Process flow of CNC EDM machining in mold enterprises

CNC EDM is an important special processing technology. It is used in mold manufacturing, aerospace, electronics, nuclear energy, instrumentation, light industry and other departments to solve the processing problems of various complex shapes and difficult materials.

The book "In-depth application of numerical control EDM machining field technology" includes the basic knowledge of CNC EDM, the key points and experience of CNC EDM practice, the ISO programming of CNC EDM, and the typical CNC EDM machining examples of selected companies. , CNC electrical discharge machining application technology comprehensive discussion. This book can help engineers and technicians in the mold manufacturing industry to quickly improve their technical level. Some application technology doubts can be found in this book. For professional college molds, CNC technology, machinery, etc. Professional teachers and students can make them feel the real enterprise processing technology and achieve the purpose of teaching.

"Introduction to the Field Application Technology of CNC EDM" was published by the Machinery Industry Press.

CNC EDM is an important method for mold manufacturing. Especially in the manufacture of injection molds, EDM can be said to be an irreplaceable process and plays an important role. Figure 1-24 shows the corner of the EDM workshop of the mold company. The following is a brief introduction to the process flow of the EDM of the mold enterprise. Please read Chapter 2 for the main points of each link.

1.6.1 Process determination of mold EDM
Before the manufacturing of the mold parts, according to their own characteristics, processing requirements to determine a reasonable processing. In general, in order to make the mold parts machined in the shortest possible time, reduce the processing cost, and improve the processing efficiency, the machining process should be selected by milling, wire cutting and other processes. EDM is performed when milling, wire cutting, etc. are not processed or the workpiece has special requirements, such as complex surfaces that are difficult to reach, where deep cutting is required, where the length to diameter ratio is particularly large, precision Small cavities, narrow slits, grooves, corners, inconvenient for cutting and clamping, the material hardness is very high, and the processing occasions for providing a fire pattern surface are specified.

Before the EDM, the parts drawing should be analyzed to understand the structural characteristics and materials of the workpiece and to clarify the processing requirements. According to the requirements of processing object, precision and surface roughness, and the machine tool function, a suitable EDM process is adopted.
1.6.2 Pre-machining the workpiece contour Generally, before the EDM machining, the workpiece contour needs to be pre-machined, as shown in Figure 1-25. Pre-machining generally uses machining methods such as machining centers, general milling machines, and the like. The purpose of the pre-machining is to reduce the amount of material removal in the EDM process, which can greatly increase the EDM speed, reduce the loss of the electrode, and reduce the number of electrodes. The roughing current can be small, so that the machined surface is less affected.

1.6.3 Design and manufacture of electrodes EDM requires the design and manufacture of electrodes. Current computer-aided design and manufacturing (CAD/CAM) technology has been widely used in the mold manufacturing industry. Those high-end CAD/CAM software, such as UG, Pro/E, CimatronE, MasterCAM, etc., provide powerful electrode design and programming functions, which reduces the tedious work of manually removing electrodes, and improves compared with traditional electrode design and manufacturing. The efficiency is ten times or even dozens of times.

According to the technological level of the enterprise, the manufacturing process of the electrode is arranged in consideration of process points such as electrode processing precision requirements and processing costs. At present, mold companies have widely used machining centers to manufacture a variety of complex electrodes. The machining center is faster than conventional milling, fully automatic, and the precision of repeated production is high, and more complicated shapes can be obtained. The recently introduced high-speed machining center is capable of manufacturing electrodes with more complex shapes and higher precision requirements, providing a perfect technical solution for manufacturing electrodes. Wire cutting is also a very common electrode processing method. It is very suitable for the manufacture of 2D electrodes. It can be used to manufacture the entire electrode separately or to clean the corners of the electrodes. In addition, the sheet-like electrode is difficult to perform by mechanical cutting, and the wire-cutting process can achieve high processing efficiency and processing accuracy. With the slow wire-cutting machine, it is possible to process complex electrodes with slopes and upper and lower profiles. High machining accuracy and surface quality.

Commonly used electrode materials are graphite and pure copper. Generally, the precision and small electrodes are made of pure copper, while the large electrodes are made of graphite.

