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Factors to be considered in the selection of surface machining methods for CNC workpieces

The machining method of CNC workpiece surface depends on the technical requirements of machining surface. However, it should be noted that these technical requirements are not necessarily the requirements of the regulations of the part drawing, and may occasionally be higher than the requirements of the part drawing in some aspects due to technological reasons. For example, the machining requirements for the surface of some CNC machining parts are raised due to the misalignment of datum. Or higher machining requirements may be put forward because it is used as a precision reference.

After understanding the technical requirements of each CNC workpiece surface, we can choose the final processing method that can guarantee the requirements, and we will definitely need several processing steps and processing methods of each step. The selected machining method of CNC machining parts should meet the requirements of parts quality, excellent machining economy and high manufacturing efficiency. For this reason, the following factors should be studied when choosing the processing method:

1. There is an equal boundary between the machining accuracy and the surface roughness of any CNC machining method, but only in a narrow boundary is economic. The machining accuracy of this boundary is economic machining accuracy. Therefore, when choosing the processing method, we should choose the corresponding processing method which can obtain the economic processing precision.

2. The nature of raw materials for CNC machining should be studied.

3. To study the structure and size of CNC parts.

4. To study the production rate and economic requirements. When making a large number of products, we should choose advanced technology with high efficiency. It is even better to fundamentally change the manufacturing mode of blank, which can reduce the workload of machining.

5. To study the existing equipment and technical conditions of the workshop or workshop, we should fully defraud the existing equipment, tap the potential of the enterprise, and develop the enthusiasm and creativity of the workers when choosing the processing mode. But it is also necessary to study and constantly improve the existing processing methods and equipment, select new technology and improve the level of technology.

Precautions in the processing of CNC lathe

Precautions in the processing of CNC lathe. The machining process of CNC lathe is the same as that of ordinary lathe. However, since CNC is a clamping process, all the turning processes are finished continuously and automatically, the following aspects should be paid attention to.

1. Correct selection of cutting parameters

In terms of high efficiency metal cutting, the raw materials to be processed, cutting equipment and cutting conditions are three major factors. These decisions determine machining time, tool life and machining quality. The economic and useful machining method must be the correct choice of cutting conditions.

Three factors of cutting conditions: cutting speed, feed rate and cutting depth directly lead to tool damage. With the increase of cutting speed, the temperature of tool tip will rise, and mechanical, chemical and thermal wear will occur. If the cutting speed increases, the tool life will be reduced by 1 / 2.

The relationship between the feed condition and the wear of the back edge of the tool occurs within a very small boundary. But the feed rate is large, the cutting temperature rises, and the rear edge wear is large. It has less influence on the cutting tool than the cutting speed. Although the influence of cutting depth on the tool is not as high as the cutting speed and feed rate, when the cutting depth is small, the hard layer of the material to be cut will also affect the tool life.

Users should choose the cutting speed according to the raw material, hardness, cutting shape, raw material variety, feed rate, cutting depth, etc. The following table:

The selection of suitable processing conditions is based on these factors. Regular and stable wear and tear is the condition of dream.

However, in the essential work, the choice of tool life is related to tool wear, dimension change, surface quality, cutting noise, machining heat, etc. When confirming the processing conditions, the requirements are discussed according to the nature. As for stainless steel and heat-resistant alloy and other hard to process raw materials, it is advisable to choose a coolant or a rigid blade.

2. Select tools correctly

1) During rough turning, the cutter with high strength and good durability shall be selected to meet the requirements of large back draft and large feed during rough turning.

2) When finishing, the cutting tools with high accuracy and good durability shall be selected to ensure the requirements of machining accuracy.

3) In order to reduce the time of tool change and make the tool setting easier, we should choose the clip knife and clip knife.

CNC lathe

3. Select fixture correctly

1) Although the general fixture is used to clamp the workpiece, the special fixture shall not be used;

2） The positioning datum of parts are overlapped to reduce the positioning deviation.

4. Confirm the processing route

Machining route refers to the moving track and target of the tool relative to the part in the process of NC machining.

1) It shall be able to meet the requirements of machining accuracy and surface roughness;

2) It is necessary to reduce the processing route and the time of tool empty travel.

