Category Archive Machinery industry

Although the gear industry is developing rapidly and there are more and more types, such as reducer spiral bevel gear, spiral bevel gear and so on, there are not many manufacturers specializing in gear mold, most of which are made by gear factory themselves, especially plastic gear in gear industry.

In terms of plastic gears, generally speaking, plastic gears and their molds are mainly distributed in two regions: Ningbo, Zhejiang Province, where there are more than 340 plastic gear factories, which is also the largest plastic gear mold production base in China; the other is Shenzhen Bao’an, which is dominated by Hong Kong funded enterprises with high product precision, which is mainly used for export. Among them, the demand for plastic gear mold is relatively large.

Throughout the current situation of gear mould in China, it can be said that there are mixed feelings. Computer gongs processing is pleased that gear mold production has a certain foundation, and the development trend of plastic gear will bring greater market space for gear mold; The worry is that there is still a gap between the level of domestic gear mould production and that of the world’s predecessors. Moreover, with the development trend of the gear industry, especially the plastic gear industry, the domestic response to market changes is not sharp enough, and the supporting research is difficult to keep up with the market demand. At present, medium and low-grade gear molds can be produced at home, and high-grade gear molds are mostly imported. The application scope of high-speed computer gongs for machining domestic gears can be roughly divided into three aspects: plastic gear mold, powder metallurgy gear mold and precision forging bevel gear mold.

It can be seen that there is still a large space for the development of China’s gear industry. Our company specializes in the production of spiral bevel gears and other products. The advanced equipment and technology ensure the quality of the products, which has been recognized by customers. Plastic gear has the advantages of low transmission noise, vibration absorption, self lubrication, high efficiency of mold processing. In recent years, the application of plastic gear in gear industry will be more and more, which will become a worldwide trend.

Domestic precision gear mould needs to keep pace with the development of world gear mould

However, at present, the middle and low-grade gear mould can be produced in China, and the high-grade gear mould mostly depends on import. There are not many factories specialized in gear mould in China, most of them are made by gear factories themselves. In the application range of gear mold, the demand of plastic gear mold is relatively large, and the market potential is huge.

Relevant experts in the industry put forward three strategies for future development

First, speed up the adjustment of industrial structure; in the future development, the gear mold industry should pay more attention to the strategic adjustment of its product structure, so as to make the high-end die with complex structure and high precision develop faster. At the same time, the mold industry should also closely follow the market demand to develop. Without product demand and product upgrading, there will be no technological progress in the mold industry, and there will be no scale and grade of mold products. The level of mold technology determines the quality, efficiency and development ability of new products to a great extent.

At present, there is neither national standard nor ready-made industrial standard for gear mold processing, especially in plastic gear mold. The technical standard is a kind of open standard, but it is very difficult to make the product standard. It is necessary to consider the test standard, precision standard and test device standard of gear mould.

Third, strengthen the density of cooperation between industries; the development of modern industry is a relationship of mutual cooperation, which is equally important for the gear mold industry. This cooperation is first of all direct cooperation in industry research. For example, several universities are engaged in the research of gear mold, concentrating the strength of gear industry and some university research institutions, and doing integrated research and cooperation in the aspects of process equipment and internal deformation law of plastics.

At the same time, from the whole industry, the voice of gear mold is very small, and it is in a spontaneous state, and the establishment of relevant professional associations is to change this situation. This is to focus on discussing and solving the problems existing in the production of small module gear, so as to promote the development of domestic precision gear mold industry.

In the trend of gear industry, especially plastic gear industry, the domestic response to market changes is not sharp enough, supporting research is difficult to keep up with the market demand, and the domestic precision gear mold still needs to keep up with the development level of the world gear mold.

Shaft gear is the most important part in the gearbox, and its machining accuracy directly affects the overall quality of the gearbox. At present, the gear tooth processing method we adopt is hobbing shaving method. In order to produce high-precision gears by hobbing and shaving, the hobbing and shaving process must be brought into full play. The shaving accuracy depends on the saddle hobbing accuracy to a large extent, so some error items in hobbing must be strictly controlled to produce high-quality gears. Gear hobbing is a common gear processing method. On the hobbing machine with high precision, gear teeth of grade 4-5 can be machined with precision hob. On the ordinary gear hobbing machine, only 8-grade precision gear teeth can be machined with ordinary precision hob. The accuracy of gear tooth of transmission shaft is required to be 8-7-7, and the positioning datum is mainly based on two center holes and end faces during gear hobbing. Therefore, it is very important to analyze the error sources of hobbing and master the methods to ensure and improve the machining accuracy.

