CNC Technology – Page 24 – CNC Machining & Turning, Milling, Metal parts

CNC computer gong processing high precision parts attention

Don’t think that high-precision parts processing is a common processing without attention. If we ignore some details, it may have a great impact on the processing of parts. Then, what are the precautions for high-precision parts processing?

For high-precision parts, the processing is very strict. The processing procedures include feed and output. There are specific requirements for the size and accuracy, such as 1 mm plus or minus micrometers. If the size is too wrong, it will become a scrap. At this time, it is equivalent to reprocessing, which is time-consuming and laborious. Sometimes, the whole processing material will be scrapped, resulting in an increase in cost. At the same time, the parts are definitely unusable.
For the processing of high-precision parts, the main requirements are the size, such as the diameter of the cylinder, there are strict requirements, positive and negative errors within the specified range are qualified parts, otherwise they are unqualified parts; There are also specific and strict requirements for length, width and height, as well as positive and negative errors. For example, if the diameter of an embedded cylinder (take the simplest basic parts as an example) is too large and exceeds the allowable error range, it will cause the situation that it cannot be inserted. If the actual diameter is too small and exceeds the lower limit of the allowable negative error, it will cause the problem that it is too loose and not firm. These are all unqualified products, or the length of the cylinder is too long or too short, which is beyond the allowable range of error. They are all unqualified products, and they have to be scrapped or reprocessed, which will inevitably lead to the increase of cost.
The requirement of high-precision parts processing is actually the most important dimension problem. It must be processed in strict accordance with the additional drawings. The actual size of the processed parts will not be exactly the same as the theoretical size of the drawings, but as long as the processing size is within the allowable error range, they are all qualified parts. Therefore, the requirement of precision parts processing is to process in strict accordance with the theoretical size Line processing.
The second is the advanced precision parts processing equipment and testing equipment. The advanced processing equipment makes the processing of precision parts simpler, higher precision and better effect. The detection device can detect the parts that do not meet the requirements, so that all the products sent to customers can really meet the requirements.

CNC computer gong processing complex parts technology

The continuous fine blanking die for complex parts is the frontier basic technology of fine blanking technology, and it is expected to promote the whole fine blanking technology in China. Taking the synchronizer gear ring, clutch plate, longitudinal compound continuous fine blanking process and continuous fine blanking die for complex parts as the breakthrough point, the key technology of fine blanking die design and manufacturing is studied, so as to realize the rapid improvement of fine blanking die technology in China and shorten the gap with advanced countries as soon as possible.

Study on the life promotion of fine blanking die and its related key technologies

Die life is a comprehensive reflection of die materials and the level of supporting products. Taking the life of fine blanking die as the leader to carry out technical research can not only solve the problem that the life of fine blanking die is too low, but also drive the technical development of die materials, fine blanking process, supporting tooling and other auxiliary products.

Research and development of fine blanking precision forging composite technology

Precision blanking and precision forging are two advanced manufacturing technologies developed in parallel. If the precision blanking parts are too thick and need precision forging, the precision forging must be too thin. They are closely related. The basic idea of developing precision forging and fine blanking compound process is to find the combination point of the two processes (such as gear parts with wheel hub and cam parts with short shaft). The precision forging in China has a long history and has a high level, so it is a good way to improve the overall level of precision blanking technology in China.

Properties of various materials processed by CNC

The positioning accuracy and repeated positioning accuracy of CNC lathe are very high, so it is easy to ensure the consistency of the size of a batch of parts. As long as the process design and program are correct and reasonable, combined with careful operation, the parts can obtain higher processing accuracy, and it is also convenient for the quality control of large-scale computer gong processing. CNC lathe is a technology intensive Mechatronics typical large-scale computer gong processing products, maintenance personnel need to understand both mechanical and microelectronic maintenance knowledge, but also equipped with better maintenance equipment.

