February 2021 – Page 2 – CNC Machining & Turning, Milling, Metal parts

How to select heat treatment for parts processing

The choice of the best span l of the computer gong processing spindle, the bearing span l of the spindle. The distance between the front bearing point of the spindle and the rear bearing point of the spindle is called span L. The support span of the spindle assembly has a great influence on the stiffness of the spindle itself and the support stiffness.

(1) Spindle bore diameter. The diameter of the inner hole of the spindle is used to fix the tool through the tool clamping device, drive the pneumatic or hydraulic chuck, etc. The larger the diameter of the spindle, the lighter the relative weight of the spindle components. The aperture size of the spindle is mainly restricted by the stiffness of the spindle.

(2) Spindle diameter. The larger the diameter of the spindle is, the higher its stiffness is, but the size of the bearing and other parts on the shaft increases accordingly. The larger the diameter of the bearing is, the larger the tolerance value of the bearing with the same grade accuracy is, and the more difficult it is to ensure the rotation accuracy of the spindle.

The determination of the spindle overhang a of CNC machining center, the spindle overhang a refers to the distance between the action point of the radial support reaction force of the front support of the spindle and the front end of the spindle, which has a great influence on the stiffness of the spindle assembly. According to the analysis and experiment, shortening the overhanging amount can significantly improve the stiffness and vibration resistance of the spindle assembly. Therefore, on the premise of meeting the structural requirements, the overhanging amount a should be shortened as much as possible.

CNC machining center spindle span diagram, discusses the structure design and progress of CNC machining center mechanical spindle, the influence of span L on the comprehensive stiffness K is not unidirectional. If l is larger, the deformation of the spindle is larger; if l is smaller, the deformation of the bearing has a greater impact on the displacement of the front end of the spindle. Therefore, l has an optimal value. If l is too large or too small, the comprehensive stiffness will be reduced. There is an optimal span l0 for the support span of the spindle, which can minimize the displacement of the front end of the spindle assembly. Due to the structural limitation and the guarantee that the center of gravity of the spindle assembly falls between the two supports, the actual support can be greater than the optimal support span.

Material selection and heat treatment of CNC machining center spindle

When the main shaft bearing of CNC machining center adopts rolling bearing, the journal can not be hardened. However, in order to improve the contact stiffness and prevent knocking from damaging the matching surface of the journal, many 45 steel main shaft journals are still subject to high-frequency quenching. When using sliding bearing, in order to reduce wear, the journal surface must have high hardness. Therefore, high frequency quenching is usually carried out at the journal; flame quenching can also be used for large diameter spindle to improve its surface hardness; 15 or 20 steel can be used for spindle with large impact, and carburizing, quenching and tempering can be carried out on the journal surface. 45 steel, GCr15, etc. are often used for spindle materials, which need nitriding and induction hardening.

The selection of spindle material is mainly based on the stiffness, load, wear resistance, heat treatment deformation and other factors. The stiffness of the spindle of CNC machining center is related to the elastic modulus E of the material, and the E value of the steel is larger, so the steel should be considered first. Moreover, the value of elastic modulus E of steel has nothing to do with the type of steel and heat treatment method. Therefore, the cheap medium carbon steel should be selected first. Alloy steel should be considered only when high load and large impact or when material deformation is reduced and high strength and wear resistance are required.

Composite material is a new type of material which has two or more kinds of different physical and mechanical properties by composite processing. For example, glass, graphite (carbon), boron, plastics and other non-metallic materials can be composite into a variety of fiber reinforced composites. Plastic composite steel plate with high strength and corrosion resistance can be obtained by sticking plastic on the surface of common carbon steel plate. Its main advantages are high strength and elastic modulus, and its mass is very small. However, it also has the disadvantages of poor heat resistance, poor thermal conductivity and conductivity. In addition, the price of composite materials is more expensive. So at present, composite materials are mainly used in aviation, aerospace and other high-tech fields. In civil products, composite materials also have some applications.

