Monthly Archive November 2020

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Attention details of CNC external grinder

12 details to be paid attention to in maintenance of CNC external grinder

  1. before grinding, please check the balance of the positive wheel of the CNC external grinder.
  2. the grinding wheel must be selected carefully according to the material and hardness of the work.
  3. the main shaft end and the grinding wheel flange shall be coated with thin oil film to prevent rust.
  4. please pay attention to the rotation direction of spindle of CNC external grinder.
  5. it is forbidden to use air gun to clean the work objects and machines.
  6. please pay attention to whether the oil circuit of oil window is smooth.
  7. vacuum box and filter steel, please clean it once a week.
  8. if the suction is weak, please check whether the dust pipe is blocked by dust.
  9. the vacuum pipe of CNC external grinder must be kept clean, otherwise it will cause combustion.
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Factors affecting cutting efficiency of CNC lathe

The cutting efficiency of CNC Lathe will be affected by human factors, environmental factors and machine itself. Let’s talk about the influence of cutting quantity and cutting tool on CNC lathe machining.

Reasonable cutting parameters can improve the efficiency of CNC lathe. When the cutting speed is increased by 10 times and the feed speed is increased by 20 times, which is far beyond the traditional cutting forbidden zone, the cutting mechanism changes fundamentally. The results are as follows: the metal removal rate per unit power is increased by 30% ~ 40%, the cutting force is reduced by 30%, the cutting life of the cutting tool is increased by 70%, the cutting heat left on the workpiece is greatly reduced, and the cutting vibration almost disappears; the cutting process has taken an essential leap. According to the current situation of CNC lathe, increase the feed per tooth, improve productivity and tool life.

The effect of cutting tools on CNC lathes is like that of wheels on automobiles. The material used to make the tool must have high temperature hardness and wear resistance, necessary bending strength, impact toughness and chemical inertia, good processability (cutting, forging and heat treatment), and not easy to deform. A good tool can improve the efficiency of machining and the accuracy of the workpiece.

Other factors, such as power supply, familiar with operation, reasonable use of materials and other factors will affect the processing of CNC lathe

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Application scope of lathe parts

Lathe parts, as the name implies, are products processed by lathe. Lathe parts can be divided into many kinds according to different types of lathes. The most common ones are automatic lathes, CNC lathes, instrument lathes, etc. The hardware materials used in lathe parts are copper, iron, aluminum, stainless steel, etc.

Lathe parts are widely used, involving electronic appliances, hardware tools, toys, plastics and other industries. Compared with other fasteners, its main feature is precision, the tolerance can reach plus or minus 0.01mm, or even more accurate. Of course, its price is much higher than other hardware.

Automatic lathe parts are parts processed by automatic lathe. The maximum processing diameter is 20 mm and the maximum processing length is 90 mm. Due to the small size and high speed of processing parts, the price is relatively low. The machining precision is high, and the tolerance can be controlled within plus or minus 0.01 mm.

CNC lathe parts are parts processed by CNC CNC lathe. The maximum machining diameter can reach 60 and the maximum processing length is 300 mm. The processed parts are large, complex in shape and high in precision. They can be turned in several times, and the tolerance can be up to plus or minus 0.002 mm. It has more advantages in processing stainless steel products. Due to the expensive machine and low processing efficiency, the processing cost is relatively high.

The reason why lathe parts have higher processing cost than other hardware products is because of the high precision, low speed and low output. After a large part of lathe parts are processed on the machine, they need secondary processing to meet the functional requirements, such as: milling groove, drilling, milling edge, chamfering and so on.

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Processing sequence arrangement of lathe parts

  1. The principle of first roughing and then finishing of lathe: the machining sequence of each surface is in accordance with rough machining and semi finishing of leaves_ Finish machining_ The precision machining is carried out in order to improve the machining accuracy and reduce the surface roughness.
  2. The first principle of lathe datum plane: the surface used as precision datum should be processed first, because the more accurate the surface of positioning datum is, the smaller the clamping error is. Since the lathe inverted 40 outer circle is the basis of coaxiality, the surface should be machined first, and then other surfaces.
  3. The principle of the lathe first and then the second: the main working surface and assembly base surface of the parts should be processed first, so as to detect the possible defects on the main surface of the blank as soon as possible. The secondary surface of the lathe can be interleaved, after the main surface is machined to a certain extent and before the final finish machining.
  4. The principle of lathe from near to far: in general, after the workpiece is clamped, the parts near the tool rest are processed first, and the parts far away from the tool rest are processed later, so as to shorten the moving distance of the cutting tool and reduce the idle travel time. Moreover, it is beneficial to maintain the chip of the blank or semi-finished product and improve its cutting conditions. For the inner hole of lathe parts, the inner conical hole should be machined first, then the inner hole of φ 30mm, and finally the inner hole of φ 20mm.

