January 2021 – Page 3 – CNC Machining & Turning, Milling, Metal parts

Basic principle of CNC high speed milling machine

The basic principle of high-speed CNC milling machine high-speed CNC electrochemical machining is to use the principle that the metal in the electrolyte can produce anodic dissolution under the condition of applied DC voltage, and the milling center can control the metal In electrochemical machining, the workpiece is connected to the positive pole of DC power supply, and the milling machine tool electrode is connected to the negative pole of DC power supply. The high voltage electrolyte flows through the narrow gap between the two poles, and the product dissolved by the anode is taken away by the fast flowing electrolyte in time. With the continuous erosion of anode material, the gap between the two poles of milling machine will increase. In order to maintain the rapid dissolution of the workpiece, the tool electrode of the gantry milling machine will continuously feed the workpiece, so that the gap between the two poles can maintain an optimal distance. The corresponding surface of the milling machine workpiece is processed into the same inverse shape as the cathode surface.

The combination of high speed CNC manual and CAM programming. The efficiency and correctness of NC programming can be greatly improved by making full use of the programming modules provided by the relevant NC machine system, such as NC milling rectangular groove, U-shaped groove, drilling cycle, NC turning end face, cylindrical cycle processing, EDM electrode shaking processing function, and expert selection of discharge process parameters in WEDM.
High speed CNC chooses reasonable CAM programming strategy. In the process of building the product processing model, we should take effective and simple measures according to the specific characteristics of the product processing object. Lathe CNC processing materials usually use lathe processing materials for free cutting steel and copper, free cutting steel with high sulfur s and phosphorus P material, sulfur and manganese exist in the form of manganese sulfide in the steel, and manganese sulfide plays a lubricating role in the steel, making the steel easier to cut, so as to improve the production progress of lathe.

The safe operation rules of large computer gong processing must comply with the safe operation rules of large computer gong processing center

Before the processing of large computer gongs, it is required to wear protective equipment, tie up cuffs, and do not wear scarves, gloves, ties or aprons. Female workers should wear braids in their hats.
Check whether the tool compensation, machine zero and workpiece zero are correct before starting the machine.
The relative position of each button shall meet the operation requirements. Work out and input NC program carefully.
To check the equipment protection, insurance, signal, position, mechanical transmission part, electrical, hydraulic, digital display and other system operation, in all normal circumstances can be cutting.
Before the large-scale computer gong is processed, the machine tool should be put into trial operation, and the operation conditions of lubrication, mechanical, electrical, hydraulic, digital display and other systems should be checked. Cutting can be carried out under normal conditions.
After the machine tool enters the processing operation according to the program, the operator is not allowed to contact the moving workpiece, cutting tool and transmission part, and is not allowed to transfer or take tools and other items through the rotating part of the machine tool.
When adjusting the machine tool, clamping the workpiece and cutter, and wiping the machine tool, the machine must be stopped.
Tools or other articles shall not be placed on electrical appliances, operating cabinets and protective covers.
It is not allowed to remove the iron filings directly by hand. Special tools should be used.
In case of abnormal situation and alarm signal, stop the vehicle immediately and ask relevant personnel to check.
Large computer gong processing is not allowed to leave the work post when the machine is running. If you want to leave for some reason, put the worktable in the middle position and return the cutter bar. You must stop the machine and cut off the power supply of the main machine. The safe operation rules of large computer gong processing must comply with the safe operation rules of large computer gong processing center
Before the processing of large computer gongs, it is required to wear protective equipment, tie up cuffs, and do not wear scarves, gloves, ties or aprons. Female workers should wear braids in their hats.
Check whether the tool compensation, machine zero and workpiece zero are correct before starting the machine.
The relative position of each button shall meet the operation requirements. Work out and input NC program carefully.
To check the equipment protection, insurance, signal, position, mechanical transmission part, electrical, hydraulic, digital display and other system operation, in all normal circumstances can be cutting.
Before the large-scale computer gong is processed, the machine tool should be put into trial operation, and the operation conditions of lubrication, mechanical, electrical, hydraulic, digital display and other systems should be checked. Cutting can be carried out under normal conditions.
After the machine tool enters the processing operation according to the program, the operator is not allowed to contact the moving workpiece, cutting tool and transmission part, and is not allowed to transfer or take tools and other items through the rotating part of the machine tool.
When adjusting the machine tool, clamping the workpiece and cutter, and wiping the machine tool, the machine must be stopped.
Tools or other articles shall not be placed on electrical appliances, operating cabinets and protective covers.
It is not allowed to remove the iron filings directly by hand. Special tools should be used.
In case of abnormal situation and alarm signal, stop the vehicle immediately and ask relevant personnel to check.
Large computer gong processing is not allowed to leave the work post when the machine is running. If you want to leave for some reason, put the worktable in the middle position and return the cutter bar. You must stop the machine and cut off the power supply of the main machine.

