April 2020 – Page 4 – CNC Machining & Turning, Milling, Metal parts

Why does the precision of precision hardware parts become worse

The accuracy of hardware parts almost determines the quality of products. The more sophisticated the hardware parts, the higher the accuracy requirements. Why does the processing accuracy of sophisticated hardware parts become worse? Here is the answer for everyone:

The first factor is the poor machining accuracy of the parts themselves. Generally speaking, if the dynamic deviation between the shafts is not adjusted well during the installation, it may also be that the change of the shaft transmission chain due to wear will affect the accuracy of the parts. Generally speaking, the accuracy caused by the deviation of this variety may be adjusted from the beginning. If the deviation is too large or even if there is an alarm, it is necessary to check the servo motor to see if its speed is too high.

The second factor is that the overshoot of the machine tool during operation will also affect the machining accuracy. It may be that the acceleration and deceleration time is too short, and the transformation time is appropriately prolonged. Of course, it may also be that the link between the lead screw and the servo motor is loose.

The third factor is that the roundness of the two shafts is out of tolerance, the axial deformation of the circle is caused by the mechanical failure to be adjusted properly, and the compensation for the clearance of the screw of the shaft is not correct, or the displacement of the shaft positioning may affect the accuracy of the fine parts.

The existing problems of high-end CNC lathe independently developed in China

The CNC lathe profession is a basic profession, and the elites in demand are also increasing year by year. With the acceleration of the upgrading pace of the Chinese system homework, the demand for CNC lathe is greatly increased. However, according to statistics, the market is now dominated by imports, and the development of domestic high-end CNC lathe is suffering. In such a case, the success of the CNC lathe industry should have a lot of outstanding lost.

At present, the added value of CNC lathe profession in China is relatively low, and the effect of self-developed high-end CNC lathe is not obvious. This is related to the low position of “made in China” in the world system and the low position of division of labor. Some experts have made an examination and analysis of why the market is dominated by imported CNC lathes, while the domestic CNC lathes are struggling, and obtained the following information: the State encourages the import of advanced skills and equipment, and expands the import of products of advanced CNC lathes

At present, the salary of CNC lathe elites in China is not very popular. For example, the research staff of a CNC lathe factory can get a salary of 3000 yuan in the third or second tier cities. Imagine that such a salary level can be obtained even if it is right or wrong for a high skilled type of work.

So the value of the creation of high skilled workers is more than 3000 yuan. Chinese machine tool enterprises are still unable to meet the urgent dream of engineers. During this period, a very important reason is that the domestic CNC lathe can not sell well. For products of the same model, the value of domestic products is much cheaper than that of overseas enterprises, so that the wife of the enterprise does not look at the product parameters, but only at the value can identify whether they are domestic products or foreign products. On the other hand, the management of Chinese enterprises seems not to be deeply aware of the importance of high-end skilled engineering staff.

报错

What are CNC machining center systems in machining

Today’s CNC machining for you to understand the CNC machining center system in machining? Let’s get to know.

CNC system is the core component of machine tool. If the CNC system controls the behavior of machine tool, the CNC system can accurately control the position, angle, speed and other mechanical and switching values of machine tool. In China, all middle and high-level machine tools will be equipped with imported CNC systems, while domestic CNC systems are usually seen in low and medium-level machines. It is impossible to configure domestic CNC systems on some high-level machines, because domestic CNC systems are not as good as imported CNC systems in performance, stability and reliability, so the general manufacturers of machine tools will not equip domestic CNC systems to a high level It is a good choice to configure the imported CNC system on the advanced computer. The performance, stability and reliability of the imported CNC system are very good.

What are the imported CNC products

There are many imported CNC systems in China, only a few of which are well-known. For example, Siemens of Germany, FANUC and Mitsubishi of Japan, Baoyuan and Xindai of Taiwan are all well-known CNC systems in China. At present, FANUC numerical control system of Japan accounts for a large market share in Chinese numerical control system, followed by Siemens of Germany and Mitsubishi of Japan. These imported CNC systems use their advanced data and the performance advantages of the CNC system to quickly seize the Chinese CNC market, so the domestic CNC system has little market share in the Chinese market.

