chengcg – Page 48 – CNC Machining & Turning, Milling, Metal parts

Debugging of CNC machine tool

How to adjust the CNC machine tool? Before debugging, the horizontal position of the machine bed should be adjusted first, the main geometric accuracy of the machine tool should be roughly adjusted, and then the relative position between the main moving parts and the host machine should be adjusted, such as the correction of the position of the manipulator, tool magazine and host machine tool change. After that, add lubricating oil, hydraulic oil and cutting fluid according to the requirements of the machine manual, and connect the external air source.

More than 80% of the machine tools must be debugged in the field before they can meet the technical specifications. The correctness of this step largely determines whether the CNC machine tool can play a normal economic efficiency and its own service life. Therefore, when the new machine tool is checked and accepted, the machine tool can be ensured to achieve its technical indicators and expected quality and efficiency at the beginning of installation. The new machine tool needs to be tested again after half a year’s use, and then it can be verified once a year. The machine tool error is detected regularly and the pitch and reverse clearance are corrected in time.

The NC machine tool should be started and debugged according to the following steps:

1、 Preparation before commissioning

Before debugging the machine tool, the horizontal position of the machine bed should be adjusted first, the main geometric accuracy of the machine tool should be roughly adjusted, and then the relative position between the main moving parts and the host machine should be adjusted, such as the correction of the position of the manipulator, tool magazine and the host machine tool change. After that, add lubricating oil, hydraulic oil and cutting fluid according to the requirements of the machine manual, and connect the external air source.

2、 Power on test run of machine tool

The power on test run of machine tool generally adopts the power on test of each component separately, and then makes a comprehensive power supply test. According to the machine tool manual, check whether the main parts of the machine tool function normally and completely, so that all parts of the machine tool can operate and move.

3、 Adjustment of machine tool accuracy and function

Using the precision level instrument and other testing tools, the level of the main bed of the machine tool is adjusted by adjusting the iron pad, so that the geometric accuracy of the machine tool can reach the allowable tolerance range;
For the automatic tool change device, adjust the position of the tool magazine, manipulator, travel parameters, etc., and then check the action with the command, which is required to be accurate;
For the machine tool with APC automatic exchange table, after adjusting the relative position, carry out automatic load exchange;
After the adjustment of the machine tool, carefully check whether the parameter setting values in the numerical control system and the programmable controller conform to the data specified in the random index, and then test the main operation functions, safety measures, execution of common instructions, etc.
Check the auxiliary functions and accessories of the machine tool.

Advanced rapid tooling manufacturing technology

With the rapid development of laser rapid prototyping (RPM), China has reached the international level and gradually realized commercialization. The commercial rapid prototyping processes in the world mainly include SLA (stereolithography), LOM (layered and separated manufacturing), SLS (selective laser sintering) and 3d-p (three-dimensional printing).

Tsinghua University first introduced sla250 (stereolithography or photosensitive resin laser curing) equipment and technology from 3D company of the United States and carried out research and development. After several years of efforts, it improved and launched the “m-rpms type multi-functional rapid prototyping manufacturing system” (with layered solid manufacturing SSM and melt extrusion molding MEM), which is the only world with independent intellectual property rights in China The system of rapid prototyping process (national patent) has good performance price ratio.

Die less multi-point forming technology is another advanced manufacturing technology that uses the height adjustable punch group to replace the traditional die for sheet metal surface forming. The die less multi-point forming system takes CAD / CAM / CAT technology as the main means to realize the automatic forming of three-dimensional surface rapidly and economically. Jilin University of technology has undertaken the national key scientific and technological research projects related to dieless forming, and has independently designed and manufactured die-free multi-point forming equipment with international leading level.

Compared with MIT, Tokyo University and Tokyo University of technology in the United States, China’s technology is in a leading position in theoretical research and practical application, and is now developing in terms of popularization and application.