CNC computer gong processing competition

As soon as the machining center is launched, it is welcomed by the industry users. After ten years of rapid development, the vertical machining center industry in China has over expanded the market, and the situation of oversupply has intensified the competition among enterprises.

According to the survey of factory stores, a famous vertical e-commerce platform in China, there are thousands of vertical machining center manufacturers in China, most of which are small and medium-sized enterprises. Most of them have no funds for R & D and produce almost the same products. Because of this, the competition among peers is more fierce, and the price war is the main one. In the face of price competition, manufacturers will lose market share or profits no matter whether they adopt the method of “you lower and I lower” or stick to the price.

Is there no way for vertical machining center enterprises

Of course not. The person in charge of the machine tool factory said in an interview with the media a few days ago that e-commerce is the only way out for enterprises in the current situation. Indeed, industry experts agree. E-commerce can be favored by enterprises mainly because of the following factors:

Low promotion cost

Compared with the cost of traditional exhibitions, magazines, newspapers and TV promotion, the cost of e-commerce is nothing. Take the widely acclaimed pay per effect mode of machine tool factory stores as an example. The way of no transaction and no charge has saved a lot of money for many enterprises. This mode has attracted a large number of international brands of machine tools. Mazak and Doosan have settled in. What are you waiting for!

Not limited by time and space

Processing center manufacturers can conduct e-commerce without the limitation of time and space.

Higher profits from direct sales of manufacturers

Generally speaking, manufacturers mainly sell vertical machining centers through agents, and a large part of product profits are taken away by middlemen. If we can get rid of the agent link and realize the direct sales of manufacturers, the manufacturers can directly face the users of vertical machining center and naturally enjoy all profits. The suppliers in the machine tool shop are all real machine tool manufacturers. The direct selling mode ensures that the vertical machining center suppliers can enjoy the most profits.

The difference of CNC machining center

Do you know the characteristics of vertical machining center and horizontal general machining center? Today CNC machining will introduce the differences and similarities of various machining centers.

1) Horizontal machining center

Horizontal machining center spindle machining center and horizontal state, usually with an automatic index turntable, it generally has three to five coordinate movement, common is three linear movement coordinates and coordinate rotation movement, workpiece card, in addition to the installation is completed, the remaining four surface treatment of the top, it is the most suitable to add body parts. In contrast, vertical machining center and horizontal machining center are easy to remove and handle chips, but the structure is complex.

2) General machining center

The general spindle machining center is a machining center which can control the change of the connecting rotation axis by processing the angle of the worktable to complete the machining of complex space surface.

It is suitable for the processing of impeller, rotor, mold and cutter with complex space surface, and other forms of centralized processing, which is extended to other types of CNC machine tools, such as turning center. It is equipped with multiple automatic tool changing devices in CNC lathe, which can control three or more coordinates. In addition to rotation, the spindle can stop or index, and the cutter can rotate milling, drilling, reaming and tapping process, Suitable for dealing with complex rotating parts.

3) Vertical machining center

Vertical machining center refers to the state of the spindle is vertical machining center, its structure is fixed column, the worktable is rectangular, no indexing rotation function, suitable for processing plate, plate part, it usually has three linear motion axis, can also be installed in the worktable along the horizontal axis rotation of the rotary table, screw part for processing.

Vertical machining center card is convenient, easy to operate, easy to observe processing conditions, debugger is easy, widely used.

However, due to the limit of column height and the change of tools, parts, cavities or concave sides can not be processed, and the chips are not easy to be discharged. In serious cases, the tools are damaged and the processing surface is damaged, which affects the smooth processing.

