If you regularly operate a print finishing press, whether for foil stamping, embossing or die cutting, it is likely that you will have experienced the problem of “double feeding”. For those of you who are non-operators, double feeding is when the suckers at the end of the feeder arm accidentally lift two sheets of stock and feed them to the platen. This obviously causes wasted stock and consumes time while removing the double-fed piece from the machinery.
Although a common problem in the print finishing industry, the following steps can be incorporated into the production process to help prevent double-fed sheets on Kluge presses:
1. Ensure good sheet separation and pile height adjustment
By ensuring sufficient sheet separation and pile height adjustment, the feeder arm can be held from pushing the top sheet against the sheet behind it, thus preventing the sheets from “sticking” together.
2. Proper “combing” of the stock
“Combers” are tongues, ridges or brushes that hold the stock in place on the feeder and help prevent double-lifting. The combers on Kluge presses are steel flexible tongues built into the front of the feeder below the stock pile. As the suckers on the feeder arm lift the top sheet of stock from the pile, the combers flex and then spring back to help hold the second sheet in place thus, preventing double lifting.
3. Create a little pressure on the front top edge of the pile
There are many make-shift ways to create pressure on the front top edge of the stock pile in the feeder, and works in a similar way to the combs except this procedure functions on the top side of the stock pile. Each method is used based on personal preference. By creating this pressure with the correct amount of flexibility, double lifting can be virtually eliminated. The additional make-ready time required is gained back multiple times during operation by the reduction of double-fed sheets. An effective way to create this light pressure as used by one of our experienced service technicians, is as follows:
You will need two 10″-12″ wire ties. These should be attached to towards the right side of the center bar of the three bars in front of the feeder, and in line with the stock pile. The wire can be attached by simply twisting it around the bar. The center bar is used as it is the only bar of the three that remains stationary during the job cycle. The excess wire should be adjusted to point upwards and to rest on the top edge of the top sheet on the pile. Repeat the procedure for the left side of the center feeder bar. The wire tie provides the correct pressure/flexibility combination. It flexes sufficiently as the top sheet is pulled away and has just enough pressure to hold the second sheet back from being “double-lifted”.