5. Correlation between machining route and machining allowance

At present, under the condition that the CNC lathe has not been widely used, it is usually necessary to place too much allowance on the blank, especially the allowance containing forging and casting hard skin layer on the ordinary lathe for processing. If the CNC lathe must be used for machining, it is necessary to pay attention to the sensitive placement of the program.

6. Key points of fixture installation

At present, the connection between hydraulic chuck and hydraulic clamping cylinder is completed by pull rod. The key points of hydraulic chuck clamping are as follows: first, remove the nut on the hydraulic cylinder with the handle, remove the pull tube, and pull it out from the rear end of the main shaft, and then remove the constant screw of the chuck with the handle to remove the chuck.

The polishing edge on the tool refers to a small section of the edge which is parallel to the tool tip milled by the target of the deviation angle of the back edge pair of the tool edge, which is mainly used for the second cutting after the cutting of the tool edge, which is equivalent to the direction burr in the finishing process. The goal is to increase the surface roughness of the workpiece, which is mostly used for the tool of finishing.

CNC processing technology of mobile phone metal shell

CNC machining technology of mobile phone metal shell. In this era of highly valued user experience, more and more manufacturers of mobile phones, laptops and wearable devices start to work on the shell materials. Only from the perspective of mobile phone boundary, mobile phone shell material is also gradually transiting from engineering plastic to metal.

There have been many combination methods in the evolution time of mobile phone shell materials: plastic and metal, glass and metal, all plastic, all glass, etc., but they did not cover the trend of all metal materials. In terms of the essential touch experience, the all metal mobile phone has an outstanding experience in many aspects. It is better than other materials in appearance and feel.

CNC machining

All manufacturers offer all metal shell products

When it comes to all metals, it comes to CNC. At present, all metal shells of 3C products are basically processed by computer numerical control machine tools (CNC). CNC has become a necessary equipment for 3C shell manufacturers because of its advantages of high efficiency, high precision and stable processing quality.

All metal one-piece CNC machining process was initiated by Apple company as early as possible – aluminum plate is die-casting from solid columnar aluminum material. After careful machining, it is cut into the prototype of one-piece fuselage. With the fuselage gradually forming, the keyboard form and various fine structures on the fuselage are milled out. This process includes nine CNC milling processes, after which a well-organized integrated shell can be obtained.

Shell manufacturers need many processes from programming to obtaining molded articles, such as rough machining, semi rough machining, semi finish machining, and finish machining. In many times, the whole process requires more than 10 stations to obtain molded articles. In order to increase the rate of high-quality products, each process needs strict control.

Meizu mx5 obtains shaped articles through 12 processes from right to left

One

Modeling and programming of CNC machining sequence

Before CNC machining, the requirement modeling and programming are the first step. The difficulty of 3D modeling is determined by the product structure. The product modeling with complex structure is more difficult. Programming includes working procedure setting, tool selection, rotation speed setting, interval of each tool feeding and so on. For the rest, the clamping methods of different products are different. Before processing, the clamps should be designed well, and some products with complex structure need special clamps.

Programming includes the processing technology of all products. Although CNC automation is completed in the future, early programming must be operated by experienced staff to prevent repeated trial and error and high cost.

Two

Key processing technology

Using high-speed drilling and tapping center, the aluminum plate is precisely milled into regular three-dimensional volume of certain size, and the next process is planned.

Rough milling: after positioning, rough milling out the inner cavity structure, the positioning column integrated with the fixture, and milling out most of the external redundant raw materials.

Milling the antenna slot: it is difficult to deal with the information problem of the all metal shell. It is necessary to mill out the antenna slot to leave a transmission path for the information and maintain the necessary connection points to ensure the strength and overall sense of the fuselage.

CNC finishing: Finish Milling inner cavity, outer structure, outer surface, side, etc.

Polishing: use high-speed and meticulous CNC machine tool to polish, eliminate knife marks, and plan for subsequent sandblasting.

Sandblasting: it can treat the metal surface into abrasive effect.

Anodizing:

Primary anode: color the mobile phone. Anodizing turns aluminum into gold. At the same time, improve the stability of surface materials

Secondary anode: solid and dense oxide film is formed on the surface of the body, and the wear resistance is further strengthened.

