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How to improve the speed of CNC engraving and milling machine

The most important point to improve the processing speed of CNC engraving and milling machine is to determine a reasonable engraving speed according to the hardness of engraving materials and the performance of CNC engraving and milling machine tools. Of course, the stability of CNC engraving and milling machine itself should also be considered, so that the machine can not be overloaded.

When using CNC engraving and milling machine for processing, try not to use the maximum tool feed to process, every kind of material tool will have a maximum tool feed. Because this value is only a reference value for users, it can not exceed this value, so in the actual operation, it should be less than this value as far as possible, and it is very ideal to control it at two-thirds of the value. In this way, the tool can be used for a long time, and the tool life will be longer.

In addition, CNC engraving and milling machine processing will be divided into rough machining and finishing two parts, the first part of the overall speed of rough machining and tool selection should be faster, better, as far as possible to cut all the margin, in order to save time and improve work efficiency, finishing is to adjust the speed of CNC engraving and milling machine properly, to ensure the precision of product processing.

1、 The mechanical performance is stable and reliable, and the structure is limited

The bed, column and other basic parts used are heavy and solid casting components, rather than those welded components. After the transformation, the machine tool has high performance and good quality, and can be used as new equipment for many years.

2、 The latest control technology can be adopted:

According to the development speed of technological innovation, the automation level and efficiency of production equipment can be improved in time, and the quality and grade of equipment can be improved.

3、 Familiar with the equipment, easy to operate and maintain

When purchasing new equipment, we don’t know whether the new equipment can meet the processing requirements. Otherwise, the machining capacity of the machine tool can be calculated accurately.

4、 We can make full use of the existing conditions

It can make full use of the existing foundation and does not need to rebuild the foundation as when purchasing new equipment.

5、 Reduce investment and short delivery time:

In some special cases, the manufacturing and installation of CNC machine tools, such as high-speed spindle and tray automatic exchange device, are too labor-consuming and expensive, and the transformation cost is often increased by about three times. Compared with the purchase of new machine tools, it can only save about 50% of the investment.

CNC milling machine, as the name suggests, is an upgraded version of milling machine, which is developed on the basis of conventional milling machine. The processing skills of the two are basically the same, and the structure is also somewhat similar. The difference is that the CNC milling machine is an automatic machine tool which uses the computer program as the guide, so its structure is also very different from the usual milling machine.

Starting NC milling machine is usually composed of NC system, main drive system, feed servo system, cooling smooth system, etc

The spindle box includes the spindle box and the spindle drive system, which is used for clamping the tool and driving the tool to rotate. The spindle speed scale and output torque have a direct impact on the processing.
The feed servo system is composed of feed motor and feed performing mechanism. According to the feed speed set by the program, the relative motion between the tool and the workpiece is completed, including linear feed motion and rotary motion.
The control system is the middle of the motion control of CNC milling machine, which performs the CNC processing program to control the machine tool for processing.
Auxiliary equipment such as hydraulic, pneumatic, smooth, cooling system and chip removal, protection equipment.
The basic parts of machine tool usually refer to the base, column, beam, etc., which are the foundation and structure of the whole machine tool.

According to the part shape, scale, accuracy and surface roughness and other skills requirements, the processing skills are determined, and the processing parameters are selected. After technical programming or active programming with CAM software, the programmed processing program is input to the controller. After processing the program, the controller sends the command to the servo equipment. The servo equipment announces the control signal to the servo motor. The spindle motor makes the tool rotate, and the servo motors in X, y and Z directions control the tool and the workpiece to move relative to each other according to a certain track, and then complete the cutting of the workpiece.

CNC computer gong processing surface quality

Some important parts must work under the conditions of high speed, high temperature, high pressure and heavy load. Any defects in the surface layer not only directly affect the working performance of the parts, but also accelerate the wear, corrosion and failure of the parts. Therefore, we must pay attention to the surface quality.

What is the surface treatment of aluminum alloy processed by computer gong

(1) Geometric properties of surfaces

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.

The deviation degree of actual geometric parameters from ideal geometric parameters is called machining error. The level of machining accuracy is measured by the size of machining error. If the error is large, the accuracy will be low, otherwise it will be high.

Machining accuracy includes dimension accuracy, shape accuracy and position accuracy.