Features of imported CNC

As there are many brands of imported CNC system with similar characteristics, it seems too slow to talk about the characteristics one by one. Besides, the small editors can’t talk about it. Take the FANUC numerical control system of Japan, which is used by Chinese machine tools, for example. The FANUC numerical control system has the characteristics of high quality, high performance, full performance, application and various machine tools and machine tools. Fanuc CNC system focuses on the following aspects:

1. The structure is simple, easy to disassemble, and each control board is highly integrated, so the reliability is greatly increased, and the maintenance and exchange are simple.

2. Its CNC system is suitable for working environment temperature of 0-45, relative humidity of 75%. It can be seen that FANUC CNC system is suitable for environment strength.

3. Fanuc numerical control system is equipped with complete software comparison, which can meet the general requirements of machine tool operation.

After the above understanding of CNC processing, I hope to be able to help you.

How to select blank for precision parts machining

1、 Casting

The forging method should be used to manufacture the parts with complex forms. At present, most castings are forged by sand mold, which can be divided into wood mold manual type and metal mold mechanical type. It has low precision, large machining surface allowance and low production efficiency. It can be used for single small batch production or forging of large parts. Metal mold machinery has high production rate and casting precision, but the cost of equipment is high and the component of casting is limited, so it can be used in a large number of small and medium-sized castings. Secondly, special forging can be selected for small castings with high quality requirements, such as pressure forging, centrifugal manufacturing and investment forging.

2、 Forging

For steel parts with high mechanical strength requirements, forging blanks are usually used. There are two kinds of Forgings: free forging and die forging. The free forging forging can be obtained by hand forging (small blank), mechanical hammer forging (medium blank) or press forging (large blank). This kind of forging has the advantages of low precision, low production rate, large machining allowance, and simple structure. It is applicable to single piece and small batch production, and large forgings.

The small braid in the well-organized parts processing field tells you that the accuracy and surface quality of die forgings are better than that of free forgings, and the form of forgings can be more complex, so the machining allowance can be reduced. The production efficiency of die forging is much higher than that of free forging, but it needs unique equipment and forging die, so it is used for large batch of medium and small forgings.

3、 Profile

Profiles can be divided into round steel, square steel, hexagonal steel, flat steel, angle steel, channel steel, I-beam and other profiles with unique sections. There are hot rolled and cold drawn sections. The hot-rolled profile has low precision but low value, which is used for the blank of common parts; the cold drawn profile has small size and high precision, which is easy to complete the automatic feeding, but it has high value, which is mostly used for the production of large batch, and it is practical for the processing of self-propelled bed.

The speed control method of machining spindle with CNC lathe

In order to meet the requirements of machining main drive of CNC lathe, the stepless speed regulation system of electric motor is often selected for CNC lathe. In order to expand the speed regulation boundary and meet the requirements of low speed and large torque, the stepless speed regulation of gear and motor is also commonly used to complete the spindle speed regulation.

1. Mechanical gear shifting

In the main drive system of CNC lathe machining, the traditional spindle box structure is greatly simplified due to the use of stepless speed regulation of electric thoughts. However, due to the limitation of the spindle motor and driving power, the constant torque transmission is often used in its low speed section. In order to make the main shaft provide the high transmission power of the main electric idea within the full speed limit as far as possible, and meet the demand of low-speed powerful cutting of CNC machine tools, it is often selected to use the combination of 1-4 gear speed change and stepless speed change, that is, the so-called stepless speed change in sections. The selection of mechanical gear slows down, which not only enlarges the transmission power, but also enlarges the speed regulating boundary.

When the CNC lathe is cutting, the spindle operates automatically according to the rotation speed specified by the s command in the part processing program. Therefore, there must be two kinds of spindle speed command information in the numerical control system, that is, to control the drive and speed regulating circuit of spindle motor by using analog or digital information (s code), and to control the implementation and organization of automatic gear shifting by using switch information (M code). Automatic shift organization is a kind of electric mechanical conversion device, commonly used are hydraulic fork and electromagnetic clutch.

