肯堂 – Page 7 – CNC Machining & Turning, Milling, Metal parts

Requirements of steel processing by computer gong

Smelting quality for high-quality die steel, the processes of out of furnace refining, vacuum treatment, vacuum smelting, powder injection treatment and electroslag remelting are widely used at home and abroad to reduce the contents of harmful elements, oxygen, hydrogen and inclusions in the steel and fine tune the chemical composition and pouring temperature. By ESR, the macrostructure and density of the steel can be effectively improved, and the isotropy of the die steel can be improved. The tests in some domestic factories show that the transverse impact toughness of 4Cr5MoSiV1 steel produced by electric arc furnace is only 31% of the longitudinal impact toughness. After ESR, the transverse impact toughness of 4Cr5MoSiV1 steel is 70% of the longitudinal impact toughness, which is more than doubled. For the die steel with special requirements, the P / m high speed steel and P / m high alloy die steel can better improve the microstructure and properties of the steel.
On the basis of a certain forging ratio, upsetting drawing forging and cross rolling should be adopted as far as possible to improve the isotropy of die material. In order to reduce machining allowance and improve material utilization, precision forging machine, fast forging hydraulic press and high-precision continuous rolling mill are widely used to provide high-precision steel to meet the needs of mold manufacturing.
For heat treatment and finishing of forged and rolled products, controlled atmosphere or vacuum heat treatment should be adopted to avoid oxidation and decarburization. Some plastic die steel and hot work die steel should be pre hardened by Metallurgical Department. For some hot working die materials with high requirements, the Metallurgical Department should refine the structure in advance to eliminate the coarse carbides and chain carbides in the steel, and obtain fine and uniform carbides, so as to further improve the various properties of the steel, especially the isotropy. According to some foreign reports, some hot work die steels are produced with high quality and high directivity by electroslag remelting, multi-directional forging (rolling) and microstructural refinement. The transverse impact toughness can be equal to more than 90% of the longitudinal impact toughness. Many steel plants have named the steel produced by this process, such as isodisc of Bole steel plant in Austria, isotropy of Hitachi metal company in Japan, and microfine of gaozhoubo steel company in Japan. Many metallurgical production departments in China are also committed to this work. In addition, considering the metallurgical quality of various parts of steel, attention should be paid to make the main working face of the mold (such as cavity or edge) close to the surface of steel; because in general, the surface of steel is the clean part of steel, while the center of steel is the area where the macrodefects are concentrated; especially in the large section ledeburite steel, the center part is the center part The inhomogeneity of eutectic carbide in steel is 2-3 grades higher than that on the surface. In addition, the main load bearing direction of the die should be consistent with the deformation direction of the steel, so as to reduce the adverse effect of the anisotropy of the steel on the die.
Thermal conductivity thermal conductivity is also one of the main performance indicators of die steel, especially some hot work die steel and plastic die steel. Mold steel with good thermal conductivity can quickly transfer the heat generated in the processing and the heat from the workpiece, avoid overheating on the working surface of the mold, and improve the working conditions of the mold. For some thermoplastics forming dies and some die-casting dies, in order to speed up the pace of production, it is hoped that the pressed workpieces can be cooled and demoulded quickly to improve productivity. In order to solve this problem, sometimes some die materials with better thermal conductivity than steel are selected, such as high-strength copper alloy, high-strength aluminum alloy, etc.

Basis of high precision CNC machining

CNC machining can change the shape and size of products, which plays a very important role. Many friends don’t know the process benchmark of high speed CNC machining.

The broad meaning of benchmark is “basis”. The datum in mechanical manufacturing refers to the points, lines and surfaces used to determine the geometric relationship between the geometric elements on the production object. According to different functions and applications, datum can be divided into design datum and process datum, and process datum can be divided into process datum, positioning datum, measurement datum and assembly datum.

The technology of high-speed CNC machining is the premise to ensure the production of high-quality parts.

On lathe, the shape and size of the blank can be changed by the rotary motion of the workpiece and the linear or curvilinear motion of the cutter, and it can be processed to meet the requirements of the drawing.

Ordinary machine tools are more and more difficult to meet the needs of processing precision parts. At the same time, due to the improvement of production level, the price of CNC machine tools is falling from time to time. CNC precision parts processing mainly includes ultra precision turning, mirror grinding and grinding.

The primary premise of CNC precision parts processing is the accuracy of process datum. Datum on mechanical drawings are represented by capital letters a, B, C, D, etc. with a specific reference symbol with circle. When the reference symbol is aligned with the surface and its extension line or the dimension limit of the surface, the surface is taken as the datum. When the datum mark is aligned with the dimension line, it means that the solid center line of the dimension is taken as the datum. It is a more general statement that the process is accurate.