① The degree of correspondence between the actual size of the machined part surface itself or between the surfaces and the ideal part size. The ideal part size refers to the median value of the dimension marked on the part.

② The degree to which the actual shape of the machined part surface is consistent with the ideal part surface shape. The ideal part surface shape is the absolutely accurate surface geometry.

④ The position accuracy is the degree to which the actual position of each surface of the machined part is consistent with the position of each surface of the ideal part. The position between the surfaces of an ideal part refers to the absolutely accurate position between the surfaces.

The common milling machine completes the pin milling operation by calculating the feed and controlling each feeding process by parts

CNC milling machine has five elements: CNC system, detection device, driving device, transmission chain of machine tool and servo motor. It is an automatic and high-precision milling pin operation controlled by computer through human programming in advance

Numerical control milling machine batch production efficiency is high, processing consistency is good, quality is stable. But when the price is high and the number of processing is small, the programming time is more, which is not cost-effective. The advantage of CNC milling machine is to produce products in large quantities. CNC milling machine processing is relatively fast and labor-saving. What are the advantages and disadvantages of CNC machine tools compared with ordinary milling machines? The processing principles are almost the same, but the milling machines are semi-automatic, while the CNC milling machines are digital controlled, and the automatic processing is controlled by program or NC.

Machining allowance of CNC lathe

The main goal of semi finish machining is to make the workpiece contour flat and the surface finish machining allowance uniform, which is particularly important for tool steel mold, because it will affect the change of tool cutting layer area and tool load during finish machining, thus affecting the stability of the cutting process and the surface quality of finish machining. Rough machining is based on volume model, and finish machining is based on surface model.

However, the geometric description of the parts in the previous CAD / CAM system is discontinuous. Because there is no intermediate information of the machining model after rough machining and before finishing machining, the distribution of the residual machining allowance and the maximum residual machining allowance of the rough machined surface are unknown. Therefore, the semi finish machining strategy should be optimized to ensure that the workpiece surface has uniform residual machining allowance after semi finish machining.

The optimization process includes: the calculation of the contour after rough machining, the calculation of the maximum residual machining allowance, the determination of the maximum allowable machining allowance, the partition of the surface with the residual machining allowance greater than the maximum allowable machining allowance (such as the areas where the transition radius is less than the rough machining tool radius such as grooves and corners), and the calculation of the tool center path during semi finish machining. Most of the existing CAD / CAM software for high-speed die machining have the function of residual machining allowance analysis, and can adopt reasonable semi finishing strategy according to the size and distribution of residual machining allowance. For example, hyper mill and hyper form software of open mind company provide pencil milling and rest milling methods to remove corners with large residual machining allowance after rough machining, so as to ensure uniform machining allowance in subsequent processes. Local milling of Pro / Engineer Software Milling) has similar functions. For example, the value of residual machining allowance in local milling process is equal to that in rough machining. In this process, only a small diameter milling cutter is used to remove the corners not cut in rough machining, and then semi finish machining is carried out. If the residual machining allowance in local milling process is taken as the residual machining allowance in semi finish machining, the process can not only remove the corners not cut in rough machining Corner, also can complete semi finishing.

The high-speed finishing strategy of finishing die depends on the contact point between the tool and the workpiece, and the contact point between the tool and the workpiece changes with the change of the surface slope and the effective radius of the tool. For the machining of complex curved surface composed of multiple curved surfaces, continuous machining should be carried out in one process as far as possible, instead of machining each curved surface separately, so as to reduce the times of tool lifting and cutting. However, due to the change of surface slope in machining, if only the step over is defined, the actual step distance on the surface with different slope may be uneven, thus affecting the machining quality.

Pro / engineer can solve the above problems by defining the scallop machine at the same time of defining the side feed; hyper mill provides equidistance machining Machine) mode, which can ensure the uniform side feed between the tool paths, and is not limited by the surface slope and curvature, to ensure that the tool always bears uniform load in the cutting process. In general, the curvature radius of finishing surface should be greater than 1.5 times of the tool radius to avoid the sudden change of feed direction. In the high-speed finish machining of the die, when cutting in and out the workpiece each time, the change of the feed direction should adopt the arc or curve transfer as far as possible, and avoid using the straight line transfer, so as to maintain the stability of the cutting process.

