3 factors that determine the processing efficiency of stepper and servo wire-cut machines, which novices must know.

What is the difference between servo and stepper wire cutting? Should I choose stepper or servo for wire cutting? Mr. Yang from Zhikai CNC will answer the three factors that determine the efficiency of wire cutting. Let me show you that processing speed refers to the number of square millimeters cut per minute, or the total number of square millimeters cut per hour. Apart from the objective factors that have little influence, the core factors that affect the speed of wire cutting are the high-frequency power supply and the three aspects of the control system.

High frequency pulse power supply

In medium-speed EDM wire cutting machines, the control circuit plays a vital role. The control circuit is responsible for controlling the movement and discharge process of the electrode to ensure the accuracy and stability of the cutting process. Mastering the design and debugging of the control circuit is one of the important skills of engineers in the research and development and manufacturing of medium-speed EDM machines. By optimizing the design of the control circuit, the machining accuracy and production efficiency of the machine tool can be improved to meet the machining requirements of different workpieces.

The high-frequency power supply is the control part of the machine tool, which is generally installed in a separate control cabinet and stands next to the machine tool. Or if the machine tool is an integrated purchase, it is installed in a separate chassis and hung on the machine tool.

The cutting speed, smoothness, molybdenum wire loss of the machine tool, and the type of cutting fluid that can cut quickly and without wire breakage all depend on the high-frequency power supply.

Molybdenum wire loss is large, not only is it easy to break the wire, but it will also directly affect the consistency of the cut product. For example, if 30 products are cut at the same time, as the diameter of the molybdenum wire becomes smaller, the product error will appear. Some high-frequency power supplies are more dependent on a certain type of cutting fluid, which increases the subsequent use cost and uncertainty.

2. The air cutting speed of the control system is different

2.1 The machine tool control system is different

It is worth noting that there are many stepper signal to servo drive machine tools on the market. Although they are servo motors, they are actually open-loop systems like steppers. They can be judged based on the following points:

1. Walking speed (idle walking and jumping speed). At present, the walking speed of real servo systems is more than 20,000-50,000 steps, because they all use high-speed FPGA control, high walking accuracy and fast speed; if it is an open-loop system of stepper to servo, it is generally around 3,000 steps, and some are even only around 1,500 steps. This will greatly improve work efficiency.

2. Whether it supports pitch compensation. The real servo system supports pitch compensation function, so that the mechanical wear can be compensated by software. The most intuitive way is to see whether the real-time walking data is fed back and displayed on the software. If not, it must be a stepper.

Fast wire generally does not use a servo system, and the stepper system does not have a pitch compensation function.

2.2, Stepper motor and servo motor have different systems

The stepper wire cutting machine uses an open-loop system, while the wire cutting machine tool has gradually transitioned from an open-loop system to a closed-loop system.

The wire cutting machine tool control system has evolved from running on the DOS computer system at the beginning, to Windows XP later, to the current cool cutting system, running on the Windows 11 computer operating system, and many new versions of drawing software are available. The system function has also developed from an open loop to a full closed-loop control system of the cool cutting system.

An open-loop control system refers to a controller that controls the movement of the motor by sending command signals, but cannot provide real-time feedback on the actual movement of the motor. The open-loop control system is what we often call a stepper card and wire cutting stepper software. The wire cutting machine tool is called a stepper.
A closed-loop control system refers to a controller that uses sensors to provide real-time feedback on the position, speed and other information of the motor, and controls the motor based on the feedback information.
A semi-closed-loop control system is a control method between an open loop and a closed loop, which controls the motor through partial feedback information. Compared with an open-loop control system, a closed-loop and semi-closed-loop control system can more accurately control the position and speed of the motor, and improve the machining accuracy and stability of the machine tool.
Closed loop and semi-closed loop are what we often call servo machines. The software is called servo wire-cut system, and wire-cut machine tools are also called servo machines. Six-axis servo machine tools and five-axis CNC machine tools are both types of servo machines.

The control system is the heart of the machine tool, and the upgrade of the control system has greatly improved the accuracy of the machine tool.

2.3 Different levels of machine intelligence
The servo-based wire-cutting machine tool control system has added many functions of the slow-cut wire-cutting machine tool. For example, the Cool Cutting servo system for wire-cutting has built-in pitch compensation function, fast air-cutting axis shifting, slow-cutting AR table, multi-user coordinate system, rotary axis processing, and automatic centering advanced functions, which greatly improve the intelligence of the machine tool. These functions are unique to the servo-based wire-cutting. In the field of spiral cutting, the Cool Cutting system can realize rotary processing, and the six-axis linkage technology can realize cutting processing of complex curved surfaces, which is suitable for precision machining fields such as automotive mold processing and aerospace mold processing.

Through the above introduction, we can understand that the core factor affecting the processing speed of stepper wire cutting and servo wire cutting is the control circuit of the machine tool, that is, the high-frequency power supply, followed by the machine tool control system. The servo-specific control system has an idling speed dozens of times faster than the stepper, which will greatly reduce the waiting time for the machine tool to idling. In addition, the Cool Cut system has added many functions that are only available in slow-cut wire cutting machines, such as calculating the Z-axis rise and fall values through the control system, and memorizing them, and cooperating with the servo motor to achieve precise descent and rise. It is convenient to remove waste with one click, and remove waste with the die, etc. Compared with manual or semi-automatic stepper motors, it greatly saves time and ensures accuracy without error. For more models of wire cutting wire cutting, purchase precautions, usage tips, etc., please follow Zhikai CNC, which will be updated from time to time. Thank you.