When CNC machining is carried out in CNC machining center, due to tool wear, regrinding or replacement of new tools, the parameters of related tools in the programmed machining program will be changed, and the tool running path will be changed. If the adjustment is not enough, the final machining accuracy of the workpiece will be affected. For example, calculate the tool path from the beginning, and correct the program. In this way, it is not only time-consuming and laborious, but also has a high error rate. The most convenient way is to call the tool radius compensation performance of CNC system. When programming the workpiece, we only need to prepare the processing program according to the appearance of the workpiece. The system will automatically calculate the tool center path, so that the tool deviates from the appearance of the workpiece by a radius value. Even if the tool parameters are changed, only the detailed tool parameters need to be changed without changing the whole machining program. This greatly improves the machining efficiency of the machining center.
1、 Establishment and revocation of tool radius compensation
In short, tool radius compensation can be divided into left compensation and right compensation. Farewell is defined by G41 and G42. When the tool center track is located on the right side of the part appearance, it is called the tool radius right compensation; otherwise, it is called the tool radius left compensation.
1. The establishment of tool radius compensation
The establishment of tool radius compensation is a process that the tool center track changes from coincide with the programmed path to deviate from a tool radius value with the programmed path when the tool approaches the workpiece at the feed speed from the starting point. G41 is responsible for the left compensation of tool radius; G42 is responsible for the right compensation of tool radius.
2. Cancellation of tool radius compensation
The cancellation of tool radius compensation is the same as the process of creating tool radius compensation. After the final section of tool radius compensation path of the workpiece is processed, the tool withdraws the workpiece and returns to the withdrawal point. In this process, the tool radius compensation should be cancelled, and its instructions are defined by G40. The undercut point shall also be located outside the part appearance, and the undercut point of the parts machined at intervals shall be close to the undercut point, which may be the same as the undercut point, and of course may not be the same.
2、 Concerns in CNC machining tool radius compensation input
The change of tool radius compensation usually occurs after machining in machining center for a period of time. For a continuous program segment, when the tool radius compensation amount changes, the vector at the end of a program segment needs to be calculated with the tool compensation amount specified in the program segment.
In the process of NC programming, we usually input the compensation amount of the tool radius into the compensation code as a positive value. If the compensation amount of the tool radius is set as a negative value, under the condition that the target of the tool path is fixed, it is equivalent to exchanging the compensation position command in the NC program, G41 and G42. It is possible that the processing center originally processed the outside of the workpiece into the inside plus There are some unexpected problems, so we must pay attention to the configuration of two compensation targets when inputting radius compensation.
There are few articles about the use of cutting tools in CNC parts machining field. Today, I will introduce some basic functions that the cutting tools in machining center should have. The material used to make the cutting tool will directly affect the service life, processing efficiency, processing quality and processing cost of the cutting tool, which shows how important it is to select the cutting tool for the machining center. In the process of machining, the tool must receive high pressure, high temperature, conflict, impact and vibration. So the tool used in the machining center must have the following basic functions.
1. Before machining the workpiece in our machining center, we must know the hardness of the workpiece. Generally speaking, the hardness of the tool used must be higher than that of the workpiece processed. Otherwise, it is not the tool that is processing the workpiece, but the workpiece is processing the tool. The hardness of the tool is usually above 60HRC. Originally speaking, the higher the hardness of the tool, the better its wear resistance, the more permanent.
2. The tool used in the strength and toughness machining center must have the strength to receive cutting force, impact force and detonation force, otherwise it will cause tool fracture or collapse, so to meet these requirements, it is necessary to select high light and high toughness raw materials to manufacture the tool.
3. High temperature machining center will produce certain high temperature when processing the workpiece. In order not to affect the machining accuracy, the material with good heat resistance must be selected to make the cutter. The cutter must be able to receive the high temperature produced by the machining center when processing the workpiece, otherwise it will cause high temperature oxidation of the workpiece or cutter, so the cutter must have heat resistance, so that the cutter can have anti-oxidation strength. 4. Process function: the material of cutting tool must have forging function, heat treatment function, welding function and other process functions, so as to facilitate the running in and change of cutting tool.
The basic goal of using the equipment is to increase the production rate of the product parts, achieve better economic benefits, and ensure the safety and stability of the product parts and meet the technical requirements. Therefore, the design of equipment accessories is not only a technical problem, but also an economic problem. In the design of accessories, it is necessary to carry out necessary technical and economic analysis to make the designed accessories obtain better economic benefits.
