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What are the common and efficient CNC thread machining methods

What are the common and efficient CNC thread machining methods? Thread machining is one of the important applications of CNC machining center. The machining quality and efficiency of thread will directly affect the machining quality of parts and the manufacturing efficiency of machining center. With the increasing function of CNC machining center and the improvement of cutting tools, the way of thread machining is constantly improving, and the accuracy and efficiency of thread machining are gradually increasing. In order to enable the process staff to correctly select the thread processing mode, improve the production efficiency, and prevent quality events in the processing, several commonly used thread processing modes in CNC machining centers are summarized as follows:

In NC machining, the commonly used processing methods of thread can be divided into: NC turning, NC milling, tapping and whirlwind milling.

CNC processing

1、 CNC lathe

It is advisable to turn metric, inch, modulus and diameter control four kinds of standard threads on CNC lathe. No matter which thread is turned, there must be a strict activity relationship between lathe spindle and cutter: that is, every revolution of spindle (i.e. one revolution of workpiece), the cutter should move an average interval of lead. If the thread is processed on the CNC lathe, it can be described as follows with a diagram

If it is to be subdivided, it can also be divided into: direct feed of radial feed; control turning method of flow feed; oblique feed method of lateral feed.

Straight forward method: applicable to small pitch, with lead less than 3mm, G32 or G92

Oblique approach: it is not easy to tie the knife, it is preferred to use G76 command without undercut

Control turning method: large profile, large pitch, lead greater than 5mm, macro program

2、 CNC milling

Thread milling, in the thread milling machine with disc milling cutter or comb milling cutter for milling. Disc milling cutter is mainly used for milling trapezoidal external thread of screw rod, worm and other workpieces. The comb milling cutter is used for milling internal and external common thread and taper thread. The length of the working part of the multi edge milling cutter is longer than the length of the thread to be processed. Therefore, the workpiece only needs to rotate 1.25 ~ 1.5 to be processed, with a high production rate. The pitch accuracy of thread milling can reach 8-9 grades, and the surface roughness is r5-0.63 μ M. This method can be used for mass production of common precision screw thread or rough machining before grinding. After the spiral slope milling of the turning tool, the screw thread is generated, which is not as ordinary as the lathe, but also has high efficiency when it is used in a unique scene.

CNC processing

Three. Tapping

Tapping is to use a certain torque to screw the tap into the bottom hole pre drilled on the workpiece to process the internal thread.

Threading is to cut the external thread on the bar (or tube) workpiece with a die. The machining accuracy of tapping or threading depends on the accuracy of tap or die. Although there are many ways to process internal and external threads, small-diameter internal threads can only be processed by taps. Tapping and threading can be operated by hand, or by lathe, drilling machine, tapping machine and threading machine.

4、 Whirlwind milling

CNC whirlwind milling is installed on CNC lathes and other lathes by Zhonghua broad users, which makes the processing efficiency of single head multi head, worm, screw, nut and other threaded products increase by 10-30 times, the processing accuracy increases by two poles, and the brightness reaches 0. 8um. There is no difference between the whirlwind milling and the numerical milling in the processing technology. If the blade is installed in the cutting cutter head and rotates around the cylindrical part, the thread can be cut out in one-time cutting, with high efficiency!

Focus on the operation of screws, worm and other unique scenes!

summary

Only by accurately selecting thread processing methods and cutting tools can we effectively improve the efficiency and quality of thread processing, increase the application efficiency of CNC machining center, and reduce the processing cost. Every NC processing staff should be skilled in charge.

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The specific maintenance measures of CNC machine tools

1. CNC system

(1) Strictly abide by the operation regulations and daily maintenance system of CNC machine tools.

(2) Prevent dust from entering the numerical control device: floating dust and metal powder are easy to cause the insulation resistance between components to drop, thus causing failure or even damage to components.

(3) Clean the cooling and ventilation system of the data control cabinet regularly.