2. Electric drive

There are two main types of speed regulating electric thoughts used in NC lathe machining spindle drive: DC and AC.

(1) DC motor speed regulation? The speed regulation boundary of ordinary CNC machine tools is relatively large. For DC motor speed regulation, two methods of voltage regulation and magnetic regulation are used simultaneously. The typical characteristic curve of DC spindle electric? Machine is shown in Figure 6-1. From its characteristic curve, it can be known that the electric idea is a constant torque speed regulation under the speed N0, that is to say, the armature voltage is selected to be changed to complete; the speed above N0 is a constant power speed regulation, which is completed by changing the excitation current.

The more commonly used “FANUC DC separately excited spindle electric machine” is a three-phase fully controlled thyristor non circulation reversible speed regulation system, which can complete the speed regulation of voltage regulation and magnetic regulation, and the speed regulation boundary is 35? ～ 3500r / min.

(2) AC motor speed regulation

At present, the cage type induction motor is used in the AC spindle drive of CNC machine tools, and the vector control variable frequency speed control method is commonly used.

With the improvement of the new DC and AC spindle speed control electric ideas, electric ideas speed control will be used in the ordinary, but in order to reduce the cost of economic CNC machine tools, mechanical gear shifting is often used to change the spindle speed.

The division of CNC machining stage

When the machining quality of parts is high, it is often impossible to use one process to meet the requirements, but to use several processes to gradually reach the required machining quality. In order to ensure the quality of CNC machining parts and the correct use of equipment and manpower, the machining process of parts can be divided into four stages: rough machining, semi finishing, finishing and finishing.

The differentiation of CNC machining stage should be based on the quality requirements, structural characteristics and manufacturing program of parts, and should not be absolute. It is unnecessary to distinguish processing stages for equipment with low processing quality requirements, good equipment rigidity, high blank precision, small machining allowance and small production program. For heavy workpieces with good rigidity, due to clamping, transportation and time-consuming, all rough and finish machining are often completed under one clamping.

As for the workpiece without distinguishing the processing stage, in order to reduce the impact of various deformations on the processing quality during the rough processing, it is necessary to loosen and accelerate the organization after the rough processing, park the workpiece for a period of time, make the workpiece fully deformed, and then use a small accelerating force to accelerate from the beginning for finishing.

Instructions for use of steel wire joint clamp accessories

Instructions for use of wire joint clamp accessories. Clamp accessories, transportation belt clamp accessories, lifting belt clamp accessories, joint clips, transportation belt connector clips, lifting belt connector clips, belt clamp plates, transportation belt connector clamp plates, lifting belt connector clamp plates, transportation belt connector installation methods, how to install the transportation belt connector.

Our company has been making steel wire rope lifting belt for more than 10 years, specializing in manufacturing steel wire rope lifting belt and its accessories: alloy clamp accessories, steel plate clamp accessories, high-strength galvanized hopper bolts, heat-resistant rubber pad, etc

Introduction to fixture accessories

1. Product classification: special alloy clamp fittings, steel plate clamp fittings

2. Product composition

Special alloy band clamp composition:

Main belt clamp: 1 inner clamp and 2 outer clamps

Accessories: special clamp bolt, steel wire buckle, filler, filling rubber, filling box

Composition of steel plate with clamp:

Main belt clamp: 1 internal clamp, 2 external clamps accessories: special clamp bolt, steel wire buckle

3. Product specification:

Width: 200mm ~ 1700mm

Fixture accessories

4. Installation method of fixture accessories:

1) . use the main belt clamp to clamp the two ends of the lifting belt with bolts.

2) . after clamping, peel off the cover glue at both ends of the lifting belt, and peel off the wire rope core.

3) . fasten the wire rope cores at both ends of the belt with the U-shaped buckle of the wire rope in sequence.

4) . cover the filling box with filling material and filling glue, wait for 15 minutes until it solidifies.