Key technologies of processing:

The key technology of precision machining of lathe parts is the overall comprehensive design technology of lathe parts and machine tool system. Conventional machine tool design and manufacturing, each link technology has a great tolerance. Each link of ultra precision machine tool is basically in a state of technical limit or critical application, which link is slightly considered or not handled properly will lead to the overall failure. Therefore, the design needs to have a very comprehensive and profound understanding of the whole machine tool system and the technology of each part. According to the feasibility and from the overall optimization, it is necessary to carry out the related comprehensive design in great detail. High rigidity, high stability machine body structure design, manufacturing technology. In particular, lodtm machine tool, because of its large body, its own weight, load-bearing workpiece weight changes greatly, any small deformation will affect the machining accuracy. In addition to meeting the requirements of material, structure form and technology, the operability of the machine tool must be taken into account in the structural design.

Spindle technology of ultra precision lathe parts. The scheme of Aerostatic Spindle is often used in medium and small machine tools. Aerostatic Spindle has small damping and is suitable for high-speed rotary machining applications, but its bearing capacity is small. The rotary accuracy of Aerostatic Spindle can reach 0.05 μ M. The spindle of lodtm machine tool bears large size and weight of workpiece, so hydrostatic spindle should be used generally. The hydrostatic spindle has large damping, good vibration resistance and large bearing capacity, but the high-speed heating of hydrostatic spindle is large, so liquid cooling and constant temperature measures should be taken. The rotation accuracy of hydrostatic spindle can reach 0.1 μ M. In order to ensure the accuracy and stability of the spindle, both pneumatic and hydraulic sources need constant temperature, filtration and pressure precision control.

High precision air, liquid, temperature, vibration and other working environment control technology of lathe parts. Vibration isolation and horizontal attitude control of machine tool. The influence of vibration on ultra precision machining is very obvious, which is affected by far driving cars. Special measures should be taken to isolate the vibration of the machine tool. The air floating vibration isolation system of machine tool should also have the function of automatic leveling to prevent the influence of horizontal state change on machining. For the machine tool with high lodtm vibration isolation requirements, the natural frequency of the vibration isolation system should be less than 1Hz.

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Speed control of CNC machining

CNC machining is developing towards high speed and high efficiency. This includes the speed control of CNC machining. If we want to make full use of the effective working stroke, we must make the moving parts accelerate to the high speed stroke in a very short time, and stop in the high speed stroke instantaneously. This is why CNC machining speed control.

According to the open control idea, we put forward a method of automatic acceleration and deceleration control for the motion of CNC machine tool according to any curve. This method pushes the automatic acceleration and deceleration control from the traditional fixed mode to the new flexible mode, and explores a new way to effectively improve the dynamic performance of CNC machine tools.

  1. Flexible acceleration and deceleration control

In CNC machining, the specific automatic speed control function is usually realized by the system program directly. In this way, it is necessary to change the acceleration and deceleration characteristics of the system or to control the addition and subtraction to modify the NC program, so ordinary users can not make the CNC machine tool have the best acceleration and deceleration performance according to their own will. Therefore, the flexible acceleration and deceleration control method is based on the principle of database. The acceleration and deceleration control is divided into acceleration and deceleration description and implementation, and the acceleration and deceleration description is separated from the system program. In the software of numerical control system, a general control channel is designed which has nothing to do with the contents of acceleration and deceleration database, which can complete acceleration and deceleration calculation and trajectory control independently.

  1. Flexible automatic acceleration control

The acceleration curve, analytic curve and non analytical curve are set and stored in the acceleration and deceleration curve library as templates in the form of data table.

  1. Flexible automatic deceleration control

As for acceleration control, it is stored in the acceleration and deceleration curve Library in the form of data table. Reasonable automatic acceleration and deceleration control is an important link to ensure the dynamic performance of CNC machine tools. Due to the lack of flexibility, the traditional automatic acceleration and deceleration control based on fixed curve is not easy to ensure that the acceleration and deceleration process is compatible with the performance of the machine tool, so it is difficult to achieve the best dynamic characteristics of the machine tool.

