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Main functions of CNC lathe electrical system

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 process characteristics of stainless steel parts processed by CNC

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.

Problems caused by improper arrangement of CNC processing technology

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

The necessity of NC transformation of machine tools

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 processing

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.

Some precision parts need CNC machining

CNC machining is now a high-level machining of precision parts. Generally, the parts for this type of machining are used for relatively small purposes. Because the requirements for precision of parts are relatively high and the value is naturally going up, so the boundary line that can be used will be a little smaller. So which precision parts need CNC machining? In the process of making homework, the processing and manufacturing of different workpieces are required, which is largely due to the constant needs of customers. Some parts are used for some precision equipment, such as medical equipment, electronic equipment, etc. the processing complexity of this type of parts will be relatively high, which is also a problem that many manufacturers cannot produce in large quantities.

Generally speaking, the number of parts requiring CNC processing is less, but the processing form is complex. Although parts do not need quite complex tooling, they need a number of different forms, which is also a difficult place for all parts manufacturing. In the process of machining, CNC machining is required because the key needs are compared with the stable quality level and the precision requirements are high. In daily life, it is common to compare the precision shaft with optical fiber tailstock and other parts. Some of these parts need to be processed to a level that cannot be observed by the naked eye, so the processing technology requirements of the operators are relatively high.

Moreover, it is impossible to make a large number of parts. This kind of parts can not be operated in a large amount to ensure the quality is relatively stable, so they can only be made in a small batch. Of course, in the current manufacturing industry, the demand for such parts is also limited, so only some large-scale manufacturers will provide corresponding production services.

The difference of open-loop, closed-loop and half closed-loop servo systems in CNC lathe machining

(1) NC machining open-loop: this kind of machine has no feedback information from the position sensor. The CNC system processes the part program, transmits the digital instruction to the servo system, and drives the machine to move. The structure of the CNC system is simple, economical and easy to care for, but the speed and precision are low, which is suitable for the small and medium-sized machine tools with low precision requirements, and it is mostly used for the CNC transformation of the old machine tools.

(2) NC machining closed-loop: this kind of machine tool is equipped with a position detection device, which directly measures the displacement of the workpiece; its precision is high, but the system design and adjustment are troublesome, the structure is complex, and the cost is high. It is mainly used in some boring and milling machines, ultra-fine lathes, ultra-fine milling machines, machining centers, etc. with high precision requirements.

(3) NC machining semi closed loop: this kind of NC machine selects the angle measuring element installed on the feed lead screw or the end of the electric motor to measure the rotation angle of the lead screw, to obtain the position feedback information tactfully; it can obtain the more desired accuracy and speed, and numerous NC machine tools choose it, such as the numerical control lathe, NC milling machine and machining center.

12 CNC processing experience summary

CNC machining, also known as CNC machining, refers to the machining with CNC machining tools. Because NC machining is controlled by computer after programming, CNC machining has the advantages of stable machining quality, high machining accuracy, high repetition accuracy, complex profile machining and high machining efficiency. In the actual processing process, human factors and operating experience, to a large extent, will affect the processing quality. Next, let’s take a look at 12 valuable experiences summed up by an old driver with ten years of CNC processing experience

1. How to divide CNC process

The division of CNC machining process can be generally carried out according to the following methods:

The method of tool centralized sequence is to divide the working procedure according to the tool used, and use the same tool CNC to finish all the parts that can be finished. Use the second knife and the third to finish other parts they can finish. In this way, the number of tool changes can be reduced, the empty travel time can be compressed, and the unnecessary positioning error can be reduced. For parts with a lot of CNC machining content, the machining part can be divided into several parts according to its structural characteristics, such as internal shape, shape, curved surface or plane, etc. Generally, plane and positioning surface are processed first, then hole; simple geometry is processed first, then complex geometry is processed; parts with lower precision are processed first, then parts with higher precision requirements are processed. For the parts that are easy to deform in CNC machining, the method of sorting by rough and fine CNC machining needs to calibrate the shape due to the possible deformation after rough machining, so generally speaking, the process should be separated for the parts that need rough and fine machining. To sum up, in the process division, it is necessary to flexibly grasp the structure and process of the parts, the function of the machine tool, the number of CNC machining contents of the parts, the installation times and the production organization of the unit. In addition, it is suggested that the principle of process concentration or process dispersion should be adopted, which should be determined according to the actual situation, but must be reasonable.

2. What principles should be followed in the arrangement of CNC processing sequence

The arrangement of the processing sequence should be considered according to the structure of the part and the condition of the blank, as well as the need of positioning and clamping. The key point is that the rigidity of the workpiece will not be damaged. Generally, the sequence shall be in accordance with the following principles:

The CNC machining of the previous process can not affect the positioning and clamping of the next process, and the machining process of universal machine tool inserted in the middle should also be considered comprehensively. First, process the internal cavity, then process the shape. It is connected by the same positioning and clamping method or the same tool CNC processing process to reduce the number of repeated positioning, tool change and moving of pressing plate. For multiple processes in the same installation, the process with small damage to workpiece rigidity shall be arranged first.