Nonmetallic materials refer to polymer materials such as plastics, rubber, synthetic fibers and ceramics. Polymer materials have many advantages, such as rich raw materials, low density, good elasticity in the appropriate temperature range, good corrosion resistance and so on. Its main disadvantage is that it is easy to aging, and many of the materials have poor flame retardancy, generally speaking, poor heat resistance. The main characteristics of ceramic materials are high hardness, wear resistance, corrosion resistance, high melting point, high stiffness and low density than steel. At present, ceramic materials have been used in seals, rolling bearings and cutting tools. Its main disadvantages are brittleness, low fracture toughness, high price and poor processing technology.

Metal materials are divided into ferrous materials and non-ferrous materials. Processing ferrous materials include all kinds of steel, cast steel and cast iron, which have good mechanical properties (such as strength, plasticity, toughness, etc.), are relatively cheap and easy to obtain, and can meet the requirements of a variety of properties and applications. In all kinds of ferrous metals, CNC machining is often used to manufacture important parts because of its excellent properties. Nonferrous metal materials include copper alloy, aluminum alloy, bearing alloy, etc., which have the advantages of low density, good thermal and conductive properties, and can also be used in the occasions with requirements of antifriction, wear resistance and corrosion resistance.

CNC computer gong processing programming

Define the responsibilities of the programmer — take full responsibility for the processing quality, processing efficiency, cost control and error control in the whole CNC manufacturing process of the mold.
When receiving the new die, the programmer must understand the requirements of the die, the rationality of the die structure, the steel used in the front and rear dies, the product tolerance requirements, and the plastic materials. Distinguish where is the glue position, where is the PL surface, where is the touch through, rub through, where can be avoided.
After receiving the new die, the programmer should open the list of copper materials at the first time in principle. Before filling in the list, the copper male must be removed. It can be that it is not repaired, but it should have the size of palm base, and determine the code of copper male and the size of spark position. The first batch of copper materials must be opened within 2 days, and all copper materials can be opened within 10 days, which can be divided into 4 times of BOM.
The construction drawings of tonggong and Yougong shall be filled in with two construction drawings respectively, and the spark position must be filled in the designated place. For the workpieces that can be processed in the old machine tool, please tick “√” with the corresponding machine tool in the machine tool column of the construction drawing, and the workpieces that must be processed in the high speed machine tool should be indicated in the remarks column. For the workpiece that can’t express clearly the placement direction in the CNC construction drawing, it must be attached with the printed orientation diagram, which can make it clear at a glance. The steel material shall confirm the datum direction, workpiece size and processing surface by comparing with the actual workpiece.
When the steel is roughened, the Z cutting amount is 0.5-0.7mm. When the copper material is roughened, the Z cutting amount is 1.0-1.5mm (the inner roughening is 1.0 mm, and the base edge roughening is 1.5 mm).
In parallel finish milling, Ma × imum Stepover is set according to the “table of best contour parameters of parallel finish milling”. Before finish milling, the remaining amount should be kept as small as possible, and the steel material should be 0.10-0.2mm. Copper 0.2-0.5mm. Don’t use r-knife to finish the plane with large area.
Leave 0.05mm allowance on the rubbing through surface or touching through surface for fit mold. For some important rubbing through surfaces with small area, leave 0.1mm allowance on the touching through surface, and process the peripheral PL surface in place. The larger back mold PL surface sealing glue position is 18mm away, and the voidable one is 0.10mm away (determined by the department head).
Fast cutting to 3mm height, use F-speed cutting (relative processing depth), normal cutting F-speed is 300 mm / m, spiral cutting and external feeding z-cutting F-speed is 900 mm / m, stepping z-cutting F-speed is 150 mm / m, internal fast moving F-speed is 6500 mm / M (must go G01).
When using Φ 63r6, Φ 40r6, and Φ 30r5 flying cutter for roughening, the allowance shall be 0.8mm on one side, and the phenomenon of stepping on the cutter shall not occur. The inner frame with smaller machining range of Φ 63r6 shall not be used for grooving. After roughening, the larger plane shall be machined again with the same cutter to ensure that the allowance of 0.2mm is left at the bottom, so that the next cutter can directly finish the bottom of the workpiece.
Before finishing milling, the corner allowance must be roughly cleared with a small diameter tool. Where it is impossible to clear the corner, the surface must be used to block it, so as to avoid tool damage caused by excessive corner allowance during finishing milling.
The length of the cutting tool cannot be accurately determined. When it is necessary to use a lengthened nozzle or a small knife with a conical head, it must be noted “please use lengthened nozzle” on the construction drawing. The length of tool extension, tool straight position and the total length of shank + tool extension must be clearly stated.
In rough machining, multi curved surface slotting is not used as far as possible to improve machining efficiency, and multi curved surface contour cutting is preferred.
When removing the copper joint, it is necessary to check whether the palm bottom is empty enough. It is necessary to insert the removed copper joint into the workpiece to be machined by spark machining, and color it carefully to check whether it is empty enough. If the copper is approximately symmetrical, it is necessary to check whether it is completely symmetrical and whether the void avoidance positions are the same. Don’t be self righteous and don’t check.
The finished copper alloy must meet the following standards:

