Automation production of stamping dies—— research and application of sensor detection technology

■ Preface

In recent years, with the vigorous development of the sheet metal industry, various sheet metal products are increasingly used in daily life. To meet the current development trend of intelligent and automated production. In stamping automation production, there must be not only an automatic feeding device, but also a safety detection device to prevent errors during the production process to protect the die and press from damage and effectively improve the quality of the stamping parts. 

The safety detection device can be set inside or outside the mold. When an error occurs and affects the normal operation of the mold, various sensors in the mold (contact sensors, proximity sensors, photoelectric sensors, etc.) can quickly feed back signals to the brake device of the press, causing the press to stop and alarm, and realize automatic protection. In order to enable the stamping die to achieve a good state of continuous and automatic production, the sheet metal mold needs to add sensor detection technology.

■ Analysis of the structure and processability of induction detection

1.Design of detection structure for blockage of parts or scrap

As shown in the figure above, the detection structure diagram of blockage of parts or scrap,when the blanking scrap or parts falls freely by its own weight, if each piece of scarp can contact the detection pin, the press will work continuously. If the scrap is blocked in the die, and no scrap passes through the detection pin in a stroke of the press, the electromagnetic clutch of the press synchronized with the detection pin will be disengaged, and the slide will stop descending. This detection form is suitable for detecting scrap with larger contour dimensions.

2.Design of structure for detecting part or scrap lifting and blockage

As shown in the figure above,Lift detection generally uses the bottom dead center (BDC) of the die's closing height for detection. The micro switch (2) is installed on the upper die holder (1). When there is no scrap or other foreign material on the surface of the spring-loaded stripper plate (3) and the die (4), the micro switch remains in an open state. If scrap or foreign material is present on the die surface, when the press slide descends to the bottom dead center, the scrap or foreign material lifts the spring-loaded stripper plate, causing it to contact the micro switch and close the circuit, stopping the press slide from descending further. This method is suitable for thick material blanking, with a sensitivity of approximately 0.1–0.15 mm.

3.Feeding Pitch Issue Detection structure desgin

Feeding Pitch issue detection is performed using the guide pin 1 to detect the pitch. This detection device is an integral part of the progressive die structure and is a comprehensive detection device that is simple and practical. It can detect the phenomenon of not being in place or over-positioning caused by inaccurate feeding, and at the same time detect the phenomenon of scrap blocking. When the feeding error is not large, it can also play the role of guiding the material. When the feeding is inaccurate or scarp blocking occurs (the blocked scrap must be on the detected hole), when the punch slide drops to a certain height, the guide pin 1 first touches the fed strip material (or blocked scrap). At this time, the guide pin overcomes the action of the spring due to obstruction and rises, pushing the force transmission pin 2 tangent to the arc at the end of the guide pin to move, pushing the micro switch 3, and this micro switch 3 cuts off the power supply of the corresponding part of the punch press, so that the pressure stops working. When the fault is handled, the Pilot pin is reset under the action of the spring.

▇  Conclusion

(1) By adopting a detection structure for parts or scrap jamming, the issues of production interruptions and die damage caused by improper scrap drop or blockages have been successfully resolved.

(2) By implementing a detection structure for parts/scrap lifting and jamming, problems such as product denting and batch quality defects due to parts or scrap rebound have been effectively addressed.

(3) Through feeding pitch issue detection mechanism, continuous misfeeds, material buckling, and resulting mold damage from feeding issues have been successfully prevented.