Know the technical requirements of product parts
After taking over the design mission of the letter of acceptance, necessary raw materials shall be prepared to design the accessories, including the design drawings and drawings of film and technology requirements, process specification, processing equipment associated with the process and other information. After understanding the product parts, dimensional accuracy yamen, mode and other technical requirements, and looking for the key points of the parts and the basic structure of the important dimensions (the size must be guaranteed), the design of the parts is basically confirmed.
Some important parts design plans should be discussed and completely revised before affirmation. At the beginning and the end of this method, it is a better design and processing plan to ensure that the equipment design can meet the requirements of the production plan.
Position reference in positive attachment
With respect to each group of equipment, the size of key parts and important parts must be used as positioning pieces (design positions) in accessories, and the design (precision design) positioning of dreams must be confirmed to confirm the reference key positioning (first reference point). ）And auxiliary positioning reference point (second reference point).
In principle, the first reference point must be the same as the design. If it can not be guaranteed, it is advisable to convert the design basis to process basis through calculation, but the design basis requirements must be guaranteed.
There must be two conditions for selecting a location reference:
The process reference should be selected as the positioning reference to complete the reference matching and reduce the positioning deviation;
Therefore, the average positioning datum should be selected not only to ensure the quality of components and improve the processing efficiency, but also to simplify the structure of accessories (usually using reference holes and positioning shafts).
For example, when designing fixture, the designer must first look at the design of positioning reference drawing from the beginning to the end of positioning reference, and then see that the processing of positioning reference is confirmed (still confirm the process specification). If the positioning reference point is general. If they are not all, the basic design becomes the reference point of the whole calculation process, but the requirements of the design reference point must be guaranteed.
When the designed components are positioned, the basic technical requirements are: good precision, good wear resistance, sufficient strength and rigidity, good processing strength, simple disassembly and other characteristics. For example, the selection of the positioning part of the welding device used for assembling components must be in the positioning mode of the positioning pin according to the requirements; there must be a certain space between the positioning pin and the reference hole of the workpiece, and the size depends on the accuracy of the hole of the workpiece, and it cannot be artificial. The locating pin is fastened by yamen service pin, while the locating pin of 45 × steel and alloy steel Cr12 must have sufficient strength and rigidity through quenching, tempering and heat treatment cooling to improve wear resistance and prolong service life
Structure design of equipment and design of 2-3 parts
Once these parts are placed in the equipment, they are usually fastened so that the parts remain in the process of being processed without being damaged. In the process of machining, workpiece will occur, displacement deformation and vibration, which will affect the machining quality of workpiece.
Therefore, the fastening of parts is also a very important problem to ensure the machining accuracy. In order to achieve good machining efficiency, it is necessary to control the displacement and vibration of parts in machining time within the boundary of machining accuracy. As a result, the handling of the fastening problem of accessories is sometimes more troublesome than the positioning design, and the problem should not be ignored.
Design and affirmation of clamping organization
After the selected connection point is confirmed, the clamping force is designed, the clamping organization is determined and the force exerted by the specific organization is maintained. In general, the clamp system is composed of, power supply and transmission mechanism.
The clamping structure refers to a perfect structure that can implement the clamping of the parts selected at the maintenance point to confirm the performance of the clamping force, and the key point includes that the force applied is a plate, pressure and structure related to the component.
The use mechanism of clamping force can select floating structure and self-locking link,,, with the following four modes:
The fastening structure of bolt and nut: simple structure, simple manufacturing, clamping line width, good self-locking performance, has been used in ordinary;
Application organization of skew force: applicable to large clamping force and small stroke, mainly based on pneumatic and hydraulic power;
Eccentric force application organization: simple structure, fast behavior, but small pressure, mainly used for small parts of accessories;
Push button organization: simple structure, large force ratio, used in pneumatic fixture, reduce the strength of cylinder or air chamber, and get ordinary use.
Careful economy and joint cooperation of parts
The key goal of using accessories is to ensure the quality of works. In detail, when using accessories, ensure the accuracy of dimension (form) and position accuracy of components. Machining deviation of parts completely reflects the deviation of process system, and accessory deviation is the key deviation component of machining deviation. Equipment error is divided into two parts: static error and dynamic error, in which static error represents an important proportion.
