Monthly Archive October 15, 2020

Opening: under the maximum load of machine tool, the most cases should choose the largest knife as possible, the maximum feed amount and the fastest feed as possible. In the same case, the feed is inversely proportional to the feed quantity. Generally, the load of machine tool is not a problem. The principle of selecting tool is mainly considered whether the two-dimensional angle and three-dimensional arc of the product are too small. After selecting the tool, the length of the tool is determined. The principle is that the length of the tool is greater than the processing depth. If the large workpiece is involved, the interference of the chuck should be considered.

Smooth knife: the purpose of the smooth knife is to meet the machining requirements of the surface finish of the workpiece and reserve appropriate allowance. Similarly, the light knife is selected as large as possible, and the time is as fast as possible, because the fine knife takes a long time, and the most suitable feed and feed are used. The larger the transverse feed is, the faster the surface feed is, the surface feed quantity is related to the finish after processing, the feeding size is related to the surface shape. In the case of no damage to the surface, the minimum allowance, the maximum knife, the fastest speed and proper feed are reserved.

2、 Clamping method:

1. All clamps are horizontal, vertical and short.
2. Vice Clamp: the height of clamping shall not be less than 10 mm. The height of clamping and machining height must be specified when machining workpiece. The machining height shall be about 5mm higher than the plane of the vise, so as to ensure the firmness and avoid damaging the vise. This kind of clamp is a general clamp, and the height of the clamping is also related to the size of the workpiece. The larger the workpiece, the higher the clamping height will increase accordingly.
3. Clamp: the clamp is coded on the workbench, and the workpiece is locked on the plywood with screws. This clamp is suitable for the workpiece with insufficient clamping height and large processing force. Generally, medium and large workpieces have good effect.
4. Iron clamp: when the workpiece is large and the clamping height is not enough, and it is not allowed to lock the thread at the bottom, the clamp shall be installed with code iron. This kind of clamp needs to be installed twice. The four corners shall be coded first, other parts shall be processed, then four sides shall be coded to process the four corners. When installing the clamp twice, do not let the workpiece loose, code and then loosen. You can also code both sides first and process the other side.
5. Clamping of tools: the diameter is more than 10 mm, the length of clamping is not less than 30mm; the diameter is less than 10 mm, and the clamping length is not less than 20mm. The clamping of the tool shall be firm, and the tool shall be strictly prevented from collision and direct insertion into the workpiece.

3、 Classification and application range of tools:

1. By material:

White steel knife: easy to wear, used for copper and small steel material to open coarse.

Tungsten steel knife: used for angle cleaning (especially steel material) and light knife.

Alloy knife: similar to tungsten steel knife.

Purple knife; used for high speed cutting, not easy to wear.

1. According to the cutting head:

Flat bottom knife: used for flat and straight side, clear plane angle.

Ball knife: used for various surface light, light knife.

Nose knife (unilateral, bilateral and five sides): used for steel material opening (r0.8, r0.3, r0.5, r0.4).

Rough leather knife: used for opening and paying attention to the method of remaining the allowance (0.3).

1. According to the knife rod:

Straight pole knife: straight pole knife is suitable for various occasions.

Inclined pole knife: but not applicable to straight body surface and face with slope less than the bar slope.

1. According to the blade:

The more the number of blades, the better the effect is, but the more work is done, the corresponding adjustment of speed and feed is, and the number of blades has long life.

1. Difference between ball knife and flying knife light knife:

Ball knife: concave ruler is smaller than the ball ruler, and when the plane ruler is less than ball R, the light can not be reached (the bottom angle can not be cleared).

Flying knife: the advantage is to clear the bottom corner. Comparison of the same parameters: v = R * ω has a lot of speed (flying knife), the things out of the force are bright, and the flying knives are used for equal height shape, sometimes the flying knife does not need medium light. The disadvantage is that the concave size and plane ruler are less than the diameter of the flying knife.

4、 CNC works with EDM and copper company:

1. What circumstances need to be made of copper:

If the knife is completely down, it is necessary to be a copper male. In a copper male, there is still something that cannot be lowered. The shape is protruding and needs to be divided again.

The knife can go down, but the knife that is easy to break also needs to be made of copper, which depends on the actual situation.

The products with spark pattern are required to be made of copper.

Copper can not be made, the bone position is too thin and too high, vulnerable and easy to deformation, deformation and spark deformation in processing, so insert is required.