3. What should be paid attention to in the determination of workpiece clamping mode

The following three points should be paid attention to when determining the positioning datum and clamping scheme:

Strive to unify the design, process and programming calculation standards. Reduce the number of clamping as much as possible. After one positioning, all surfaces to be machined can be processed by CNC. Avoid manual adjustment of occupation plan. The fixture shall be smooth, and its positioning and clamping mechanism shall not affect the cutter (such as collision) in CNC machining. In such cases, it can be clamped by means of vise or screw extraction with base plate. 4. How to determine the tool setting point is reasonable? What is the relationship between workpiece coordinate system and programming coordinate system?

1. The tool setting point can be set on the part to be machined, but it must be the reference position or the part that has been finished. Sometimes the tool setting point is damaged by CNC machining after the first process, which will cause the second process and the subsequent tool setting point cannot be found. Therefore, when the first process is used for tool setting, it is necessary to set a relative pair at the place that has a relatively fixed dimension relationship with the positioning benchmark Knife position, so that the original tool setting point can be retrieved according to the relative position relationship between them. This relative tool setting position is usually set on the working table or fixture of the machine tool. The selection principles are as follows:

Alignment is easy. Easy to program. The tool setting error is small. It is easy to check during processing.

2. The origin position of the workpiece coordinate system is set by the operator himself. After the workpiece is clamped, it is determined by tool setting, which reflects the distance position relationship between the workpiece and the zero point of the machine tool. Once the workpiece coordinate system is fixed, it is generally not changed. The workpiece coordinate system and the programming coordinate system must be unified, that is, when machining, the workpiece coordinate system and the programming coordinate system are the same.

4. How to choose the cutting route

Tool path refers to the path and direction of the tool relative to the workpiece in the process of NC machining. The reasonable choice of machining route is very important, because it is closely related to the CNC machining accuracy and surface quality of parts. The following points are mainly considered in determining the tool path:

Ensure the machining accuracy of parts. It is convenient for numerical calculation and reduces programming workload. In order to improve the efficiency of CNC machining, it is necessary to find a short CNC machining route and reduce the time of blank cutting. Minimize the number of program segments. To meet the requirements of the surface roughness after CNC machining, the contour should be processed by a continuous cutter. The advance and retreat (cut in and cut out) routes of the tool should also be carefully considered to minimize the tool marks caused by tool stop (elastic deformation caused by sudden change of cutting force) at the contour, and avoid cutting vertically on the contour surface and scratching the workpiece.

How to determine NC machining route in CNC machining

Numerical control skill of numerical control lathe, referred to as numerical control, refers to the skill of using the method of digital control to automatically control the completion of a certain course schedule. It usually controls the direction, viewpoint, speed and other mechanical quantities and the switch quantities related to the flow direction of mechanical energy. The origin of CNC lathe is the origin of machine coordinate system. For a specific machine tool, the origin of the machine tool is constant, which is a physical orientation of the machine tool manufacturer on the machine tool.

The key mission of NC lathe process planning is to determine the detailed processing content, cutting amount, process equipment, positioning device method and tool moving track of the process, so as to prepare for the programming.

The setting of the machining path of CNC lathe is a very important link. The machining path is the moving path of the cutter point related to the workpiece in the machining progress. It not only includes the content of the machining process, but also reflects the organization of the machining sequence. Therefore, the machining path is an important evidence for the preparation of the machining program.

The processing route shall ensure the accuracy and appearance roughness of the workpiece to be processed. Planning the processing route should reduce the time of empty travel and improve the processing power. Simplify the numerical calculation and reduce the program section, and reduce the programming workload. According to the form of workpiece, rigidity, machining allowance and rigidity of machine tool system, the number of cycle machining can be determined.

Correct selection of the down milling or reverse milling method in milling. Generally speaking, CNC lathe uses ball screw, so the leisure time is very small, so the advantages of forward milling are more than reverse milling. CNC lathe machining in CNC lathe has not yet reached the conditions of universal application, usually we should put too much allowance on the blank, the unique is that the allowance structure containing forging and casting hard skin layer is processed on the ordinary lathe. If must use numerical control lathe processing, must pay attention to the vivid organization of the program.

Plastic guide rail of CNC lathe

The plastic guide rail of CNC lathe is a kind of plastic soft belt with the same static and dynamic conflict coefficient on the sliding guide rail matching with the bed guide rail, which is wear-resistant and vibration absorbing. Maybe the plastic guide rail is made by injection molding between the fixed and dynamic guide rails. This kind of plastic guide rail has excellent conflict characteristics, wear resistance and vibration absorption, so it is commonly used in CNC lathe.

The plastic soft belt is based on polytetrafluoroethylene, with bronze powder, molybdenum disulfide, graphite and other fillers added, sintered and made into a soft belt. China has already made a TSF soft belt for guide rail, and a matching DJ adhesive. The process of using the guide rail soft belt is simple, as long as the surface roughness of the guide rail paste surface is semi-finished to ra1.6-3.2um, after cleaning the paste surface, the adhesive is used for bonding, after pressure curing, and then the finish machining can be carried out. Because this kind of guide rail soft belt adopts the bonding method, it is usually called “stick plastic guide rail”.

The raw materials for guide rail injection molding are epoxy resin and molybdenum disulfide as the matrix, plasticizer is added, and the mixture is a two-component plastic with paste shape as one component and curing agent as another component. The Chinese brand is hNT. The injection molding process of the guide rail is simple. After adjusting the mutual position accuracy between the constant guide rail and the movable guide rail, the two-component plastic is injected. After curing, the fixed and movable guide rails are separated into plastic guide rails. The plastic guide rails manufactured in this way are customarily called “injection molding guide rails”