CNC computer gong processing mold precision concept

Strengthen the understanding of mold precision concept

Die is a kind of precision forming tool used for batch forming, stamping and other products. Mold accuracy includes the accuracy of parts obtained in processing and the quality awareness of ensuring the accuracy of products in production, but generally speaking, mold accuracy mainly refers to the accuracy of working parts of mold.

① The concept of precision in mold processing refers to the degree of conformity between the actual geometric parameters and the design geometric parameters after the mold parts are processed and assembled.

② The concept of precision in mold production refers to a thinking mode and a quality consciousness formed gradually by enterprise employees in production practice to guide their production behavior. That is to say, the quality consciousness of grasping product precision is always carried out in the behavior of enterprise employees.

The mold precision includes four aspects: dimension precision, shape precision, position precision and surface precision. Because the mold is divided into two parts: upper mold and lower mold, the position accuracy between the upper mold and the lower mold is the most important among the four kinds of accuracy.

When the machining accuracy is very high, the mold often has more than enough force. Now the precision of a very good precision mold is about 0.1 ~ 0.01mm. Compared with the previous mold, the precision has been greatly improved. However, components such as engines require an accuracy of less than one thousandth of a millimeter, or even less. Therefore, it is impossible to completely replace cutting with mold now.

Difficulties in CNC machining stainless steel parts

The main difficulties are as follows: 1. Large cutting force, high cutting temperature of mechanical parts; high strength of this type of material, large tangential stress and plastic deformation during cutting, so the cutting force is large. In addition, the extremely poor thermal conductivity of the material causes the cutting temperature to rise, and the high temperature is often concentrated in the narrow area near the cutting edge, thus speeding up the tool wear.

Severe work hardening of stainless steel parts — austenitic stainless steel and some high temperature alloy stainless steel are austenitic structure, and the tendency of work hardening is large when cutting, which is usually several times of that of ordinary carbon steel. Cutting tools in the work hardening area shorten the tool life.
Stainless steel parts are easy to stick to the tool when machining — both austenitic stainless steel and martensitic stainless steel have the characteristics of strong chip and high cutting temperature. When the strong and tough chips flow through the rake face in the machining of Dongguan Mechanical parts, there will be adhesion, fusion welding and other adhesion phenomena, which will affect the surface roughness of the machined parts.
The tool wear of stainless steel parts is accelerated – the above materials generally contain high melting point elements, high plasticity and high cutting temperature. CNC machine tool processing accelerates the tool wear, and tool grinding and changing are frequent, which affects the production efficiency and improves the tool cost.

Precision inspection technology of CNC parts processing

In the selection of CNC complex parts processing, the best way, of course, is through a variety of ways to compare, so as to select the best quality CNC. Optical aspheric surface testing technology should be able to quickly judge the surface error in the process of mirror processing, give further correction instructions by random feedback, and solve the final inspection of parts.

At present, the most widely used method of aspheric surface measurement is light wave interferometry, which has higher measurement accuracy and better spatial resolution. It can measure the whole surface quickly, and the highest resolution can reach sub nanometer level. But for different optical aspheric surfaces, the corresponding optical template must be prepared to measure. The structure of this measurement system is usually very complex.

Aspheric surface can be measured by holographic interferometry, but a hologram must be made whether standard aspheric surface or CGH is used, and there must be corresponding holograms for aspheric surface with different equations. But up to now, the domestic technology of making hologram is only limited to some traditional technology, and the hologram for ultra precision measurement of aspheric surface basically depends on imports, which greatly limits the testing and processing of optical aspheric parts. At present, it costs about US $10000 to import a hologram for ultra precision measurement of aspheric surface, and we need to tell each other the equation of aspheric surface. For the model task, it involves confidentiality and other issues. Especially for some pre research or in research projects and unformed projects, due to the large variety and quantity of aspheric surfaces involved, the cost is very considerable, so it is urgent to develop the hologram for aspheric surface measurement.

At present, the most advanced technology abroad is to use computer generated hologram ram for aspheric surface measurement and laser writing system to make hologram, which not only greatly reduces the production cost, but also shortens the production cycle. The most typical prototype is the laser plotter clws300 laser engraving system developed by Stuttgart University in Germany. The diameter of laser recording point is 0.5 μ m, the positioning accuracy of radial coordinate is 0.08 μ m (RMS), and the positioning accuracy of angular direction is 0.1s “(RMS).