The use of a fast clamping positioning system to manufacture electrodes is an advanced process of EDM. It is manufactured by clamping the electrode blanks on the clamping system of the processing machine. After the manufacturing is completed, the electrodes can be directly mounted on the EDM. The electric discharge machining on the fast clamping system of the machine tool brings great convenience to the machining operation, improves the manufacturing efficiency of the electrode, and ensures the clamping and positioning accuracy of the electrode.

1.6.4 Fixing and Correction of Workpiece and Electrode EDM machining mounts the workpiece on the workbench and corrects the workpiece. Since the electrode does not contact the workpiece in the EDM process, the macro force is small, so the workpiece clamping is generally simple. Permanent magnet chucks are usually used to clamp the workpiece. In order to adapt to the needs of various workpieces, other tools can be used for clamping, such as flat jaws, magnetic blocks, sinusoidal magnets, and angled magnetic blocks. After the workpiece is clamped, it should be calibrated to ensure that the coordinate system direction of the workpiece is consistent with the coordinate system of the machine. A calibration is often used in actual machining to calibrate the workpiece.

The electrode is mounted on the machine tool spindle, so that the electrode axis is aligned with the axis of the spindle to ensure that the electrode and the workpiece are processed perpendicularly. There are two types of electrode clamping: automatic clamping and manual clamping. The automatic clamping electrode is an automatic function of the advanced CNC EDM machine. It is through the electrode automatic exchange device (ATC) of the machine tool and the electrode-specific fixture (EROWA, 3R) to complete the electrode replacement. The electrode-specific fixture can realize the natural correction of the electrode without correcting or adjusting the electrode. The correct positional relationship between the electrode and the machine tool is ensured, and the time for clamping and repeated adjustment during the EDM process is greatly reduced. Manually clamping the electrode means using a common electrode holder to correct the electrode by a collet that can adjust the angle of the electrode, and manually performing electrode clamping and correcting operations.

1.6.5 Positioning of the machining After the workpiece and the electrode are clamped and corrected, it is necessary to align the electrode with the machining position of the workpiece to machine an accurate cavity on the workpiece. Mold manufacturing The most common positioning method for EDM is to use the distance between the center of the electrode reference and the center of the workpiece to determine the machining position, which is called “four sides”. It is also common to use the distance between the center of the electrode and the one side of the workpiece to determine the positioning position of the machining position, which is called "one-side split". In addition, there are some other ways to locate.

Various positioning methods are realized by certain methods. Usually, the contact sensing function of the EDM machine is used to obtain the correct machining position. It can directly realize the positioning by using the contact surface of the electrode and the reference surface of the workpiece. Precision mold EDM uses the reference ball for contact sensing positioning. Point contact reduces errors and enables higher precision positioning. In addition, there are positioning methods such as dial gauge comparison and discharge positioning. The use of the quick-clamp positioning system eliminates the need for repeated positioning operations. When equipped with an ATC device, it can fully realize long-time unmanned automated processing, which can effectively enhance the competitiveness of the enterprise.
At present, the numerical control EDM machine tools have the functions of automatically finding the inner center, finding the outer center, finding the angle, and finding the one side. These functions can be easily realized by inputting the relevant measurement values, which is convenient for manual positioning. Much more.

1.6.6 Configuration of electrical parameters After completing the basic operations such as calibration and positioning, it is necessary to select reasonable electrical parameters according to the processing requirements. The choice of electrical parameters directly affects the various process indicators of processing. The ultimate goal of selecting electrical parameters is to achieve the desired processing dimensions and surface roughness requirements. When selecting electrical parameters, basically consider the factors such as the number of electrodes, electrode loss, working fluid treatment, surface roughness requirements, electrode scaling, processing area, and processing depth. The main basis for the selection of roughing parameters is the size of the electrode scaling. The size of the roughing electrode is generally large, and the electrical parameters whose safety gap is close to the size of the electrode can be selected. The main basis for the selection of finishing parameters is the final surface roughness requirement. Multiple sets of electrical parameters are selected, and the discharge energy is translated from large to small to achieve the requirements of surface roughness and processing size.