Analysis of hobbing accuracy

The accuracy of shaft teeth is mainly related to motion accuracy, stability accuracy and contact accuracy. Common control method in Hobbing

CNC machining simulation system can reduce or even completely eliminate the process of trial cutting and manual verification. Before the new NC machining program is actually processed, the programmer can use the NC machining simulation system to carry out virtual machining environment and processing process on the computer, and detect the possible problems in the program design.

In the process of NC machining, it is easy to appear over cutting, undercutting and other phenomena. At the same time, the damage of cutting tools, or the processing of waste products, the interference and collision between parts and tools, tools and fixtures, tools and worktables, will cause a certain cost waste. Computer gong processing and numerical control machining simulation system can well simulate the relevant program, reduce the loss to the greatest extent.

Before the actual machining, the programmer can confirm whether the finished cutting product is consistent with the original design drawing through the simulation system, and can make better detailed analysis.

collision detection

In the actual processing, five axis CNC machining has more advantages than three axis CNC machining, can achieve a wider range, has faster material and efficiency, can reduce processing time and improve surface accuracy. However, due to the high degree of freedom of the two additional rotating axes, it is easy to cause collision and damage to the machine tool.

Therefore, before the actual processing, it is necessary to detect the collision with the help of NC machining simulation system. The main detection algorithms are as follows:

The machine tool includes many parts, but the collision detection algorithm between different parts is similar. The simulation system takes the tool, workpiece and fixture as the main research object to detect the possible global collision.

1. According to the tool location, the grid voxel model of the tool head scanning body and the grid voxel model of the tool holder scanning body are solved respectively. The tool holder scanning body is used to detect whether there is a global collision between the tool, workpiece and fixture, and the tool head scanning body is used to calculate the intersection between the tool and the workpiece.
2. A feature attribute of voxel model is cuboid envelope box. The envelope box is used for rough judgment. If the envelope box does not intersect, the objects enclosed in the envelope box must not intersect. At this time, the position data information of the object envelope box is updated, and other information remains unchanged. Computer processing is used to prepare for the generation and collision detection of the next tool location scanner It can speed up the detection.
3. Once a collision occurs, the system stops reading data and reports the error message and the precise location of the collision.

CNC machining of milling machine is carried out according to the instruction given by digital style. Under normal environment, the labor process does not need manual interference, and the computer gong processing eliminates the man-made deviation of the dominator. When planning to manufacture CNC machine tools, many methods are adopted to make the machine parts of CNC machine tools reach higher accuracy and stiffness. The movement equivalent of CNC machine tool worktable is widely up to 0.01 ~ 0.0001 mm, and the reverse clearance of feed drive chain and screw pitch deviation can be compensated by CNC device. The high-grade CNC machine tool adopts the closed-loop control of working table movement with grating ruler. The machining accuracy of the computer gong machine tool has improved from ± 0.01 mm to ± 0.005 mm or even higher. The positioning accuracy has reached ± 0.002mm to ± 0.005mm in the early 1990s. In addition, the transmission system and layout of CNC machine tools have high stiffness and thermal stability. Computer gongs processing decision compensation skills, CNC machine tools can get higher precision than its own. In particular, it improves the generality of the production of unified batch parts, with high qualified rate and stable processing quality. The selection of milling cutter diameter depends on different products and production batches. The selection of cutter diameter mainly depends on the specification of equipment and the processing size of workpiece.

Plane milling cutter

When selecting the diameter of the plane milling cutter, the power required by the cutter should be within the power range of the machine tool, and the diameter of the spindle of the machine tool can also be used as the basis for selection. The diameter of plane milling cutter for computer gong processing can be selected as d = 1.5D (D is the diameter of the spindle). In mass production, the tool diameter can also be selected according to 1.6 times of the cutting width of the workpiece.

end mill

The selection of end mill diameter should mainly consider the requirements of workpiece processing size, and ensure that the power required by the cutter is within the rated power range of the machine tool. If it is a small diameter end mill, whether the highest speed of the machine tool can reach the minimum cutting speed (60m / min) should be mainly considered.

