The text consists of three parts: overview, text and summary, and the number of words in the text is not less than 3000 words.

1. 1 Overview

The overview part briefly introduces the basic situation of the internship unit, internship positions and the completion of internship tasks. More than 300 words.

1.2 main body

The main part mainly introduces what the internship process has done, internship experience, including the main work and achievements completed by individuals, ideological and professional gains and experiences, and their own internship attitude and discipline. It is the display and expression of students' internship results and the reproduction of the whole internship process. This part accounts for most of the internship report. This part of the content requires clear thinking, strict logic, objective, scientific and complete content, and tries to let facts and data speak. If it is difficult to express clearly in words or it is complicated, it can be expressed in tables or pictures, and the number of words is required to be more than 2000 words.

1.3 summary

Summary is the overall summary and suggestions of the internship process, mainly answering "what have you got", "what are the shortcomings" and "what to do in the future". It is an induction and summary of the internship results, as well as suggestions for setting courses in schools, the requirements of internship units for talent quality, their own gaps, future career planning and so on. When writing a summary, you should pay attention to: clear, concise, complete, accurate, tightly worded and unambiguous. The conclusion is divided into two parts, on the one hand, it includes the internship results, on the other hand, it is worth improving.

thank

Acknowledgement is a kind of gratitude to the leaders, teachers, colleagues and related personnel who provide internship training guidance in the internship unit.

The contents of the document are in Song Style or Imitation Song Style; Row spacing 1.25 times row spacing; The first line of the paragraph is indented by 2 characters; Illustrations and charts should be numbered.

thesis

A, the history of the development of numerical control system in China.

1. In China, starting from 1958, a group of scientific research institutes, universities and a few machine tool factories began to develop numerical control systems. Due to the low level of domestic electronic components and the constraints of departmental economy, it has not achieved great development.

2. After the reform and opening up, China's numerical control technology has gradually made great progress. After the introduction of foreign technology in the Sixth Five-Year Plan (8 1-85), the digestion and absorption in the Seventh Five-Year Plan (86-90) and the scientific and technological research organized by the State in the Eighth Five-Year Plan (91-95), China's numerical control technology has developed. Huazhong I of Huazhong CNC Company, Lantian I of Shenyang National Engineering Research Center for High-grade CNC, and other domestic CNC systems tested by the National Machine Tool Quality Supervision and Inspection Center, such as the products of Nanjing Case Company.

3. China CNC machine tool manufacturing industry had a high-speed development stage in 1980s, and many machine tool factories realized the transformation from traditional products to CNC products. But generally speaking, the technical level is not high and the quality is not good. Therefore, in the early 1990s, faced with the transfer and adjustment of the national economy from a planned economy to a market economy, it experienced the most difficult depression in recent years, when the production capacity dropped to 50% and the inventory exceeded four months. After199595, the country started the machine tool market by expanding domestic demand, strengthened the examination and approval of restricting the import of CNC equipment, and mainly invested in supporting the research of key CNC systems, equipment and technologies, which greatly promoted the production of CNC equipment. Especially after 1 9 9 9, the state invested a lot of technical transformation funds in the national defense industry and key civilian industries, which made the CNC equipment manufacturing market prosperous.

Three, CNC lathe technology and tool cutting

Reading: 133

The processing technology of CNC lathe is similar to that of ordinary lathe, but because CNC lathe is clamped at one time and all turning processes are automatic and continuous processing, we need to pay attention to the following aspects.

1. Reasonable selection of cutting parameters

For efficient metal cutting, machining materials, cutting tools and cutting conditions are three major elements. These determine the machining time, tool life and machining quality. An economical and effective machining method must be a reasonable choice of cutting conditions.

The three elements of cutting conditions: cutting speed, feed rate and cutting depth directly cause tool damage. With the increase of cutting speed, the temperature of the tool tip will increase, resulting in mechanical wear, chemical wear and thermal wear. If the cutting speed is increased by 20%, the tool life will be reduced by 1/2.

The relationship between the feed condition and the wear behind the tool is generated in a very small range. However, the feed rate is large, the cutting temperature rises and the back wear is large. Its influence on the tool is less than the cutting speed. Although the influence of cutting depth on the tool is not as great as cutting speed and feed, the hardened layer of the cut material will also affect the service life of the tool at micro-cutting depth.