Feed speed optimization at present, many CAM software have the function of feed speed optimization adjustment: in the semi finishing process, when the cutting layer area is large, the feed speed is reduced, while when the cutting layer area is small, the feed speed is increased. The application of feed rate optimization can make the cutting process stable and improve the surface quality. The area of cutting layer is automatically calculated by CAM software, and the feed rate can be adjusted by the user according to the processing requirements.

The use of CNC computer gong CMM

The CMM can measure the dimensional accuracy, geometric accuracy, positioning accuracy and contour accuracy. At present, computer gong processing has been widely used in automobile, hardware, plastic, electronics, mold and other industries.

In the manufacturing of high-precision parts, the size, shape and geometric tolerance of the workpiece can be precisely detected to complete the shape measurement, part detection, process control and other tasks. CMM plays an increasingly important role in precision parts manufacturing.

The development potential of China’s precision parts processing industry is huge, and the production and sales of precision parts processing are also increasing year by year. Precision parts processing is a process of using processing machinery to change the size of the workpiece. Therefore, there are some important accuracy requirements for these deformations. These need three coordinate measuring instrument to detect whether the size of the processed parts meet the processing requirements. Only the parts that meet the requirements can promote the mold or other industries. However, many enterprises fail to meet the requirements of the parts and can not adapt to the market competition, resulting in bankruptcy. Therefore, a good parts processing manufacturer must have high-precision coordinate measuring instrument as a guarantee.

With the development of society, the precision requirements of mechanical parts processing precision parts processing mold will be higher and higher. The precision of precision die has been increased from 5 μ m to 2 ~ 3 μ m, even to 1 μ M.

CMM is a kind of high-precision measuring instrument. The operator of CMM must undergo professional training and operation. CNC machine tool processing. The following is the operation steps of starting and shutting down CMM organized by Surrey measurement for you

Startup steps

Wipe the machine, keep the appearance of the machine clean, and ensure that the three-axis guide rail of the machine is clean;

Turn on the main gas source;

Turn on the computer;

Open the air valve of CMM triplet to supply air and ensure that the air pressure reaches the required air pressure of the machine;

Shutdown steps

After using three coordinates, Dongguan high-speed computer gong will raise the Z-axis and rotate the probe angle a to 90 degrees, move to a safe position, and then close the PC-DMIS measurement software;

Turn off the computer;

Turn off the power supply of the control cabinet;

Close the pneumatic valve of the triplet;

Clean the worktable and keep it clean;

Automatic lathe machining center tool change

CNC machining mainly refers to the use of digital information recorded on the media to control the machine tool, so that it can automatically perform the specified processing tasks. Numerical control machining can ensure the products to achieve high machining accuracy and stable machining quality; the operation process is easy to achieve automation; high productivity, short production cycle; can reduce a large number of process equipment to meet the needs of rapid product upgrading; it is usually closely linked with CAD to achieve the transformation of design ideas to the final product.

In the whole CNC process, we should focus on the relationship between the processes and the significance of each step. Broadly speaking, the whole process consists of product analysis graphic design process planning path generation path simulation path output processing inspection.

Product analysis through product analysis should obtain certain composition information and some specific processing requirements.
Graphic design graphic design should be based on the detailed analysis of the product, determine the type of graphics by analyzing the processing requirements, and draw through the graphics software.
Path generation the process of path generation is that we realize the process planning by software, and optimize the tool path by setting parameters.
Through the analysis of the appearance and processing requirements of the workpiece product in the early stage of process planning, each processing step is reasonably established from the overall situation of processing.
After the path simulation path is generated, we generally have no intuitive sense of its final performance on the machine tool. Here we can check the possible problems through path simulation, so as to reduce the scrap rate of actual processing. The general inspection focuses on the effect of the workpiece appearance, whether it is overcut or undercut, and whether the process planning of the path is reasonable.
Path output path output is a necessary step for software design and programming to realize on the machine tool. Through path output, the intermediate reference can establish a connection between the two. If you have NC professional background, it can also be understood as the post-processing of tool path. Analysis of tool change action in machining center of automatic lathe

The tool changing procedure of this machine tool is more than 900 steps, so it is difficult to understand its working principle. Computer gong processing | mechanical parts processing | CNC machine tool processing | Dongguan high-speed computer gong processing here, the ATC data exchange, transmission, storage and tool number storage and other contents are briefly transported, and the tool change action is described as follows: CNC machining manufacturer’s CNC tool change instruction (M06) → tool sleeve down → drop to position → manipulator rotation → rotation deceleration → rotation to position (x4.7) → spindle tool release → release to position Position → manipulator rotation → rotation deceleration → rotation in place → spindle tool clamping → clamping in place (x2.5) → manipulator reversal → machinery in place, tool change is completed. Among them, the fast and slow speed of the manipulator is realized by the frequency converter, and the motor drives the mechanical cam to drive the manipulator up and down.