Clamp accessories, transportation belt clamp accessories, lifting belt clamp accessories, joint clips, transportation belt connector clips, lifting belt connector clips, belt clamp plates, transportation belt connector clamp plates, lifting belt connector clamp plates, transportation belt connector installation methods, how to install the transportation belt connector.

The production content mainly includes: cotton canvas, nylon, polyester conveyor belt, steel wire core conveyor belt, bucket elevator steel wire rope lifting belt, large angle corrugated edge conveyor belt, electronic skirt belt, pattern conveyor belt, ring conveyor belt, all kinds of cold, high temperature, burning, acid and alkali, oil, tear, flame-retardant, flame-retardant rubber conveyor belt, food conveyor belt, Rubber base plate and steel wire rope lifting belt alloy clamp accessories, steel plate clamp accessories and other special accessories for conveyor belt. The products are widely sold in China’s metallurgy, coal, cement, transportation, electric power, building materials, chemical industry and transportation machinery industries. Some of the products are directly sold or exported to Australia, Ukraine, India, Vietnam, North Korea, Mongolia, Africa, the Middle East and other countries and regions. They enjoy a high reputation among users. The market share keeps rising. The comprehensive technical ability of the same industry ranks first.

How to determine the machining coordinate system of CNC lathe

CNC lathe processing is a cause with high requirements. If there is a small error in coordinate configuration during the processing and manufacturing of workpieces, the products will be scrapped, and even may bring safety incidents. So how to confirm the coordinate system of CNC lathe?

(1) Reference point of CNC machine tool: the reference point is also an invariable point on the machine tool. It is the limit position of the tool holder movement limited by mechanical stop or electrical device. Its key function is to locate the coordinate system of machine tool.

(2) Machine coordinate system: the right-hand Cartesian Cartesian coordinate system is selected as the coordinate system on the CNC machine tool.

(3) Workpiece coordinate system: workpiece coordinate system is the coordinate system set by the programming staff during programming, also known as programming coordinate system.

Origin of workpiece coordinate system:? In NC programming, first of all, set a point on the part drawing as the origin of programmed coordinate according to the form characteristics and dimensions of the parts to be processed, which is called the origin of programmed coordinate. From the point of view, it’s OK to choose the origin of the workpiece coordinate system at any point on the workpiece, but this may represent tedious calculation problems and add programming troubles. In order to make the calculation simple and simplify the programming, the origin of the workpiece coordinate system is usually selected on the turning center of the workpiece, and the detailed position can be studied and configured on the left end face (or right end face) of the workpiece, even if the programming datum coincides with the design datum and positioning datum.

Tool setting: the coordinate system of machine tool is the only benchmark of machine tool, so it is necessary to know the position of program origin in the coordinate system of machine tool and finish the tool setting. The essence of tool setting is to confirm the only position of the origin of workpiece coordinate system in the machine coordinate system. Tool setting is an important skill in NC machining. At the same time, the efficiency of the tool also directly affects the efficiency of NC machining.

Tool change: when it is necessary to change the tool in the process of NC machining, it is necessary to study and select the appropriate tool change point when programming. The so-called tool change point refers to the position of tool holder rotation and tool change. When the CNC lathe confirms the workpiece coordinate system, the tool change point may be a fixed point or an arbitrary point relative to the workpiece origin. The tool change point shall be set on the outside of the workpiece or fixture, so as to ensure that the tool holder does not touch the workpiece and other parts during tool change.

What causes the abnormal machining accuracy of CNC machine tools

1、 Causes of abnormal machining accuracy of CNC lathe

The reasons for the abnormal machining accuracy of CNC lathe are highly hidden and difficult to diagnose. Five main reasons are summed up: the feed unit of machine tool is changed or changed; the zero point offset of each axis of machine tool is abnormal; the reverse clearance of axis is abnormal; the running state of motor is abnormal, that is, the electrical and control parts are abnormal; the mechanical faults, such as lead screw, bearing, coupling and other parts. In addition, the programming of NC lathe, the selection of cutting tools and human factors may also lead to the abnormal machining accuracy of NC lathe.