(1) the dimensions are accurate with tolerance of ± 0.02mm for young and ± 0.04mm for coarse;

(2) there is no deformation;

(3) the knife pattern is clear, and there is no particularly rough knife pattern;

(4) the line is clear, and there is no step at the cutting point;

(5) there is no obvious drape front which is difficult to remove;

(6) the thickness of palmar floor should be 15-25 mm, and the standard is 20 mm;

(7) the copper code is correct;

(8) reduce the spark level around the reference level.

Consideration principle of dismantling Copper Company:

(1) processing feasibility;

(2) practical;

(3) enough strength without deformation;

(4) convenient processing;

(5) copper cost;

(6) beautiful appearance;

(7) the less copper is removed, the better;

(8) for symmetrical products, the left and right copper male should be processed together as far as possible, and the number shifting processing should be used.

Tool use guidelines

(1) when roughening the general size steel, try to choose Φ 30r5, and when roughening the larger size steel, try to choose Φ 63r6;

(2) the M16 tool is selected for the height of copper surface below 70mm; the M20 tool is selected for the height between 70-85mm; the M25 tool is selected for the height between 85-120mm; the Φ 25r0.8 and Φ 32r0.8 flying tool handles are selected for the height above 120mm; the parts that must be removed in the middle of the night are inspected by the programmer tomorrow morning and confirmed by the programmer the next day. For large workpieces, the team leader or clerk shall inform the technician to collect the workpieces

(3) the copper male 2D shape light knife, the height below 50 mm, select the M12 tool; the height is 50-70 mm

M16 tool is selected for the height between 70-85mm, M20 tool is selected for the height between 85-120mm

M25 is used when the diameter is more than 120mm, and Φ 25r0.8 and Φ 32r0.8 flying tools are used when the diameter is more than 120mm;

(4) for flat surface or higher surface, try to choose Φ 20r4, Φ 25r5 and Φ 40r6

As a light knife tool;

(5) the specific processing parameters are shown in the table of rough and finish processing parameters.

Workpiece inspection regulations:

(1) the programmer is responsible for the test results;

(2) workpiece inspection shall be conducted according to the seven requirements of Article 14;

(3) in principle, the steel material will not be removed from the machine until it is tested on the machine tool, and the steel material processed in the night shift will be sent to the machine as far as possible

(4) in principle, tonggong should be tested in the “to be tested area”. After the test is OK, the programmer should place it in time

In the “qualified area”, the tooling technician is only allowed to take the workpiece in the “qualified area”;

(5) if the unqualified workpiece is detected, it shall be reported to the director of the Department, who shall decide whether to add it again

Work, refuel or check according to the qualified workpiece;

(6) if the head of the department checks the unqualified parts as qualified ones, which leads to mold quality problems

Therefore, the head of the Department is mainly responsible.

Relevant standards and regulations:

(1) the four sides of the mould material in the front and rear moulds are divided into the middle, and the bottom surface is zero;

(2) in the four sides of the original body mold, if the PL surface is a plane, the plane takes the number; if the PL surface is not a plane, the bottom takes the number. Get the datum angle of the non original mold embryo;

(3) the two sides of the row are divided into the middle, the bottom of the row touches one side, and the depth is zero on the top in principle. If the technician has done other water transportation and inclined holes before CNC machining, the bottom is zero;

(4) tonggong is represented by T, R and f respectively;

(5) the reference angle is the corner with the die number printed on the front and rear die material;

(6) the profile of the stop copper male of the R package should be reduced by 0.08mm to ensure that the product does not scratch hands;