The surface of the East and West (especially the surface will be smooth and even) can overcome many problems in the gong and many problems in the drawing.

If the precise shape or surplus is required, the coarse copper male must be made.

1. Copper company’s practice:

Select the surface to be made of copper, fill the surface to be repaired, or extend the extended surface to ensure that all edges of copper male are larger than the surface to be punched, and the surface of other products will not be damaged. Unnecessary plane angle (deeper glue position is at the intersection of plane angle) shall be removed to form regular shape; find out the maximum shape of copper male, and then project it to the supporting surface with one side boundary; determine the size of reference frame , cut off the supporting surface, and the copper common drawing is basically completed; material preparation: length * width * height, length and width ≥ ymax and xmax are the actual copper material length and width of the reference frame must be larger than the reference frame on the drawing. The theoretical dimension of the high or equal to copper male + the height of the reference frame + the height of the clamp.

5、 Drawing sizing:

1. Under the condition of no ready-made processing surface, the plane is divided into four sides, the center is to the origin, the top face is zero, and the top surface is not normally (for copper male) to leave a margin of 0.1, that is, when the number of collisions is 0 (z), the figure is lower than 0.1.
2. When there are ready-made machining surfaces, make the ready-made face 0 (z) on the drawing, and divide the plane energy into the middle. Otherwise, if the ready-made edge impact number (one side) processing surface is used, the actual height, width, length and drawing difference shall be checked, and the actual material shall be used to program. Generally, the dimensions on the drawing are processed first and then the shape on the drawing is processed

In CNC machine tools, the motorized spindle usually adopts the method of frequency conversion and speed regulation. There are three kinds of control modes: ordinary frequency conversion drive and control, vector control driver drive and control and direct torque control.

Ordinary frequency conversion is scalar drive and control, its drive control characteristic is constant torque drive, output power is proportional to speed. The dynamic performance of ordinary frequency conversion control is not ideal, the control performance is not good at low speed, the output power is not stable enough, and has no c-axis function. But the price is cheap, the structure is simple, and it is used in grinder and ordinary high-speed milling machine. The vector control technology imitates the control of DC motor, orients the rotor magnetic field and realizes the drive and control by vector transformation, which has good dynamic performance. The vector control driver has a large torque value when it is just started. In addition, the motorized spindle has a simple structure and small inertia, so the starting acceleration is large, which can realize the instantaneous allowable limit speed after starting. The latter can realize position and speed feedback, which not only has better dynamic performance, but also can realize c-axis function; while the former has poor dynamic performance and does not have c-axis function, but its price is relatively low.

Direct torque control (DTC) is a new type of High-Performance AC speed regulation technology developed after vector control technology. Its control idea is novel and the system structure is simple and clear. It is more suitable for the drive of high-speed motorized spindle. It can meet the requirements of dynamic and static characteristics of high-speed motorized spindle with high speed, wide speed range and high-speed instantaneous stop. It has become the field of AC drive A hot technology.

Scope of application:

Granite, marble, bluestone, sandstone and other stone carving

Granite and other hard stones can be carved to 5mm in layers

Marble and bluestone can be carved to 5mm at a time

1. Stepper driver + stepper motor

Stepping system is the most used drive system in the market at present, the most popular is the three-phase hybrid stepping motor, which accounts for more than 90% of the market share. The reason is that the price is cheap, and the effect is good when equipped with the lassico subdivision driver. However, the defects are also obvious, such as resonance, noise, increased speed, reduced torque, easy to lose step when working for a long time, and excessive temperature rise of motor.

1. Hybrid servo driver + motor

The use of hybrid servo has not been popular in China. There are many reasons for this. There are not many foreign manufacturers of hybrid servo. Compared with AC servo, the price has no great advantage, so it can only be used in some special industries. The improvements include: improving high speed performance, reducing heating and resonance.