Tool drop fault

The phenomenon of tool drop has occurred for a long time. At the beginning, it happened once in a while, once a month, or even once in two or three months. Thinking that it was caused by accidental factors, it did not attract enough attention. Slowly, it happened once a week, or even twice. At the same time, it was accompanied by the situation that the tool on the spindle was not in place. Later, it gradually evolved into a shift with multiple failures, which seriously affected the production progress and caused waste products. After careful observation, there are two cases of tool drop fault, one is tool drop after the processing of this step, the other is tool drop on the worktable when this step is not processed at all. In the process of machining, the tool change action is carried out and the action sequence is normal, so there is no alarm phenomenon when the tool drop and loading (installed on the spindle) are not in place. Only when the operator checks the workpiece or hears the abnormal sound of tool drop, the fault will occur. Therefore, in the automatic lathe production line, sometimes there will be batch waste products due to tool drop.

Fault analysis and treatment

(1) Check the manipulator to carry out the troubleshooting steps of ATC tool change, and stop the manipulator at the vertical limit position. Check the two claws on the manipulator arm and the spring supporting the claw and other accessories. No problem was found, indicating that the manipulator clamping tool is tight, and the tool will not drop when the manipulator is rotating.

(2) Check the clamping condition of the tool. According to the analysis of the phenomenon that the tool can not be installed on the spindle, it may be that the disc spring in the inner hole of the spindle can not clamp the tool tightly, resulting in the phenomenon that the tool is not installed in place, or even can not be installed and the tool falls off. When the spindle was disassembled, several pairs of disc springs were found broken. So all disc springs were replaced. There was no problem during the test run. After running for one shift, the tool fell off again

CNC machine tool enterprises transform into service oriented enterprises

From the actual situation of our country, in the traditional low-end metal forming machine tool products, the industry concentration is low, the market is scattered, and the entry barriers are low. In the research and development, production and manufacturing of high-end machine tools, China has been in a missing stage. Due to the limitations of technology, capital and brand recognition, it is difficult to occupy a place in the market in a short time. Technical barriers and the difficult road of R & D as well as accepting the market test are the “challenges” for the development of high-end machine tools in China

Technology

Metal forming machine tool industry is a technology intensive industry, the development of the industry needs a lot of technology investment. From the perspective of enterprises with good performance at present, most of them are large-scale enterprises that have accumulated technology for many years, or state-owned or private enterprises that have entered the industry earlier and have strong technology R & D capability. Due to the advanced technology and equipment of these enterprises, it is difficult for new entrants to compete with them in the field of high-end products.

From the product point of view, mechanical presses, especially high-speed precision mechanical presses, present the development trend of specialization, high-speed, precision and automation, which not only requires enterprises to use computer optimization design to carry out strength design to prevent technical problems, but also puts forward high requirements for the manufacturing technology and process level of enterprises. In view of the current situation of this industry, the company increases investment in R & D, introduces senior technical talents, and pays attention to the cultivation of internal staff, so as to stimulate the enthusiasm of staff through incentive mechanism and improve the enterprise’s technological innovation ability.

Funds

Metal forming machine tool industry is a capital intensive industry, in order to ensure high-precision products, it needs a lot of capital investment. Only from the perspective of fixed assets investment of production machine tools, the production of a machine tool requires a complete set of parent machine tools such as turning, milling, planing and grinding. In addition, a large amount of money should be invested in the production of machine tools to purchase land, build factories and purchase raw materials. On the whole, the industry has high capital barriers for new entrants.

Brand and reputation

Metal forming machine tool products belong to large fixed asset investment and have a long service life. Their quality and performance are directly related to the quality and cost of terminal products. Therefore, customers often have great trust and dependence on their original high-quality suppliers or well-known manufacturers. Early entrants gradually establish their own brand awareness and reputation in the industry. Therefore, for the new entrants who want to enter the industry, it needs a long-term process to obtain the recognition of customers, which constitutes a certain brand and reputation barrier.

