Rooster's Revenge

The main pad in a die with aerial cams must hold the stamping in place on the lower tool during the press downstroke before the cam steels make initial contact.

On the press upstroke, the main pad must hold the stamping on the lower tool until the cam steels clear the stamping.

The simplest way to ensure the proper timing of the main pad when aerial cams are present is to calculate the main pad travel.

The equation for main pad travel with aerial cams is:

• Tpad = ESM + {[Tacs • sin(α + β)] / cos α }

where:

• Tpad = main pad travel (mm)
• ESM = engineered safety margin (mm)
• Tacs = aerial cam steel travel (mm)
• α = upper driver angle from horizontal (degrees)
• β = work angle from horizontal (degrees)

NOTE: if there are multiple aerial cams, then calculate for all and use the greatest result for the main pad travel. Also, if the direct cutting or forming requires more travel than the aerial cam(s), then the direct operation will drive the main pad travel.

For example, assume an aerial cam has cam steels with a work travel of 12 mm. The upper driver angle is 30° from horizontal. The work angle is 20° from horizontal. The engineered safety margin on the main pad is a minimum of 5 mm. The direct steels have 10 mm work travel.

The required main pad travel for this die is:

• Tpad = ESM + {[Tacs • sin(α + β)] / cos α }
• Tpad = 5 + {[12 • sin(30° + 20°)] / cos 30°}
• Tpad = 5 + {[12 • sin50°] / cos 30°}
• Tpad = 5 + (9.19 / 0.866)
• Tpad = 5 + 10.61
• Tpad = 15.61
• Tpad = 16 mm minimum

This tool requires a minimum main pad travel of 16 mm so the die operates properly with the aerial cam. Since the direct steels have only 10 mm work travel, the 16 mm minimum main pad travel will work fine.