Using metal mold, filling mold under high pressure and high speed, rapid solidification under pressure is a metal forming method with high efficiency and high precision, but the manufacturing cost of die-casting machine and die-casting mold is high; mass production, small and medium-sized thin-walled castings mainly composed of zinc alloy, aluminum alloy, magnesium alloy and copper alloy, are also used for iron and steel castings.
Use wax mould to make a whole refractory shell mold outside the wax mould. After the wax pattern is melted off by heating, it is poured by gravity. The casting has high precision and good surface quality, but the cost of die making is high and there are many processes. Manual operation, poor working conditions; various production batches, mainly carbon steel, alloy steel alloy and difficult to process high melting point alloy complex parts are suitable, casting quality is generally less than 10kg.
Casting with metal mold under gravity can refine the structure of non-ferrous alloy castings. Gray iron castings are easy to produce white, with high productivity, no dust, high equipment cost, and poor labor conditions in manual operation. Mass production is mainly made of non-ferrous alloy, and can also be used for thick wall, simple or medium complex small and medium-sized castings of cast steel and cast iron.
Using metal mold, graphite mold and sand mold to fill mold and solidify under gas pressure, the casting is compact, the metal yield is high, and the equipment is simple; single piece, small batch or mass production, medium large thin-walled casting mainly made of non-ferrous alloy.
High precision pattern, self hardening refractory slurry, gravity casting, high precision casting, fine surface roughness, but expensive ceramic slurry; single piece, small batch production of medium, small, thick wall medium complex castings, especially suitable for metal mold, template, hot box and various kinds of hot forging die.
Casting with metal sand or sand mold under the action of centrifugal force, and processing with computer gong, the structure of casting is compact, the equipment is simple, the cost is low, and the productivity is high, but the machining capacity is large; large quantities of iron pipe, copper sleeve, roller, metal bearing bush, cylinder sleeve and other rotary body castings are produced in single piece and batch.
use foam polystyrene plastic moulds to replace wood or metal mold parts locally or completely, and burn them when pouring. It can save wood and simplify the working procedure, but the dust and harmful gas are relatively large; for medium and large castings produced in single piece or small batch, 1-2 pieces are suitable, or for the parts of castings with difficult mold removal. Machining is now accessible to many industries, it also has a lot of processing methods, such as, gantry grinding and so on, the machining center can choose the best process line and cutting parameters, effectively reduce the auxiliary time in processing, so as to improve production efficiency. The production efficiency of machining center is high. And because of its automatic tool changing function, it can usually save complex tooling, reduce the installation, adjustment and multiple tool setting of processing parts and other relatively complex and tedious work.

CNC computer gong vmc-650 model

Vmc-650 mechanical characteristics and control system characteristics: mechanical characteristics:

1、 High rigidity, heavy cutting

All of them are made of high-quality resin sand wear-resistant casting, strong and tough rib, super large column, wide and low seat, honeycomb structure. After annealing treatment, the stress is removed and the deformation does not occur for a long time.
The three-axis adopts the rectangular guide rail with strong rigidity, which can bear heavy cutting, precision grinding of worktable and quenching treatment, greatly enhancing the surface hardness.

2、 High precision

The three-axis drive adopts Taiwan C3 precision ball screw and P3 bearing, which ensures the positioning accuracy and repeated positioning accuracy.
The three-axis adopts Mitsubishi servo motor and spindle motor, direct drive, which provides strong power and ensures the feeding accuracy under the strong bearing capacity.
P3 grade spindle of international famous brand is adopted to ensure the advantages of high reliability, long service life, low noise, small vibration and high precision of the spindle.

Control system characteristics:

1、 Good stability, fast speed and high precision

It adopts the world’s advanced Mitsubishi CNC system, and the M60s series adopts servo drive, which ensures the high stability, high speed and smooth surface of the control system.

2、 It has the advantages of high precision, has the function of manufacturing mold, and is the best choice for mold production.

All M60s series controllers are equipped with RISC 64 bit CPU.
It can correspond to Ethernet and IC card interface.
Coordinate display value conversion can be freely switched (program value display or manual insertion display switching)
Standard internal waveform display function, working position coordinate and center point measurement function.
Buffer correction function expansion: can correspond to IC card / computer link B / DNC / record MDI mode.
The editing mode in the editing screen can be automatically switched to full page editing or full name editing.
Graphic display function improvement: can contain props path data to fully display the working coordinates and the actual position of props compensation.
Simple dialogue program software (developed by APLC, magicpro)_ Navimill dialog program).
It can develop PLC software corresponding to Windows95 / 98 / 2000nt40 / me / XP.