(7) in principle, the X direction is the long dimension, and the Y direction is the short dimension;

(8) when “contour contour” and “optimum contour” are used for finish machining, the machining direction shall be “parallel milling” as far as possible; when flying knife is used for finish milling, the “parallel milling” must be adopted;

(9) in principle, there are four corners at the bottom of the copper palm, one corner corresponds to the mold datum angle, the chamfer angle C4, and the other three corners are rounded R2;

(10) when white steel cutter is used to process copper profile, the spark position parameter should be 0.015mm more than the required value;

(11) the copper male reference level shall be machined to the bottom, and 0.2mm shall be left at the bottom (to prevent the cutter from touching the code board);

(12) the tolerance of tool path compiling and calculating surface: 0.05mm, 0.025mm and 0.008mm respectively;

⒀ when alloy knife is used for finishing straight body surface of steel, Z cutting amount is 1.2mm, when handle is used, Z cutting amount is 0.50mm. The straight body surface must be milled in order;

(14) in principle, the length of the list should be controlled within 250mm and the height should be controlled within 100mm.

When cutting copper material, the length and width of one side should be 2.5mm, and the total height should be 2-3mm, that is, 105 × 65 × 45 should be cut for 100 × 60 × 42. If the length and width are multiples of 5, the height can be any integer, and the minimum copper size is 40 × 20 × 30 (after processing).

The unified regulations of numbering are as follows:

Tn23001 A1 (tn23001 front die copper male 1)

Tn23001 r-a1 (tn23001 right front die copper male 1)

Tn23001 l-a1 (tn23001 left front die copper male 1)

Tn23001 R1 (tn23001 rear die copper male 1)

Tn23001 r-r1 (tn23001 right rear die copper male 1)

Tn23001 l-r1 (tn23001 left rear die copper male 1)

Tn23001 sla1 (tn23001 row a copper male 1)

Tn23001 ina1 (tn23001 phase a copper male 1)

Tn23001 xda1 (tn23001 square a copper male 1)

Tn23001 tb1 (tn23001 push plate copper male 1)

Tn23001 MG1 (tn23001 modified copper male 1)

Unified regulations on storage of drawings:

D: 03 / tn23001d.mc8 (3D product drawing)

\ ASM.MC8 (internal model combination diagram)

\CAV\ CAV.MC8 (3D drawing of mould and Copper drawing of front mould)

\Cav-1.mc8 (front die copper male 1, including tool path)

\CAV- CNC.MC8 (front die tool path diagram)

\COR\ COR.MC8 (3D drawing of back die and Copper drawing of back die)

\Cor-1.mc8 (rear die copper male 1, including tool path)

\COR- CNC.MC8 (road map of rear die)

\IN\ IN.MC8 (phase part 3D drawing and phase part Copper drawing)

\SL\ SLA.MC8 (row position a3d diagram and its copper map)

\Sla-1.mc8 (row position a copper male 1, including tool path)

\XD\ XDA.MC8 (oblique a3d diagram and its coppergraph)

\Xda-1.mc8 (bevel a copper male 1, including knife path)

\EDM \ *. MC8 (all spark count charts)

\EDW \ *. MC8 (all WEDM drawings)

\Modify / modify 1

\Modify2 the second modification

CNC Internal shared file*
The paper should be concise, clear and easy to understand. Copper map lines should be thick, try to use integer dimensions. The standard angle of copper should be marked clearly, with die number, copper number, copper 3D drawing, spark position size, precautions (connection sequence, shift machining, rotary machining, machining after removing insert, copper wire cutting, etc.), programmer’s signature for confirmation, and department director’s review (specific according to the sample).
Copper wire cutting drawings shall be concise, clear and easy to understand. The parts to be cut should be indicated by section line, including die number, copper number, spark position, datum position of computer drawing, cutting slope, precautions, website of computer drawing, signature and confirmation of programmer, and approval of department head (according to the sample).