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The concept of machining precision of computer gongs

The whole computer network can ensure 24-hour uninterrupted operation. At the same time, the advanced power-saving system can minimize the cost of human and material resources, shorten the production cycle by 50%, with high capacity and faster delivery time.

Online integrated production, computer simulation of the production process, error reporting device to ensure product accuracy. Professional precision automation equipment can ensure the error is within 0.01mm, which is 500 times of traditional equipment.

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

Machining accuracy includes three aspects: dimensional accuracy, shape accuracy and position accuracy.

① Dimensional accuracy 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 middle 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 surface shape of parts refers to the absolutely accurate surface geometry.

④ The degree of correspondence between the actual position of each surface of the part and the position between the ideal parts after position precision machining. The position between the surfaces of an ideal part refers to the absolutely accurate position between the surfaces.

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CNC machining non-standard parts

  1. In the machining process of parts, the surface as the positioning datum should be processed first, and the computer gong processing can provide precise reference for the subsequent processing as soon as possible.
  2. The machining stage is divided into three stages: rough machining, semi finishing and finishing. It is mainly to ensure the quality of processing; it is conducive to the scientific application of equipment; it is convenient to arrange the heat treatment process; and it is convenient to find the blank defects.
  3. For parts such as box, bracket and connecting rod, the plane should be machined first and then the hole should be processed. In this way, the hole can be processed by plane positioning, which ensures the position accuracy of plane and hole, and brings convenience to the processing of hole on the plane.
  4. Finishing the main surface finishing, such as grinding, honing, finishing and rolling, should be placed at the end of the process route. The general principle of drawing up the process route of precision parts and the formulation of the process regulation of precision parts can be roughly divided into two links. First of all, it is to draw up the process route of parts processing, and then determine the process size of each process, the equipment and process equipment used, as well as the cutting specifications, man hour quota, etc. In the machining process of non-standard parts, the foundation is the most important, and the same is true for precision mechanical parts processing. The precision datum is always processed first, and then the other surfaces are positioned and processed by the precise datum. Next, we’ll go into details about me. For box parts, the main hole is generally used as the rough datum to process the plane, and then the plane is used as the precision datum to process the hole system; for the shaft parts, the outer circle is generally used as the rough datum to machine the central hole, and then the center hole is used as the fine datum to process the outer circle, end face and other surfaces. If there are several precision datum, the machining of base surface and main surface should be arranged according to the sequence of datum transformation and the principle of gradually improving machining accuracy.

For the box, bracket and connecting rod, the plane should be machined first and then the hole should be processed. Because of the flat contour and large area of the plane in high-speed CNC machining, machining the plane first and then machining the hole by plane positioning can not only ensure that the hole has a stable and reliable positioning reference, but also is conducive to ensuring the position accuracy requirements between the hole and the plane. A part is usually composed of multiple surfaces, and the machining of each surface generally needs to be carried out in stages. In high-speed CNC machining, when arranging the machining sequence of precision mechanical parts, the roughing of each surface should be arranged first, then the semi finishing should be arranged in turn according to the needs, and finally the finishing and finishing should be arranged. In order to reduce the influence of deformation caused by rough machining on finish machining, roughing and finishing should not be carried out continuously, but should be carried out in stages and at appropriate intervals. The general principle of machining non-standard parts is: the front work must be prepared for the later work, lay a good foundation, and do a good service.

The specific working principle of CNC machining non-standard parts can be divided into four aspects: the main surface of parts is generally the surface with high machining accuracy or surface quality requirements. Their processing quality has a great impact on the quality of the whole part, and its processing procedures are often more. Therefore, the processing of main surface should be arranged first, and then other surface processing should be properly arranged in them In the middle. Generally, the assembly base surface and working surface are regarded as the main surface, while the keyway, smooth hole and screw hole for fastening are regarded as the secondary surface.

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Computer gong processing programming

CNC machine tool is a machine tool manufacturing industry, the revitalization of each field needs a large number of advanced CNC machine tools. In recent years, the production of CNC machine tools in China continues to grow, and the industry of CNC machine tools and CNC systems will develop rapidly.