Plastic shell molding using injection molding technology, only need to open mold can be mass produced, yield is very high. While the CNC machining yield of all metal fuselage is determined by the complexity of the shell structure and the accuracy requirements. It is difficult to reach the high yield of plastic shell. In order to average high cost, most manufacturing enterprises will choose to purchase a large number of CNC equipment to reduce the comprehensive cost and reach the production rate in the face of value war.

Application of fixture

The fixture is a process device used to fasten the workpiece quickly and maintain its precise relative position. That is to say, fixture is an indispensable part of machining. With the development of technology to the goal of high speed, high efficiency, thoughtfulness, integration, intelligence and environmental protection, fixture technology is developing towards the goal of high precision, high efficiency, module, combination, generality and economy.

Fixture is also called fixture. In a broad sense, any process in the process, which is used to install workpiece quickly, simply and safely, can be called fixture. For example, welding fixture, inspection fixture, equipped fixture, machine tool fixture, etc. Often referred to as fixture.

When processing the workpiece, in order to make the surface of the workpiece reach the technical requirements such as the size, geometric form and the mutual position accuracy with other surfaces in the drawing regulations, the workpiece must be installed (positioned) and clamped (clamped) before processing.

The use of jigs is conducive to ensuring the processing accuracy, safe and stable production of the workpiece; to increasing the production rate and reducing the cost; to improving the working conditions of the workers and ensuring the safe production; to enlarging the process boundary and completing the “one machine and multi use”.

The fixture is usually composed of positioning elements (to confirm the exact position of workpiece in the fixture), clamping device and indexing device, so that the workpiece can be processed in several positions in one installation, including two types of rotary indexing device and linear moving indexing device, connecting elements and clamp details (fixture base), etc.

In order to improve the production efficiency and product quality, in the middle and back section of the production, the fixture is often used for performance test or auxiliary equipment (can be equipped with constant appearance and height, etc.). The essence is widely used in the manufacturing plant, because the right and wrong mark is customized, so there is only something unexpected but not impossible

Maintenance rules of grinding machine for precision parts processing equipment

Grinding machine is one of the basic equipment used in precision parts processing, its shape will also have a positive impact on the processing quality, so if you want to improve the precision of precision parts processing, you must carry out regular inspection and care for the grinding machine, so that it will always maintain a good shape.

First of all, we need to know that as a precision parts processing equipment, the grinder should be specially assigned to be in charge of maintenance and application. When its homework is completed, it is necessary to clean all parts of the machine, especially the sliding parts, and then apply oil to maintain excellent smoothness. At the same time, it is also necessary to eliminate the grinding debris at all parts of the grinder, so as to avoid adverse effects on the processing process. Some parts are still subject to rust prevention treatment,

Before using the grinder, don’t forget to correct the grinding wheel average, and choose the grinding wheel carefully according to the material and hardness of the work materials, which is one of the key factors affecting the processing efficiency of precision parts. Don’t forget to pay attention to the rotation target of the grinder spindle, prevent the use of air to clean the work materials and machinery, and keep the dust collection pipeline clean, otherwise it will lead to burning.

Secondly, we pay attention to the suction cup of the grinding machine for precision parts processing equipment, whether it is the permanent magnetic casting suction cup or the electromagnetic suction cup, and the disk surface is the basis of whether the grinding precision of the working object can be dream, so we must properly and precisely care for and maintain it.

If the precision of the work object is poor or the disk surface is damaged, the disk surface must be grinded again. Only when the precision of the disk surface of the suction cup of the grinder meets the requirements, can the precision of the precision parts be ensured. In addition, there is a smooth system of conditioning, but it is nothing more than the replacement of smooth oil and wash filter.

CNC machining hardware parts suitable for processing

1. For the content of hardware parts suitable for NC machining, the following sequence research can be carried out during selection:

(1) The content that cannot be processed by general machine tool shall be the priority;

(2) General machine tools are difficult to process and their quality is difficult to guarantee;

(3) General machine tools have low machining efficiency and high manual operation intensity, which can be selected when there is abundant machining strength in CNC machine tools.