1. AC servo driver + AC servo motor

The use of AC servo in engraving machines is still relatively small, mainly because of the high price. In addition, the application of AC servo has certain requirements for the structure, electrical appliances, control system and transmission system of the machine tool. Just like the barrel principle, the shortest board determines the amount of water in the barrel. Therefore, the AC servo is generally applied to high-end models. AC servo has: fast response, high torque, high speed, high precision, less heating, long-time work, complete alarm system, etc. Disadvantages: different equipments need different servo parameters. High level technical engineers are required to adjust the parameters

The processing procedure of self inspection of computer gong 1. The processor must see the contents of process card before processing, know the parts, shape, drawing dimensions of the workpiece to be processed and know the processing contents of the next process. 2. Before clamping, the blank size shall be measured to meet the requirements of the drawing. When clamping, it is necessary to carefully check whether the placement of workpiece is consistent with the programming operation instruction. 3. After rough machining, self inspection shall be carried out in time to adjust the error data in time. The self inspection content is mainly the position dimension of the processing part. For example: (1) whether the workpiece is loose; (2) whether the workpiece is correctly divided; (3) whether the dimension from the processing part to the reference edge (reference point) meets the requirements of the drawing; (4) the position dimension between the processing parts. After checking the position dimension, the rough machined shape ruler shall be measured (except for circular arc). 4. After rough machining, the finishing can be carried out only after self inspection. After finishing, workers shall check the shape and dimension of the processed parts: check the basic length and width dimensions of the processing parts of the vertical plane; measure the base point dimension on the drawing for the machining parts of the inclined plane. 5. The workers can remove the workpiece and send it to the inspector for special inspection after they have completed the self inspection of the workpiece and confirmed that they are in conformity with the drawings and process requirements. High speed CNC is based on the characteristics of digital control technology. Because the effective control machine tool adopts servo motor and digital technology realizes the direct control of the working sequence and movement displacement of the parts executed by the machine tool, the transmission structure of traditional machine tool is cancelled or partially cancelled, so the mechanical structure also greatly simplifies the digital control, and requires the mechanical system to have high transmission rigidity and no transmission clearance To ensure the implementation of control instructions and the realization of control quality. At the same time, with the continuous improvement of computer level and control ability, it is possible to allow more functional parts to perform all kinds of auxiliary functions required at the same time on the same machine tool. Therefore, the mechanical cutting of CNC machine tool has higher integration function requirements than traditional machine tools. From the perspective of the requirements of manufacturing technology development, with the emergence of new materials and new processes, and the market competition for low cost requirements, metal cutting is developing towards the direction of higher cutting speed and precision, higher production efficiency and more reliable system. This requires that the CNC machine tools developed on the basis of traditional machine tools have higher precision, more driving power, better static and thermal stiffness of mechanical mechanism, more reliable work, and can achieve continuous operation and as little downtime as possible. The mechanical structure of the typical CNC milling machine is mainly composed of the basic parts, the main transmission system, the feed transmission system, the rotary table and other mechanical function accessories. The foundation of CNC milling machine is usually the structural parts of bed, column, beam, workbench and base. The size of the basic parts is large (commonly known as large piece), and the well constitutes the basic frame of the machine tool. Other components are attached to the base member, and some parts also need to move along the base member. Because the foundation plays a role of support and guidance, the requirements for the foundation are good stiffness

The importance of CNC machining spindle 1. The parameters of input starting point shall be reviewed in high-speed CNC processing. It is strictly forbidden to knock or impact the rotor end of spindle motor during operation. The operator is required to pay attention to the starting point of z-axis when aligning the tool to prevent misoperation. To avoid the impact and knife binding phenomenon in the operation process, the bearing of the spindle motor will be damaged. Once there is a phenomenon of knife binding, stop the machine immediately to prevent the bearing from causing more damage due to high-speed operation. Then, start running in from low speed, and the time is slightly longer than normal running in time, until the motor is running smoothly and normally before starting to work. 2. To ensure the motor cooling cycle system of the carving and milling machine works normally, before starting the machine. Then turn on the spindle motor, and it is strictly forbidden to use the spindle motor without cooling. The working environment temperature should not be higher than 30 ℃, when the ambient temperature is higher than 30 ℃, air conditioning shall be used, or forced cooling of the main shaft motor shall be performed by using a refrigerator. 3. The spindle motor of high speed CNC machining shall be preheated step by step according to the principle of running from low speed to high speed. When the motor reaches the required speed and the no-load operation is stable and the temperature is cooled, the machining can be carried out, so as to ensure the better machining accuracy. 4. When planning the cutter path, it is necessary to ensure the reasonable force on the spindle motor and carve according to the principle of knife provided by the technical service personnel. It is necessary to prevent vertical cutting, and it is strictly forbidden to overload the spindle motor, so as to ensure the normal service life of the spindle motor. 5. Generally, the spindle motor should be disassembled and reassembled for about one year, so as to ensure the bearing accuracy and extend the service life. In order to ensure the normal and good operation of the spindle motor, the assembly and assembly of the spindle motor must be carried out by experienced professional operators, in a clean environment and with appropriate tools. Do not knock it randomly. For the temporarily unused spindle, the residual water in the water chamber shall be blown out with compressed air, and the sleeve and shaft hole of shaft head shall be oil protected and put in a cool and dry place. 6. The high speed CNC processing water quality must be clean, and the cooling water of spindle motor uses pure water. In order to prevent the occurrence of microorganism and scale, water should be changed every seven days under normal conditions. When the surrounding environment is higher than 30 ℃ and there is no forced cooling measures, the purified water should be replaced once a day when the water temperature is the highest. In addition, operators should develop the habit of observing the water temperature during work, and change water when the water temperature exceeds 30 ℃