The high precision laser engraving system mainly includes the following aspects

Optical part: including laser, acousto-optic modulator, auto focusing system and the overall design and layout of optical path, etc;

Mechanical part: high precision air bearing, high precision motion guide rail, vibration isolation platform, etc;

Electric control part: motion and positioning control of high-precision mechanical system, laser, modulator and automatic focusing control, including coordination control of mechanical and optical systems

Method of deburring in CNC machining

This is to use electric energy and chemical energy to dissolve the anode and remove the burr. The anode is between the part and the positive pole of the DC power supply, and the cathode is between the forming tool and the negative pole of the DC power supply. There is a certain gap between the two poles to make the electrolyte circulate. When the anode and cathode are immersed in the solution and charged with direct current, the electrochemical reaction occurs on the anode surface, the dissolved metal and electrolyte form viscous liquid on the part surface, which is concentrated in the low concave part of the part surface, with higher resistance and less corrosion; while the burr protrudes from the part surface, under the influence of temperature difference, the liquid film is difficult to form, and the power line is highly concentrated in the burr after power on The burr nearest to the cathode will be dissolved at the fastest speed until the burr is completely dissolved, and the edge will gradually form a fillet, that is to achieve the purpose of deburring.

Electrolytic deburring machine can be used. When the production batch is not large, the rectifier can be used to convert alternating current into direct current to make simple equipment. According to the structure of the parts, the special fixture (tool cathode) with similar shape to the parts is made of brass or red copper and other conductive materials, and the unprocessed parts are coated with epoxy resin for isolation and protection. The commonly used electrolytes are NaCl, NaNO2 > and NaNO3.

This method is suitable for non-ferrous and ferrous metal parts, especially for parts with complex shape, inner holes, cross holes and inner surface burr which are difficult to remove by mechanical and manual methods. It can remove burr of extra hard parts such as molybdenum, nickel, titanium and quenched parts. The cleaned metal parts will be put into chemical solution (50 ℃), and the metal on the surface of parts will be transferred to the solution in the form of ions. These ions gather on the surface of the workpiece and form a layer of mucus film with high resistance and low conductivity by chemical reaction to protect the workpiece surface from corrosion, while the burr protrudes from the surface and the chemical action will remove the burr. When processing, only one slot is needed. According to different deburring materials, different chemical solutions are used. The main components of the base can be hydrochloric acid, phosphoric acid, sulfuric acid, dihydroxyaniline hydrochloride and water. Chemical deburring is suitable for small metal parts, which can remove the small burr with thickness less than 0.07 mm.

Milling: refers to the use of rotating multi edge tool cutting workpiece, is an efficient processing method. When the tool rotates (as the main motion) and the workpiece moves (as the feed motion), the workpiece can also be fixed, but at this time the rotating tool must also move (complete the main motion and feed motion at the same time). Milling machines include horizontal or vertical milling machines, as well as large gantry milling machines. These machine tools can be ordinary machine tools or CNC machine tools.

Main processing objects:

1) Plane parts

The characteristics of plane parts are that the surface can be parallel to the horizontal plane, or perpendicular to the horizontal plane, or at a fixed angle with the horizontal plane; at present, the vast majority of parts processed on the CNC milling machine belong to plane parts, and plane parts are the simplest type of parts in CNC milling, generally only need to use the two-axis linkage or three-axis linkage of the three-axis CNC milling machine Linkage can be processed. In the process of machining, the machining surface is in contact with the cutter, and the end milling cutter or nose cutter can be used for both rough and finish machining.