(4) Frequently monitor the power grid voltage of CNC system: the power grid voltage range is 85% – 110% of the rated value.

(5) Replace the battery for memory regularly.

(6) Maintenance of CNC system when it is not used for a long time: often power on the CNC system or make the CNC machine run warm program.

2. Tool magazine and tool change manipulator

(1) When installing the knife into the magazine manually, ensure that it is installed in place and check whether the locking on the knife seat is reliable.

(2) It is strictly prohibited to install the over weight and over long tools into the tool magazine, so as to prevent the tool from dropping when the manipulator changes the tool or the tool from colliding with the workpiece, fixture, etc.

(3) In order to select tools in sequence, it is necessary to pay attention to whether the order in which the tools are placed on the magazine is correct. Other tool selection methods should also pay attention to whether the tool number is the same as the required tool to prevent accidents caused by changing the wrong tool.

(4) Pay attention to keep the handle and sleeve clean.

(5) Frequently check whether the zero return position of the tool magazine is correct, check whether the tool change point position of the machine tool spindle is in place, and adjust it in time, otherwise the tool change action cannot be completed.

(6) When the machine is started, the tool magazine and manipulator shall be operated empty first, and check whether all parts work normally, especially whether all travel switches and solenoid valves operate normally.

3. Ball screw

(1) Regularly check and adjust the axial clearance of screw nut pair to ensure the reverse drive accuracy and axial stiffness.

(2) Regularly check whether the connection between the lead screw support and the bed is loose and whether the support bearing is damaged. In case of any of the above problems, fasten the loose parts in time and replace the support bearing.

(3) Clean the old grease on the ball screw with lubricating grease every half a year and replace it with new grease. The ball screw lubricated with lubricating oil shall be oiled once a day before the machine tool works.

(4) Pay attention to prevent hard dust or chips from entering the lead screw protective cover and bumping the protective cover during the working process. Replace the protective device in time once it is damaged.

4. Main drive chain

(1) Adjust the tightness of the spindle drive belt regularly.

(2) Prevent all kinds of impurities from entering the oil tank, and change the lubricating oil once a year.

(3) To keep the connection between the spindle and the handle clean, it is necessary to adjust the displacement of the hydraulic cylinder and the piston in time.

(4) Adjust the counterweight in time.

5. Hydraulic system

(1) Filter or change the oil regularly.

(2) Control the temperature of the fluid in the hydraulic system.

(3) Prevent hydraulic system leakage.

(4) Check and clean the oil tank and pipeline regularly.

(5) Implement daily point inspection system.

CNC machining generally follows several principles

The determination of CNC machining route in CNC lathe machining generally follows the following principles:

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

② Make the processing route shortest, reduce the empty travel time, and improve the processing efficiency.

③ Try to simplify the workload of numerical calculation and the processing procedure.

④ For some reused programs, subroutines should be used.

What are the components and working steps of CNC machine tools

1. Composition of CNC machine tools

CNC machine tool is composed of program, input / output device, CNC unit, servo system, position feedback system and machine body. Here is a brief introduction.

(1) CNC unit

CNC unit is the core of CNC machine tools, which consists of three parts: information input, processing and output.

CNC unit receives digital information, after decoding, interpolation and logic processing by the control software and logic circuit of the numerical control device, outputs various instruction information to the servo system, and the servo system drives the executive part to move forward. Other signals include speed change, direction change and start stop of main moving parts, tool command signals for selecting and exchanging tools, auxiliary command signals for cooling and lubrication, workpiece and machine tool parts loosening, clamping, indexing table turning, etc.

(2) Servo system

It is composed of a driver and a driving motor, and a feed system of a numerical control machine tool is composed of an executive part and a mechanical transmission part on the machine tool. Its function is to convert the pulse signal from the numerical control device into the movement of the moving parts of the machine tool. For stepping motor, each pulse signal makes the motor turn an angle, and then drives the moving parts of the machine tool to move a small distance. Each actuator of the feed motion has a corresponding servo drive system, and the performance of the whole machine depends on the servo system.