Users should choose cutting speed according to machining material, hardness, cutting state, material type, feed speed and cutting depth.

The selection of the most suitable processing conditions is based on these factors. Normal and stable wear is an ideal condition to achieve service life.

However, in practice, the choice of tool life is related to tool wear, the change of machining size, surface quality, cutting noise, machining heat and so on. When determining the processing conditions, it is necessary to study according to the actual situation. For difficult-to-machine materials such as stainless steel and heat-resistant alloy, coolant or blades with good rigidity can be used.

2. Reasonable choice of cutting tools

1) When rough turning, tools with high strength and good durability should be selected to meet the requirements of large back feed and large feed.

2) When turning, choose tools with high precision and good durability to ensure machining accuracy.

3) In order to reduce the tool changing time and facilitate tool alignment, machine-clamped tools and machine-clamped blades should be adopted as far as possible.

3. Reasonable selection of fixture

1) Try to clamp the workpiece with general fixture and avoid using special fixture;

2) The positioning datum of parts coincide, which reduces the positioning error.

4. Determine the processing route

Machining route refers to the trajectory and direction of the tool relative to the parts during the machining process of CNC machine tools.

1) should be able to ensure the machining accuracy and surface roughness requirements;

2) The machining route should be shortened as far as possible to reduce the idle travel time of the cutter.

5. Contact between machining route and machining allowance

At present, under the condition that CNC lathes have not been widely used, it is generally necessary to arrange extra allowance on the blank, especially the allowance containing forged hard skin, and process it on ordinary lathes. If it is necessary to use CNC lathe for machining, we should pay attention to the flexible arrangement of the program.

6. Key points of fixture installation

At present, the connection between the hydraulic chuck and the hydraulic clamping cylinder is realized by a pull rod, as shown in figure 1. The key points of clamping the hydraulic chuck are as follows: firstly, remove the nut on the hydraulic cylinder, remove the cylinder and pull it out from the rear end of the spindle, and then remove the chuck fixing screw with the handle to remove the chuck.

Fourthly, effective and reasonable turning.

Reading: 102

Effectively save processing time.

The integrated machining unit of G200 turning center of Index Company has the functions of modularization, high-power dual spindle and four-axis linkage, which further shortens the machining time. Contrary to other concepts of clamping by working shaft, this product can automatically clamp the workpiece in place and process it by using the integrated intelligent machining unit. In other words, automatic clamping will not affect the machining of the other spindle, which can shorten the machining time by about 10%.

In addition, the four-axis machining speed is very fast, and two tools can be used for machining at the same time. When machine tools are put into use in pairs, the improvement of efficiency is more obvious. In other words, conventional turning and hard turning can set two machine tools in parallel.

The only difference between ordinary turning and hard turning is the tool rest and the central constant temperature coolant system. But it is different from conventional machining: conventional machining can be processed with two tool holders and one tailstock; Only one tool holder can be used in hard turning. Both types of machine tools can be used for dry machining, but the manufacturer of process plan needs to carefully design a balanced takt time, and the modular structure provided by the index machine tool makes it more flexible.

Improve productivity with high precision

With the continuous improvement of production efficiency, users also put forward high requirements for accuracy. When machining with G200 turning center, at most 4 workpieces need to be machined after cold start, and the tolerance can reach 6mm. In the process of machining, the accuracy is usually kept at 2mm. Therefore, Index company provides customers with a complete solution with high precision and high efficiency, and to provide this high-precision solution, it is necessary to carefully select functional components such as spindle and bearing.

The application of G200 turning center in the automobile factory of German national treasure Malanshute Company has achieved good results. The factory not only produces engines, but also parts made of light metal and plastic decorative parts in automobiles and steering shafts. Quality supervision believes that the machining accuracy is very accurate: continuous tolerance zone 15mm, bearing seat tolerance 6.5 mm

In addition, the machined universal joint adopts the fully automatic intelligent machining unit of Index Company. The first two turning centers are used to pretreat the workpiece before numbering, measure it online after machining, and then send it out by conveyor belt for hobbing, cleaning and quenching. In the last process, the second index processing system is adopted. The steering knuckle bearing seat is hard turned by two G200 turning centers. On-line measurement is completed in the machine tool and then sent to the unloading unit. The integrated processing unit is completely integrated into the layout of the workshop, which meets the requirements of ergonomics and greatly reduces the floor space. Only two employees are needed to look after the manufacturing unit.