Assembly benchmark refers to the precision used to determine the position of parts in components or products during assembly. Measurement datum refers to the specification for the size and position of the machined surface to be measured during the inspection of parts. Positioning datum refers to the datum used for positioning the workpiece in the machine tool or fixture during machining.

Safety precautions – computer gong processing

When processing parts, the protective door must be closed. It is not allowed to stretch the head and hand into the protective door. It is not allowed to open the protective door during processing;
In the process of computer gong processing,

The operator shall not leave the machine tool without permission, and shall keep a high degree of concentration and observe the running state of the machine tool. In case of abnormal phenomenon or accident, the program operation shall be terminated immediately, the power supply shall be cut off and the instructor shall be informed in time, and other operations shall not be carried out;

It is strictly forbidden to tap the control panel and touch screen. It is strictly forbidden to knock the worktable, dividing head, fixture and guide rail;
It is strictly forbidden to open the control cabinet of the numerical control system to watch and touch without permission;
The operator shall not change the internal parameters of the machine tool at will. Interns are not allowed to call or modify other programs that are not compiled by themselves;
On the control microcomputer of machine tool, no other operation is allowed except program operation, transmission and program copy;
CNC milling machine belongs to large precision equipment,

It is strictly forbidden to stack any tools, clamps, cutting edges, measuring tools, workpieces and other sundries on the machine tool except for the tooling and workpieces on the workbench;

It is forbidden to touch the blade tip and scrap iron with hands. Scrap iron must be cleaned with iron hook or brush;
It is forbidden to touch the rotating spindle, workpiece or other moving parts by hand or in any other way;
It is forbidden to measure the workpiece and change the speed manually in the process of processing. It is also forbidden to wipe the workpiece with cotton yarn and clean the machine tool;
Trial operation is forbidden;
When using the hand wheel or fast moving mode to move the position of each axis,

Make sure to see the “and -” signs in X, y and Z directions before moving. When moving, slowly turn the hand wheel to observe the correct direction of the machine before speeding up the movement.

Center positioning datum – computer gong processing

1、 Selection of positioning datum for computer gong machining center

(1) Try to choose the design datum on the part as the positioning datum.

(2) One time clamping can complete the machining of all key precision parts.

(3) When the machining center not only processes the datum but also completes the processing of each station, the selection of its positioning datum needs to consider the completion of as many processing contents as possible.

(4) When the positioning datum and design datum of a part are difficult to coincide, the assembly drawing should be carefully analyzed to determine the design function of the design datum of the part. Through the calculation of the dimension chain, the tolerance range between the positioning datum and design datum should be strictly specified to ensure the machining accuracy.

2、 Selection and use of fixture for CNC machining center

(1) According to the characteristics and processing needs of machining center, the commonly used fixture types include special fixture, modular fixture, adjustable fixture, group fixture and workpiece unified reference positioning clamping system.

(2) The high flexibility of machining center requires that its fixture structure is more compact and simple than ordinary machine tool, clamping action is more rapid and accurate, auxiliary time is reduced as far as possible, operation is more convenient, labor-saving and safe, and enough rigidity and flexibility should be ensured. Therefore, pneumatic and hydraulic clamping devices are often used.

(3) In order to keep all the surfaces to be machined fully exposed, the fixture should be open as far as possible, and the space position of the clamping element should be low as possible, so there must be space for the tool path.

(4) Considering the minimum distance between the machine tool spindle and the worktable and the clamping length of the tool, the installation position of the fixture on the machine tool worktable should ensure that the processing content of the workpiece can be completed within the stroke range of the spindle.

(5) Automatic tool change and worktable exchange can not interfere with the fixture or workpiece.

(6) Sometimes, the positioning block on the fixture is used when installing the workpiece. In the process, in order to meet the processing of the front, back, left and right stations and prevent interference, the workpiece can be removed after clamping. In this regard, we should consider the problem of maintaining the positioning accuracy of the workpiece after removing the positioning element.

(7) Try not to change the clamping point in the middle of machining.

3、 CNC machining to determine the best position of parts on the machine tool table

报错笔记

High gloss traceless mold – brain Gong processing

Main features of high gloss and no trace die:

First, the mold forming temperature is higher. At higher mold temperature, injection molding can eliminate weld mark, flow mark, internal stress and other defects. Therefore, the mold needs to be heated when it is working. In order to prevent heat loss, the resin heat shield is usually added on the fixed mold side;

Second, the cavity surface is extremely bright (generally mirror 2 or higher). The products produced by high gloss mold can be directly used to assemble the whole machine without any surface treatment, so this process has high requirements for mold steel and plastic materials;

Thirdly, there are many hot nozzles in hot runner system (generally 6-8 nozzles, sometimes more). Each nozzle must be equipped with a sealing needle and an independent air passage, which can be controlled separately by solenoid valve and timing controller to realize time-sharing glue feeding, so as to achieve control and even eliminate weld marks.