(3) Position feedback system

The feedback of the angle displacement of the servo motor and the displacement of the actuator (table) of the CNC machine tool. Including grating, rotary encoder, laser rangefinder, magnetic grating, etc.

The feedback device converts the detection results into electrical signals and feeds them back to the numerical control device. Through comparison, the deviation between the actual position and the command position is calculated, and the deviation command is issued to control the feed movement of the executive part.

(4) Mechanical parts of machine tools

For CNC machine tools of machining center type, there are also parts such as tool magazine for storing tools, manipulator for exchanging tools, etc. the composition of mechanical parts of CNC machine tools is similar to that of ordinary machine tools, but the requirements of transmission structure are simpler, in terms of accuracy, rigidity, seismic resistance, etc., and its transmission and transmission system is more convenient to realize automatic expansion.

2. Working steps of CNC machine tools

The following steps are required for machining parts on CNC machine tools:

(1) Preparation stage

According to the drawings of machining parts, determine the relevant machining data (tool path coordinate point, machining cutting amount, tool size information, etc.), and select other auxiliary information according to the process plan, selected fixture, tool type, etc.

(2) Programming phase

According to the machining process information, write the NC machining program (the description of the machining process) in the language recognized by the CNC system of the machine tool, and fill in the program sheet.

(3) Prepare information carrier

According to the compiled program list, the program is stored on the information carrier (perforated tape, tape, disk, etc.), and all the processing information is transmitted to the CNC system through the information carrier. If the CNC machine tool is connected with the computer, the information can be directly loaded into the CNC system.

(4) Processing stage

When the program is executed, the CNC system of machine tool will decode and calculate the statement of the processing program, convert it into the action instruction of driving each moving part, drive the timely movement of each moving part under the unified coordination of the system, and automatically complete the processing of the workpiece.

What are the advantages of CNC precision machining

1. Multi axis control linkage: generally, three-axis linkage is the most frequently used, but the machining centers with four, five, seven or more linkage axes can be achieved through some adjustments.

2. Parallel machine tool: common machining centers have fixed functions. They can combine machining centers with turning centers, or vertical and horizontal machining centers, which can increase the machining range and processing capacity of machining centers.

3. Tool damage early warning: by using some technical detection means, the tool wear and damage can be found in time, and the alarm can be given, so that the tool can be replaced in time to ensure the processing quality of parts.

4. Tool life management: it can manage multiple tools working at the same time and multiple blades on the same tool, so as to improve production efficiency.

5. Overload and power-off protection of machine tool: according to the maximum load set according to the load in the production process, when the load reaches the set value, the machine tool can realize automatic power-off and shutdown to protect the machine tool.

What are the general principles of precision parts processing?

1. Benchmark first

That is to say, the datum plane should be processed first. In the process of machining, the surface as the positioning datum should be processed first, so as to provide the precision datum for the subsequent processing as soon as possible.

2. Division of processing stages

The appearance with high machining quality request can be divided into three stages: rough machining, semi finish machining and finish machining. The main purpose is to ensure the processing quality; to facilitate the scientific application of equipment; to facilitate the arrangement of heat treatment process; and to facilitate the detection of blank defects.

3. Face before hole

For the box, bracket, connecting rod and other parts, the plane shall be machined before the hole is machined. In this way, the hole can be machined by plane positioning, ensuring the position accuracy of plane and hole, and bringing convenience to the machining of hole on plane.

4. Finishing

Finishing of main surfaces, such as grinding, honing, finishing, rolling, etc., shall be placed at the end of the process route. The general principle of drawing up the processing route of precision parts and the formulation of the processing procedure of precision parts can be roughly divided into two parts. First of all, it is to draw up the process route of parts processing, and then determine the process size of each process, used equipment and process equipment, cutting specifications, working hours quota, etc.

