Can Lid Stamping and Forming Process Overview

1. Blanking

When the metal strip enters the upper and lower dies, the upper die descends. The upper blade (1) and lower blade (4) cut the metal into blanks—usually circular—based on the dimensions of the blades.

2. Stamping Formation

As the upper die continues downward, the upper core (3) and lower core (6) compress the metal to form an expansion ring. Simultaneously, the upper ring (2) and lower ring (5) create the countersink structure, shaping the metal into the desired cap form.

3. Beading

Beading takes place in a beading machine equipped with two molds featuring circular grooves.

• Outer Mold: Fixed onto the machine plate
• Inner Mold: Mounted on a rotating disk

When the cap falls, its edge is caught and rotated in the grooves, creating a beaded edge. For single-head stamping presses, a horizontal beading machine is commonly used at the discharge outlet, whereas a double-column vertical beading machine is typically paired with double-head stamping presses.

4. Relationship Between Cap Die and Cap Shape

Various aspects of the final cap rely on the dimensions and shapes of the upper and lower stamping dies:

1. Blanking Size
Determined by the blade size (outer diameter of the upper blade).

2. Inner Diameter of the Shoulder Base
Determined by the outer diameter of the upper core, a key dimension for sealing and standardization.

3. Outer Diameter of the Shoulder
Determined by the inner diameter of the lower ring (or lower core if it is a single piece).

4. Shoulder Angle
Defined by the gap between the upper and lower cores and the metal thickness, typically around 4°.

5. Expansion Ring Slope and Size
Dependent on the contours and dimensions of the upper and lower cores.

6. Depth of the Countersink
Established by how deeply the upper die presses into the lower die.

7. Edge Thickness
Controlled by the blanking size of the upper blade, the gap between the upper blade’s inner diameter and the lower ring’s outer diameter, plus the beading groove design.

8. Cap Edge Arc
Influenced by the groove shapes in the beading mechanism’s inner and outer disks, as well as the edge thickness from blanking.