When it comes to colors, stamping plants prefer green over red. No, this is not a reference to Michigan State versus Ohio State in college football. In this instance, “green” represents profit and “red” represents loss. Stampers stay “in the green” when they run continuous production without interruptions and achieve high strokes per minute (SPM) rates.
How can you be sure your transfer die ends up in the green instead of red? By applying best practices. But before you can do that, you have to understand transfer die fundamentals.
Understanding Transfer Die Basics
A transfer die lineup typically begins with a blank or a coil-fed strip. The blank or strip is then moved through several stations that finish or partially finish the part or parts. Unlike a progressive die, the parts do not stay connected from one station to the next. Instead, a transfer mechanism is required to move the parts from one station to the next.
The transfer mechanism can be mounted to the press, or it can be mounted to the die. The motion can be fixed (unchangeable) or it can be programmable, allowing the operator to change the travel distances and the timing for when motions begin and end.
Robotic transfers allow for even more motion freedom. Several single-station presses can be put in a line with robotic arms moving the parts press to press.
Three Steps to Better Throughput
- Evaluate Up Front. What is the first step a stamper can take to make sure a transfer die is headed in the green direction? Up-front evaluation is the foundation of the entire project. It is the key for choosing the pathway toward green or red. It can mean happiness or headaches for the entire life of the die.
Initially, engineers look at the part size and characteristics, the material used, how many parts are needed a year, and how many years the die will run. This helps them choose whether a transfer die is the best fit or not.
Typically, transfer press selection is based on die size, transfer space, tonnage requirements, press availability, and the SPM required to make money and stay in the green.
Up-front evaluation is more than just figuring out which stations should be used to form, trim, and pierce the metal. At this stage you also should decide which kind of transfer fingers to use, how many are needed, and where to place them on the parts. Where are the best locations for gauges to locate the part properly without restricting or limiting the transfer motion speed?
One important area to focus on during initial evaluation is how you will transport the blanks. Depending on the material, blanks can tend to sag and droop in the middle during transport into the first station. Make sure you have adequate fingers for transporting the blanks. Shovels that simply scoop up the corners may not work if the blank tends to sag and pull in. Gripper clamps bite hard and hold tension well. Consider using four grippers—one on each corner—to transport blanks that sag.