Technology and maintenance of CNC machining center

Machining center (MC) is a kind of automatic tool changing NC machine tool which is developed rapidly to meet the requirements of labor-saving, time-saving and energy-saving era. It is a combination of mechanical technology, electronic technology, computer software technology, pneumatic technology Drag technology, modern control theory, measurement and sensing technology, communication diagnosis, cutting tool and programming technology are high-tech products. It integrates the functions of milling machine, drilling machine and boring machine. Automatic tool changing device is added. It is a highly efficient and automatic machine controlled by computer. Because the machining center has a variety of tool change or tool selection functions and automatic workbench exchange device (APC), it can automatically drill, ream, ream, bore, tap thread, mill and other multi process processing on the workpiece after one clamping, and automatically complete or nearly complete the multi process processing of multiple planes or angles of the workpiece, so as to greatly improve the production efficiency and the degree of automation.

Because the machining center can greatly reduce the workpiece clamping, measuring and machine adjustment time, reduce the turnover, handling and storage time of the workpiece, so that the cutting time utilization rate of the machine tool is 3-4 times higher than that of the ordinary machine tool; and the machining center has a good consistency, compared with the single machine and man-made operation mode, it can eliminate the human interference in the process flow, and has a higher productivity Production and stable quality, especially when processing 1000 pieces with complex shape, high precision and frequent variety change, it has good economy.

With the rapid development of electronic technology and the appearance and application of various sensors with good performance, the functions of machining center are becoming more and more perfect. These functions include: tool life monitoring function, tool wear and damage monitoring function, cutting state monitoring function, abnormal cutting monitoring, alarm and automatic shutdown function, automatic detection and self diagnosis function and adaptive control function And so on. The machining center is also organically connected with the automatic supporting plate with accompanying fixture, and can cut eyebrows automatically, which makes the machining center become the key equipment and basic unit of flexible manufacturing system, computer integrated remanufacturing system and automatic chemical plant

Fault diagnosis method of CNC lathe

In case of failure of precision CNC lathe, it should be stopped immediately, diagnosed and eliminated in time, otherwise it will lead to greater damage or even danger. The principle of fault diagnosis of precision CNC lathe should be mastered.

Outside before inside

The reliability of modern precision CNC lathe system is higher and higher, the failure rate of CNC system itself is lower and lower, and most of the failures are caused by non system reasons. Because the precise numerical control lathe is a machine tool with mechanical, hydraulic and electrical integration, the occurrence of its fault will also be reflected by the three. Maintenance personnel should check from outside to inside one by one. Try to avoid unsealing and disassembling at will, otherwise it will enlarge the fault and make the machine lose precision and performance. The external faults of the system are mainly caused by the problems of detection switch, hydraulic components, pneumatic components, electrical actuators and mechanical devices.

First static then dynamic

First, in the static state of power failure of the precision CNC lathe, through understanding, observation, testing and analysis, it is confirmed that the failure will not expand after power on, and after the accident occurs, the machine tool can be powered on. In the running state, dynamic observation, inspection and testing are carried out to find the fault. However, if there is a destructive failure after power on, the danger must be eliminated before power on.

Mechanical before electrical

Generally speaking, mechanical fault is easy to find, but the diagnosis of numerical control system and electrical fault is more difficult. Before the troubleshooting of precision CNC lathe, we should first pay attention to the elimination of mechanical faults.

Simple before complex

When there are many kinds of faults intertwined, we should solve the easy problems first, and then solve the more difficult problems. After solving simple problems, difficult problems may become easier.

CNC computer gong processing circuit

CNC Lathe Feed processing path refers to the path that the turning tool starts to move from the tool setting point (or the fixed origin of the machine tool) until it returns to the point and ends the processing program, including the path of cutting and the path of non cutting empty stroke such as cutting in and cutting out.

The feed route of finishing machining is basically carried out along the contour of the parts. Therefore, the key point of determining the feed route is to determine the feed route of rough machining and empty stroke.

In the CNC lathe processing, the determination of the processing route should generally follow the following principles.

① It should be able to ensure the accuracy and surface roughness of the workpiece to be processed.

② The processing route is shortest, the idle travel time is reduced, and the processing efficiency is improved.

③ The workload of numerical calculation should be simplified as much as possible.

④ For some repeated programs, subroutines should be used.

Advantages and disadvantages of CNC CNC CNC machining has the following advantages:

① The number of tooling is greatly reduced, and complex tooling is not needed to process complex parts. If we want to change the shape and size of the parts, we only need to modify the processing program of the parts, which is suitable for the development and modification of new products.