CNC computer gong processing instructions

When only x-axis or y-axis is mirrored, the cutting sequence (forward milling and reverse milling), cutting direction and arc interpolation direction will be opposite to the actual program. When the x-axis and y-axis are mirrored at the same time, the sequence of tool feeding, the direction of tool compensation and the direction of arc interpolation remain unchanged.

Note: after using the mirror command, you must cancel it with M23 to avoid affecting the following program. In G90 mode, the mirror or cancel command can only be used after returning to the origin of workpiece coordinate system. Otherwise, the CNC system can not calculate the movement track behind, and the phenomenon of random tool walking will appear. At this time, we must implement manual origin reset operation to solve the problem. The spindle steering does not change with the mirror command.

[pause instruction]

G04X(U)_ /P_ It refers to the tool pause time (feed stop, spindle not stop). The value after address P or X is the pause time. The value after X should have a decimal point, otherwise it is calculated as one thousandth of the value in seconds (s), and the value after P cannot have a decimal point (that is, an integer), but in milliseconds (MS). However, in some hole system processing instructions (such as g82, G88 and g89), in order to ensure the roughness of the hole bottom, when the tool is processed to the hole bottom, there is a pause time. At this time, it can only be expressed by the address P. if it is expressed by the address x, the control system thinks that x is the x-axis coordinate value for execution.

[differences and relations among M00, M01, M02 and M03]

M00 is the program unconditional pause instruction. When the program is executed, the feed stops and the spindle stops. To restart the program, you must first return to jog state, press CW (spindle forward) to start the spindle, and then return to auto state, press start key to start the program.

M01 is program selective pause instruction. Before the program is executed, the opstop key on the control panel must be opened. The effect after execution is the same as that of M00. To restart the program, it is the same as above. M00 and M01 are often used for inspection of workpiece size or chip removal during machining. M02 is the main program end instruction. Execute this command, feed stop, spindle stop, coolant off. But the program cursor stops at the end of the program. M30 is the main program end instruction. The function is the same as M02, the difference is that the cursor returns to the program head position, regardless of whether there are other program segments after M30.

[address D and H have the same meaning]

Tool compensation parameters D and H have the same function and can be interchanged at will. They all represent the address name of compensation register in CNC system, but the specific compensation value is determined by the address of compensation number after them. However, in the machining center, in order to prevent errors, it is generally stipulated that h is the tool length compensation address, the compensation number is from 1 to 20, D is the tool radius compensation address, and the compensation number starts from 21 (the magazine of 20 tools).

CNC computer gong processing parts features

Due to the centralized process and automatic tool change, the machining center reduces the time of workpiece clamping, measurement and machine adjustment, so that the cutting time of the machine tool reaches about 80% of the starting time of the machine tool (only 15-20% for ordinary machine tools); at the same time, it also reduces the time of workpiece turnover, handling and storage between processes, shortens the production cycle, and has obvious economic effect. Machining center is suitable for small and medium batch production with complex shape, high precision and frequent product replacement. Now, manufacturing large-scale aircraft in China is one of the important development directions of China’s aviation industry in the future. The development of large-scale aircraft needs high support, elegant and sharp related technology. The very large wall part refers to the whole wall part which is widely used in large aircraft with large scale (20m) length direction. This part has the characteristics of large size, complex structure and high precision, which makes it difficult to manufacture large aircraft structure.

Very large parts of the wall have different loopholes to strengthen the overall structure, such as the rod due to high dimensional accuracy requirements, most of the production CNC processing means to complete. The development of China’s domestic large aircraft is used for the structural parts of large wall. The accuracy requirements are as follows: the thickness tolerance of network and rod is + / – 0.15mm, the height tolerance of rod is + / – 0.2mm, the outer wall surface is flat, and the distortion is not more than 5mm, which cannot be encouraged. It is necessary to have scientific and reasonable processing deformation control technology to meet the processing requirements.