2. Hardware parts not suitable for NC machining

(1) It takes a long time to adjust. If the first fine datum is located and processed with the rough datum of the blank, the content of special tooling coordination is required;

(2) Processing location distribution, need to install and configure the origin repeatedly. At this time, it is very difficult to select CNC machining, and the effect is not obvious, so general machine tools can be placed for supplementary machining;

(3) The appearance of the profile machined according to certain manufacturing documents (such as sample plate, etc.). The key reason is that it is difficult to obtain data, easy to conflict with checking credentials, which increases the difficulty of programming.

Working range of AC rotating axis of CNC five axis machining center

Generally speaking, the axis around the x-axis of the five axis CNC machining center is defined as the a-axis. The working boundary of the a-axis is + 30 ° to – 120 °. The worktable of the five axis machining center is equipped with a rotating shaft. This rotating shaft ring rotates around the z-axis. We define it as the c-axis. The working boundary of the c-axis is 360 degree rotation. For the five axis machining center with a rotating shaft and C rotating shaft, the workpiece can be clamped once to finish machining other than the mounting surface. Generally, the small graduation value of a-axis and c-axis is 0.001 degrees. In this way, it is better to remove the other surfaces of the installation surface without angle, and to process the skew surface, skew hole and other complex processes. It can be realized that if the a-axis, c-axis and XYZ linear three-axis are processed in five-axis linkage, the complex curved surface workpiece can be processed. Of course, good CNC system, servo motor system and software support are needed.

Structural advantages of AC rotating shaft configuration in five axis machining center

The advantages of the above AC rotating shaft configuration are simple structure, good rigidity of the main shaft, low manufacturing cost and so on. Generally, the worktable can not be configured too large, and the load-bearing is also relatively small. The unique reason is that when the rotation axis of a turns to 90 degrees or more, when the workpiece is processed, it will bring a lot of load-bearing moment to the worktable.

Matters needing attention in the process of NC lathe machining

What should be paid attention to in the process of NC lathe machining. The machining process of CNC lathe is the same as that of ordinary lathe. However, since CNC is a clamping process, all the turning processes are finished continuously and automatically, the following aspects should be paid attention to.

1. Correct selection of cutting parameters

Users should choose the cutting speed according to the raw material, hardness, cutting shape, raw material variety, feed rate, cutting depth, etc. The following table:

The selection of suitable processing conditions is based on these factors. Regular and stable wear and tear is the condition of dream.

CNC lathe

2. Select tools correctly

1) During rough turning, the cutter with high strength and good durability shall be selected to meet the requirements of large back draft and large feed during rough turning.

2) When finishing, the cutting tools with high accuracy and good durability shall be selected to ensure the requirements of machining accuracy.

3) In order to reduce the time of tool change and make the tool setting easier, we should choose the clip knife and clip knife.

3. Select fixture correctly

1) Although the general fixture is used to clamp the workpiece, the special fixture shall not be used;

2） The positioning datum of parts are overlapped to reduce the positioning deviation.

4. Confirm the processing route

Machining route refers to the moving track and target of the tool relative to the part in the process of NC machining.

1) It shall be able to meet the requirements of machining accuracy and surface roughness;

2) It is necessary to reduce the processing route and the time of tool empty travel.

5. Correlation between machining route and machining allowance

6. Key points of fixture installation

What are the characteristics of precision parts processing

What are the characteristics of precision parts processing? Five axis linkage processing center is a processing center with high technology content and high weekly density, which is specially used to process complex curved surface. This processing center system has full weight lifting influence on aviation, sail sea, military, scientific research, sophisticated equipment, high-precision medical equipment and other industries in a country.

1、 What is a five axis machining center

Five axis linkage machining has the characteristics of high efficiency and high precision, and the complex machining can be completed as soon as the workpiece is clamped once. It can be suitable for the processing of present moulds such as auto parts, aircraft structural parts, etc. There is a big difference between five axis machining center and pentahedral machining center. Many people don’t know this. They mistakenly regard the pentahedron machining center as a five axis linkage machining center. Five axis machining center has x, y, Z, a, C five axis, XYZ and AC axis to create five axis machining, specializing in space surface processing, special-shaped processing, hollow processing, drilling, oblique hole, oblique cutting, etc. The “pentahedron machining center” is the same as the three-axis machining center, but it may as well do five faces at the same time, but it can not do special-shaped processing, such as drilling, cutting bevel, etc.

