I. Overview
In the field of metal materials, 60%-70% are sheet metal, and most sheet metal is processed into finished products through stamping. Stamping has a wide range of applications in various sectors of the national economy.
A punch press is a stamping press. In national production, compared with traditional machining, stamping technology saves materials and energy, and is highly efficient. It does not require high operator skills, and through the application of various molds, it can produce products that cannot be produced by machining.
As a drive component for punch press control, frequency converters have evolved from general-purpose products to punch press-specific frequency converters. The performance of frequency converters plays a decisive role in the output stability, accuracy, reliability, and load-bearing capacity of high-speed punch presses.
II. Process Requirements for High-Speed Punch Presses
After the equipment undergoes frequency conversion energy-saving retrofit, the following requirements must be met: stable speed increase during startup without mechanical shock, protection of the punch press's mechanical parts, extended maintenance intervals, adjustable speed according to product requirements, ensuring product quality, reducing scrap rate, and increasing product profits. The frequency converter will automatically alarm and stop working when the punch press motor is overloaded, protecting the punch press's molds and punches, saving production costs for the enterprise, improving punch press automation, increasing production efficiency, and reducing worker labor intensity.
III. Weichuang Solutions
The following problems can be easily solved by using the Weichuang AC80C series frequency converter:
1. Dead point problem of crank-connecting rod mechanism
Punch presses typically use a crank-connecting rod mechanism to convert rotary motion into reciprocating motion. However, the crank-connecting rod mechanism has dead points (both "top dead point" and "bottom dead point"). Throughout the entire motion cycle, the load changes unevenly, exhibiting periodic fluctuations.
2. Sudden load problem during stamping operation
There are basically at least three working points in a punch press, and the load has abrupt characteristics: (a) past the top dead center; (b) past the bottom dead center; (c) when contacting the workpiece during punching;
3. Problems with low-speed operation during stamping of some workpieces.
Automatic continuous punch presses, with robotic arms involved in material handling, naturally benefit from higher speeds. However, in some applications, a punch press with good low-speed characteristics is required.
4. Inching issue during mold adjustment
When adjusting the die on a punch press, inching is required. This involves the clutch constantly engaging and disengaging, which causes the motor to be loaded and unloaded very frequently. In this case, the frequency converter needs to have a good current suppression function.
IV. Conclusion
The external cylindrical grinding machine system implemented with the Weichuang AC80C frequency converter operated smoothly and reliably throughout the entire process, bringing significant economic benefits to the company. Through actual production testing, the customer was highly satisfied with Weichuang's overall solution. Its advantages are mainly reflected in the following aspects:
1. True current vector control technology, perfect low-frequency torque.
2. Fast and stable speed tracking and restart function.
3. Current limiting function to protect the frequency converter and motor.
4. Perfect voltage suppression function.