Research on deformation control technology of super large wall parts processing, the whole deformation control technology, the whole verification in the actual processing deformation control technology, can effectively control the deformation of super large wall parts, the general processing accuracy is 0.2mm, has achieved good results, has important engineering application value.

Deformation control process of integral machining

The whole process of the super large wall part is analyzed, and the whole size blank large tensile aluminum alloy plate is formed. Finally, the asymmetric integral wall part with “one side smooth, one side” structure is formed. Generally, the material removal rate reaches 95%. In the process of creating pre stretched aluminum alloy plate, the machining deformation is mainly caused by the release of residual stress, especially for large-size parts. In the process of machining removal rate, if the residual stress release of this problem can not be well solved, it is easy to lead to the machining and treatment process of large deformation parts, resulting in the size out of tolerance scrap or the product does not meet the requirements.

Combined with the machining process of the very large wall part, the following deformation is set to control the whole process. The process includes: large edge cavity, positioning, surface finishing, roughing, seasoning, vacuum clamp, online measurement and completion, etc. The main purpose of the process of releasing residual stress in a large margin groove cavity is not to form the characteristic size. It is the key to control the deformation process by quickly deleting a large number of residual stress releasing blanks in surplus materials; positioning surface finishing, rough machining and natural aging rough machining release residual stress, and further release residual stress, Processing process has formed a unified allowance part blank, and the role of natural aging, easier to control processing deformation. During the preparation of vacuum clamp and on-line measurement allowance process, vacuum clamp is a way to ensure the stability of clamping part. Through the change of on-line measurement, through rough machining and natural aging allowance, the processing technology can be adjusted to ensure the accuracy of feature size. After finishing the finishing process, the wall plate can be treated,

In the above processes, each process considers releasing pressure and unified pressure to control the part of machining deformation. No matter in the process of form feature size rough machining or dimension precision machining, the analysis and consideration of parts machining is an important part of deformation control, so as to realize the overall control of machining deformation, Controlling the influence of machining deformation is to ensure the machining accuracy of parts.

In the process of precision parts processing, because of its complex structure and special materials, there will be a variety of stress and deformation problems that can not be predicted by engineers in the process of processing

Vertical machining center and horizontal machining center

Machining center is usually divided into vertical machining center and horizontal machining center according to the state of spindle in space.

The vertical machining center whose spindle is vertical in space is called vertical machining center, and the horizontal machining center whose spindle is horizontal in space is called horizontal machining center. Spindle can be vertical and horizontal conversion, known as vertical and horizontal machining center or five machining center, also known as composite machining center. According to the number of machining center columns, there are single column type and double column type (gantry type).

According to the coordinate number of machining center movement and the coordinate number of simultaneous control, there are three axis two linkage, three axis three linkage, four axis three linkage and five axis four linkage.

Six axis five linkage, etc. Three axis and four axis refers to the number of motion coordinates of the machining center. Linkage refers to the number of coordinates that the control system can control at the same time, so as to realize the position and speed control of the tool relative to the workpiece. Machining center can be divided into vertical, horizontal and composite machining center from the appearance. The spindle of the vertical machining center is perpendicular to the worktable, which is mainly used for processing plate and shell workpieces, and can also be used for mold processing.

The spindle axis of the horizontal machining center is parallel to the worktable, and its worktable is mostly a CNC rotary table controlled by servo motor. In the one-time clamping of workpieces, multiple machining surfaces can be processed through the rotation of the worktable, which is suitable for the processing of box workpieces. The compound machining center mainly refers to that there are two vertical and horizontal spindles on one machining center, or the spindle can change the angle by 90 degrees, so it can realize the machining of five surfaces in one clamping of workpiece.

CNC machining parts process

CNC machining mainly refers to the use of digital information recorded on the media to control the machine tool, so that it can automatically perform the specified processing tasks. Numerical control machining can ensure the products to achieve high machining accuracy and stable machining quality; the operation process is easy to achieve automation; high productivity, short production cycle; can reduce a large number of process equipment to meet the needs of rapid product upgrading; it is usually closely linked with CAD to achieve the transformation of design ideas to the final product.

In the whole CNC process, we should focus on the relationship between the processes and the significance of each step. Broadly speaking, the whole process consists of product analysis graphic design process planning path generation path simulation path output processing inspection.

