Pad Travel with Die Mount Cams

Posted by stephens on Jul 17, 2009 in Cam Dies, Engineering Decisions, Equations, Tips & Techniques | 0 comments

The main pad in a die with die mount 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 die mount cams are present is to calculate the main pad travel.

The equation for main pad travel with die mount cams is:

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

where:

• Tpad = main pad travel (mm)
• ESM = engineered safety margin (mm)
• Tdcs = die mount cam steel travel (mm)
• α = driver angle from vertical (degrees)
• β = work angle from horizontal (degrees)

NOTE: if there are multiple die mount 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 die mount cam(s), then the direct operation will drive the main pad travel.

For example, assume a die mount cam has cam steels with a work travel of 12 mm. The upper driver angle is 60° from vertical. The work angle is 10° 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 + {[Tdcs • cos(α - β)] / sin α }
• Tpad = 5 + {[12 • cos(60° - 10°)] / sin 60°}
• Tpad = 5 + {[12 • cos 50°] / sin 60°}
• Tpad = 5 + (7.71 / 0.866)
• Tpad = 5 + 8.903
• Tpad = 13.903
• Tpad = 14 mm minimum

This tool requires a minimum main pad travel of 14 mm so the die operates properly with the die mount cam. Since the direct steels have only 10 mm work travel, the 16 mm minimum main pad travel will work fine.