Service network

Metal forming machine tool manufacturers should have perfect after-sales service system, which can provide fast maintenance service. Especially in the peak production season of customers, it is easy to cause loss to the production equipment. If it can not be repaired in time, it will cause huge loss to customers. Therefore, only suppliers with extensive service network can timely and effectively help customers deal with various emergencies, which forms a barrier to new enterprises entering the industry. In order to remain invincible in the fierce world market competition and truly become a “manufacturing power”, China’s machine tool manufacturing enterprises must establish a “user-centered” business philosophy, meet the needs of users, help users solve problems, and transform to service-oriented manufacturing.

Independent innovation to achieve independent R & D and production of key technologies and parts

At present, there is a considerable problem in the development of China’s machine tool industry, that is, the medium and high-end equipment and key parts are heavily dependent on imports, and the domestic production is mainly made of medium and low-end equipment, which is not conducive to the healthy development of China’s machine tool industry in the long run. Therefore, China’s machine tool manufacturing enterprises should continue to innovate, independent research and development, and strive for the localization of key parts and key technologies.

Take the customer as the center, tailor to provide personalized service for customers

One of the core of machine tool industry manufacturing service is to take the customer as the center, customize according to the customer’s needs, and actively provide personalized services for customers.

Implement the strategy of integration of industrialization and industrialization, speed up the Informatization Transformation of machine tool enterprises

We should adhere to the new road of industrialization and vigorously promote the integration of informatization and industrialization. In order to develop equipment manufacturing industry, it is necessary to make full use of information technology and high and new technology to advance to all-round informatization. Machine tool enterprises should actively carry out information transformation to realize automation, flexibility, ecology, personalization and diversification of manufacturing process.

Improve the industrial chain, improve the allocation and use efficiency of resources, machine tool enterprises should adapt to changes in market demand,

Improve the supporting development of heavy and large machine tools and other products, form a complete industrial chain, and provide strong support for national energy, shipbuilding, metallurgy, aerospace, military industry, transportation and other pillar industries.

Large scale development to improve the reliability, stability and precision of products

To be truly competitive in the world, enterprises must have a certain scale. At present, there are a large number of machine tool enterprises in China. Except for a few enterprises such as Shenyang machine tool and Dalian machine tool, the vast majority of machine tool enterprises are generally small in scale, resulting in scattered resources, poor industry concentration and weak overall competitiveness, which makes it difficult to compete with large foreign enterprises. Therefore, it is necessary to speed up the resource integration and enterprise restructuring of the machine tool industry, and establish a machine tool enterprise with a certain scale.

With the rapid development of aerospace, electronics, military and other industries, the requirements for the reliability, precision and stability of machine tools are higher and higher. To enhance the share of domestic machine tools in these industries, we must improve their reliability, stability and precision.

Abnormal rotation of computer gong spindle

During the work, it was found that there was abnormal sound in the spindle and gearbox when the spindle speed was below 500r / min. by observing the power meter of the motor, it was found that the output power of the motor was unstable, and the pointer swayed greatly. However, the abnormal sound disappeared again when it was used for more than 1201r / min. After startup, the power meter of the motor will swing automatically without rotation command, and the motor will drift and rotate automatically. After normal operation, the braking time is too long, and there is no alarm for the machine.

According to the phenomenon, the cause of the fault may be that the spindle controller is out of control, and the mechanical transmission or motor can not be eliminated. Due to the heavy workload of disassembling the mechanical part for inspection, the spindle controller of the electrical part is inspected first, and the controller is Siemens 6sc-6502. Firstly, check the preset parameters in the controller, and then check the control board, and there is no abnormality. After checking that the circuit board is dirty, clean the circuit board as required, but the power failure is still the same after it is installed. Therefore, the fault causes in the controller can be eliminated temporarily. In order to determine whether the fault is in the motor or the mechanical transmission part, the motor and the machinery must be separated. After the separation, it is found that when the motor speed command is close to 450R / min, the continuous abnormal sound begins to appear, but when the motor speed command is given to 1201r / min, the abnormal sound disappears again. For this reason, we analyzed the spindle part. The original 450R / min command at low speed and 4500r / min command at high speed are the same for the motor. At the highest speed, the motor is decelerated through the gear at low speed, so the fault can be basically determined in the motor part. After analysis, the abnormal sound may be caused by poor bearing.