Today’s precision parts processing for you to understand the fine mechanical parts free grinding tools finishing technology, together with it.
In the process of precision parts processing, it is necessary to deburr every part. In the process of deburring, file, sandpaper, etc. are used to remove the burr of sophisticated mechanical parts. With the continuous development of modern science and technology, it is still difficult to use human deburring methods to meet the needs of society. Therefore, the new finishing technology is born.
This technology is still used by some large-scale enterprises for surface finishing of carefully machined parts, which is also incorporated into the process by the technical staff, and a standard process is still gradually built. For all kinds of machining techniques, such as turning, milling, forging, stamping, etc., there is no one that will bring certain trace on the surface of carefully machined spare parts, with the emphasis on: rough surface, burr, crack, etc., which will have a positive impact on the normal use of parts, making the quality and quality of parts The index of appearance index is reduced. This processing technique is introduced below.
Free grinding tool finishing technology. With regard to the rolling and polishing process, the processed and meticulous mechanical parts are placed in the roller of the medium, that is, the grinding block and grinding agent are included. Following the complicated relative activities, the free grinding block and grinding agent are gradually colliding, rolling and micro grinding the surface of the parts under the certain pressure, so that the rough surface is continuously refined, so as to enter the detailed mechanical parts After finishing, improve the surface physics and mechanical function, and improve the quality and use function of the machined surface of the meticulous mechanical parts. After selecting a piece of equipment, confirm the abrasives used according to the raw materials and use requirements of the finished parts, as well as the parameters of the appropriate abrasives and grinding blocks, including the variety, loading number and inclusion ratio.
The so-called inclusion ratio refers to the proportion of inclusion grinding block, grinding agent, water and workpiece, processing time, etc. The form, size, size, surface particle size, material ratio, sintering hardness of the grinding block, etc. only in this way can the effect of finishing become more and more dream. In the process of finishing, the off plan is often used. Generally speaking, in the process of finishing, ensure that the grinding block parts, i.e. each polished mechanical parts processing is included nearby, and the raw materials of the polished parts, i.e. steel, copper, aluminum, stainless steel, etc., are classified according to the requirements. The grinding agents of different varieties are required for the different parts raw materials.
Programmable logic controller is the logic control center of machine tools. In the future, all kinds of activities and efficiency instructions from CNC will be logically sequenced, so that they can operate safely and accurately, coordinately and orderly; all kinds of information and work information not from machine tool will be transmitted to CNC, so that CNC can quickly and accurately send out further control instructions, so as to complete the control of all machine tools.
The electrical hardware circuit of CNC lathe follows the function of PLC constantly. The main mission of electrical hardware circuit is the generation and control circuit of power supply, the part of barrier relay and all kinds of promotion appliances (relays and Contactors). There are few relay logic circuits.
CNC lathe (electrical part) includes all electric ideas, solenoid valves, brakes, various switches, etc. They are promoters of various behaviors of machine tools and reporters of various essential situations of machine tools. The possible main obstacles here are the breakage of electrical appliances and the disconnection or cracking of connecting wires and cables.
The spindle drive system of CNC lathe receives the drive instruction from CNC, and drives the main electric idea to rotate through the speed and torque (power) Regulation and transmission drive information, and receives the speed feedback together to promote the speed closed-loop control. At the beginning and the end, PLC announced that CNC was used to control the functions of the spindle.
The feed servo system receives the speed command from CNC for each active coordinate axis, drives the servo motor to rotate through the speed and current (torque) Regulation and transmission drive information, completes the machine coordinate axis activity, and receives the speed feedback information together to promote the speed closed-loop control.
Welding repair of mechanical parts is more difficult than that of steel structure parts, because welding repair parts not only need to meet the requirements of strength and rigidity, but also need to meet the requirements of overall size, shape and position accuracy and machinability after repair. For the welding repair of large and complex parts, the welding repair process must be formulated and strictly implemented according to the wear and damage conditions of the parts. Generally, the key points of parts welding repair process are as follows.
① Pre welding planning. In addition to equipment planning, pre welding planning mainly includes preparation of welding groove and preheating of weldment.
