How to judge the real medium-speed EDM CNC machine tool

Wed Jun 08 13:55:47 CST 2022

How to judge the real medium-speed EDM CNC machine tool

1. Meet the national standard of wire cutting

You are not mistaken, it is such a basic requirement that cannot be more basic. Including accuracy standards and safety standards. This looks very ridiculous, but it is actually a basic requirement. The reason for writing this is that most of the wire-cutting products currently on the market do not meet the national standards for reciprocating wire-cutting machine tools. In fact, it is to go fast. The silk standard can't even reach the repeat positioning accuracy and positioning accuracy in the most basic accuracy standards, so the compliance with the national standards is listed as the first. This is already the minimum requirement for medium wire. If even the basic wire-cutting national accuracy standards and safety standards are not met, are you ashamed to call it a higher-end medium wire than fast wire? The most basic national standard documents are listed below.
Attachment: GB/T 7926-2005 Accuracy Inspection of Wire-cut Electric Discharge Machine (Reciprocating Wire Type) GB/T 7926-2005
Electrical discharge wire cutting machine (reciprocating wire type) technical requirements JB/T 10082-2010

2. Multiple cutting function

The function of the multi-cutting function is to use fast cutting to remove the margin, and then use a small pulse to scan to improve the accuracy and smoothness. This is a commonly used processing method on slow-moving wire. This is also the function possessed when the concept of middle wire was first proposed. Now most of the middle wire can meet this rule.

3. Adopt C-type structure/linear guide/ball screw

Although the accuracy of linear guide rails and ordinary V-flat guide rails is better in the industry, and the advantages and disadvantages of C-shaped structure and tuning fork structure are still being debated in the industry, in reality, the current linear guide products are far better than the wire cutting manufacturers themselves. The made V-flat guide has good accuracy and good retention; this is because the manufacturing equipment of the linear guide manufacturer is far better than the manufacturing equipment of the wire cutting manufacturer. The rigidity and mechanical stability of the C-shaped structure is better than that of the tuning fork structure. Especially when the molybdenum wire shakes during processing, the vibration caused by the tuning fork structure will aggravate the vibration. This can be used as a condition to ensure that the product adopts high-precision structures and components.

4. Adopt AC servo drive

Although international machine tool manufacturers use stepper motors to make high-precision machine tools, the price of high-precision stepper motors is about the same as that of AC servos. As far as the actual situation on the market is concerned, AC motors are required to be selected because of the market. The drive unit of the AC motor is relatively complete, so that the response speed and positioning accuracy of the AC motor system are much higher than the relatively low-end stepping system currently on the market. Of course, the price is also quite different. The common AC motor system is basically 3500-4000/axis, while the reactive stepper motor is used, the motor is 200-300, the driver is made by itself, and the 100, better hybrid stepper motor is used. , Motor 500-600, and hundreds of drives can be taken. We still have to believe that you get what you pay for.

5. The processing parameter interface is adjustable and equipped with an expert database.

Seeing this article, it is estimated that many people will find it strange, can't the processing parameters of the middle threading be adjusted on the interface? But in fact, many of the so-called middle wire processing parameters are adjusted by a separate operation panel. The reason for this is because the previous editing and control system is used. It is clear that the editing and control system can only be programmed, and it was added later. The control function only controls the trajectory, so the WEDM manufacturer has no choice but to add a separate panel to adjust the processing parameters. What is required here is that the discharge system is under the control of the control system, because the independent trajectory control system and the discharge system cannot be automated. At this point, the middle wire must be in line with the slow wire, and some systems are on the surface of the system. The processing parameters are set here, the background is actually independent, you can only use the wire control to select 8 groups of processing parameters of the discharge unit. The standard that the middle wire should have is: in the operation interface, the processing parameters can be selected arbitrarily, and the parameter library is equipped, that is, the preset processing parameters or the processing parameters used last time can be called.

6. Processing parameters can be changed in the program

In slow-moving wire processing, the processing parameters can be automatically changed in the program according to the position when the thickness of the processed workpiece changes. This method can be used to change the workpiece parameters or use different feed speeds for the straight corner part. . Therefore, manual intervention in the processing process is reduced. For the middle wire, changing the compensation is the most useful. Because of the loss of the molybdenum wire, when cutting large workpieces, the cut to a certain extent, because of the loss of the molybdenum wire, the compensation is changed. It means that the accuracy of processed parts can be improved.

7. Constant tension function

In fact, it is the automatic tension adjustment function, because the tension change actually has a great impact on the cutting effect. At present, most wire cutting machine tools adopt the method of tightening the molybdenum wire with a heavy hammer. The advantage of this structure is that the structure is simple, easy to implement, and disadvantage It can automatically compensate for low-frequency tension changes, and the ability to compensate for high-frequency tension changes is basically zero. Now there are electronic tension adjustments. One method is to use a motor to control the displacement of the wire barrel. The common method is to control the motor to tighten the guide wheel in the molybdenum wire loop. These methods have their own advantages and disadvantages. , But at least this function is required.

8. Electronic handwheel

The previous wire cutting used hand control boxes. If you want to move a small distance, it will test the operator's electronic game qualifications. The amount of movement is determined by the time of pressing; it is very inaccurate, and it is naturally impossible to improve the accuracy. Therefore, it is considered necessary to have the control function of 1 micron movement, and the ideal is to have 1 micron. 10 micron and 100 micron options, you can use the electronic handwheel to move the worktable.

9. Automatic positioning function

For a variety of different processed parts, the middle wire should have the function of automatic positioning, which helps to correct the reference point of the workpiece, which means that the processing accuracy can be improved. If the processing reference is not accurate, how can the processing accuracy be? At least it should have the functions of inner circle, cylinder, edge positioning, and automatic positioning of inner and outer corners. At the same time, the positioning accuracy should be less than 2 wires.

10. Pitch compensation function

In fact, this article is related to the first article. If there is no pitch compensation, the accuracy can meet the national standard in theory. However, in reality, it is difficult for wire cutting without pitch compensation to meet the accuracy index. The reason is here. This article is taken out separately because it also involves a problem of accuracy retention. After a medium-threaded machine tool is used for a period of time, the accuracy loss can be corrected by the function of pitch compensation, so that the accuracy of the machine tool can return to the national standard range. Inside.

In fact, the ideal middle wire should have many functions, such as: high-speed movement, absolute coordinates, protection against wire collision during movement, self-diagnosis function, etc., which are not listed for the time being.

When judging whether a machine tool conforms to the middle wire, we can measure it against the above standards.