The bottom flange electric eye emits an infrared beam of light to a reflector, which bounces the light back to the electric eye. When the beam of light is broken, the output of the electric eye goes low (DC return), which turns on an input in the control console.

The bottom flange electric eye is used to detect the presence of the material prior to performing any operations on the bottom flange of the material.

In typical operation, the bottom flange remains out of the way of the material as operations are processed on the web and top flange. When the time arrives to process the bottom flange operations the material moves to a position in front of the bottom flange frame and stops. (See Figure 1.) This position is determined by the BF_OFF, FRAMEOFF constant plus the BF_INOUT, FNDMBPOS constant. The FNDBMPOS constant is a negative dimension, usually 6 to 7 inches.

When the material is in position in front of the bottom flange frame, the frame moves in until the electric eye turns on (finds the material). (See Figure 2.) Once the frame is properly positioned with respect to the material, processing of the material will continue.

The electric eye is manually adjusted to allow the bottom flange of the material to fit between the stripper and the die seat. There will be more clearance between the material and the die seat when running thin flange material. This allows for different thicknesses of material to be processed without the necessity of further adjustment of the electric eye.

There are several constants related to the bottom flange electric eye, and they can be found in the BF_INOUT section of the constants. These constants were set when the machine was installed and most will not need to be adjusted, unless mechanical changes have been made to the machine. However, the MAXFNDTM constant may need to be adjusted occasionally.

The MAXFNDTM constant tells the computer the maximum amount of time to look for the material (see Figure 2), and is usually set to about 18000 (18 seconds). If the bottom flange electric eye does not locate the material within the alloted time the program will stop with an error. This condition may arise if the bottom flange moves in too slowly. (If this condition occurs, press escape twice and the program will continue.)

To avoid error conditions and unnecessary delays, we recommend the following method. Prior to running parts that have bottom flange operations, manually move the bottom flange frame in so it does not have as far to travel when looking for the material.