Reader: in this case, many production plants are placed on CNC machine tools, we can imagine the importance of CNC machine tools. I want to know, how do we master NC machine programming technology, NC machine programming experts?

Editor: NC machine programming technology is not a very short period of time can learn, need to learn step by step, and slowly accumulate experience. Master this technology, small editor is not only the theoretical level of engineers, but also the practical experience and practical ability of senior technicians. How to become the master of NC machine programming?

1, the process is the basis of programming. If you don’t know the technology, it can’t be called programming. Therefore, to master the programming technology of CNC machine tools, you must first become a craftsman.

  1. Proficient in CNC programming and computer software application.
  2. Proficient in CNC machine tools. It takes 2-3 years to study. In this process, we need to learn how to operate the system, fixture installation, part datum alignment, tool presetting, zero point offset setting, tool length compensation, radius compensation, tool and handling handle, cutting tool grinding, part measurement (skilled use of vernier caliper, micrometer card, micrometer, diameter bar gauge), etc.
  3. There must be good fixture foundation and measurement technology.
  4. Familiar with CNC machine tools. Proficient in the maintenance of CNC machine tools.
  5. Cultivate good habits and adapt to the characteristics of CNC processing. In this case, suitable for CNC machining master should be humble, rigorous, calm, serious thinking, orderly and persuasive people.
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CNC machining repeatability of CNC lathe

CNC CNC lathe processing repetitive production of parts: the use of CNC grinding machine process preparation time occupies a high proportion. For example Process analysis preparation, programming, adjustment and trial cutting of the first part of the part, the sum of these comprehensive working hours is often dozens to hundreds of times of the working hours of a single part of the part. However, the work contents of these CNC lathes can be saved and reused. Therefore, when a part is successfully trial produced on a CNC grinder and put into production again, the production cycle is greatly reduced, and the cost is also less, which can achieve better results The economic benefits of.

It is required to focus on ensuring the processing quality and producing the key parts in small and medium batches: CNC grinder can realize high precision, high quality and high efficiency grinding under the control of computer. Compared with the special grinding machine processing, it can save a lot of special process equipment, has strong flexible manufacturing ability and obtains better economic benefits. Compared with ordinary grinding machine, it can eliminate many artificial interference factors in the long process of complex machining, and has good precision consistency and interchangeability, and high processing efficiency.

The parts processed by CNC CNC lathe should conform to the process characteristics that can give full play to the multi process centralized processing of CNC grinder. When CNC grinding machine processes parts, the situation of grinding wheel cutting workpiece is exactly the same as that of corresponding non CNC grinder, but it can carry out some complex processing with processing accuracy requirements. For example, in the grinding range, ordinary grinder is mainly used for grinding cylindrical surface and circular CNC lathe In addition, it can also grind toroidal surface and complex combined surface of various forms mentioned above.

The processing batch size of parts should be larger than that of economic batch of parts by ordinary lathe. When NC lathe is used to process medium and small batch parts by non CNC grinder, due to various reasons, the pure cutting time only accounts for 10% – 30% of the actual working hours. When CNC machining is carried out on the CNC grinding machine with multi process concentration, such as grinding center, the proportion may rise to 70% – 80%, but the man hour to be adjusted is often much longer, so it will be uneconomical if the parts batch is too small.

Some special parts processed by CNC lathe are considered to be processed. Although some parts are processed in small batches, ordinary lathes have complex shapes, high quality and good interchangeability, which can not meet the above requirements on non CNC grinding machines. CNC machining can only be arranged on CNC grinding machines, such as parabola, cycloid cam and special surface mirror mirror.

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Computer gong processing and knife loading

1、 Try to install the clamping material first and then the cutting tool,

In order to prevent the hand from touching the tool when loading the material. If the tool has been installed, the worktable should first be moved to the outside to ensure that the clamping material will not interfere with the tool, so as to avoid injury or breakage of the tool.

2、 When disassembling the tool, you must first observe whether the spindle stops rotating.

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

5

In the process of CNC machining, operators are not allowed to observe the cutting position closely to prevent chips from falling into eyes.

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

7、 When the machining gap is suspended for observation, the worktable must be moved away from the cutting position.

8、 After the machining is completed and before the workpiece is disassembled, we should first conduct the preliminary inspection of the necessary size or appearance. Only after the inspection is qualified can the workpiece be disassembled, so as to avoid the positioning problem of secondary processing and the scrapping of the workpiece.