Wonderful use of G00 in NC turning and skills to ensure dimensional accuracy.

CNC turning technology has been widely used in machinery manufacturing. Every engineer and technician engaged in this industry has more or less his own experience in how to finish the processing of workpieces efficiently, reasonably and with good quality and quantity. The author has been engaged in NC teaching, training and machining for many years, and has accumulated some experience and skills. Taking GSK980T series machine tools produced by guangzhou cnc Equipment Factory as an example, this paper introduces several NC turning techniques.

First, the first sentence of the program skillfully uses G00 skills.

At present, in the teaching materials and technical books of NC turning, the first sentence of the program is to establish the workpiece coordinate system, that is, G50 Xα Zβ is the first sentence of the program. According to this instruction, a coordinate system can be set so that the coordinate value of a certain point of the tool in this coordinate system is (Xα Zβ) (the origin of the workpiece coordinate system in this paper is set at the right end face of the workpiece). Using this method to write the program, after tool alignment, the tool must be moved to the established position set by G50 before machining. The process of finding a location is as follows.

1. After tool alignment, clamp the workpiece blank;

2. The spindle rotates forward, and the right end surface A of the workpiece is leveled by the handwheel reference knife;

3. Without moving the Z axis, release the tool to point C along the X axis and enter G50 Z0, and the computer will remember this point;

4. Program input mode: input G0 1 W-8 F50 to turn the workpiece into a step;

5. Without moving the X-axis, release the tool to point C along the Z-axis, stop to measure the step diameter γ of the turned workpiece, input G50 Xγ, and the computer will remember this point;

6. In the program input mode, input G00 Xα Zβ, and the tool will run to the program origin specified by programming, and then input G50 Xα Zβ, and the computer will remember the program origin.

Among the above steps, the sixth step, that is, positioning the tool at XαZβ, is very important, otherwise the workpiece coordinate system will be modified and the workpiece cannot be machined normally. Anyone with machining experience knows that the tool positioning process at the position of XαZβ mentioned above is complicated. In the event of an accident, there is no servo in X or Z axis, tracking error and power failure, etc., the system can only be restarted. After restarting, the system loses the memory of the workpiece coordinate values set by G50, and the "reset to zero operation" no longer works. It is necessary to run the tool to the position of XαZβ again and reset G50. If it is mass production, after processing one piece, go back to the starting point of G50 to continue processing the next piece. If the operation is slightly wrong, it is possible to modify the workpiece coordinate system. In view of the disadvantages of using G50 to establish the workpiece coordinate system in the first sentence of the above program, the author tried to fix the workpiece coordinate system on the machine tool, and after changing the first sentence of the program from G50 XαZβ to G00 Xα Zβ, the problem was solved. The operation process only needs to adopt the first five steps of the G50 search process mentioned above, that is, after completing steps 1, 2, 3, 4 and 5, run the tool to a safe position, call up the program, and press automatic operation. Even if there are unexpected situations such as power failure, after restarting the system, move the cursor to a program section that can be safely machined without affecting the workpiece machining process in edit mode, and continue machining in automatic operation mode. The essence of replacing G50 with G00 in the first sentence of the above program is to fix the workpiece coordinate system on the machine tool, which is no longer limited by the origin of G50 Xα Zβ program and does not change the workpiece coordinate system. The operation is simple, the reliability is strong and the unexpected effect is achieved. China metalworking online

Second, the skills of controlling dimensional accuracy

1. Modify the tool compensation value to ensure the dimensional accuracy.

When the workpiece error exceeds the workpiece tolerance due to the first tool alignment error or other reasons and cannot meet the machining requirements, the workpiece can reach the required size by modifying the tool compensation, and the radial size can be guaranteed as follows:

A. absolute coordinate input method

According to the principle of "great reduction and increase", the position of tool supplement 00 1 ~ 004 was modified. If the workpiece size increases by 0. 1mm when cutting with No.2 tool, and the tool compensation at 002 is displayed as X3.8, you can enter X3.7 to reduce the tool compensation of No.2 tool.

B. Relative coordinate method

As in the above example, you can get the same effect by typing U-0. 1 in the 002 tool patch.