The resin stamping die has been successfully applied in the trial production of domestic car for the first time. The main features of the former and the second models of the former and the second type of the former and later parts of the car were manufactured by the former and the latter, respectively The gap between punch and die is accurately controlled by imported special wax. The dimension precision of the die is high. The manufacturing cycle can be shortened by half to two thirds, and the manufacturing cost can be saved about 10 million yuan (12 sets of dies). It opens up a new way for trial production and small batch production of cars in China. The experts of Ciba fine chemicals in Switzerland believe that it can reach the international level in the 1990s.
On site inspection technology of mould

With the development of precision mould, the requirement of measurement is higher and higher. For a long time, the precise CMM is limited by the environment and seldom used in the production site. The new generation CMM has the characteristics of temperature compensation, anti vibration material, improving dust-proof measures, improving environmental adaptability and reliability, so that it can be easily installed in the workshop and used in order to realize the field measurement.

Laser surface quenching repair of mould

The main purpose of die surface treatment is to improve the surface hardness, wear resistance and corrosion resistance. The application of laser surface strengthening technology has greatly improved the surface performance of mold. For the key parts of the mold, the conventional heat treatment is manual flame quenching. Flame quenching has many limitations, such as low hardness, easy deformation and cracking, which needs further processing and correction. The laser quenching can not only solve the above problems, but also can improve the wear resistance and service life of the same hardness, and local quenching can be carried out for the difficult parts.

For improving the service life of large-scale dies and reducing the heat treatment deformation of precision dies, laser surface strengthening technology has great technical advantages, mainly including laser surface quenching and laser surface cladding.

laser surface hardening

Laser surface hardening is a kind of technology that uses high energy laser beam to scan the workpiece to harden the scanned area.

The characteristics of laser quenching

(1) Laser quenching is rapid heating and self-excited cooling, without furnace heat preservation and coolant quenching. It is a pollution-free green heat treatment process, which can easily implement uniform quenching of large mold surface.

(2) Because the laser heating speed is fast, the heat affected zone is small, and the surface scanning heating quenching, namely instantaneous local heating quenching, the deformation of the treated die is very small.

(3) Because the divergence angle of the laser beam is very small and has good directivity, the mold surface can be accurately quenched by the light guide system.

(4) The hardened layer depth of laser surface quenching is generally 0.3 ~ 1.5mm.

Diamond grinding and polishing of mould

In order to avoid scratches and burns to the surface of the workpiece, special care must be taken when polishing with ා 1200 and ා 1500 sandpaper. Therefore, it is necessary to load a light load and use two-step polishing method to polish the surface. When each type of sandpaper is used for polishing, it should be polished twice along two different directions, with each rotation of 45 ° to 90 ° between the two directions.

Diamond grinding and polishing should pay attention to the following points:

(1) This kind of polishing must be carried out under light pressure as far as possible, especially when polishing pre hardened steel parts and polishing with fine grinding paste. When polishing with ා 8000 grinding paste, the common load is 100 ~ 200g / cm2, but it is difficult to maintain the accuracy of this load. To make this easier, make a thin, narrow handle on the wood, such as adding a piece of copper, or cut a part of the bamboo strip to make it softer. This helps to control the polishing pressure to ensure that the die surface pressure is not too high.

(2) When using diamond grinding and polishing, not only the working surface is required to be clean, but also the worker’s hands must be carefully cleaned.

(3) Each polishing time should not be too long, the shorter the time, the better the effect. If the polishing process is too long, it will cause “orange peel” and “pitting”.

(4) In order to obtain high quality polishing effect, polishing methods and tools which are easy to heat should be avoided. For example: polishing wheel polishing, the heat generated by polishing wheel can easily cause “orange peel”.

(5) When the polishing process stops, it is important to ensure that the surface of the workpiece is clean and that all abrasives and lubricants are carefully removed, and then a layer of mold antirust coating shall be sprayed on the surface.

At present, mechanical polishing is still the main factor affecting the quality of mold polishing. In addition, it is also related to mold material, surface condition before polishing and heat treatment process. High quality steel is the prerequisite to obtain good polishing quality. If the surface hardness of steel is uneven or there are differences in characteristics, polishing difficulty will often occur. All kinds of inclusions and pores in the steel are not conducive to polishing.

3.1 the influence of different hardness on the polishing process increases the difficulty of grinding, but the roughness decreases after polishing. Due to the increase of hardness, the polishing time required to achieve lower roughness increases correspondingly. At the same time, the possibility of over polishing decreases with the increase of hardness.