When engaged in precision machining, carefully do the following before work:

1. Carefully read the shift records to understand the operation and existing problems of the machine tool in the previous shift.
2. Check that the safety protection, brake (stop), limit and reversing devices are complete and in good condition.
3. Check the exposed guide rail surface, sliding surface, rotating surface and worktable of the machine tool. If there are tools, obstacles, impurities, oil stains and chips in the work center of computer gongs processing plant, they must be cleaned, wiped and oiled.
4. Check that the oil quantity of the oil storage part of the lubrication system meets the requirements and the sealing is good. The oil mark, oil window, oil cup, nozzle, oil line, felt, oil pipe and oil distributor shall be complete and in good condition and installed correctly. According to the performance requirements of lubrication diagram, carry out manual oil filling or motor-driven pump oiling, and check whether oil is coming from oil window in large gantry machining center.
5. Check whether there are new pulling, grinding and bumping on the working table, guide rail surface and main sliding surfaces of the machine tool. If any, inform the team leader or equipment personnel to check together and make records.
6. Check that the mechanical, hydraulic and pneumatic operators, such as C, valve, switch should be in the non working position.
7. Check that the electrical distribution box should be closed firmly and the electrical grounding is good.
8. If the machine tool is shut down for more than one shift, it shall run in idle for more than five minutes according to the operation procedures and requirements specified in the manual and the use of hydrostatic device.

1、 Acceptance requirements

1. Appearance inspection

(1) Check whether the finish of machined parts meets the drawing requirements.

(2) Check whether the surface of machined parts is damaged, rusted and bruised, and whether the thread shape and angle are correct.

(3) If the above problems are found, detailed records shall be made for future reference.

1. Quantity acceptance

(1) Based on the supply contract and processing voucher, check the material, specification and quantity of processed parts strictly against the drawings, and check them one by one.

(2) Make a record of quantity acceptance, indicating the place, time, participants, type, product name, quantity to be arrived and actually arrived.

1. Quality acceptance

(1) Assembly shall be carried out in strict accordance with the requirements and procedures of the general assembly drawing.

(2) Record carefully during quality acceptance. In case of quality problems of machined parts, the outsourcing processing unit shall be informed of the details in writing. Decide whether to return or replace according to the situation.

(3) In case of special requirements, the processing unit can be consulted for joint acceptance and assembly, and the acceptance documents can be signed after the installation is qualified.

2、 Acceptance procedure

1. After the processing parts of large mechanical parts are received, the full-time acceptance personnel shall be sent to check and accept the material, specification, model and quantity of the processed parts according to the requirements of the contract drawings.
2. The acceptance period is generally 1-2 days. The special situation depends on the effect of use. In case of quality problems, we can return the products to the processing unit, claim for compensation, and bear the economic losses of the processing unit.
3. Generally, the processing contract signed by the non production department will be directly accepted by the user department, and the acceptance report will be filled in.
4. If the unqualified parts are accepted by experience, the acceptance personnel must handle the maintenance and return procedures within the specified acceptance period.
5. For the acceptance of special precision machining parts, the full-time acceptance personnel shall organize relevant personnel for joint acceptance, and fill in the acceptance report in detail. For the unqualified parts, fill in the inspection form in detail. CNC machining is the condition to improve the machining accuracy and determine the selection direction of the parts outsourcing manufacturer in the future.

The main reason for the failure of plastic mold is due to improper heat treatment process, such as heating temperature, holding time, cooling speed and so on. Plastic mold in the process of processing, cracks or deformation, surface oxidation and decarburization phenomenon, is mainly because the mold failure.