Slot milling cutter

The diameter and width of the groove milling cutter should be selected according to the size of the workpiece to be processed, and the cutting power should be within the allowable power range of the machine tool. Before using the CNC machine tool, you should carefully read the machine tool manual and other relevant information, so as to correctly operate and use the machine tool, and pay attention to the following points:

(1) The PLC program of the machine tool is designed by the machine tool manufacturer according to the needs of the machine tool and does not need to be modified. Incorrect modification may cause damage to the machine tool and even damage the operator;

(2) It is suggested that the machine tool can be operated continuously for up to 24 hours. If the continuous operation time is too long, the service life of the electrical system and some mechanical components will be affected, thus affecting the accuracy of the machine tool

(3) The operators and maintenance personnel of machine tools must be professionals who have mastered the corresponding professional knowledge of machine tools or have received technical training, and must operate the machine tools according to the safety operation rules and regulations

When there is a large plane on the part that can be used as the positioning reference, the plane is always processed first, and then the hole is positioned by the plane to ensure the position accuracy between the hole and the plane. In this way, the positioning is relatively stable, the clamping is convenient, and the deflection caused by the drilling on the rough surface can be avoided.

c) The principle of “first primary and then secondary” is to process the main surface (datum plane and working surface with high position accuracy requirements) before processing the secondary surface (such as keyway, screw hole, fastening hole, etc.). The secondary surface is generally after the main surface reaches a certain precision and before the final finishing.

d) According to the principle of “first rough and then fine”, for parts with high precision requirements, it is carried out in order from coarse to fine, so as to gradually improve the machining accuracy. High speed computer gongs processing this point for poor rigidity parts, especially can not be ignored. In order to solve such problems, the characteristics of titanium alloy materials, machining characteristics, tool data selection, milling processing characteristics, coolant and other aspects are analyzed to improve the one-time acceptance rate of titanium alloy parts, so as to control the product quality of the parts. In order to better control the product quality, it is necessary to control the cutting parameters of non-standard equipment parts and understand and master the processing characteristics of materials.

Mechanical processing technology is to change the shape, size, relative position and nature of the production object on the basis of the process. CNC processing makes it a finished product or semi-finished product. It is a detailed description of each process. For example, as mentioned above, rough machining may include blank manufacturing, grinding, etc., and finishing may be divided into turning, fitter, milling machine, etc., and each step is just like this There must be detailed data, such as how much roughness and tolerance should be achieved.

The classification of machining is as follows:

Design datum: the datum used to determine the position of other points, lines and planes on the part drawing, which is called design datum.

Process datum: the datum used in the process of machining and assembling parts, which is called process datum. According to different uses, the process datum of die and mould can be divided into assembly datum, measuring datum and locating datum.

(1) Assembly datum: the datum used to determine the position of parts in parts or products during assembly, which is called assembly datum.

(2) Measurement datum: the datum used to check the size and position of machined surface, which is called measuring datum.

(3) Positioning datum: the datum used for workpiece positioning during machining, which is called positioning datum. For the surface (or line, point) as positioning reference, only the rough surface can be selected in the first working procedure. This positioning surface is called rough datum. The machined surface can be used as the positioning datum in the following processes, and the positioning surface is called the precise datum.

The correct use and maintenance of equipment parts processing mold is also a major factor to improve the quality of mold. Mechanical parts processing, such as: large CNC processing mold device debugging mode should be appropriate, in the case of hot runner, the power wiring should be correct, the cooling water circuit should meet the design requirements, and the parameters of injection molding machine, die-casting machine and press machine should be consistent with the design requirements. In order to improve the surface wear resistance of the die parts and improve the quality of the die, the surface strengthening of the main parts of the die is carried out in the precision parts processing. For the surface strengthening, different strengthening methods should be selected according to the mold for different purposes.

(1) The large-scale machining workshop shall be of grade I and II fire-resistant rating, and other simple buildings shall not be built in the workshop.

(2) For used oil rags, oil cotton yarn and oil sawdust. CNC processing should be concentrated in the metal cylinder (box) with cover and processed every day.