High gloss traceless injection molding technology has some basic requirements for molds

The inner surface of the mould requires very high finish to ensure the surface quality of the products. The setting of pipes inside the mould must be reasonable to ensure rapid heating and cooling. The pipe inside the mold should have good thermal conductivity. Due to the need to keep heating and cooling in the production process, the mold needs to choose high-quality steel. In the process of use, we should pay special attention to the maintenance of the mold to ensure that it is dry and dust-free.

In addition, the performance and service life of high gloss traceless mold are directly related to the steel used in the mold. Due to different working conditions of plastic mold parts, the external influence is also different. Therefore, in addition to the basic requirements, the steel should also be emphasized. For example, large high gloss plastic mold cavity steel, in addition to the requirements of good cutting, EDM and welding performance, also need to have excellent throwing rotation and high hardness and other characteristics. This can not only form a bright and beautiful product, but also reduce the wear of plastic on the cavity surface, which not only extends the service life of the mold, but also reduces the injection pressure and protects the injection molding machine. At present, the high-performance and high gloss non marking die steels used in different processing conditions of flat-panel TV include polmax, lkm838h, lkm818h, s-star (a), NAK80, Stavax S136, Stavax s136h, Optimax, x13t6w (236), x13t6w (236h), etc.

Application in the field of home appliances

In recent years, the traditional CRT TV in the TV industry has been gradually eliminated, and replaced by the flat-panel TV with novel appearance, thin volume and high-grade visual sense. The surface quality of the front shell directly affects the grade of the flat-panel TV. However, the TV front shell produced by the traditional mold is difficult to eliminate the defects such as the surface weld mark and the surface finish is not enough, which can not achieve the beautiful effect. Therefore, it also needs to go through the secondary processing such as surface coating, which brings the problems such as the lengthening of the TV manufacturing cycle and the rising of the manufacturing cost.

High gloss traceless mold can solve the above problems of traditional mold. High gloss traceless mold technology has been rapidly applied in the home appliance industry since it was officially announced in the 2004 German rubber and plastic Exhibition: in 2005, Samsung of South Korea began to use high gloss mold technology to produce LCD TV shell, Chinese TV manufacturers also began to carry out the application research of this technology in 2006, and began to widely use it in the production of flat panel TV shell in 2008.

Computer gong processing machine debugging

Before the debugging of CNC computer gong processing machine tool, the debugging methods for the precision and function of CNC computer gong processing machine tool are as follows:

Using precision level instrument and other testing tools, the main bed level of the computer gong processing machine tool is precisely adjusted by adjusting the pad iron, so that the geometric accuracy of the machine tool can reach the allowable tolerance range;
For the automatic tool changing device, adjust the position of tool magazine, manipulator, stroke parameters, etc., and then check the action with instructions to ensure accuracy;
For the machine tool with APC automatic exchange table, after adjusting the relative position, carry out automatic exchange;
After the adjustment of the machine tool, carefully check whether the parameter setting values in the numerical control system and the programmable controller conform to the data specified in the random index, and then test the main operation functions, safety measures, and the execution of common instructions.
Check the auxiliary functions and accessories of the machine. CNC computer gong NC machining is the basis of modern manufacturing technology, this invention for the manufacturing industry, has epoch-making significance and far-reaching influence.

Introduction of CNC machining center coordinates

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

According to the coordinate number of machining center movement and the coordinate number of simultaneous control, there are three axis two linkage, three axis three linkage, four axis three linkage, five axis four linkage, six axis five linkage, etc. Three axis and four axis refers to the number of motion coordinates of the machining center. Linkage refers to the number of coordinates that the control system can control at the same time, so as to realize the position and speed control of the tool relative to the workpiece. Machining center is often divided into vertical machining center and horizontal machining center according to the state of the spindle in the space. The vertical machining center whose spindle is vertical in the space is called vertical machining center, and the horizontal machining center whose spindle is horizontal in the space is called horizontal machining center. Spindle can be vertical and horizontal conversion, known as vertical and horizontal machining center or five machining center, also known as composite machining center. According to the number of machining center columns, there are single column type and double column type (gantry type).

CNC computer gong processing sequence

1、 Face before hole

For the box, bracket and connecting rod, the plane should be machined first and then the hole should be machined

In this way, the hole can be processed by plane positioning to ensure the orientation accuracy of the plane and the hole, and bring convenience to the processing of the hole on the plane.

2、 Machining datum first

Parts in the processing process, as a positioning reference surface should be processed first, in order to provide fine reference for the subsequent process as soon as possible. It is called “benchmark first”.

3、 Finishing

The main surface finishing (such as grinding, honing, finishing, rolling, etc.).