Product analysis through product analysis should obtain certain composition information and some specific processing requirements.
Graphic design graphic design should be based on the detailed analysis of the product, determine the type of graphics by analyzing the processing requirements, and draw through the graphics software.
Path generation the process of path generation is that we realize the process planning by software, and optimize the tool path by setting parameters.
Through the analysis of the appearance and processing requirements of the workpiece product in the early stage of process planning, each processing step is reasonably established from the overall situation of processing.
After the path simulation path is generated, we generally have no intuitive sense of its final performance on the machine tool. Here we can check the possible problems through path simulation, so as to reduce the scrap rate of actual processing. The general inspection focuses on the effect of the workpiece appearance, whether it is overcut or undercut, and whether the process planning of the path is reasonable.
Path output path output is a necessary step for software design and programming to realize on the machine tool. Through path output, the intermediate reference can establish a connection between the two. If you have NC professional background, it can also be understood as the post-processing of tool path.

Advantages of CNC computer gong processing

Master the processing principle and process. When using the common CNC machining technology, the processor should follow the principles of rough machining first, then finish machining, preventing the workpiece from thermal change, reducing vibration and so on. At the same time, also have the ability to deal with all kinds of unexpected problems, such as: how to adjust the tool speed.
Familiar with automatic or manual operation of CNC machining. The machinist should know clearly what process needs manual operation, what is the normal operation state of the machine tool when it is operated manually, what process is suitable for automatic operation, and what state the machine tool should be in. Professional CNC processing staff said, familiar with the above operation, help to carry out the processing work, and can deal with any situation freely.

The above is the basic skills of professional CNC processing personnel. Only by mastering these skills can we complete CNC processing operation independently. In order to become a qualified CNC machining worker, only by constantly asking questions and practicing in the work can we make our technology more solid.

How to install workpiece in CNC machining center

Selection of machining center positioning datum:

There are three basic requirements for selecting benchmarks

(1) The selected datum should be able to ensure the accuracy of workpiece positioning, convenient and reliable loading and unloading.

(2) The calculation of the selected datum and the size of each processing part is simple.

(3) Ensure the machining accuracy.

6 principles for selecting positioning datum:

(1) Try to choose the design datum as the positioning datum;

(2) When the positioning datum and design datum cannot be unified, the positioning error should be strictly controlled to ensure the machining accuracy;

(3) When the workpiece needs to be clamped for more than two times, the selected datum can complete the machining of all key precision parts in one clamping and positioning;

(4) The selected benchmark should ensure the completion of as many processing contents as possible;

(5) In batch machining, the positioning datum of parts should coincide with the tool setting datum of workpiece coordinate system as far as possible;

(6) When multiple clamping is needed, the datum should be consistent.

Determination of machining center fixture:

Basic requirements for fixtures:

(1) The clamping mechanism shall not affect the feed, and the processing part shall be open;

(2) The fixture can be installed directionally on the machine tool;

(3) The rigidity and stability of the fixture are better.

Common fixture types:

(1) General fixture: such as vice, dividing head, chuck, etc;

(2) Modular fixture: modular fixture is composed of a set of general components with standardized structure and standardized size;

(3) Special fixture: fixture designed and manufactured for one or several similar processing items;

(4) Adjustable fixture: the combination of modular fixture and special fixture can ensure the machining accuracy and more flexible clamping;

(5) Multi position fixture: it can clamp multiple workpieces at the same time;

(6) Group Fixture: it is specially used for clamping workpieces with similar shape, size, positioning, clamping and processing methods.

Selection principle of machining center fixture:

(1) On the premise of ensuring machining accuracy and production efficiency, general fixture is preferred;

(2) Simple special fixture can be used for batch processing;

(3) Multi position fixture and high efficient special fixture for air pressure and hydraulic pressure can be considered for mass processing;

(4) When group process is used, group fixture should be used;

The best clamping position of the workpiece on the worktable of the machine tool: the clamping position of the workpiece should ensure that the workpiece is within the processing stroke range of each axis of the machine tool, and make the length of the tool as short as possible to improve the processing rigidity of the tool