Y-groove is used for single side welding (plate thickness ≤ 30mm), double V-groove is used for double side welding (plate thickness > 30mm), and U-groove is used for butt welding of shaft parts. Groove is formed by machining, or by gas cutting or gouging, but oxide skin must be eliminated. The groove shall be clean and free of oil stain and rust. The groove of butt welding shall be symmetrical to ensure good positioning. The groove of the crack depends on the depth and length of the crack, which shall be convenient for welding and reduce the filler metal.
The preheating temperature of the welding repair parts is determined by the carbon content of the base metal. Some steels which maintain austenite structure at normal temperature have no hardening condition and can not be preheated.
② Tack welding. When one side of the shaft parts or some parts welded and butted has been broken from the whole, the butt position of the parts to be welded shall be accurate to prevent excessive deformation during welding. For this reason, tack welding shall be carried out first: spot welding shall be carried out with the welding rod whose diameter is smaller than that of welding, and then the position shall be corrected again, and spot welding shall be carried out at several symmetrical points.
③ Selection of weld passes and electrode diameter. The wide or deep weld needs to be completed with multiple weld layers, and the weld procedures are interwoven. The functions can be improved, and the annealed weld bead can be applied. The weld bead shall be welded symmetrically. For the thicker part of the welding layer, the welding rod with good toughness or austenitic stainless steel welding rod shall be used to weld near the working size first, then the welding rod shall be used to weld to the required size, and machining allowance shall be reserved if necessary. For multi pass welding, the first 1-3 passes of fine-diameter electrode can be used to fully weld the bottom corner, and then the rest passes can be completed with coarse-diameter electrode. The diameter of the bead shall be smaller than that of the electrode used for welding, so as to control the temperature of the part during the bead welding.
1、 First, explain the processing method of stainless steel parts for everyone:
Stainless steel parts are widely used in equipment and machinery, and their processing methods and processes are becoming more and more advanced. Here are six processing methods of key stainless steel parts:
1. Forging method: use the swaging machine to stretch at the end or part of the pipe to reduce the outer diameter. The common swaging machines are rotary type, connecting rod type and roller type;
2. Bulge method: one is to place rubber in the pipe, and shrink it with a punch to make the pipe protrude; the other is to bulge the pipe with hydraulic pressure, and fill the middle of the pipe with liquid. The liquid pressure bulges the pipe into the required form, which is mostly used in the production of wave pipe;
3. Bending forming method of stainless steel elbow: there are three commonly used methods, one is stretching method, the other is stamping method, the third is roller method, there are 3-4 rollers, two unchanging rollers, one adjusting roller, adjusting unchanging roller distance, forming article pipe fittings is bending;
4. Stamping method: the pipe end is expanded to the required size and form by the core with taper on the punch;
5. Rolling method: usually without mandrel, suitable for the inner circular edge of thick wall pipe;
6. Roller method: the core is placed in the pipe, and the outer circumference is pushed and pressed by roller, which is used for round edge processing.
2、 Requirements of stainless steel parts for welding technology:
Due to the different sizes of stainless steel parts, the special welding places of stainless steel parts shall be followed, and the heat input shall be reduced as much as possible. Therefore, manual arc welding and argon arc welding shall be used. For d > Φ 159mm, argon arc welding shall be used as the backing and manual arc welding cover. D ≤ Φ 159 mm. Requirements for welding technology of stainless steel parts are as follows:
1. In manual arc welding, DC reverse connection is used for welding machine and DC positive connection is used for argon arc welding;
2. Before welding, the welding wire shall be brushed with stainless steel wire to remove the oxide skin on the surface and washed with * *; the welding rod shall be dried at 200-250 ℃ for 1H and used as needed;
3. Before welding, the oil stain within the 25 mm boundary line on both sides of the workpiece groove shall be cleaned, and the 25 mm boundary line on both sides of the groove shall be washed with * *;
4. During argon arc welding, the diameter of nozzle is Φ 2 mm, and the specification of tungsten electrode is Φ 2.5 mm;
5. When argon arc welding stainless steel, the reverse side must be filled with argon for protection to ensure the reverse forming. The flow rate is 5-14l / min and the flow rate of argon on the opposite side is 12-13l / min. During backing welding, the thickness of the weld shall be thin, with excellent fusion with the root, and it shall be in a gentle slope shape during arc closing. If there are arc closing shrinkage holes, they shall be ground off with a grinder. Make sure to start and extinguish the arc in the groove, and fill the crater during arc extinguishment to prevent the crater crack.