② The machining quality is stable, the machining accuracy is high, and the repetition accuracy is high, which can meet the machining requirements of aircraft.

③ In the case of multi variety and small batch production, the production efficiency is high, which can reduce the time of production preparation, machine adjustment and process inspection, and reduce the cutting time due to the use of the best cutting quantity.

④ It can process complex surface which is difficult to be processed by conventional methods, and even process some parts which cannot be observed.

Surface treatment of aluminum alloy processed by computer gong

The processing quality of machine parts, in addition to the processing accuracy, also has the processing surface quality, which is the representation of the integrity of the surface layer after processing.

With the rapid development of modern machine manufacturing industry, the requirements for machine parts are increasing day by day. Some important parts must work under the conditions of high speed, high temperature, high pressure and heavy load. Any defect in the surface layer not only directly affects the working performance of parts, but also causes accelerated wear, corrosion and failure of parts. Therefore, we must pay attention to the surface quality.

① Surface roughness surface roughness refers to the micro geometric error of machined surface. In Figure 5-8 (a), R. Represents the arithmetic mean deviation of the roughness profile. The surface roughness is usually formed by the movement path of cutting tool in machining, and the ratio of wavelength to wave height is generally less than 50.

② Surface waviness and surface transition are periodic geometric errors between macro geometric errors (△ *) and micro geometric errors (roughness). In Fig. 58 (b), a represents the height of waviness. The surface waviness is usually caused by the low frequency vibration of the process system in the process of machining, and the ratio of the surface waviness to the wave height is generally 50 ~ l ∞ 0

CNC precision mold processing technology and development

Research on key technology of design and manufacture of continuous fine blanking die for complex parts

The continuous fine blanking die for complex parts is the frontier basic technology of fine blanking technology, and it is expected to promote the whole fine blanking technology in China. Taking the synchronizer gear ring, clutch plate, longitudinal compound continuous fine blanking process and continuous fine blanking die for complex parts as the breakthrough point, the key technology of fine blanking die design and manufacturing is studied, so as to realize the rapid improvement of fine blanking die technology in China and shorten the gap with advanced countries as soon as possible.

Study on the life promotion of fine blanking die and its related key technologies

Die life is a comprehensive reflection of die material, small process and supporting product level. Taking the life of fine blanking die as the leader to carry out technical research can not only solve the problem that the life of fine blanking die is too low, but also drive the technical development of die material, fine blanking process, supporting tooling and other auxiliary products.

Research and development of fine blanking precision forging composite technology

Precision blanking and precision forging are two advanced manufacturing technologies developed in parallel. If the precision blanking parts are too thick and need precision forging, the precision forging must be too thin. They are closely related. The basic idea of developing precision forging and fine blanking compound process is to find the combination point of the two processes (such as gear parts with wheel hub and cam parts with short shaft). The precision forging in China has a long history and has a high level, so it is a good way to improve the overall level of precision blanking technology in China.

CNC computer gong milling machine

Machining center is developed from CNC milling machine. The biggest difference between CNC milling machine and machining center is that the machining center has the ability to exchange machining tools automatically. By installing different tools on the tool magazine, the machining tools on the spindle can be changed through the automatic tool changing device in one clamping, and a variety of machining functions can be realized.

CNC machining center is composed of mechanical equipment and CNC system, which is suitable for processing complex parts. CNC machining center is one of the most widely used CNC machine tools with the highest output in the world. Its comprehensive processing ability is strong, the workpiece can complete more processing content after clamping at one time, and the processing accuracy is high. For the batch workpiece with medium processing difficulty, its efficiency is 5-10 times higher than that of ordinary equipment, especially it can complete the processing that many ordinary equipment can’t complete, and it is more suitable for single piece processing with complex shape and high precision requirements or small and medium batch multi variety production. It concentrates the functions of milling, boring, drilling, tapping and cutting threads on one equipment, so that it has a variety of technological means. According to the space position of spindle machining, there are horizontal and vertical machining centers. According to the classification of process uses: boring and milling machining center, composite machining center. According to the special functions, there are single table, double table and multi table machining centers. Machining center of single axle, double axle, three axle and changeable headstock

CNC computer gong processing tool

1、 Try to install the material first and then the cutter, so as to prevent the hand from touching the cutter when installing the material. If the cutter has been installed, when loading the material, the worktable should be moved to the outside to ensure that the material will not interfere with the cutter, so as to avoid injury or breaking the cutter.