(2) Surface parts

The feature of curved surface parts is that the machined surface is a space curved surface. In the process of machining, the machined surface and the milling cutter are always in point contact. Ball end milling cutter is often used for surface finishing

Process classification of CNC machining parts

The process is to change the shape, size, relative position and nature of the production object on the basis of the process, so as to make it into finished or semi-finished products. It is the detailed description of each step and each process. For example, as mentioned above, rough machining may include blank manufacturing, grinding and so on, and finish machining may be divided into turning, fitter, milling machine, and so on. Each step requires detailed data For example, how much roughness and tolerance should be achieved. According to the product quantity, equipment conditions and workers’ quality, technicians determine the process to be adopted, and write the relevant contents into process documents, which are called process procedures. This is more targeted. Every factory may be different, because the actual situation is different. Generally speaking, the technological process is the program, the processing technology is the detailed parameters of each step, and the technological procedure is the specific processing technology compiled by a factory according to the actual situation.

Machining process includes: five axis machining, ceramic machining, chemical numerical control machining, electrical discharge machining, electrical discharge drilling, numerical control titanium, emergency construction / on-site machining, casting machining, grinding, micro machining (micro parts machining), plastic machining, turning, spiral machining, Swiss turning, CNC machining, etc.

The reduction of loading times avoids the error accumulation caused by positioning datum conversion. At the same time, most of the current turn milling compound processing equipment has the function of on-line detection, which can realize the in-situ detection and precision control of the key data in the manufacturing process, so as to improve the processing accuracy of the product; the high-strength integrated bed design improves the gravity processing ability of the difficult cutting materials; the high-strength integrated bed design improves the processing ability of the hard cutting materials; The machine is equipped with an automatic feeding device, which can realize automatic feeding for continuous operation and basically realize the assembly line operation of a single machine.

Reduce floor space and production cost.

Compact and beautiful shape design, improve the space utilization, maintenance and repair more convenient, so that customers get the maximum satisfaction; Although the single unit price of turn milling compound processing equipment is relatively high, due to the shortening of manufacturing process chain and the reduction of equipment required for products, as well as the reduction of the number of fixtures, the floor area of workshop and equipment maintenance costs, it can effectively reduce the investment, production operation and management costs of the overall fixed assets.

Shorten the manufacturing process chain and improve production efficiency.

It can install a variety of special tools, new tool layout, reduce the tool change time, improve the processing efficiency, turn milling composite processing can achieve a clamping to complete all or most of the processing procedures, thus greatly shortening the product manufacturing process chain. In this way, on the one hand, the auxiliary production time caused by the change of clamping is reduced, and the fixture manufacturing cycle and waiting time are also reduced, which can significantly improve the production efficiency.

Flexible shaft machining

When turning long and thin parts that cannot be supported in the middle, turning milling can prevent the parts from bending. Compared with turning, in theory, milling can cut parts under very small pressure. But in fact, a lot of technical problems need to be solved.

Long time processing

In the cutting of difficult to machine materials, the service life of a turning tool is very short, and the milling cutter can be used for a long time because it distributes the cutting load through multi edge cutting. Because the milling cutter has a long service life, it can save the trouble of changing the cutter many times during cutting.

Discontinuous cutting

Turning tools are usually not very good for discontinuous cutting, while milling tools can do very well. Milling is often defined as a kind of discontinuous cutting. Therefore, in the case of discontinuous cutting, it should be thought of turning to turn milling.

Excellent chip breaking process

It has been proved by many machining practices that turning milling instead of turning can eliminate the “bird’s nest” chip phenomenon in the past. Because the milling process with the advantage of natural chip breaking is combined in cutting, the continuous chips are broken into small pieces which are easy to be eliminated

Machining characteristics of CNC high speed computer gong

Processing characteristics of high speed CNC computer gong

Reasonable selection of equipment. High machining accuracy is required. Roughing is mainly to cut off most of the machining allowance. Rough machining should be carried out on the machine tool with high power and low precision, while finish machining should be carried out on the machine tool with high precision.
In order to ensure the machining accuracy, rough and finish machining should be carried out separately. The amount of cutting is large, because when rough machining. For some parts with high machining accuracy. After roughing and before finishing, low temperature annealing or aging treatment should be arranged to eliminate the internal stress. The cutting force and clamping force of the workpiece are large, the calorific value is large, and there is a significant work hardening phenomenon on the surface of the workpiece. There is a large internal stress in the workpiece. If the rough and rough machining is carried out continuously, the precision of the finished part will be lost quickly because of the redistribution of the stress.
Heat treatment process is often arranged in machining process. In order to improve the mechanical properties of parts, quenching and tempering are generally arranged after machining. The location of heat treatment process is as follows: in order to improve the cutting performance of metal, such as annealing, normalizing, quenching and tempering, it is generally arranged before machining. In order to eliminate the internal stress, such as aging treatment, quenching and tempering treatment, it is generally arranged after rough machining and before finishing.

