At present, many automobile factories in the world, including Shanghai General Motors Company in China, have partially replaced modular machine tools with production lines composed of high-speed machining centers. The feeding speed limit of hypermach machine tool of Cincinnati company is 60m / min, the speed is 100M / min, the acceleration is 2G, and the spindle speed has reached 60000r / min. It takes only 30 minutes to process a thin-walled aircraft part, while it takes 3 hours for the same part to be processed on a general high-speed milling machine and 8 hours on a general milling machine. Due to the specialization of each component of the mechanism, under the development of professional spindle factory, spindle high-speed is increasingly popular. In the past only used for high-speed automobile industry models (15000 rpm or more), now has become a necessary mechanical product requirements.
In the machining industry, iron parts belong to the more common processing work pieces. When machining iron parts with machining center, do you choose the hard rail machining center or the line rail machining center? Today, I’d like to answer your questions
When choosing the hard rail machining center and the line rail machining center, the machining manufacturers need to know the size of the iron pieces they are machining, whether they are finishing or rough machining and other details. Only by understanding these details, can the manufacturers who are specialized in CNC machining center give an accurate answer.
Generally, the quality of large-size iron parts is large, and the amount of cutting is relatively large. In this case, it is more appropriate to choose the hard rail machining center. The hard rail machining center has strong rigidity, earthquake resistance and load-bearing capacity, and is more suitable for heavy-duty cutting. In this case, if the line rail machining center is used for a long time, the guide rail may be damaged. Generally, customers are advised to use hard rail CNC machining centers. For example, T-8, T-10, T-12, T-13 and T-15 belong to hard rail machining centers. Compared with 850, 1060 and 1270 in the market, these hard rail CNC machining centers are generally suitable for heavy load cutting.
At present, numerical control machining can not get rid of the fate of the industry in the modern era, and there will be some errors in the process of machining
Wrong processing principle
The main error of CNC machining is caused by approximate machining motion or approximate tool profile. Because of the error of machining principle, it is called machining principle error. As long as the main error is within the allowable range, this type of processing is still feasible.
Geometric error of machine tool
Machining error, installation error and wear during use directly affect the machining accuracy of the workpiece. It includes the rotation of the spindle, the linear motion of the guide rail and the error of the transmission chain.
Manufacturing error and wear of tools
The manufacturing error, installation error and wear of CNC machining tools in the process of machining will affect the machining accuracy of the workpiece. In the cutting process, the cutting edge, cutting surface, workpiece and chip produce strong friction, which leads to tool wear. When the tool wear reaches a certain value, the surface roughness of the workpiece increases, and the color and shape of the chip change. With the vibration, the tool wear will directly affect the cutting productivity, processing quality and cost.
Fixture error
CNC machining fixture error includes positioning error, clamping error, fixture installation error and tool setting error. These errors are mainly related to the manufacturing and assembly accuracy of the fixture. CNC machining accuracy is not perfect, as long as the error is controlled in a certain range, it will not have any significance. Tool manufacturing error and wear.
Positioning error
Positioning error mainly includes reference misalignment error and locator manufacturing error. When machining the workpiece on the machine tool, several geometric elements on the workpiece must be selected as the positioning reference. If the selected positioning reference and design basis are used (reference is used to determine the table on the part drawing)
Face size and location). If misalignment occurs, a reference misalignment error will occur. The positioning surface of the workpiece and the positioning part of the fixture form a positioning pair. Large displacement of workpiece caused by inaccurate positioning position and matching gap between positioning pairs is called positioning. Sub manufacturing inaccuracy
Wrong. The inaccuracy in positioning and manufacturing only occurs when the adjustment method is used, and will not occur in the trial cutting process.
Adjustment error
In each process, the process system is always adjusted in some way. Because the adjustment is impossible to be accurate, there is an adjustment error. In process
In the system, by adjusting the machine tool, cutter, fixture or workpiece, the mutual position accuracy of workpiece and cutter on the machine tool is ensured. When the original accuracy of machine tool, tool, fixture and workpiece blank meets the process requirements without considering the dynamic factors, the adjustment error plays a decisive role in the machining error.
Measurement error
When measuring parts during or after machining, the measurement accuracy is directly affected by the measurement method, measuring tool accuracy, workpiece and subjective and objective factors. To a certain extent, the above seven machining errors can be avoided, so the operators who need to process can test the six machining processes that may cause machining errors more carefully. After machining operation, the influence of machining error can be reduced better.