Centerless cylindrical grinder

The grinding machine which uses centerless grinding method to grind the rotating surface of workpiece is usually referred to as centerless cylindrical grinder. In centerless cylindrical grinder, the workpiece is not centered and supported by the center, but placed between the grinding wheel and the guide wheel, supported by the supporting plate and guide wheel. Generally, the grinding wheel is installed at the end of the spindle, and the grinding wheel with width greater than 250 mm is installed in the middle of the spindle, and the maximum width of the grinding wheel can reach 900 mm. The grinding wheel rotates at a high speed, and the guide wheel rotates in the same direction at a slow speed to drive the workpiece to rotate for circular feed.

In the process of through grinding, the axial feed is realized by adjusting the small inclined angle of the guide wheel axis, which is suitable for grinding slender cylindrical workpiece, short shaft without central hole and sleeve type workpiece. In cut in grinding, radial feed is realized by the movement of guide wheel frame or grinding wheel carrier. It is suitable for grinding workpieces with shoulder or boss, as well as workpieces with cone, sphere or other lines being curved. The productivity of centerless grinder is high, and it is easy to realize automation after various loading and unloading devices. Most of them are used in mass production and can be operated by unskilled workers. The grinding accuracy of centerless grinder is generally 2 μ m in roundness and 4 μ m in size. High precision centerless grinder can reach 0.5 μ m and 2 μ m respectively. In addition, there are centerless internal grinder and centerless thread grinder.

The centerless grinder can repair and compensate automatically. The guide wheel feed guide rail is double V-shaped needle roller guide wheel, which is fed by servo motor and can compensate each other with grinding wheel dressing. The machine tool is equipped with automatic loading and unloading mechanism, which can carry out automatic cycle grinding.

Geometric modeling of parts

(1) Geometric modeling of parts

For NC programming of complex shape parts based on drawings and measurement data of feature points, the first step is to establish the geometric model of the parts to be processed.

(2) Reasonable selection of processing scheme and processing parameters

The efficiency and quality of NC machining depend on the reasonable selection of processing scheme and parameters. The optimal selection of tool, cutter axis control mode, tool path and feed speed is the premise to meet the processing requirements, normal operation of machine tool and tool life.

(3) Tool path generation

Tool path generation is the most important content in NC machining of complex shape parts. The possibility, quality and efficiency of machining are directly determined by the generation of effective tool path. The primary goal of tool path generation is to make the generated tool path meet the requirements of no interference, no collision, smooth path, smooth cutting load and high code quality. At the same time, the tool path generation should also meet the conditions of good universality, good stability, high programming efficiency and small code amount.

(4) NC machining simulation

Due to the complexity of the shape of the parts and the complexity of the machining environment, it is very difficult to ensure that the generated processing program does not have any problems, among which the most important are the over cutting and undercutting in the machining process, the interference and collision between various parts of the machine tool, etc. For high speed machining, these problems are often fatal. Therefore, it is necessary to take some measures to check and correct the processing program before actual processing. Numerical control machining simulation tests and optimizes the processing program by simulating the processing environment, tool path and material removal process by software. It has the characteristics of good flexibility, low cost, high efficiency and safety and reliability, and is an important measure to improve the efficiency and quality of programming.

(5) Post processing

Post processing is an important part of NC machining programming technology. It transforms the tool position data generated by general pre-processing into NC machining program suitable for specific machine tool data. Its technical contents include kinematic modeling and solution of machine tool, compensation of machine tool structure error, check and correction of non-linear error of machine tool motion, stability check and correction of machine tool motion, feed rate check and code conversion, etc. Therefore, post-processing plays an important role in ensuring the machining quality, efficiency and reliable operation of the machine tool.

Machining performance of CNC and RP

In the past, great progress has been made in prototyping. At first, most RP technologies have obvious advantages in terms of speed, but their further development is limited due to the problems of accuracy and material properties. Since the advent of RP, due to the threat of some competition, CNC can improve its speed and bring well-known benefits. Similarly, RP has been improved in accuracy, material properties and surface polishing. Understanding these two technologies is particularly important for selecting the right machining tool for the job. The following guidance can help in the selection of tools.

