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Exactly what is an automatic labeling system? Labeling Head (Label Applicator) Dancer Arm Label Sensor Detects the 1/8" gap between labels to alert the control system to initiate a label stop sequence. This is accomplished with an electro-mechanical switch (still standard on some brands), photoelectric sensor, or capacitive sensor (usually an option for clear labels). Peel Plate The peel plate actually separates the label from the backing paper. As the web breaks sharply over the peel plate, the label continues on in a straight line. Drive Roller The Drive roller is actually the workhorse of the labeling head. In conjunction with a pinch roller, the drive roller pulls the web backing, starting and stopping with each labeling sequence. These are very similar on all machines. The difference in quality in labelers is not so much by the drive roller itself by the means by which the roller is driven and stopped. It is worth taking some time to go over the types of drive systems available and their advantages or disadvantages. Stepper Motors This is another confusing area for the purchaser of a labeling machine. There are A.C. (alternating current) and D.C. (direct current) stepping motors. D.C. stepping motors are further categorized as 2-phase and 5-phase. A.C. Stepping Motors A.C. Stepper motors are used on a few labeling systems, but not many. The advantage is they are relatively inexpensive. But the disadvantage is that they have a large step angle (about 12 degrees) creating inaccuracy and have limited speed capability. D.C. Stepping Motors What is a Stepping Motor? A stepping motor is an electromechanical device that converts electrical power to torque. But what makes a stepper motor different is that the shaft rotates in fixed angular units (steps) when its phases are energized in a predetermined order. 2-phase motors typically have 200 steps per revolution, whereas 5-phase motors typically have 500 steps per revolution. Stepper Motors are connected to a special driver which is actually a very high speed switching device that accepts input pulses from an encoder or PLC. For each input pulse it receives the motor advances one step. A 5-phase motor therefore requires 500 pulses to advance one full revolution. However, to smooth out the operation of the motor and get greater accuracy, most drivers can be operated in what is called "half step mode". Half step mode allows the motor to advance with double the resolution or 1000 steps per revolution. So now the input pulses must also be doubled to 1000 pulses per revolution. Further divisions can be made by micro stepping. However. micro stepping results in considerable loss of torque at each division and is not widely used in labeling applications. Conveyor or "Product Transport" For a product to accept a label some means must be provided to transport it through the labeling station. In the overwhelming majority of cases this will be a conveyor for transporting boxes, bottles, candles, or any of the myriad of products you can imagine. In very special circumstances where the product is unwieldy, or labeling must be done on a special production line due to some unique circumstance we can build a custom product transport or systems integration. The most important feature that should concern you is not the type of conveyor you buy (although it must obviously be able to physically handle your product dimensions and loads) but how it is driven and its controls.
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