The above is for you to share the “CNC processing to pay special attention to a few places.”.
First of all, let’s understand the so-called mechanical processing. As long as it is related to mechanical processing, it can be said that it is a mechanical processing industry. It can be divided into a broad sense of mechanical industry and a narrow sense of mechanical processing industry. At present, China’s mechanical processing industry is relatively backward. Compared with the west, most of them are self-employed small workshops, and they are generally processing with supplied materials, All the drawings of the equipment are from foreign countries. However, in the coastal areas, although they are small individual workshops, most of them already have CNC equipment, and the processing efficiency is relatively high. Generally, CNC processing is the main method, as well as mechanical parts processing.
In the Pearl River Delta region, it is very common for machining manufacturers to have CNC processing equipment, which is suitable for processing complex precision parts, especially for small batch and large batch parts processing. Improve the quality of parts processing, but also improve the efficiency of production and processing! At present, the machining capacity is improving rapidly, and most of the machining manufacturers can meet the needs of small batch processing. However, compared with the west, the machining industry still has a long way to go. It can be divided into three parts
Unbalanced development and low overall product standard. Although the products of individual enterprises have reached or approached the international standard, there is still a big gap between the precision of precision parts processing, roughness of special surface, production cycle, life and other indicators and foreign standards.
Backward technology and equipment, poor organization and coordination ability. Although some enterprises have undergone technological transformation in recent years, their technology and equipment level has been compared, and the equipment level of some foreign-funded enterprises is not behind that of foreign countries.
The above is the overall level of machining capacity. It is believed that through the continuous development of domestic small and medium-sized enterprises, they will soon draw closer to the West and even catch up with the West.
To see what is the efficiency factor of CNC machining, we must first know that CNC machining center belongs to numerical control equipment, which is mainly operated by the computer programming command of technical engineers. In the process of production, how to improve the efficiency of CNC processing
Selection of machine tools
Before arranging CNC parts processing, we must ensure the weight that the worktable can bear and consider the smooth processing of mechanical parts. Nowadays, the efficiency of production and processing has a direct impact on whether small and medium-sized processing enterprises can make profits. If the machine tool table can not meet the requirements of use, the processing efficiency will be reduced, and the accuracy of the machine tool itself will also be affected.
Reasonable processing steps
For the machining industry, it can be said that reasonable production and processing technology is one of the important steps. CNC parts processing is very difficult, so we must choose a reasonable processing route, which can save time and improve the production and processing efficiency. On the contrary, if the selection of processing technology is unreasonable, the production efficiency will be reduced.
Small batch processing
Whether it can be processed in small batch, when it comes to processing in small batch and large batch, the advantage of precision CNC processing is very obvious, which saves the time of programming, adjusting machine and so on. Only need to clamp parts repeatedly, the production and processing efficiency can be improved many times! Therefore, most machining manufacturers prefer small batch processing
The above is the mechanical plus CNC processing rate factor
For the precision machining industry, the tolerance of production drawing parts processing. A precision parts processing drawings will have dimensions, special position machining accuracy requirements, that is, positive and negative tolerance. The marked tolerance is to ensure that the actual geometric parameters are consistent with the dimensions specified on the drawing in the process of precision parts processing, and the degree of inconsistency between them is called processing error. In order to ensure the accuracy tolerance and avoid the machining error, the following three points should be paid attention to
Benchmark:
According to the shape of different parts, the same datum plane can be selected for processing to ensure that the clamping of parts in the processing process can reduce a certain error range, which is the importance of datum plane.
Shape:
For different drawings provided by our customers, the workpiece with special shape can’t be clamped normally. At this time, we can consider designing clamping fixture for positioning processing and selecting datum plane. Its main function is to assist the processing to meet the accuracy requirements and improve the production and processing efficiency.
Technology
In the precision machining industry, some people say that the drawing processing technology is an art, reasonable technology will save a lot of time, but also can improve the efficiency of production and processing. So a reasonable process is very important.
Machine tool:
Previous articles have also mentioned that the accuracy of the machine tool itself will affect the error, because there are several kinds of errors of the machine tool itself, mainly including the head spindle rotation error, guide rail error and transmission chain error.
The above is about the tolerance of precision parts processing, for parts processing requirements are higher and higher, how to ensure the accuracy of the size.
In the field of machining industry, precision CNC parts processing is widely involved in the industry. Let’s take a look at CNC milling technology!