Material Science

RP restricted

The research of materials has gone through a long process. The range of material selection is enlarged, and the performance is guaranteed. At present, the available materials are metal, plastic, ceramic and composite materials, and the selection of materials is still limited. Moreover, the properties of most of the materials are not well matched with those of processing, molding and pouring.

CNC machining is almost unlimited

The machining center can cut almost all materials.

The maximum size of the part, the maximum size of RP is 600x900x500mm

Although the existing industrial equipment can not process dashboard or baffle, the existing prototype can be used to produce most of the daily necessities and industrial products. If the parts to be produced by the equipment are too large, the components can be produced first and then combined into a complete part. It must be noted that size has an effect on time and it takes longer to make larger parts.

CNC machining can produce aircraft parts

CNC machining can produce the actual size of parts and modules, from small desktop devices to large bridge equipment. It can be said that the limitation of CNC size only comes from the mechanical tools used.

Complexity of parts

RP unlimited

If a sample can be molded with design software, the time or cost of manufacturing is hardly affected. Rapid and cheap production of complex parts is one of the greatest advantages of RP

Analysis of electrode wire loss

1、 Analysis and measures of electrode wire loss

In NC WEDM, the loss or broken wire of electrode wire seriously affects its continuous automatic operation, especially in high-speed WEDM, due to the repeated use of electrode wire in the processing, with the increase of electrode wire loss, the cutting seam becomes narrower and narrower, which will not only increase the size error of the machining surface; and once the wire breakage occurs in the processing, the processing must be carried out Restart, which not only costs more man hours, but also affects the quality of the machined surface. The causes and measures of electrode wire loss or breakage are as follows:

1) When the electrode wire moves rapidly (8-10 M / s), it will rub with the guide wheel and the conductive block, causing the wear of the guide wheel and the conductive block. When the conductive block is used for a long time, the V-groove bottom of the guide wheel is pulled out of the groove by the electrode wire. When the conductive block is used for a long time, the side contacting the electrode wire is also pulled out of the groove. As a result, the friction resistance of the guide wire is increased and the electrode wire is broken due to hindered movement.

2) When the weight of the cutting material is large, it is easy to deflect and shift at the end of the processing, which will cause the electrode wire to be broken. For this reason, a piece of ground permanent magnetic steel can be added to the plane of the workpiece and the cutting material, so as to keep the cutting material in a fixed position during the cutting process.

3) When the internal stress of workpiece material is too large, the relative equilibrium state of internal stress in workpiece material will be destroyed, which will easily cause the cutting gap to narrow and the electrode wire will be jammed. Therefore, the following measures can be taken:

a. The improvement of heat treatment process is mainly to improve the tempering process in order to reduce the internal stress of the workpiece;

b. Before heat treatment, process holes or slots are added to the cut part to reduce the residual stress released during WEDM.

4) In WEDM, when the workpiece material is eroded and cut into shape, the electrode wire will also be corroded by discharge, that is, the electrode wire will be lost. When the electrode wire is used for a long time, the wire diameter becomes smaller and full of micro discharge pits, the tensile strength decreases, and finally fracture occurs. Generally speaking, when the diameter of the measured wire is 0.03 ~ 0.05mm less than that of the new wire, the new wire should be replaced in time.

5) The electrode wire should be evenly and neatly wound on the wire storage cylinder. The unbalanced inertia will be produced when the inner and outer circles of the silk storage cylinder are different, which will lead to the breakage of the electrode wire. Therefore, the dynamic balance must be corrected.

6) When the electrode wire is folded and threading, the electrode wire is partially broken. At the discount place, the tensile strength and the ability to bear the thermal load decrease, which is easy to fracture. In order to avoid the discount of electrode wire, first of all, the electrode wire with good linearity and high tensile strength should be selected; secondly, careful and standard operation should be carried out during wire feeding and threading.