2、 When removing the tool, first observe whether the spindle stops rotating.

4、 The wrench should be put in the tool storage area after use.

5、 In the process of machining, the operator is not allowed to observe the cutting position closely to prevent chips from crashing into the eyes.

6、 Before the start of processing, check the position of the oil nozzle before opening the oil pump switch to avoid spraying oil to other positions.

7、 When pausing to observe the machining gap, the worktable must be moved away from the cutting position.

8、 After processing and before disassembling the workpiece, we must first carry out the necessary preliminary inspection of size or appearance, and only after the inspection is qualified can we disassemble the workpiece, so as to avoid the positioning problem of secondary processing and the scrapping of the workpiece after disassembly.

Classification of CNC computer gong processing

The common ones are classified by the following four methods.

Classification by process use

(1) General CNC machine tools. This kind of machine tools is the same as the traditional general machine tools. There are CNC turning, milling, boring, drilling, grinding machines, etc., and there are many kinds of each kind. For example, CNC milling machines include vertical milling, horizontal milling, tool milling, gantry milling, etc. The technological possibility of this kind of machine tool is similar to that of general machine tool, but the difference is that it can process complex shape parts.

(2) CNC machine tool center machine tool. This kind of machine tool is developed on the basis of general CNC machine tool. It is a kind of NC machine tool with automatic tool changing device (also called multi process NC machine tool or boring milling machining center, conventionally referred to as machining center) which is composed of a tool magazine (which can hold more than 10-100 tools) and automatic tool changing device on the general NC machine tool, which makes the NC machine tool further develop towards automation and high efficiency.

The difference between NC machining center machine tool and general NC machine tool is: after the workpiece is clamped once, the NC device can control the machine tool to automatically change the cutting tool, and continuously complete the milling (turning), boring, drilling, reaming, tapping and other processes on each processing surface of the workpiece. This kind of machine tools are mostly boring and milling, mainly used to process box parts. Compared with general NC machine tools, it has the following advantages

① Reduce the number of machine tools, easy to manage, for multi process parts as long as a machine can complete all processing, and can reduce the inventory of semi-finished products;

② Since the workpiece is clamped only once, the positioning error caused by multiple installation is reduced, and the machining quality can be guaranteed by the accuracy of the machine tool;

③ Process concentration reduces the auxiliary time and improves the productivity;

④ As the parts can be processed in multiple processes in one clamping on one machine tool, the number of special fixtures is greatly reduced, and the production preparation time is further shortened.

Due to the advantages of CNC machine tools, it is very popular with users, so it plays an important role in the production of CNC machine tools.

In addition, there is a kind of machining center, which is developed on the basis of lathe, with shaft parts as the main processing object. In addition to turning and boring, it can also drill, mill and tap any part of the end face and peripheral surface. This kind of machining center also has a tool magazine, which can install 4-12 tools. It is used to call this kind of machine tool turning center (TC).

(3) Multi coordinate CNC machine tool. Some complex shape parts can’t be processed with three-dimensional CNC machine tools, such as propeller, aircraft surface parts, etc. it needs more than three coordinate synthetic motion to process the required shape. Therefore, the emergence of multi coordinate CNC machine tools, which is characterized by the number of axes controlled by the CNC device is more, the structure of the machine tool is more complex, the number of coordinate axes usually depends on the processing requirements of parts. Now commonly used is 4, 5, 6 coordinate CNC machine tools. Figure 1 is the schematic diagram of five axis NC machining. At this time, the X, y, Z coordinates can be linked with the turntable rotation and tool swing at the same time to process wing and other parts.