(3) It is forbidden to use gasoline, alcohol and other wiping machine tools in the workshop. The residual oil after washing parts shall not be poured into the sewer or trench at will, but shall be poured into the container at the designated place for unified treatment.

(4) Gasoline shall not be stored in the workshop. The storage capacity of machine oil and kerosene should not exceed one day’s consumption. CNC processing and storage in covered iron drums. If the storage capacity is large, a special oil storage room should be set up. No other combustible materials shall be stored in the oil storage room, and the indoor ventilation shall be maintained. The electrical switch shall be installed in the outdoor distribution box.

(5) In the workshop, due to careless use of the stove for heating, using waste oil cotton yarn to light a fire, throwing cigarette butts, match sticks and so on, fires are often caused. Therefore, strict management should be carried out on site smoking and stove heating.

(6) If it is necessary to carry out open flame welding and cutting in the workshop, the surrounding environment should be checked first, combustible materials should be removed, and the nearby machine tools should be covered with refractory materials. At the same time. Special person must be assigned to be responsible for monitoring, and residual fire should be checked and eliminated after operation.

(7) The electrical equipment of the machine tool must be checked frequently, and the hidden danger should be eliminated in time. It is not allowed to run with a fault. CNC processing, installation, removal, maintenance, debugging must be operated by professional electricians according to the regulations. The metal shell of all electrical equipment shall be reliably grounded, and its grounding resistance shall not be greater than 4 Ω.

Cutting tool is the most important for cutting stainless steel.

How to select tool geometry parameters when cutting stainless steel?

Front angle G0: the hardness and strength of stainless steel are not high, but its plasticity and toughness are good, and the thermal strength is high, and the chip is not easy to be cut off during cutting. In order to reduce the plastic deformation of the metal to be cut, cutting force and cutting temperature can be reduced, and the depth of hardened layer can be reduced. The front angle of turning various stainless steels is about 12 ° to 30 °. For martensitic stainless steel (such as 2Cr13), the front angle can be larger; for austenitic and austenitic + ferritic stainless steel, the front angle should be smaller; for the stainless steel without quenching and tempering treatment or with low hardness after quenching and tempering, the larger front angle can be adopted; for the small diameter or thin-walled workpiece, the larger front angle should be adopted. For high-speed steel milling cutter, GN = 10 ° – 20 °, for carbide milling cutter, GN = 5 ° – 10 °, for reamer, G0 = 8 ° – 12 ° and for tap, G0 = 15 ° – 20 ° for machine use or G0 = 20 ° for manual use.

Back angle A0: increasing the rake angle can reduce the friction between the flank and the machined surface, but reduce the strength and heat dissipation capacity of the cutting edge. The reasonable value of the back angle depends on the cutting thickness. When the cutting thickness is small, the larger back angle should be selected. Stainless steel turning tool or boring cutter is usually taken as A0 = 10 ° to 20 ° for finish machining or A0 = 6 ° to 10 ° for rough machining); A0 = 10 ° to 20 ° for high-speed steel end milling cutter and A0 = 15 ° to 20 ° for end milling cutter; A0 = 5 ° to 10 ° for hardness alloy end milling cutter and A0 = 12 ° to 16 ° for end milling cutter; A0 = 8 ° to 12 ° for reamer and tap.

Selection of cemented carbide: YG cemented carbide has better toughness, larger front angle can be used, and the blade can be grinded sharper, so that cutting is light and fast, and the chip and cutter are not easy to bond, so it is more suitable for stainless steel processing. Especially in rough turning and intermittent cutting, the advantage of YG alloy is more important. In addition, the thermal conductivity of YG alloy is better than that of high-speed steel by nearly two times and that of YT type alloy. Therefore, YG alloy is widely used in stainless steel cutting, especially in the manufacture of rough turning tool, cutting tool, reamer and reamer.

When I and K are zero, they can be omitted; regardless of G90 or G91 mode, I, J, K are programmed according to relative coordinates; when circular interpolation, tool compensation instruction G41 / G42 cannot be used.

1. Advantages and disadvantages between G92 and G54-G59

G54-G59 is the coordinate system set before machining, while G92 is the coordinate system set in the program. If G54-G59 is used, there is no need to use G92 again, otherwise G54-G59 will be replaced and should be avoided, as shown in Table 1.