How to process precision machine parts?

(1) Rough machining stage. Most of the machining allowance of each machining surface shall be cut off and the precision datum shall be machined. The first consideration is to improve the productivity as much as possible.

(2) Semi finishing stage. Remove the possible defects after rough machining, prepare for the finish machining of the surface, require to reach a certain machining accuracy, ensure the appropriate finishing allowance, and complete the processing of the secondary surface together.

(3) Finishing stage. In this stage, large cutting speed, small feed rate and cutting depth are selected to cut off the finishing allowance left by the previous process, so as to make the part surface meet the technical requirements of the drawing.

(4) Finishing stage. It is mainly used to reduce the surface roughness value or strengthen the surface processing. It is mainly used for the surface processing with high surface roughness requirements (RA ≤ 0.32 μ m).

(5) Super fine machining stage. The machining accuracy is 0.1-0.01 μ m, and the surface roughness Ra ≤ 0.001 μ M. The primary processing methods are: fine cutting, fine mirror grinding, fine grinding and polishing.

What are the advantages of precision hardware processing?

1. CNC machining precision of fine metal shaft is high, with stable processing quality;

2. Multi coordinate linkage can be carried out, and parts with disordered shapes can be processed;

3. When the fine hardware CNC machining parts are changed, generally only the NC program needs to be changed, which can save the production preparation time;

4. The machine tool itself has high precision and rigidity. It can choose favorable processing amount and high production rate (generally 3-5 times that of general machine tools);

5. The machine tool has a high degree of automation, which can reduce the labor intensity;

The short cutting tool is the main feature of CNC fine machining. The short cutting tool will obviously reduce the deviation of cutting tool, and then achieve outstanding surface quality, avoid rework, reduce the use of electrode, and shorten the EDM processing time. When considering the five axis machining, it is necessary to consider the principle of using the five axis machining die: finish the whole workpiece machining with the shortest cutting things as possible, also including cutting programming, clamping and machining time, but get more perfect surface quality.

The effect of precision machining technology

Generally in normal temperature processing, and do not cause changes in the chemical or physical phase of the workpiece, called cold processing. Generally, the processing above or below normal temperature will cause chemical or phase change of the workpiece, which is called hot processing. Cold working can be divided into cutting and pressure machining according to different machining methods. Hot working includes heat treatment, casting, casting and welding.

The technological functions of precision machining are as follows:

1. The accuracy of several shapes and orientations of parts can reach micron or angular second;

2. The tolerance of the boundary or feature dimension of the part is below micrometer;

3. The surface micro unevenness (average height difference of surface unevenness) of parts is less than 0.1 μ m;

4. Mutual fittings can meet the requirements of combining force;

5. Some of the parts can also meet the requirements of accurate mechanical or other physical characteristics, such as the torsional rigidity of the torsion bar of the float gyroscope, the rigidity coefficient of the flexible element, etc.

Key technologies of CNC machining and cutting development

In order to reduce the auxiliary time and increase the efficiency, it is required that the starting and stopping time of the main shaft of CNC machine tool CNC Mechanical and electrical engineering be as short as possible, so high starting and stopping plus (minus) speed is required. At present, the start-up and stop acceleration of the main shaft of CNC Mechanical and electrical engineering of overseas machine tools can reach above LG, and the time of full speed start-up and stop is within 1 s.

The CNC mechanical and electrical engineering spindles made by these companies have the following characteristics compared with those made in China: high power and high speed; high-speed and high rigidity bearings are selected; high-speed and high rigidity bearings are selected for overseas high-speed and compact spindles, with the emphasis on ceramic bearings and liquid dynamic and static pressure bearings; air smooth bearings and magnetic bearings are selected for unique scenes; The process level of careful processing and equipment is high; the level of supporting control system is high. These control systems include rotor automatic average system, bearing oil and gas smooth and careful control system, stator and rotor cooling temperature careful control system and spindle deformation temperature compensation careful control system, etc. On this basis, these foreign manufacturers, such as the United States, Japan, Germany, Italy, Switzerland and other industrialized countries, have made a variety of commercialized high-speed machine tools.