Using CNC processing equipment for processing, high efficiency, good quality, but if the process design is not properly placed, it can not well reflect its advantages. From the experience of some CNC processing plants, there are some problems as follows:
1. Over distribution of CNC process
The reason for this problem lies in the fear of complexity (referring to planning time), the simple programming, the simplified manipulation and processing, the use of a knife for processing, the easy adjustment of the tool, and the habit of ordinary processing. In this way, it is not easy to guarantee the goods (location yamen) and the production efficiency can not be well developed. Therefore, CNC processing staff and operators should have a comprehensive understanding of CNC processing knowledge, try more to be in charge of the related knowledge, and try to select the way of process set for processing, and use more times, which will naturally reflect its advantages. After the selection of working procedures, the unit processing time increases. We have deployed two equipment face to face, and completed the operation of two equipment by one person. The efficiency has been greatly increased, and the quality has been well guaranteed.
2. Sequential bifurcation theory of CNC processing
Some CNC processing operators study some problems in planning, and often put the processing order in a very different way. NC machining is usually carried out according to the requirements of normal machining process planning, such as first coarse and then fine (tool change), first inside and then outside, correct selection of cutting parameters, etc., so that the quality and efficiency can be improved.
Careful use of G00 (g26, G27, g29) quick positioning instruction has brought great convenience to programming and application. However, if it is not properly configured and used, it will usually lead to adverse consequences such as overshoot when returning to zero due to excessive speed configuration, precision drop, equipment guide rail surface pull, etc. The route of returning to zero is not concerned, which is easy to cause safety incidents of collision with workpieces and equipment. Therefore, when studying and using G00 instruction, we should study carefully and not casually.
In NC machining, more and more attention should be paid to strengthening the retrieval and test run of programs. After the program is input into the control system, the operator should swindle the SCH key and the ↑, ↓, ←, → mobile key to search indefinitely and positively, and correct the program if necessary to ensure the accuracy of the program. At the same time, before the formal implementation of the program processing, the program test run must be carried out from the beginning to the end (turn on the power amplifier) to confirm whether the processing route is the same as the design route.
The above are some common problems and solutions when using CNC processing equipment. There may be some other problems in the essential work, but as long as the CNC processing engineering technicians and operators are open-minded and carefully in charge of the related CNC knowledge and technology, the CNC equipment can well promote the benefits for the enterprise
It can finish the process actively, and it is flexible actively, and then the power can be 3-7 times higher than the traditional machine tools. Because the computer has the ability to recall and store, it can record and store the input programs, and then actively implement them in the order of program rules, and then complete the product polarization. CNC machine tools only need to change one program to finish the enthusiasm of another workpiece processing, and then to make single piece and small batch production active, so it is called “flexible enthusiasm”
The precision of machining parts is high and the standard distribution is small, which makes the installation simple and no longer requires “repair”. It can complete the concentration of multiple processes and reduce the frequent transfer of cutting parts between machine tools. It has a variety of self-discipline effects, such as active alarm, active monitoring, and active compensation, so it can complete the long-term unattended processing.
Advantages derived from the above. It reduces the work intensity of workers, saves the work force (one person can guard multiple machine tools), reduces the tooling, reduces the trial production cycle and production cycle of new products, and can respond to the market demand quickly. The above advantages and disadvantages are beyond the imagination of predecessors, which is a very important break.
In the rest, CNC machine tools are the basis for the implementation of FMC (flexible manufacturing unit), FMS (flexible manufacturing system) and CIMS (Computer Integrated Manufacturing System) and other enterprise information changes. The numerical control skill still becomes the core skill and the basic skill of the production polarization.
What are the requirements for precision parts? For example, when machining a cylinder, there are strict requirements for the diameter of the cylinder. The positive and negative deviations in the requirements of the articles of association are qualified parts, otherwise they are all parts with different grids; For example, if the diameter of the embedded cylinder is too large to exceed the allowable deviation boundary, the insertion condition will be caused. If the intrinsic diameter is too small to exceed the lower limit of the allowable negative deviation value, it will be caused. The insertion is too loose. There is an unsafe problem.
The length of the cylinder is very long or too short, which exceeds the allowable deviation line. These are all products of different grids. They should be scrapped or processed from scratch, which will definitely result in cost increase.
Secondly, advanced non-standard precision parts processing equipment and testing equipment, advanced processing equipment makes the processing of sophisticated parts simpler, more accurate and more efficient.