According to the movement track classification of CNC machine tools

According to the relative motion path between the tool and the workpiece, the CNC machine tools can be divided into point control CNC machine tools, point line control CNC machine tools, contour control CNC machine tools, etc. It is described as follows:

(1) Point position control CNC machine tool. The numerical control device of this kind of machine tool can only control the moving parts of the machine tool to move accurately from one position (point) to another position (point), that is, it only controls the coordinate value of the end of the stroke, and does not carry out any cutting during the moving process. As for the moving speed and route between the two related points, it depends on the productivity. In order to have as high productivity as possible on the basis of accurate positioning, the movement between the two related points first moves to the new position quickly, and then decelerates by 1-3 levels to make it approach the positioning point slowly, so as to ensure its positioning accuracy. This kind of machine tool mainly includes CNC coordinate boring machine, CNC drilling machine, CNC punch machine and CNC measuring machine, and its corresponding CNC device is called point position control device.

(2) CNC machine tool controlled by point and line. When this kind of machine tool works, it is necessary to control not only the position (i.e. distance) between two related points, but also the moving speed and route (i.e. trajectory) between two related points. Its route is generally composed of straight lines parallel to each axis. It is different from the point control CNC machine tool in that when the moving parts of the machine tool move, it can cut along the direction of a coordinate axis (generally, it can also cut along a 45 ° oblique line, but it can not cut along a straight line with any slope), and its auxiliary functions are more than those of the point control CNC machine tool, for example, to increase the spindle speed control, cycle feed processing, cutting tool Selection and other functions. This kind of machine tool mainly has the simple numerical control lathe, the numerical control boring milling machine and the numerical control processing center and so on. The corresponding numerical control device is called point position linear control device.

(3) Contour control CNC machine tool. The control device of this kind of machine tool can continuously control two or more coordinate axes at the same time. When machining, it is necessary to control not only the starting point and the end point, but also the speed and position of each point in the whole machining process, so that the machine tool can process complex shape parts that meet the requirements of the drawing. Its auxiliary functions are also quite complete.

This kind of machine tools mainly include CNC lathes, CNC milling machines, CNC grinding machines and electrical machining machines. The corresponding numerical control device is called contour control device (or continuous control device).

According to the control mode of servo system

CNC machine tools can be divided into open-loop and closed-loop according to whether there is a detection feedback device for the controlled quantity. In the closed-loop system, according to the position of the measuring device, it can be divided into full closed-loop and half closed-loop. Based on the open-loop system, an open-loop compensation CNC system is developed.

(1) Open loop control of CNC machine tools. In the open loop control, there is no feedback device

The signal process of numerical control device is unidirectional, so there is no system stability problem. Because of the unidirectional flow of the signal, it does not check the actual position of the moving parts of the machine tool, so the machining accuracy of the machine tool is not high, and its accuracy mainly depends on the performance of the servo system. The working process is: the input data is calculated by the numerical control device, the command pulse is distributed, and the controlled worktable is moved by the servo mechanism (the servo element is usually a stepping motor).

This kind of machine tool works stably, reacts quickly, debugs conveniently and maintains simply, but its control precision is limited. It is suitable for medium and small CNC machine tools with general requirements.

(2) Closed loop control of CNC machine tools. Because the accuracy of open-loop control can not meet the requirements of precision machine tools and large-scale machine tools, it is necessary to detect its actual working position. Therefore, the detection feedback device is added to the open-loop control CNC machine tools to detect the position of the moving parts of the machine tools at any time during processing, so as to make it consistent with the position required by the CNC equipment, so as to achieve high processing accuracy.

Classified by numerical control device

CNC machine tools can be divided into hard wire (part) CNC and soft wire (part) CNC according to the CNC devices that realize the control of CNC logic function.

(1) Hard wire numerical control (called ordinary numerical control, namely NC). The input, interpolation and control functions of this kind of CNC system are realized by integrated circuits or discrete components. Generally speaking, different CNC machine tools have different control circuits, so the universality of the system is poor. Because it is all composed of hardware, the function and flexibility are also poor. This kind of system was widely used before 1970s.

(2) Flexible wire numerical control (also known as computer numerical control or microcomputer numerical control, namely CNC or MNC). This kind of system uses medium, large scale and super large scale integrated circuits to form CNC device, or microcomputer and special integrated chip. Its main NC functions are almost completely realized by software. For different NC machine tools, only different software can be programmed, while hardware can be almost universal. Therefore, it has strong flexibility and adaptability, and is also convenient for mass production. Modular software and hardware improve the quality and reliability of the system. Therefore, modern CNC machine tools all use CNC device.