Development trend of spindle technology in CNC Mechanical and electrical engineering

Continue to develop towards the goal of high speed and high rigidity

Due to the demand of high-speed CNC machining and essential use, with the development of spindle bearing and its smooth technology, careful machining technology, careful moving average technology, high-speed cutter and its interface technology and other related technologies, the high-speed spindle of CNC Mechanical and electrical engineering for CNC machine tools has become the current development trend, such as CNC Mechanical and electrical engineering for drilling and milling, ibag in Switzerland The speed of hf42 reached 140000 R / min, and that of d1733, a PCB drilling machine of westwind company in the UK, reached 250000 R / min. The main shaft of CNC Mechanical and electrical engineering for machining center was 42000 R / min for Fischer in Switzerland and 75000 R / min for camfior in Italy. In terms of the system rigidity of CNC Mechanical and electrical engineering spindles, the system rigidity of CNC Mechanical and electrical engineering spindles is increasing due to the development of bearings and their smooth technology, which meets the needs of the development of CNC machine tools in high-speed, high-efficiency and precision machining.

Towards the goal of high speed, high power, low speed and high torque

According to the demand of essential application, numerous CNC machine tools can meet the requirements of Heavy CNC machining and high-speed CNC machining at the same time. Therefore, the CNC Mechanical and electrical engineering spindle of machine tool should have the performance of low speed, high torque and high power. The main shaft of CNC Mechanical and electrical engineering for machining centers made by camfior, step Tec of Switzerland and GMN of Germany is satisfactory. It is not difficult for the main shaft of CNC Mechanical and electrical engineering of Cytec of Germany to transmit torque above 200 N · m in low speed section. The main shaft of CNC Mechanical and electrical engineering of CNC milling machine and lathe of Cytec of Germany has reached 630 n · m in large torque, and in high speed section, it is usually at 10-50 kW; The great transmission power of cyteccnc CNC CNC Mechanical and electrical engineering spindle is 50 kW; the great power of Swiss step teccnc mechanical and electrical engineering spindle is 65 kW (S1), which is used for aircraft manufacturing and mold processing; and the report of CNC Mechanical and electrical engineering spindle power reaching 80 kW is more.

Further development to the goal of high precision, high reliability and long working life

Users put forward higher and higher requirements for the accuracy and reliability of CNC machine tools. As one of the core performance components of CNC machine tools, CNC Mechanical and electrical engineering spindle requires higher and higher accuracy and reliability. For example, the radial runout of the main shaft is within 0.001 m m, and the axial positioning accuracy is below 0.5 μ M. At the same time, the service life of CNC Mechanical and electrical engineering spindle has been lengthened and its application reliability has become higher and higher due to the selection of special and careful spindle bearing, advanced smooth mode and unique preload application mode. Step TEC’s CNC Mechanical and electrical engineering spindle is also equipped with acceleration sensor to reduce the vibration acceleration level of bearing. In order to monitor and limit the vibration on the bearing, a vibration monitoring module is installed to prolong the working life of CNC Mechanical and electrical engineering spindle.

The performance and mode diversification of the spindle’s built-in electromechanics in CNC

In order to meet the demand of essential use, the performance of spindle motor in CNC Mechanical and electrical engineering has been improved. For example, the ratio of constant torque and high speed to constant power and high speed (i.e. constant power speed regulation boundary) delivered by Fischer spindle motor in Switzerland has reached 1:14. In the rest, permanent magnet synchronous motor CNC Mechanical and electrical engineering spindles appear. Compared with asynchronous motor CNC Mechanical and electrical engineering spindles of the same power, the appearance size of synchronous motor CNC Mechanical and electrical engineering spindles is small, which is conducive to increasing power density and completing small size and large power rate.

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