Common Issues and Solutions in Can Lid Stamping

Common Issues and Solutions in Can Lid Stamping

The quality of can lid is crucial in the production of metal cans, necessitating thorough quality checks. Below are common issues in can lid stamping and suggested solutions:

1. Uneven Width of Bottom Lid Outer Flange  

- Cause: Uneven pressure from the upper die ring on the sheet metal during the downward punch, leading to varying outer flange widths.

- Solutions:

- (1) Check if the punch installation is correct and whether there is any uneven tightness on one side.

- (2) Verify that mold fit tolerances meet requirements to enhance mold processing precision and accuracy.

2. Bottom Cap Breakage  

- Cause 1: Misalignment in the pusher head's positioning.

- Solution: Adjust the positioning of the pusher head.

- Cause 2: Poor tightness of the pressure plate.

- Solution: Adjust the pressure plate tightness.

- Cause 3: Inadequate tightness of the discharge pressure strip.

- Solution: Adjust the tightness of the discharge pressure strip.

- Cause 4: Worn or loose parts in the transmission mechanism (e.g., transmission shaft, bevel gear, or eccentric wheel).

- Solution: Replace parts or tighten the transmission mechanism.

3. Bottom Cap Scratches  

- Cause 1: Rough pusher head surface.

- Solution: Polish the pusher head surface with metallographic sandpaper.

- Cause 2: Raised burrs on the baffle.

- Solution: Polish the baffle with sandpaper or apply adhesive tape.

- Cause 3: Tight fit between upper and lower dies or insufficient chamfering/surface smoothness.

- Solution: Round the edges of upper and lower die cores, ensure precise tolerance fit according to drawings, and increase the oil application on the sheet metal as needed.

4. Cap Surface Impressions  

- Cause 1: Poor quality of incoming material printing.

- Solution: Sort through incoming materials.

- Cause 2: Trash in the mold cavity.

- Solution: Use a cloth or air gun to remove debris.

5. Wrinkled Outer Flange  

- Cause 1: Excessive gap between the upper die ring and the lower die core’s outer flange.

- Solution: Adjust the gap between the upper die ring and the lower die core's outer flange.

- Cause 2: Uneven pressure during rolling, leading to uneven sheet metal shrinkage.

- Solution: Increase pressure on the lower die spring (or rubber gasket) and adjust the gasket’s position to ensure even pressure distribution.

6. Failure to Pick Up Sheets  

- Cause 1: Damaged or deformed suction head (air leakage).

- Solution: Replace or repair the suction head.

- Cause 2: Uneven suction head height.

- Solution: Adjust all suction heads to the same plane.

- Cause 3: Low position of the travel limit switch.

- Solution: Raise the travel limit switch position.

- Cause 4: Faulty vacuum pump.

- Solution: Replace or repair the vacuum pump.

7. Poor Cap Ejection  

- Cause 1: Blocked exhaust holes in the upper and lower die cores.

- Solution: Enlarge the exhaust holes and clear any blockage.

- Cause 2: Insufficient spring tension in the lower die discharge ring, or issues with upper die discharge ring flexibility.

- Solution: Increase the tension of the spring ring (increase the thickness of the rubber gasket), and check the upper die ring and inner chamfer of the upper blade.

8. Burrs  

- Cause: Dull cutting edge or excessive gap between upper and lower blades.

- Solution: Perform heat treatment on the cutting edge to enhance hardness, followed by grinding to ensure sharpness and proper fit between upper and lower blades.

9. Triangular Cap Edge  

- Cause: Poor groove design in the circular capping machine, oversized inner diameter of the upper blade, or excessive cap edge length after forming.

- Solution: Ensure proper fit between the upper blade and lower die core, form a right angle at the cap edge, and maintain accurate groove design and dimensions in the circular capping machine.