Table 1 difference between G92 and working coordinate system`

Note: (1) once G92 is used to set the coordinate system, G54-G59 will not work unless the system is restarted after power failure or G92 is used to set the required new workpiece coordinate system. (2) After using G92 program, if the machine tool does not return to the original point set by G92, the program will be started again, and the current position of the machine tool will become the new workpiece coordinate origin, which is prone to accidents. Therefore, we hope that readers will use it carefully.

1. Compile tool changing program.

In the machining center, tool change is inevitable. However, there is a fixed tool change point when the machine tool leaves the factory. If it is not in the position of tool change, it is impossible to change the tool. Moreover, before changing the tool, the tool compensation and circulation must be cancelled, the spindle is stopped and the coolant is turned off. There are many conditions. It is not only easy to make mistakes but also inefficient to ensure these conditions before each manual tool change. Therefore, we can compile a tool change program to save the memory and MDI status

Under the call of M98, the tool change action can be completed at one time.

Taking pmc-10v20 machining center as an example, the program is as follows:

O2002; (program name)

G80g40g49; (cancel fixed cycle, cutter compensation)

M05; (spindle stop)

M09; (coolant off)

G91g30z0; (Z axis returns to the second origin, i.e. tool change point)

M06; (tool change)

M99; (end of subroutine)

When the tool needs to be changed, just type “t5m98p2002” in MDI state to replace the required tool T5, thus avoiding many unnecessary mistakes. According to the characteristics of their own machine tools, the majority of readers can work out the corresponding tool change program.

1. Others

The sequence number of the program segment is represented by address n. Generally, the memory space of NC device itself is limited (64K). In order to save storage space, the sequence number of program segment is omitted. N only means the segment label, which is convenient to find and edit the program, and has no effect on the processing process. The sequence number can be increased or decreased, and the continuity of the value is not required. However, some loop instructions, jump instructions, calling subroutines and mirror instructions can not be omitted.

1. In the same program segment, the later occurrence of the same instruction (the same address symbol) or the same set of instructions takes effect.

For example, tool change procedure, t2m06t3; instead of T2, T3 is replaced;

G01g00x50.0y30.0f200; G00 is executed (although there is f value, G01 is not executed).

If the instruction codes are not in the same group, the effect is the same if they are exchanged in the same program segment.

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

The feed path of finish machining is basically carried out along the contour sequence of the parts. Therefore, the key to determine the feed path is to determine the feed path of rough machining and idle stroke.

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

① The accuracy and surface roughness of the workpiece to be processed shall be guaranteed.

② It can shorten the processing route, reduce the idle travel time and improve the processing efficiency.

③ Simplify the workload of numerical calculation and simplify the processing program.

④ Some subroutines should be reused.

Advantages and disadvantages CNC machining has the following advantages:

① A large number of tooling is reduced, and complex tooling is not needed to process parts with complex shapes. In order to change the shape and size of parts in CNC machining, we only need to modify the part processing program, which is suitable for the development and modification of new products.

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

③ In the case of multi variety and small batch production, the production efficiency is higher, the time of production preparation, machine tool adjustment and process inspection can be reduced, and the cutting time is reduced due to the use of the best cutting amount.

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

The disadvantage of CNC machining is the high cost of machine tools.

Machining surface roughness is one of the important marks to measure the quality of machined surface. It has a great influence on the wear resistance, corrosion resistance, fatigue strength and matching properties of parts. However, there are many factors affecting the surface roughness in machining. In order to achieve good surface roughness, we will learn what these factors are.

1、 The reason of rough machining surface

1. Residual area: residual area refers to the area that remains on the machined surface after cutting by the main and auxiliary cutting edges of the tool.
2. In the process of high speed machining, it is often called as stainless steel with low speed. The appearance of scale will increase the surface roughness of the machined surface significantly.
3. Scab: in the process of cutting, when a chip is formed, the protruding part can replace the cutting edge to cut into the workpiece by computer gong machining | Dongguan computer gong machining | Shenzhen computer gong machining | mechanical parts processing | Guangzhou computer gong processing. The grooves of different depths are drawn on the machined surface; when the chip accretion falls off, part of the accumulated debris adheres to the machined surface and forms Small burr will increase the surface roughness.
4. Vibration: in cutting process, due to the periodic vibration of the process system, the machined surface appears streaks or ripple marks, and the surface roughness value increases significantly.

