Can Lid Stamping and Forming Process Overview

Can Lid Stamping and Forming Process Overview

The structure of the capmaking die is a composite die. Here’s a detailed explanation of the complete forming process of the die.

1. Blanking  

When the metal strip enters the upper and lower dies, the upper die moves down. The upper blade (1) and lower blade (4) cut the metal into blanks (usually circular), with the size of the blanks determined by the dimensions of the upper and lower blades.

2. Stamping Formation  

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

3. Beading  

The beading of the cap occurs in a beading machine. The main components of the beading machine are two molds with circular grooves: the outer mold is fixed to the machine plate, while the inner mold is fixed to a rotating disk that spins at high speed toward the cap entrance. When the cap falls, its edge is caught in the grooves of the inner and outer molds, and the cap is rotated and rubbed against the inner mold's groove, creating a beaded edge. The beading machine for singlehead stamping presses is usually a horizontal setup at the discharge outlet, while doublecolumn vertical beading machines are used for doublehead stamping presses.

4. Relationship Between Cap Die and Cap Shape  

The shape and dimensions of the cap depend on the relevant sizes and shapes of the upper and lower stamping dies. The relationships are as follows:

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

Inner Diameter of the Shoulder Base: Determined by the outer diameter of the upper core, which is a critical size for matching the sealing head and serves as a basis for cap die design and standardization.

Outer Diameter of the Shoulder: Determined by the inner diameter of the lower ring (if the lower ring and lower core are a single structure, this size is determined by the inner diameter of the lower core).

Shoulder Angle: Determined by the gap between the upper and lower cores and the thickness of the metal, generally around 4°.

Expansion Ring Slope and Size: Determined by the shapes and sizes of the upper and lower cores.

Depth of the CounterSink: Determined by the depth of engagement when the upper die presses down against the lower die.

Edge Thickness: Determined by the blanking size of the upper blade, the gap between the inner diameter of the upper blade and the outer diameter of the lower ring, and the shape of the beading groove.

Cap Edge Arc: Determined by the groove shapes of the inner and outer disks of the beading mechanism and the thickness of the edge at the time of blanking.