Prefeeding: The Key to Consistent Length Accuracy
When it comes to fully automatic processing, bad or non-existent prefeeding accounts for approximately more than 50 percent of all inconsistencies in total length and stripping length.
The tension on the wire or cable when simply being pulled off a reel or spool can temporarily stretch the material and cause length inconsistencies - simply because the material often retracts long after having been processed.
Depending on the material to be processed, prefeeding keeps the tension on the wire or cable at an absolute minimum by compensating the acceleration (pull) of an automatic wire processing machine.
There are two ways of prefeeding:
- Active dereeling (reel driven)
- Puller-driven dereeling
Active Dereeling (Reel-driven)
Because the reel is electrically driven, the wire or cable is not being stressed by any pull forces. The dereeling speed is controlled either by means of a pendulum arm, accumulator, or a sag control.
PreFeeder 1000: motorized reel with pendulum arm to control the dereeling speed (here in action with a PowerStrip 9500 RS)
The accumulator is best suited for feeding flexible mid-sized cables. It "stores" cable and can therefore quickly release it when the automatic cutting or cut & strip machine pulls at a much higher feed rate than a reel could be accelerated by a small motor.
PreFeeder 2500: motorized reel with accumulator
Delicate or small and very thin wires are normally fed with a system using sag control. With this method the least possible tension is applied to a wire or cable.
PreFeeder 2500: motorized reel with sag control (PreFeederControl 2)
It is adviseable to have a minimal tension on the wire in order to keep it straight at all times during production.
Puller-Driven Dereeling
The cable is pulled off the reel by means of a traction device. This method is ideal for processing wires and cables that come out of a barrel or from loose coils. This cost-efficient solution is also used to feed wires and cables to the processing machine which are stored in large racks and/or have a relatively high adhesion between the jacket and the conductor(s).
PreFeeder 2200: Traction speed controlled by means of an accumulator |