Feeding circuit of precision CNC milling plane parts: when milling plane mechanical parts, the side edge of end mill is usually used for cutting. In order to reduce the tool trace and ensure the appearance quality of the parts, the cutting in and cutting out procedures are carefully designed.
In the process of machining, when milling the surface, the cutting in and cutting out points of the cutter should cut in and cut out the surface of the part along the extension line of the part outline curve, instead of cutting directly into the part along the normal direction, so as to avoid scratches on the surface and ensure the lubrication of the part.
In the process of precision CNC machining and milling closing, if the curve of internal generalization is allowed to be extended, it should be cut in and out along the tangent direction. If the inner generalization curve does not allow extension, the cutter can only cut in and out along the normal direction of the inner generalization curve, and the cutting in and out points are selected at the intersection of two elements of the mechanical part generalization. When there is no intersection point of several internal elements, the cutting point should be far away from the corner in order to avoid the notch left at the general corner when the cutter compensation is withdrawn.
The above are the skills in the process of precision CNC milling, simple and complex precision parts processing, CNC milling technology will be different, according to the appropriate processing line.
In the field of machining industry, CNC machining is often mentioned, which is divided into three-axis CNC machining and four axis CNC machining. There are also five axis CNC machining. At present, it is widely used in the three-axis and four axis markets.
Three axis CNC machining: generally refers to three different directions of linear motion axis, such as up and down, front and back, left and right. Three axis can only process one face at a time, which is suitable for processing some plane parts. The technology of parts is simple and small batch parts processing.
Four axis CNC machining: add a rotation axis on the three axis, generally 360 ° Spin. But it can’t rotate at high speed. It can make the product multi-faceted processing by rotating, greatly improving the processing efficiency and reducing the clamping times. In particular, the processing of cylindrical parts is more convenient. And it can reduce the repeated clamping of the workpiece, improve the overall processing accuracy of the workpiece, simplify the process and improve the production efficiency. It is suitable for machining some box and complex precision parts.
The above is the difference between three-axis and four axis CNC processing. You may ask why five axis CNC processing is not mentioned. Although five axis CNC processing has outstanding advantages over four axis and three-axis CNC processing, not all products are suitable for five axis CNC processing, and those suitable for three-axis CNC processing are not necessarily suitable for five axis CNC processing. If the original three-axis products can be processed by five axis CNC processing, Not only will it increase the cost, but the effect is not necessarily good. Only reasonable arrangement, for the product to develop the appropriate machine tools, so as to play out the value of the machine itself.
Now understand the CNC parts processing technology and operation skills. Mechanical parts processing is under the established production conditions. For the reasonable process and operation method, the processing method is compiled in the prescribed form to guide the production and processing steps after approval. With the continuous change of CNC machining system, take a look at the precision machining manufacturers of CNC parts processing, and summarize the following points.
It can be understood as a small skill in the process of precision CNC machining
In the process of precision parts processing, when the hexagon wrench is short and can not bear the pressure, the pipe with the inner diameter slightly larger than the wrench can be inserted into the groove from a part of the milling groove. Inside the slot, it can be used as a long handle. In the process of CNC machining, many precision parts are not produced at one time, but when mechanical parts are produced, it is just a rough model. If the processing factory becomes a real product, it is also processed by some mechanical equipment according to different production and processing processes. Processing can eventually become a valuable product.
Precision CNC machining, using magnet to absorb small parts (cost) is not convenient to suck. The iron plate can be sucked under the magnet, which can not only suck many small pieces, but also pull out the iron plate from the small pieces, which will automatically pour into the collection box immediately. Not impressive enough, but very practical.
When driving the pulley in precision CNC machining, the pulley often slides between the pulley and the shaft. Draw a series of sockets on the shaft with 15 ~ 18mm trocar. This can form adsorption to prevent slipping, and turn waste into treasure, improving the value of long-term use.
In CNC machine tool processing, it is necessary to remove the jaws of vise, add two M4 threaded holes, two steel plates with jaws and 1.5mm thickness, rivet the hard brass plate with aluminum countersunk head rivet and 0.8mm thickness, and fix the hard brass plate on the jaws with M4 countersunk head screw to form a durable soft jaw. This can also protect precision parts from being damaged by clamping, and can be reused. It can be regarded as protecting the appearance details of precision CNC machining.
The above is about CNC parts processing technology tips, many precision parts processing requirements are relatively high, the use of tips can avoid quality problems and improve production and processing efficiency!