Machining: all factors that affect the residual area, scale, scale and vibration affect the surface roughness.

1. Cutting parameters: feed rate has the greatest influence on the residual area. When the feed rate decreases, the residual area decreases.

When cutting plastic metal, when cutting speed is very low or high, the surface roughness value is small. The reason is that it is not easy to produce chip lump at low speed, and the plastic deformation decreases when cutting speed is high, which can eliminate the formation of scale. When cutting brittle materials, the influence of cutting speed is small, because the deformation of material is small, the surface roughness value also decreases.

1. Geometric parameters of tool: the radius of tool tip arc, main deflection angle and secondary deflection angle have great influence on residual area and vibration. Generally, when the radius of the tool tip arc increases and the main and secondary deflection angles decrease, the surface roughness value is small. However, if the machine tool stiffness is low, the tool tip arc radius is too large or the main deflection angle is too small, the vibration will occur due to the increase of cutting force, which will increase the surface roughness value.
2. Tool material: the size of the edge arc radius and the time to keep sharp are different with different tool materials. High speed steel cutting tools can be grinded very sharp, but the holding time is short, so the surface roughness value is small when cutting at low speed. After grinding, the radius of the edge arc is larger, and the surface roughness is smaller at high speed.
3. Workpiece material: when processing plastic materials, the lower the plasticity and the higher the hardness of the workpiece material, there will be scaling, scaling and hardening, and the surface roughness will be smaller. Therefore, the surface roughness of high carbon steel, medium carbon steel and quenched and tempered steel is smaller than that of low carbon steel. When processing cast iron, the surface roughness value of cutting cast iron is larger than that of steel because the chip is of crumbling type.

In large-scale computer gong processing, the workpiece can enter the automatic processing stage after the alignment and program debugging are completed. In the process of automatic machining, the operator should monitor the process of cutting to prevent the quality problems and other accidents caused by abnormal cutting. Monitoring the quality of cutting tools largely determines the machining quality of the workpiece. In the process of automatic machining and cutting, the normal wear condition and abnormal damage condition of cutting tools should be judged by means of sound monitoring, cutting time control, pause inspection during cutting and workpiece surface analysis. According to the processing requirements, the cutting tools should be treated in time to prevent the processing quality problems caused by the cutting tools not handled in time. Monitoring the cutting process mainly considers the following aspects:

Monitoring of cutting sound in the process of automatic cutting, the sound of cutting tool cutting workpiece is stable, continuous and light, and the movement of the machine tool is stable. With the cutting process going on, when there are hard points on the workpiece, tool wear or tool clamping, the cutting process will become unstable. The instability performance is that the cutting sound changes, the tool and workpiece will collide with each other, and the machine tool will vibrate. At this time, the cutting parameters and cutting conditions should be adjusted in time. When the adjustment effect is not obvious, the machine tool should be suspended to check the condition of cutting tools and workpieces.

The main consideration of rough machining in process monitoring is the rapid removal of excess allowance on the workpiece surface. In the process of automatic machining, according to the set cutting parameters, the tool automatically cuts according to the predetermined cutting path. At this time, the operator should pay attention to observe the change of cutting load in the process of automatic machining through the cutting load table, and adjust the cutting parameters according to the bearing force of the cutter, so as to give full play to the maximum efficiency of the machine tool.

Finish machining process monitoring finishing, mainly to ensure the machining size and surface quality of the workpiece, high cutting speed and large feed rate. At this time, we should pay more attention to the effect of chip accretion on the machined surface. For cavity machining, we should also pay attention to the over cutting and tool passing at the corner. To solve the above problems, the first is to adjust the spray position of cutting fluid to keep the machined surface in the best cooling condition at all times; the second is to observe the quality of the machined surface of the workpiece, so as to avoid the quality change as much as possible by adjusting the cutting parameters. If the adjustment still has no obvious effect, we should stop to check whether the original procedure is reasonable. Special attention should be paid to the position of the tool when the inspection is suspended or stopped. If the tool stops in the cutting process and the spindle stops suddenly, tool marks will be generated on the surface of the workpiece. In general, when the tool leaves the cutting state, the shutdown should be considered.