When the motor was disassembled for inspection, it was found that the bearing was damaged. At high speed, the bearing was stuck, causing the load to increase, causing the power meter to swing and deflect. After stopping, the motor drifted and brake too slowly. After inspection, the encoder disc was scratched. After replacing the bearing and encoder, all the faults were eliminated. The main reason for the fault is that there is abnormal sound when the spindle rotates. Therefore, the sound source should be found out before checking. There is abnormal sound, common for mechanical friction, jam and bearing damage.

CNC machining center spindle orientation is usually used in three ways, magnetic sensor, encoder and mechanical orientation. When using the magnetic sensor and encoder, in addition to adjusting the position of the components, the machine parameters can also be adjusted. There is no alarm when orientation error occurs, and it can only be found when interruption occurs during tool change.

Once in a refitted CNC machining center, there was a fault of inaccurate orientation. At the beginning, the machine tool was often interrupted in the work, but the number of times was not very many. When the machine was restarted, it could work again, and the fault occurred repeatedly. After careful observation of the machine tool after the failure, it was found that the real cause of the failure was the position deviation of the spindle after orientation. It was strange that if the spindle was touched by hand after orientation (similar to the situation when the tool was inserted into the spindle during tool change), the spindle would drift in the opposite direction. There was no alarm in the electrical part, and the mechanical part was very simple.

The orientation of the machine tool uses encoder, so from the fault phenomenon and possible parts, the possibility of the electrical part is relatively small, the main mechanical part is the connection. So we decided to check the mechanical connection part. When we check the connection of the encoder, we found that the set screw of the coupling sleeve on the encoder is loose, which makes the coupling sleeve retreat, causing the gap between the coupling part and the spindle to be too large and the rotation is not synchronous. After the set screw is fixed as required, the fault is eliminated. If the spindle orientation fault occurs, it should be analyzed and handled according to the specific structure of the machine tool. Check the electrical part first, and consider the mechanical part after confirming that it is normal.

What is CNC three axis linkage

CNC machining center refers to the spindle axis and vertical machining center setting table, which is mainly suitable for processing plate, plate, shell and small complex parts. Vertical machining center can complete milling, boring, drilling, tapping and thread cutting process. Vertical machining center is at least 3-axis linkage device, generally can realize three-axis linkage. Some five axis and six axis controls can be implemented.

The height of the vertical machining center is limited, which reduces the processing range of the workpiece, which is the disadvantage of the vertical machining center. However, the workpiece clamping and positioning is convenient for vertical machining center; the cutting path is easy to observe and debug, the program inspection and measurement is convenient, the problems can be found in time, and the treatment or modification can be stopped; the cooling conditions are easy to establish, and the cutting fluid can directly reach the surface of the cutting tool and processing; the three-axis and Cartesian coordinate system, intuitive feeling, in line with the design point of view, the chip is easy to exclude and modify, Surface treatment to avoid scratches.

Vertical machining center

Mainly used for:

Using grease and oil circulation in machining center will produce abnormal heating.
Spindle, need high-definition washing, high-speed bearing sealing place

Working principle: using compressed air flow pipe, the continuous flow of transmission oil along the pipe, stirring and transportation of oil and gas processing center spindle and other parts of the screw need lubrication. The constant pressure dry compressed air (bar) 5 – 8 continuous supply, according to the spindle and lubricating oil lubrication, screw oil and other parts of the fuel consumption different quantitative supply. Therefore, each lubrication circuit must use a separate micro pump power supply of oil. After the oil pump, it must enter the oil and natural gas mixing valve. In the oil and natural gas mixing valve, the compressed air flow blows into small oil drops and adheres to the wall to form an oil film. The flow direction of the air flow between the oil film and the pipe wall, and the thickness of the medium oil film gradually becomes thinner, but not together.

Four processing stages of CNC model

When the requirements of surface precision and roughness of parts are relatively high, it is often impossible to complete the processing in one process, and it is divided into several stages for processing.

Four processing stages in the process of making CNC model

(1) Rough machining stage. Rough machining is mainly to cut off most of the machining allowance on each surface to make the shape and size of the blank close to the finished product. This stage is characterized by the use of high-power machine tools, the selection of larger cutting tools, as far as possible to improve productivity and reduce tool wear.

