EDM is an important process in mold manufacturing, especially in injection mold manufacturing. However, some misunderstandings in EDM in die and mould factories often lead to the failure of machining accuracy, surface and efficiency to meet the requirements. The following will analyze the common misunderstandings of EDM in mold factory.

01

When touching the workpiece with an electrode, it is often "biased"

The method of directly touching the workpiece with an electrode belongs to surface contact. There are inevitably more or less fine objects between the contact surfaces, and there are clamping accuracy errors on the contact surfaces, which will directly affect the accuracy of edge finding and centering. Using this method, the contact surface must be wiped clean strictly, but the accuracy will be unstable due to human factors.

For NC discharge machine, it is recommended to use the method of reference ball separation, which is a necessary method for discharge in mold factory. The usual approach is:

Clamping workpiece;

Place a reference ball on the workbench;

Install the probe on the spindle head;

Use the probe to center the workpiece;

Use the probe to center the reference ball;

Remove the probe and install the electrode;

The subsequent electrodes are used to center the reference ball

Because the process of splitting is point-to-point perceptual contact, it can be realized μ M-class high-precision positioning accuracy. In addition, the moving distance of the electrode sub reference ball becomes smaller, the stroke of the machine tool can be fully utilized, and the efficiency is also improved.

Of course, if the production process is more perfect, the electrode eccentricity can be measured outside the machine through three coordinates, and the eccentricity value can be transmitted to the EDM machine tool. There is no need to score on the EDM machine tool, which can greatly improve the productivity of the machine tool and the overall production efficiency of EDM.

02

Choose the same electrode material

Most domestic mold enterprises use red copper as electrode material. In the pursuit of high-efficiency processing today, have you ever investigated the processing advantages of graphite electrode? Perhaps you will simply think that graphite electrode is only suitable for large mold machining or rough machining. In fact, this understanding is one-sided or still stays in the traditional concept of molding.

At present, more and more mold enterprises begin to use graphite electrode to greatly shorten the mold manufacturing cycle. Because both milling electrode and EDM process can greatly improve the machining efficiency, which is the significant advantage of graphite electrode. In addition, the graphite is large, the electrode weight is light, the narrow slot processing is not easy to deform, the CNC milling has no burr, and the overall electrode can be designed to reduce the number of electrodes, which fully reflects the advantages of graphite material. Of course, in asking Ra0 four μ For fine surface processing below m, graphite processing is not suitable.

For micro machining, very low electrode loss is required. At this time, it is necessary to choose high-quality red copper electrode or chromium copper electrode. For EDM of high value-added parts, using more expensive copper tungsten alloy can obtain less electrode loss, especially in machining cemented carbide parts.

03

The electrode spark position is too small, which greatly reduces the machining efficiency

Most enterprises upgrade from using traditional discharge motors to CNC discharge motors. When many factories use CNC discharge motors, the electrode spark position process still refers to the traditional discharge motors. For example, the spark position of rough machining electrode is 0.15mm on one side and that of finishing electrode is 0.05mm on one side.

The small electrode spark position greatly limits the NC discharge motor from using higher current for high-speed machining. In fact, after high-speed cutting machining, the side of the cavity can be quickly polished only by translational machining, which is a process method to achieve the perfect effect of discharge surface, efficiency and accuracy. Here is a reference. The spark position of rough machining electrode of NC discharge motor is 0.3 ~ 0.15mm on one side, and that of finish machining electrode is 0.15 ~ 0.05mm on one side. It is necessary to refer to the discharge area and processing volume. If the area allows, the spark position should be made as large as possible to obtain even several times the processing efficiency.

04

The use of CNC machine tools, without side and oblique functions

The NC discharge motor can realize side beating, oblique beating and multi axis linkage machining. For example, there are some injection mold molding inserts with thin and deep glue positions around, which are very suitable for side beating.

It is a common type of machining to remove the R angle of the remaining tool after cutting. If the X, y and Z axis linkage method, i.e. oblique machining, is adopted, the phenomena of unstable discharge and local electrode loss due to the small area of the machining part can be avoided.

Many factories process the inclined gate on the mold according to the z-vertical by tilting the mold. In fact, it can be completed by using the oblique beating function of NC EDM machine tool. The machining of oblique gate can be realized by setting the starting point and end point. When designing the electrode, it is necessary to design the electrode according to the oblique method.

06

Large area high finish machining is difficult to meet the requirements

If the mold EDM of the company belongs to the type of large area (more than 30 square centimeters) and the surface is required to be below vdi18, uniform spark texture is required, such as the cavity of TV remote control. Then EDM is a headache. It often makes repeated trimming for texture, and the machining efficiency is also very low.

For batch EDM of large area and large cavity molds, powder mixing processing technology should be considered, which can greatly improve the processing efficiency and make it easier to obtain a large area of fine texture or mirror.

08

Misunderstanding of mirror EDM

For mold enterprises that have not been in contact with mirror EDM, they will be very interested in this technology. Unfortunately, due to the lack of practical experience, some of their incorrect cognition can easily lead to cases of processing failure.

In fact, it is not difficult to realize mirror machining for NC discharge motor, such as vdi7 (Ra0.2 μ m) The level of sub mirror is very difficult to process. Whether the high-quality mirror effect can be achieved depends largely on the workpiece material in addition to the selected processing parameters. Some materials such as SKD11, DC53 and counterfeit S136 can not achieve good mirror effect in any case. Therefore, it is necessary to judge the material before deciding to carry out mirror discharge, otherwise it may waste time and fail to meet the requirements.

The main experience of mirror machining is time control. How much area should be set and how much time should be set. Experienced masters can flexibly realize efficient mirror production.