Similarly, the control of axial dimension is the same. If 1 cylindrical cutter is used to process a shaft section, and the dimension is 0. 1mm longer, you can enter W0. 1 where 00 1 cutter is added.

2. Semi-finishing eliminates the influence of screw clearance to ensure dimensional accuracy.

For most CNC lathes, after a long period of use, due to the influence of lead screw clearance, the machined workpiece size often appears unstable. At this time, after rough machining, we can carry out a semi-finish machining to eliminate the influence of screw clearance. If you use 1 cutter G7 1 to rough the excircle, you can enter U0.3 at 00 1 cutter compensation point and call G70 finishing lathe once. After the measurement is stopped, enter u0.3 at 00 1 tool compensation point, and call G70 fine car again. After this semi-finish turning, the influence of screw clearance is eliminated and the stability of dimensional accuracy is ensured.

3. Programming to ensure dimensional accuracy

A. Absolute programming ensures dimensional accuracy

There are absolute programming and relative programming. Relative programming refers to determining the coordinate system of the end position of each line segment with the starting point of the line segment as the coordinate origin on the machining contour curve. That is to say, the coordinate origin of relative programming is constantly changing, and constant displacement will inevitably produce cumulative errors. Absolute programming has a relatively unified reference point in the whole machining process, that is, the coordinate origin, so the cumulative error is smaller than that of relative programming. When NC turning a workpiece, the accuracy of the radial dimension of the workpiece is generally higher than that of the axial dimension. Therefore, when programming, it is best to use absolute programming for radial dimensions. Considering the convenience of machining and programming, relative programming is often used for axial dimensions, but absolute programming is best for important axial dimensions.

B. Numerical conversion ensures dimensional accuracy

In many cases, the dimension datum on the pattern is inconsistent with the dimension datum required by programming, so the dimension datum on the pattern should be converted into the dimension in the programming coordinate system first. As shown in fig. 2b, except for the size of 13.06mm, all other dimensions are programmed dimensions directly converted from the size shown in fig. 2a. Among them, φ29.95mm, φ 16mm and 60.07mm are the programming dimensions obtained by taking the average of the two limit dimensions respectively.

4. Modify the program to control the tool compensation size.

In NC machining, we often encounter such a phenomenon: after the program runs automatically, we stop measuring and find that the size of the workpiece can not meet the requirements and the size changes irregularly. If the workpiece shown in Figure 3 is machined with a 1 cylindrical cutter, the radial dimensions of each shaft segment after rough machining and semi-finish machining are: φ30.06mm, φ23.03mm and φ 16.02mm respectively. In this regard, the author adopts the methods of modifying the program and repairing the knife, and the methods are as follows:

A. Modifying procedures

In the original scheme, X30 is unchanged, X23 is changed to X23.03, and X 16 is changed to X 16.04. As a result, the uniform tolerance of each shaft section exceeds the nominal size by 0.06mm；;

B.change the knife and repair it.

Enter U-0.06 in the position of 1 tool supplement 00 1.

After the modification of the above program and tool compensation, the workpiece size can be effectively guaranteed by calling the finishing program.

NC turning is an automatic machining method based on NC program. In actual machining, only the operator has strong ability to use program instructions and rich practical skills can he work out high-quality machining programs and produce high-quality workpieces.

Six, CNC machine tool troubleshooting methods and matters needing attention

Because I often participate in maintenance tasks, I have some maintenance experience, which is listed below in combination with relevant theories, hoping to attract more attention.

First, troubleshooting methods

(1) Initialization and reset method: In general, the system alarm caused by instantaneous fault can be cleared by hardware reset or switching the system power supply in turn. If the working storage area of the system is chaotic due to power failure, unplugging the circuit board or battery undervoltage, the system must be initialized and cleared, and the data copy record should be made before clearing. If the fault cannot be eliminated after initialization, hardware diagnosis should be carried out.

(2) Parameter change and program correction: System parameters are the basis for determining system functions, and wrong parameter setting may lead to system failure or a certain function is invalid. Sometimes, due to user program errors, it will also lead to downtime. In this regard, the block search function of the system can be used to check and correct all errors to ensure its normal operation.