First of all, on the impact of oxidation and decarburization, mainly because the mold quenching is stopped at high temperature, but can not be strictly controlled. In addition, after decarburization on the surface of the die, quenching cracks are caused due to the difference of microstructure between the inner and outer layers and the larger structure stress during cooling.

The second is about the rate of heating. Because the die steel contains more carbon and alloy elements and poor thermal conductivity, the heating speed should not be too fast and should be stopped slowly to avoid deformation and cracking of the die. In order to avoid oxidation and decarburization during heating and quenching in air furnace, the heating speed should not be too fast and the diathermy should be slow.

The above will not produce large thermal stress, relatively safe. If the heating speed of the mold is fast and the diathermy is fast, the thermal stress inside and outside the mold will be very large. If the control is not good, such as deformation or crack, it is very easy to occur, in the prevention, it is necessary to use preheating or slow down the heating rate.

Due to the large size of the worktable and die, it must be able to meet the requirements of large-scale worktable and die, In addition, small diameter end mills with large elongation are often used to process the mold cavity, so chatter is easy to occur in the processing process.

In order to ensure the machining accuracy and surface quality of parts, the high-speed universal milling machine manufactured by mould must have high dynamic and static stiffness to improve the positioning accuracy, tracking accuracy and anti vibration ability of the machine tool.

High speed and high-power high-speed machining is the development direction, high-speed milling has shown great advantages in mold processing. In order to adapt to the processing of the mold cavity surface, the radius of the tool should be less than the minimum radius of the cavity surface, so as to avoid “interference” between the tool and the workpiece. Because of the small diameter of the tool, the spindle speed is required to be very high. The main shaft speed of foreign high-speed machine tools has reached 40000-100000 R / min, and the rapid feed speed can reach 30000-60000 min. The rough and finish machining of the cavity and other parts of the mold parts is often completed in one-time clamping of the workpiece, so the spindle power should be high. The spindle power of the medium-sized mold milling machine and machining center is usually 10-40kw, some even higher.

The die cavity is composed of complex six curved surfaces and grooves, and many dies have deep cavity. In order to achieve high precision, high speed and high stability machining of 3D surface, the machine tool needs multi axis linkage, and has good comprehensive cutting ability of deep hole cavity. Five axis linkage machining center can be used, in addition to the linear motion of three coordinates, there are also two rotation coordinates of feed motion. The milling head or worktable can realize continuous rotary feed by multi axis linkage, so it is suitable for machining mold parts with complex cavity surface. It can be said that compound machining is one of the development directions of mold processing.

Processing center is written language, English Name: CNC machining center; computer gong is a common saying, more in Hong Kong, Taiwan and Guangdong. In this area, milling machines are called gongs when they are in the machining center, so milling machines are also called gongs, and computer gongs are also derived from this. Computer gongs, as the name implies, are gongs controlled by computers, so they are also called CNC milling machines. In fact, they are upgraded from CNC milling machines. The original principle is the same. The difference is that the machining centers use good materials with high precision, high speed and load The traditional CNC milling machine is half cover type, and most of the machining center has been changed to full cover type, which is more safe for processing and can effectively prevent the overflow of iron chips and the splashing of chips. Computer gong is an automatic machine tool equipped with program control system. The control system can process and decode the program with control code or other symbol instructions logically, so that the machine tool can move and process parts. Also known as CNC machining mold or CNC machine tools.

The computer gong can be divided into two parts, the body part and the system part.

Fuselage part:

1) Casting, which is the most important part of computer gongs, directly affects the accuracy, stability, wear resistance and the life of machine tools. After the casting is finished, it is not immediately used in production. A good casting is that it is subjected to wind and rain, sunlight exposure, natural weathering, and some of them are soaked in sea water. After the casting does not change, the machine tool is not easy to change and can maintain the stability and accuracy of the machine tool for a long time.

2) Spindle, the spindle is used to directly face the workpiece. It is driven by the motor to rotate at a high speed. If the tool holder is installed on the spindle, the workpiece can be cut to meet various production needs. The quality of the spindle will also directly affect the machining accuracy. If the internal bearing is worn, it will easily cause the spindle to swing, and the accuracy of the processed things will naturally have a deviation of several wires 。 At present, the speed of the spindle is generally around 8000 rpm, and the high-speed machine can achieve more than 20000 revolutions. Each machine has only one spindle.

3) Screw rod is also a machine