Requirements of power supply for CNC machine tools

The power supply is the energy support part to maintain the normal operation of the system. The direct result of its failure or failure is the shutdown of the system or the destruction of the whole system. In addition, some operation data, setting data and processing programs of the CNC system are generally stored in the RAM memory. After the power failure of the system, they are maintained by the backup battery or lithium battery of the power supply. As a result, the downtime is relatively long, plug power or memory may cause data loss, so that the system can not run.

At the same time, because the CNC machine tool uses three-phase AC 380V power supply, so the safety is also an important part of the pre installation work of CNC equipment

The fluctuation of power grid voltage should be controlled between + 10% and – 15%. However, the fluctuation of power supply in China is large, the quality of power supply is poor, and the interference such as high-frequency pulse is hidden, plus human factors (such as sudden switch off, etc.). During the peak period of electricity, such as about an hour before going to work or leaving work in the daytime and at night, there are often more out of tolerance, even up to ± 20%. It makes the machine alarm and cannot work normally, and damages the power supply system of the machine. It even leads to the loss of parameter data. This phenomenon has happened in CNC machining center or turning center, and the frequency is high, so we should pay attention to it.

It is suggested that the workshop with more centralized CNC machine tools should be equipped with AC voltage stabilizing power supply system with automatic compensation and regulation function; a single CNC machine tool can be equipped with AC voltage stabilizer separately to solve the problem.

It is recommended to connect mechanical and electrical equipment to a single power supply. If it is necessary to use other power supply to supply some parts of electrical equipment (such as electronic circuit, electromagnetic clutch), these power supply should be taken from the components (such as transformer, transducer, etc.) that are part of mechanical and electrical equipment as far as possible. For large and complex machinery, including many machines that work together in a collaborative way and occupy a large space, more than one power supply may be needed, which depends on the configuration of the site power supply.

Unless the mechanical and electrical equipment is directly connected to the power supply by plug / socket, it is recommended that the power line be directly connected to the power terminal of the power cut-off switch. If this is not possible, a separate terminal block shall be provided for the power cord.

The handle of the power cut-off switch shall be easy to access and shall be installed between 0.6m and 1.9m above the easy operation position. The upper limit is suggested to be 1.7m. In this way, the power can be cut off quickly in case of emergency, and the losses and casualties can be reduced.

CNC equipment for compressed air supply system requirements, CNC machine tools generally use a lot of pneumatic components, so the plant should be connected to clean, dry compressed air supply system network. The flow and pressure should meet the requirements. The compressed air machine should be installed far away from the CNC machine. According to the layout of the plant and the amount of gas consumption, it should be considered to install the chilled air in the coal machine, air filter, gas storage tank, safety valve and other equipment for the compressed air supply system network.
The requirements of CNC equipment for working environment precision CNC equipment generally has the requirements of constant temperature environment, only in constant temperature condition, can ensure the accuracy and processing degree of machine tool. Ordinary CNC machine tools have no specific requirements for room temperature, but a lot of practice shows that when the room temperature is too high, the failure rate of CNC system increases greatly.

Humid environment will reduce the reliability of CNC machine tools, especially in the humid environment with large acid gas, it will rust the printed circuit board and connectors, and increase the electrical failure of machine tools. Therefore, some users in southern China should take dehumidification measures in summer and rainy season.

1) The working environment temperature should be between 0 ℃ and 35 ℃. Computer gong processing, mechanical parts processing, CNC machine tool processing, Dongguan high-speed computer gong processing should avoid direct sunlight on CNC machine tools, and the room should be equipped with good lighting equipment.

2) In order to improve the accuracy of machining parts and reduce the thermal deformation of the machine tool, if possible, the CNC machine tool can be installed in a relatively closed workshop with air conditioning equipment.

3) The relative humidity of working environment should be less than 75%. CNC machine tools should be installed in the place far away from liquid splashing, and prevent plant dripping.

4) Keep away from excessive dust and corrosive gas.