(3) adjustment, optimization adjustment method: adjustment is the simplest method. By adjusting the potentiometer, the system fault is corrected. For example, when a factory is in maintenance, its system display screen is chaotic and normal after adjustment. For example, in a factory, the main shaft belt slips when starting and braking, because the load torque of the main shaft is large, and the climbing time of the driving device is set too short, which is normal after adjustment.

Optimal adjustment is a comprehensive adjustment method that matches the servo drive system with the dragged mechanical system. The method is simple. Use multi-line recorder or double-track oscilloscope with storage function to observe the response relationship between instructions and speed feedback or current feedback respectively. By adjusting the proportional coefficient and integration time of the speed regulator, the servo system can achieve the best working state with no oscillation and high dynamic response characteristics. When there is no oscilloscope or recorder on site, adjust the motor to start vibration according to experience, and then adjust it slowly in the opposite direction until the vibration is eliminated.

(4) Spare parts replacement method: Replace the diagnosed bad circuit board with good spare parts, and make corresponding initialization and startup, so that the machine tool can be put into normal operation quickly, and then repair or repair the bad board, which is the most commonly used troubleshooting method at present.

(5) Method of improving power quality: At present, stabilized power supply is generally used to improve power supply fluctuation. Capacitance filtering method can be used for high frequency interference, and these preventive measures can reduce the failure of power board.

(6) Maintenance information tracking method: Some large manufacturing companies constantly modify and improve the system software or hardware according to unexpected failures caused by design defects in actual work. These modifications are continuously provided to maintenance personnel in the form of maintenance information. Based on this, troubleshooting can be done correctly and thoroughly.

Second, the matters needing attention in maintenance

(1) When taking out a circuit board from the whole machine, pay attention to record its corresponding position and the number of connected cables. For the fixedly installed circuit board, the corresponding crimping parts and screws should also be removed before and after for recording. The removed compression parts and screws should be placed in a special box to avoid loss. After assembly, everything in the box should be used up, otherwise the assembly will not be complete.

(2) The soldering iron should be placed in front, away from the maintenance circuit board. The welding head should be properly trimmed to adapt to the welding of integrated circuits and avoid damaging other components during the welding process.

(3) When measuring the resistance between lines, cut off the power supply. When measuring resistance, the red and black pens should be interchanged for two times, with the larger resistance as the reference value.

(4) Most of the circuit boards are coated with solder mask, so the corresponding solder joints should be found as test points during measurement, and the solder film should not be removed. All boards are coated with insulation, so the insulation should be scraped off only at the solder joints with a blade.

(5) The printed circuit should not be cut off at will. Some maintenance personnel have certain experience in home appliance maintenance and are used to disconnection inspection. But the circuit boards on CNC equipment are mostly double-sided metal perforated boards or multi-layer perforated boards, and the printed lines are thin and dense. Once cut, it is not easy to weld, and it is easy to cut off adjacent lines when tangent. Moreover, some points cannot be separated from a line when cutting a line, so it is necessary to cut several lines at the same time.

(6) Do not disassemble and replace parts at will. Some maintenance personnel immediately disassemble and replace the faulty parts without determining the faulty parts, which leads to higher misjudgment rate and higher man-made damage rate of the disassembled parts.

(7) When disassembling parts, you should use a tin absorber and a tin rope, and it is forbidden to take them by force. Do not heat the same pad for a long time, and disassemble it repeatedly to avoid damaging the pad.

(8) When replacing a new device, properly handle its pins, and do not use acidic welding oil for welding.

(9) Record the positions of switches and jumpers on the line, and do not change them at will. When checking more than two poles, or replacing components, pay attention to mark components on each board to avoid confusion and make a good board ineffective.

(10) Understand the power configuration and type of the circuit board, and supply power individually or completely according to the inspection requirements. Attention should be paid to high pressure. Some circuit boards are directly connected with high voltage, or there is a high voltage generator in the board, which needs proper insulation, so special attention should be paid to the operation.

Finally, I think: to maintain things that can't stick to the rules, we must broaden our thinking, analyze them step by step and eliminate them one by one in combination with the local actual situation at that time until we find the real reason for the failure.

To sum up, the development of numerical control technology is synchronized with the development of modern computer technology and electronic technology, and also developed according to the needs of production development. Now that the numerical control technology has matured, its development will be deeper, wider and faster. The future numerical control system will make machinery better and cheaper.

Landlord, I wish you success ~ ~