2、 Fault diagnosis principle of CNC machine tools

1. The first external and then internal CNC machine tool is a machine tool integrating mechanical, hydraulic and electrical, so the occurrence of its fault will also be comprehensively reflected by the three. The maintenance personnel shall check one by one from the outside to the inside first, and try to avoid opening and disassembling at will, otherwise the fault will be enlarged, the machine tool will lose precision and performance.

2. Generally speaking, mechanical fault is easy to detect, while the fault diagnosis of CNC system is more difficult. Before troubleshooting, first of all, pay attention to eliminate mechanical faults, which can often achieve twice the result with half the effort.

3. The machine tool can be powered on only when it is confirmed as a non-destructive fault through understanding, observation, test, analysis under the static state of power failure of the machine tool; under the operation condition, it can be dynamically observed, inspected and tested to find the fault. Wechat for metal CNC lathe processing, good content, worthy of attention.

For destructive faults, the danger must be eliminated before power on.

4. Simple first, then complex. When there are many kinds of faults interwoven and covered up, and there is no way to start for a while, the easy problems shall be solved first, and then the difficult problems shall be solved. Often after simple problems are solved, difficult problems may become easy.

3、 Fault diagnosis method of CNC machine tools

1. Intuitionistic method: (looking, hearing, questioning and cutting) ask – the fault phenomenon of machine tool, CNC lathe processing status, etc.; see – CRT alarm information, alarm indicator light, capacitor and other components deformation, smoke burning, protector tripping, etc.; listen – abnormal sound; smell – the smell of electrical components burning and other peculiar smell; touch – heating, vibration, poor contact, etc. Wechat for metal CNC lathe processing, good content, worthy of attention.

2. Parameter inspection method: the parameters are usually stored in RAM. Sometimes, the battery voltage is insufficient, the system will lose or be confused due to long-term power failure or external interference. The relevant parameters shall be checked and calibrated according to the fault characteristics.

3. Isolation method: for some faults, it is difficult to distinguish whether they are caused by CNC part or servo system or mechanical part, isolation method is often used.

4. In the same kind of method, the spare board with the same function is used to replace the suspected faulty template, or the templates or units with the same function are exchanged with each other.

5. The function program test method compiles some small programs for all the instructions of G, m, s, t and functions, and runs these programs when diagnosing faults to judge the lack of functions.

Classification and repair of lathe common faults

Because the CNC lathe adopts the computer control skills, the mechanical structure is greatly simplified compared with the common machine tools, and the opportunity for the mechanical system to expose the defects is greatly reduced. The common mechanical defects are mainly as follows: the defects of lathe spindle components. Because of the application of adjustable speed motor, the structure of spindle box of CNC lathe is simple, the disadvantages of which are the tool handle active tension equipment, active speed control equipment, etc.

Disadvantages of ATC. More than 50% of the disadvantages of machining center machine tools with active tool change equipment are related to active tool change equipment, which are mainly revealed in: the disadvantages of tool magazine activity, large missing of positioning difference, unstable clamping handle of manipulator, large error of manipulator activity, etc. When the disadvantages are serious, the tool change is stuck and the lathe is forced to stop working.

It is used to detect the disadvantages of the travel switch voltage in the moving direction of each axis. On CNC machine tools, in order to ensure the reliability of active homework, a lot of travel switches are selected to detect the active position. During the long-term operation of the machine tool, the moving characteristics of the moving parts change. The reliability of the travel switch pressing equipment and the change of the quality characteristics of the travel switch itself have a great impact on the generation and elimination of the defects of the lathe.

Disadvantages of lathe feed drive chain. Because the rolling collision pairs are widely used in the guide rail of CNC machine tools, the main disadvantages of the feed transmission chain are caused by the falling of the active quality, such as the mechanical parts are not moving to the regular position, the operation is stopped, the positioning accuracy is falling, the reverse leisure is increased, the mechanical crawling, the noise of the bearing is increased (usually exposed after the collision), etc., which can be adjusted and maintained from beginning to end Force, adjust the loose link, improve the accuracy of activities and adjust the compensation link.