Principle of electric erosion

Scope of application

Remove taps, drills, reamers, screws, plug gauges and other tools / tools with various diameters broken in the workpiece
It can be processed on workpieces of various sizes and shapes
Processing of various angle positions on workpiece
Machining non precision required hole

Introduction to jx-200a

Power supply: portable power supply

Electrode: use brass rod as electrode

Non destructive machining: remove the broken object without damaging the thread

Working fluid: ordinary water can be used as working medium

Large workpiece: it is very convenient to process the broken tap on the large workpiece

characteristic

Using the principle of electric erosion to remove the broken tool, non-contact processing, no force in the processing, no damage to the workpiece
Portable design, easy to use in various environments
With magnetic base, the processing device can be sucked to the workpiece for processing
The working head can be adjusted at any angle
Automatic feed processing, no occupation of personnel
Single 220 V power supply (or 110V), touch key operation, easy to use
Water can be used as working fluid

Working methods

For general taps, a half diameter electrode is used to remove broken taps. Large taps are processed three times with thin electrode or sheet electrode, or with copper tube electrode. The broken screw is processed with hexagon electrode, and then taken out with hexagon wrench. Other broken tools and cutting tools shall be processed with electrodes of suitable shape and size.

2、 Processing sequence: put metal plate into plastic container – fix the processed parts and head – (magnetic base should not be put into water) – brass electrode should be fixed in clamp head, and the electrode diameter should be half of the nominal diameter of tap – connect the cable, connect the wire clamp to the processed part – align the position of electrode and tap, the distance is 1-2 mm, and adjust the stroke finger Position indication – add working fluid into the container, at least 10 mm higher than the surface of the part – turn on the main power switch – select the processing current – press the start key to start processing – finish machining (reaching the set depth), automatically stop processing, and manually operate to make the electrode rise. The tap in the blind hole can be taken out with a driver or tweezers.

Design method of die nozzle

(1) Large gate mold: the runner and gate are on the parting line, and demould together with the product when opening the mold. The design is the simplest, easy to process, and the cost is low. Therefore, many people use the large water gate system for operation.

(2) Fine nozzle mold: the runner and gate are not on the parting line, but directly on the product. Therefore, it is necessary to design an additional set of nozzle parting lines. The design is more complicated and the processing is more difficult. Generally, the fine nozzle system should be selected according to the product requirements.

（3） Hot runner mold: the structure of this kind of mold is roughly the same as that of the fine nozzle. The biggest difference is that the runner is located in one or more hot runner plates and hot pumps with constant temperature. There is no cold material demoulding. The runner and gate are directly on the product, so the runner does not need to be demoulded. This system is also known as no nozzle system, which can save raw materials and is suitable for situations where raw materials are expensive and product requirements are high, It is difficult to design and process, and the mold cost is high.

The so-called 2-plate mold generally refers to the large water mouth system mold, and the 3-plate mold generally refers to the water nozzle system mold. 3-plate die can not be simply considered as one more template than 2-plate mold. According to the product shape and mold design needs, the mold can have more than 3-plate knot

Hot runner system, also known as hot runner system, is mainly composed of hot runner sleeve, hot runner plate and temperature control electric box. Our common hot runner system has two forms: single point hot gate and multi-point hot runner. Single point hot gate is to use a single hot gate sleeve to directly inject the molten plastic into the mold cavity, which is suitable for the plastic mold with single cavity and single gate; the multi-point hot gate is to branch the molten material into each sub Heat Gate sleeve and then into the cavity through the hot runner plate, which is suitable for single cavity multi-point feeding or multi cavity mold

Advantages of hot runner system

(1) No water mouth material, no need for post-processing, so that the entire molding process is fully automated, save working time and improve work efficiency.

(2) The pressure loss is small. The temperature of the hot runner is equal to that of the nozzle of the injection molding machine, which avoids the surface condensation of the raw materials in the runner and reduces the injection pressure loss.

(3) The reuse of nozzle material will degrade the properties of plastic, but the use of hot runner system without nozzle material can reduce the loss of raw materials and reduce the cost of products. In the mold cavity, the temperature and pressure are uniform, the stress of plastic parts is small, and the density is uniform. Under the small injection pressure and short molding time, the injection molding can produce better products than the general injection molding system. For transparent parts, thin parts, large plastic parts or high demand plastic parts, it can show its advantages, and can produce larger products with smaller machines.

(4) The hot nozzle adopts standardized and series design, equipped with various nozzle heads for selection, and has good interchangeability. The electric heating ring with unique design and processing can achieve uniform heating temperature and long service life. The hot runner system is equipped with hot runner plate, temperature controller, etc., with exquisite design, various types, convenient use, stable and reliable quality