It should be carried out in the final stage of the process road. The surface finish after processing is above ra0.9um. Slight bumps will damage the surface. In Japan, Germany and other countries, after finishing, flannelette should be used for maintenance. It is definitely forbidden to touch the workpiece directly by hand or other objects to avoid damage to the surface of finishing due to the transfer and device between processes.

4、 Distinguish processing stages

The appearance with high processing quality requirements can be divided into three stages: rough processing, semi finishing and finishing. First of all, it is to ensure the processing quality; it is conducive to the rational use of equipment; it is convenient to organize the heat treatment process; and it is convenient to find the defects of blank.

Introduction of CMM for CNC machining

This paper introduces the development of three coordinate measuring instrument, which is a new type of high efficiency precision measuring instrument developed in recent 30 years. It is widely used in mechanical manufacturing, electronics, automotive and aerospace industries. It can detect the size, shape and mutual position of parts and components, such as box, guide rail, turbine and blade, cylinder block, cam, gear shape and other space surface measurement. In addition, it can also be used for scribing, centering hole, photolithography integrated circuit, etc., and can scan continuous curved surface and prepare machining program of CNC machine tool. Because of its versatility, wide measurement range, high precision, high efficiency, good performance, and can be connected with flexible manufacturing system, it has become a kind of large precision instrument.

With the development of CMM market, CMM, as a modern large-scale precision instrument, has shown its importance and broad development prospects. It can measure the three-dimensional dimension of space conveniently and realize on-line detection and automatic measurement.

Its advantages are as follows:

It has strong versatility, can realize the measurement of spatial coordinates, and can easily measure the three-dimensional outline size and position accuracy of various parts;
The measurement is accurate and reliable
It is convenient for data processing and program control. Therefore, it can be incorporated into automatic production and flexible processing line, and become an important part. At present, CMM is developing rapidly at home and abroad. Famous foreign manufacturers include Zeiss and Leitz of Germany, DEA of Italy, Brown & Sharpe of America, Mitutoyo of Japan, etc. Since the development of CMM in 1970s, great progress has been made in China. The main manufacturers in China are China Aerospace Precision Machinery Research Institute, Qingdao Qianshao yingkefa measuring equipment Co., Ltd., Shanghai machine tool factory, Beijing Machine Tool Research Institute, Harbin Measuring Tool and cutting tool factory, Kunming Machine Tool Factory and Xintian optical instrument factory, etc. At present, China has the ability to produce hundreds of various types of CMM annually. With the development of various industries, the development of coordinate measuring instruments will also be rapid. Many small manufacturers choose second-hand CMM because they can’t afford to buy the new CMM, so the price is more favorable, and they can also use the new type of CMM imported work.

Introduction of vertical CNC lathe

(1) Vertical CNC lathe vertical CNC lathe referred to as CNC vertical lathe, the lathe spindle is vertical to the horizontal plane, a large diameter circular worktable, used to clamp the workpiece. This kind of machine tool is mainly used for processing large complex parts with large radial size and relatively small axial size.

(2) Horizontal NC lathe horizontal NC lathe is divided into NC horizontal guide horizontal lathe and NC inclined guide horizontal lathe. The inclined guide rail structure can make the lathe more rigid and easy to remove chips.

Classification according to the basic types of machined parts

(1) Chuck type CNC lathe has no tailstock, which is suitable for turning disc (including short shaft) parts. The clamping mode is mostly electric or hydraulic control, and the chuck structure has adjustable claw or non quenched claw (soft claw).

(2) This kind of lathe is equipped with ordinary tailstock or CNC tailstock, which is suitable for turning long parts and disc parts with small diameter.

According to the number of turrets

(1) Single turret CNC lathe is generally equipped with various forms of single turret, such as four position horizontal rotation turret or multi position turret automatic rotation turret.

(2) Double turret CNC lathe this kind of lathe double turret configuration parallel distribution, can also be mutually vertical distribution.

By function

(1) The simple CNC lathe, which is formed after the feed system of ordinary lathe is transformed by stepping motor and single chip microcomputer, has low cost, but the degree of automation and function are relatively poor, and the turning accuracy is not high. It is suitable for the turning of rotary parts with low requirements.

(2) According to the turning requirements, the general CNC lathe is specially designed in structure and equipped with general CNC system. The CNC system has strong function, high degree of automation and machining accuracy, and is suitable for turning general rotary parts. The CNC lathe can control two coordinate axes, namely X axis and Z axis.

(3) On the basis of ordinary CNC lathe, turning center adds c-axis and power head. More advanced CNC lathe has tool magazine, which can control x, Z and C coordinate axes. Linkage control axes can be (x, z), (x, c) or (Z, c). Due to the addition of c-axis and milling power head, the machining function of this CNC lathe is greatly enhanced. In addition to general turning, it can be used for radial and axial milling, surface milling, drilling of holes and radial holes whose center line is not in the rotation center of parts.