CNC EDM machines have many optimal sets of electrical parameters that are configured to automatically select electrical parameters; as long as the required input conditions are accurately entered, the electrical parameters can be automatically configured. The electrical parameters of the machine tool configuration generally meet the processing requirements, and the operation is simple, avoiding human intervention during the processing. The traditional EDM machine tool requires the operator to have a wealth of work experience, and can flexibly configure the electrical parameters according to the processing requirements.

1.6.7 Monitoring of the machining process When EDM is ready, the machine can be started to start machining. In the process of processing, it is necessary to monitor the processing status at any time, and take appropriate treatment methods for the abnormal discharge state during processing to ensure smooth processing. It is mainly to prevent the occurrence of arcing. Generally, the discharge condition can be improved by modifying the parameters of the lifting knife, cleaning the electrode and the workpiece, and adjusting the parameters of the electrical standard.

The processing performance of the current CNC EDM machine tool has been comprehensively improved, and the intelligent control technology of some advanced CNC EDM machines can almost replace manual monitoring. During the processing, the computer monitors and judges the state of the EDM machining gap, and automatically selects the machining condition that maximizes the machining efficiency within the range of maintaining stable arc; however, the intelligent control technology of the machine tool is not omnipotent, and the effect of manual monitoring cannot be ignored. Especially in some special processing occasions such as deep hole machining, large taper machining, and large area machining, manual monitoring has its significance.


The above content is excerpted from the "In-depth application of CNC EDM processing field application technology" published by Mechanical Industry Press.

Author: Wu Duanyang with ISBN: 978-7-111-25607-6
Pricing: 35.00 yuan
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table of Contents:
Preface Chapter 1 The basis of CNC EDM technology
1.1 Production, physical nature and realization conditions of EDM
1.2 Two important effects of EDM
1.3 Characteristics and application of EDM
1.4 Main process indicators of EDM and its influencing factors
1.5 CNC EDM process
1.6 Process flow of CNC EDM machining in mold enterprises
1.7 Advanced CNC EDM Machine Tool Chapter 2 Essentials of CNC EDM Application Technology
2.1 Design electrodes
2.2 Selecting electrode materials
2.3 Manufacturing electrodes
2.4 Work clamping and correction
2.5 electrode clamping
2.6 Electrode correction
2.7 Positioning between the electrode and the workpiece
2.8 translation processing
2.9 Processing condition conversion
2.10 Electrical parameter configuration and optimization
2.11 Working fluid treatment
2.12 Numerical Control EDM Processing Stage Chapter 3 Numerical Control EDM ISO Programming
3.1 CNC EDM ISO programming basis
3.2 CNC EDM processing commonly used instructions
3.3 Thinking mode and method of CNC EDM programming
3.4 Numerical Control EDM Programming Comprehensive Example Chapter 4 Numerical Control EDM Field Application Examples
4.1 EDM of injection mold exhaust inserts
4.2 Threading plug Huff mold slider EDM
4.3 EDM of integrated circuit plastic mold
4.4 EDM machining of cable ties plastic molds
4.5 EDM of precision electronic product slider
4.6 EDM of mobile phone mold cavity
4.7 EDM machining of Coke bottle threads
4.8 EDM of injection mold deep gate
4.9 Electric spark machining of bevel gear forging model cavity
4.10 EDM of moving model core
4.11 EDM of regulating valve parts
4.12 EDM of special materials Chapter 5 Comprehensive discussion on application technology of numerical control EDM
5.1 Discussion on the process of improving the efficiency of EDM
5.2 Causes and improvement measures of unstable discharge in EDM
5.3 Precision EDM Technology for High Value Added Dies
5.4 Analysis of Mistakes in EDM Processing in Die and Mold Enterprises
5.5 Abnormal problems and analysis of EDM in mold manufacturing
5.6 Discussion on the cavity electric discharge machining of cavity cavity
5.7 Development relationship between electric spark and high speed milling
5.8 Automated process of CNC EDM machine with automatic electrode replacement function
5.9 Development of CNC EDM Technology and Application of New Process Appendix References