(2) Semi finishing stage. Semi finishing is to finish the machining of secondary surface and prepare for the finishing of primary surface.

(3) Finishing stage. Finish machining is to ensure that the main surface meet the requirements of the drawing.

(4) Finishing stage.

Finishing is a kind of surface with high requirements for surface roughness and machining accuracy, and it also needs finishing. This stage can not be used to improve the position accuracy of parts.

It should be pointed out that the division of processing stages is based on the whole process of parts processing, and cannot be judged by the processing of a certain surface or the nature of a certain process. At the same time, in the specific application, it can not be absolute. For some heavy parts or parts with small allowance and low precision, rough and finish machining can be completed after one clamping.

How to prevent the spindle from colliding with the workpiece

The feed speed of CNC machining center has increased from 16m / min in 1980s to 24-40m / min now. The spindle speed of CNC machining center has also increased from 2500r / min to 6000-40000 R / min now. The structure of CNC machining center has also changed from open type to closed type. Under the condition of such high speed and structure, once the operator has no time to press the emergency stop button due to programming and operation errors, the tool has collided with the workpiece.

In order to prevent machine tool and personal troubles, the following methods can be adopted in programming and operation (take FANUC system as an example).

Under normal conditions, the origin of workpiece coordinate system can be set anywhere, as long as the origin has a certain connection with the origin of machine coordinate system. But in practice, if the command value is zero or close to zero, the tool will point to zero or close to zero. In milling, the cutter will run to the table or fixture base surface; in turning, it will run to the chuck base surface. In this way, the tool will penetrate the workpiece and point directly at the reference plane. At this moment, if you want to move quickly, you will have trouble.

FANUC system generally set: when the decimal point is omitted, it is the minimum input unit, generally μ M. When the decimal point is omitted, the input value will be reduced to one thousandth. At this moment, the input value will be close to zero. Perhaps, due to other factors, the tool should be separated from the workpiece, but the practice is not separated from the workpiece and into the workpiece. In this case, the zero point of the workpiece coordinate system should be set outside the workpiece or on the base surface of the worktable (or fixture), and the result will be different.

Programmers and operators should be more careful about decimal points when writing programs.

FANUC system is the minimum setting unit when the decimal point is omitted, while most domestic systems and some European and American systems are mm when the decimal point is omitted, which is the input method of calculator. If you are used to calculator input method, there will be problems in FANUC system. Many programmers and operators may use both systems. In order to prevent the scale from getting smaller due to decimal point, decimal point should be added to the input program of calculator. To do so is surplus for a certain kind of system, but after the habit is formed, there will be no problems due to the decimal point.

In order to make the decimal point eye-catching, the isolated decimal point is usually written as “. 0” in programming. Of course, when the system is executed, the zero after the decimal point of the value is ignored.

When adjusting the workpiece coordinate system, the operator should set the reference point beyond the physical (geometric) length of all tools, at least on the tool position of the longest tool.

For the workpiece coordinate system on the workpiece installation drawing, the operator obtains it by setting the machine coordinate system offset on the CNC machining center. In other words, the operator sets a reference point on the CNC machining center, finds the scale between the reference point and the zero point of the workpiece coordinate system set by the programmer, and sets this scale as the workpiece coordinate system offset.

On the lathe, the datum point can be set on the base of turret rotation, the datum tool tip or other directions. If there is no additional movement, the zero of the programmer’s instruction is the zero position of the tool rest (CNC machining center) moving to the offset. At this moment, if the datum point is set at the base of turret rotation, the turret must collide with the workpiece. In order to avoid collision, the datum point of CNC machining center should not only be set outside the tool holder, but also outside all tools. In this way, even if the tool is installed on the tool holder, the datum point will not collide with the workpiece.

In CNC machining center, the datum points of X and Y axes are on the axis line of spindle. However, the reference point of the z-axis can be set at the spindle end or at a point other than the spindle end. If it is at the spindle end, when the command is zero, the spindle end will reach the zero position specified in the coordinate system. At this moment, the end key of the spindle end will collide with the workpiece: if the spindle is equipped with a tool again, it will collide with the workpiece. To ensure that there is no collision, the reference point on the z-axis should be set beyond all tool lengths. Even if no other motion is attached, the reference point will not hit the workpiece.