Registration Application Guide

In many closed-loop servo systems it is often necessary to maintain synchronizationClosed Combines an axis or axes group (as slave) with an axis as master. The slave executes its path with synchronization to the progress of the master. This is linked to a one dimension source for synchronization. and accurate positioningClosed Position means a point in space which is described by different coordinates. Depending on the used system and transformation it can consist of a maximum of six dimensions (coordinates).This means three Cartesian coordinates in space and coordinates for the orientation. In ACS there can be even more than six coordinates. If the same position is described in different coordinate systems the values of the coordinates are different. repeatedly throughout a process. This can be difficult when the product or process itself is inconsistent. Using registration helps you to overcome this difficulty.

Many factors can contribute to inconsistency. Some examples are:

To overcome the various product and process inconsistencies registration capabilities may be required and can be applied on any servo or digitizing axis, and with any move type. Typically in these applications, sensorsClosed A type of transducer that converts one type of energy into another for various purposes including measurement or information transfer. are used to detect the position of the product. With non-rigid materials, which may stretch or shrink or are unevenly spaced, a photo eye can detect registration marks on the material. With rigid products or processes a proximity sensor can detect leading or trailing product edges for material spacing.

With registration, the registration sensor is wired to the fast inputClosed The inputs are taken into account at each cycle depending on the system periodicity (i.e., each millisecond). Under certain circumstances, this can be insufficient when more accuracy is needed or if a quick response is required from the system. To fill the gap, a drive may have some Fast Input connections (generally one or two). When an event happens that triggers a Fast Input (e.g., when a sensor sends a rising edge), the detection of a signal occurs faster. This can be 1000 times more accurate than the system periodicity. The timestamp associated with this input can be provided to the IPC to take corrective action. on the servo driveClosed A special electric amplifier used to power electric servo motors. It monitors feedback signals from the motor and continually adjusts for deviation from expected behavior. providing the means for the registration trigger that will capture the axis position at the instance of the registration event. When the event occurs, the system will calculate a registration correction to compensate for the inconsistency and then can apply the correction to the registration axis and/or change the numerical representation of the registration axis position.

This is important in applications such as printing, packaging, and converting where the process must be precisely coordinated and any non-rigid material cannot be depended upon to retain dimensional relationships. These applications usually involve master/slave moves. Not only does registration provide correction but the fast input signals can also be used as repeatable references to which the master and all subsequent slaves continually synchronize. Two main types of registration are Mark to Mark Registration and Mark to Machine Registration.

Mark to Mark Registration

Mark to Mark Registration is implemented with the function blockClosed A function block groups an algorithm and a set of private data. It has inputs and outputs. MC_MarkRegist and is based on the desired distance between two registration marks. This distance is used to qualify a “good” mark and then calculate a registration correction. Examples of the different mark to mark registration variations include:

  • Clear Lane Registration
  • Print Registration
  • Product Registration
  • Rotary Registration

Clear Lane Registration is the most common type of registration used in industry. A dedicated lane on the material is reserved solely for registration purposes. Only the registration marks in the lane will trigger the sensor and fast input on the servo driveClosed In electrical engineering, a drive is an electronic device to provide power to a motor or servo. Control device for regulating the speed, torque and position of a motor. A unit controlling a motor using the current and timing in its coils.. The distance between one registration mark and the next mark is the basis for registration correction calculations.

Print Registration is less common than Clear Lane Registration. Print registration involves picking out a distinct distance between print features. Here too, this distance is the basis for registration correction calculations. Print registration is used when it is not practical to have a clear lane.

Product Registration uses cycle position where the relationship of the product position in the process cycle is important. Product registration can occur synchronously or asynchronously. In synchronous product registration, products typically flow continuously through the process. Registration will measure and calculate small adjustments required to move each product to the correct position. The distance between products is the basis for registration correction calculations. Asynchronous applications may require the axis to sit and wait for the product to pass the sensor and, when it does, initiate a move and also apply registration correction based on the position of the product.

Rotary Registration is used to maintain a fixed axis position reference point on a rotary axis that has non-integer feedback in one revolution. If the axis position is not adjusted, the actual axis position would walk away from the desired position every revolution because of the non-integer number of feedback units per revolution.

Mark to Machine Registration

Mark to Machine Registration is implemented with the functionClosed A function calculates a result according to the current value of its inputs. A function has no internal data and is not linked to declared instances. block MC_MachRegist and is based on a desired target position on a machine axis. Like mark to mark registration, mark to machine registration uses the desired distance between two registration marks to qualify a “good” mark (using Clear Lane, Print, and Product registration). But instead of using the mark to mark length, it uses an axis position as its basis for correction.