For the rest, the practical boundary of the five axis CNC machining center is quite ordinary. It is understood that the current five axis CNC machining center system is the only way to process impellers, blades, marine propellers, heavy-duty generator rotors, automobile wheels, large diesel engine crankshafts, etc.

Precision parts processing

2、 Advantages of five axis machining center

1. Reduce processing time and improve processing accuracy.

The big characteristic of five axis machining center is that it is advisable to process all five surfaces by one-time clamping. That is the so-called processing angle avoidance. If it’s a linked bed, axis C can rotate endlessly, and axis a can rotate by 130 degrees. These characteristics of the equipment make it possible to process without interference.

The advantage of this method is that one-time clamping can not only finish the processing, but also prevent the repeated positioning deviation caused by repeated clamping. At the same time, it also saves a lot of time and improves the working efficiency. It can reduce the time from product to delivery and reduce the inventory.

2. Reduce equipment investment cost, workshop area and workshop number.

The five axis linkage machining center controls the compound machining machine, usually with turning performance, which can be included from lathe to milling machine to vertical mill. Everyone knows that the value of vertical mill equipment is quite high at present. After cost, processing beat and other accounting, we can find that the value of five axis is high. Before that, many people’s production and processing may be based on engineering segmentation. The problem with such a production method is that there is a lot of waiting time that cannot be eliminated. However, the engineering intensive production represented by the five axis compound processing equipment only needs the early waiting time for debugging, and with the popularity of all kinds of complete machine simulation software in China at present, even if only the introduction of rough data is required, the programming can be completed and the early planning can be greatly reduced. So at present, overseas auto parts and high-end manufacturing are basically based on five shafts.

3. No need for unique fixture, can complete automation.

Another prominent feature of the five axis is that the dependence on the fixture will be reduced. The rule workpiece can be clamped directly with three claws and four claws chuck, while the rule workpiece can be clamped with one side and two pins. At the same time, the five axis machining center can complete the automation of the workshop and reduce the number of people. For example, machining robot’s key point and base. In the past, horizontal plus and vertical plus combined processing were used. Now, only zero point tray and five axis linkage processing center are used to complete 24-hour operation processing.

The method of determining the tool clamping force in CNC machining

When designing the clamping device for NC machining tools, the clamping force must include three factors: the target, the action point and the size of the clamping force. So how to confirm the clamping force of NC machining tools?

1. The point of action of the tool clamping force in NC machining the point of action of the clamping force is a small area of contact between the clamping piece and the workpiece. The problem of selecting the action point is to confirm the position and quantity of the action point of the clamping force when the clamping target has been determined. The choice of the action point of the clamping force is the key factor to reach a good clamping shape. The correct choice of the action point of the clamping force must follow the following principles?

The roughness value of grinding surface is reduced from 2.0 to 1.1 CNC tool

2. The target of the clamping force of the tool in NC machining is related to the basic configuration of the positioning of the workpiece and the target of the external force on the workpiece. The following criteria must be followed when selecting NC tools:

① The target of the clamping force shall be helpful for the stable positioning, and the main clamping force shall face the key positioning base plane.

② The aim of the clamping force should be to reduce the clamping force to reduce the deformation of the workpiece and the working strength.

③ The target of clamping force should be the one with better rigidity of workpiece. Due to the different stiffness of the workpiece in different targets, the deformation of different stressed surfaces is also different due to the size of their contact area. More and more attention should be paid to make the target of clamping force point to the best target of workpiece rigidity when clamping thin-walled parts.

3. CNC machining tools simplify the process flow and reduce the cost of production in some use situations. The surface quality of high-speed milling can be comparable to grinding, and high-speed milling can be directly used as the final finishing process. Therefore, the process flow is simplified, the production cost is reduced, and the economic benefit is considerable.

4. The energy consumption of NC machining tools is low, and the volume of cutting layer material per unit power increases significantly when saving resources for high-speed cutting. For example, aluminum alloy high-speed cutting, spindle speed from 4000 1 /. When the cutting force rises to 20 000, the cutting force drops 30 ^, and the cutting rate of raw material increases 3 times. The material removal rate per unit power can reach 130? 160 (1) compared with 30? Avulsion in common milling). Due to the high removal rate, low energy consumption, the working time of the workpiece