Registration Control Types:

 RC Type:
The RC400, constantly scans the web registration mark. It then compares this mark's position with cylinder/die station to be controlled. The microprocessor then generates a correcting signal to adjust the relative position of the print/die station to ensure proper and accurate registration.

Provides output to correction (registration?) motors (split phase reversible) to adjust the relative position of the print cylinder ( or die) to the web. These systems are used on single pass (not pre-printed) operations without accumulating repeat errors. 

The typical arrangement of a RC system consists of: 
An operator interface to allow for monitoring and entering of information
An encoder - Provides web position information
Scanner's) - Provides repeat (impression) information
Correction motor's - to adjust print (die) cylinder position to the web. 

The output of a RC system is a proportional time based signal, proportional to the measured error, on press speed and phase error detected. 

The RC was developed to control the random registration errors that are caused by slippage, roll changes, tension changes and other momentary upsets that may occur.

See - Web path compensation functions in web compensation mode.

Presses need to capable of being fitted with the correction motors. The system will accommodate presses with 360 degree running register or presses with limited travel correction capabilities.

MLS Type:

Provides an output to correction motors, typical stepper or servo, to adjust the relative position of the print cylinder (die) to the web.

These systems are used on multiple pass operations, printing or die cutting on pre-printed web, screen printing or other operations with or without accumulation of repeat error.

The typical arrangement of a MLS system consists of:
An operator interface enclosure's) with display and keypad.
A main enclosure with drive's) and all electronics.
A line shaft encoder with cable.
Motor's with cable's.

The output of a MLS system is a pulse rate based on the constant length error and phase (registration) error detected.

The MLS was developed to control the following:

Random phase errors that are caused by slippage, roll changes, tension changes and other momentary upsets that may occur.

Length errors between the actual repeat length of the preprinted web and the repeat length of the print cylinder or die.

Length errors due to trending caused by tension changes during the first pass of printing.

Presses need to have 360° running register capability using a harmonic gear box with a position control shaft. The existing adjustment motor will be replaced by the motor provided with the system.

ELS Type: The ELS400, "Electric Line Shaft" replaces the mechanical connection of a print, screen or die station to the press line shaft. The stepper or servo drive of the ELS400 establishes and maintains the print, screen or die cylinder repeat to the repeat of the web. The system controls the registration by constantly scanning the web registration mark and comparing its position with the target mark of the print, screen or die station to be controlled. The microprocessor then adjusts the station's relative position.

Provides an output to a stepper, servo or vector drive to adjust the speed and relative position of a direct driven print or die station with respect to the web.

These systems are used on multiple pass operations, printing or die cutting on pre-printed web, screen-printing or operations with or without accumulation of repeat error.

The typical arrangement of a ELS system consists of:
An operator interface enclosure's with display and keypad.
A main enclosure with drive's) and all electronics.
A line shaft encoder with cable.
Motor's with cable's.

The output of a ELS system is pulse rate based on the press speed, constant length error and phase (registration) error detected.

The ELS was developed to control the following:
Random phase errors that are caused by slippage, roll changes, tension changes and other momentary upsets that may occur.

Length errors occurring based on the difference between the actual repeat length of the preprinted web and the repeat length of the print cylinder of die.

The print station or die station on press not equipped with 360° running register control. (Converts a non 360 degree system into a full 360 adjustment.)

Stand alone rotary screen print stations, die stations, embossing stations or gluing stations.

There are two types of register error:

RANDOM PHASE: error caused by: Slippage

              Roll changes
              Tension changes
              Other momentary upsets

LENGTH ERROR:
Constant length errors caused by the difference between the actual repeat length of the preprinted web and the repeat length of the printed cylinder or die. Trending length errors caused by changes in the repeat length of the preprinted web.

RC-400 provides a solution for RANDOM PHASE registration error on presses that are or can be fitted with registration correction motors.

MLS-400 provides a solution for RANDOM PHASE registration error and LENGTH ERROR on presses that are or can be fitted with 360 degree running registration correction motors.

ELS-400 provides a solution for RANDOM PHASE registration error and LENGTH ERROR on presses that cannot be fitted with 360 degree running registration correction motors.

ELS-400 provides a solution for applications requiring a stand alone unit to be operated in register with a moving web. Applications include ROTARY SCREEN STATIONS and GLUING STATIONS in addition to stand alone PRINT AND DIE STATIONS.

ELS PRESS REGISTRATION
Advances in technology have allowed the development of an economical electronic line shaft or ELS. Programmable Electronic Systems (PES), which include Programmable Logic Controls (PLC), Computer Numeric Controllers (CNC), Personal Computers (PC) and Micro Processors (uP) have increased in both speed and capability to allow real time control of fast occurring events. The development of rare earth servo and stepper motors provides higher torque in smaller frame sizes at reasonable prices.

The ELS is intended to replace the mechanical drive mechanisms and components that couple a motor driven shaft of a machine to its working sections. This eliminates the pinion, miter and other gears required to drive the machine components. It can also replace the need for change gears or differential gearboxes required to match the actions of one section of the machine to another. Eliminating these gears removes inaccuracies caused by backlash, misadjustment and wear.

ELS Systems On Printing Presses

On printing presses, the ELS can be used to drive and control print cylinders or impression rolls, rotary dies or anvils, in-feed rolls, step and repeat stations, inspection stations and sheeter sections. The ELS can also drive the control shaft of a differential gearbox where high horsepower is required to drive a press section.

Installation of ELS systems is easy and economical. On new presses or press sections, the servo or stepper drive can be directly incorporated within the section. On existing presses, removal of the mechanical drive parts to the press section from the line shaft and the addition of the servo or stepper motor is usually economically achieved and can be done "on site" eliminating the need to return the section to the manufacturer for modification.

The system consists of four main components; an incremental encoder, an ELS control system, a servo or stepper motor and an operator's control. The encoder is used to measure the web movement as it is pulled through the press. The encoder is usually attached to the pull roll or to the drive shaft connected to the pull roll. The control system processes the pulses from the encoder moves the servo or stepper to the appropriate position such the print or die cylinder matches the position of the web. The operator's control allows the press operator to control and monitor the process.

ELS Controls Position not Speed
It is not the purpose of the ELS system to match the speed of each print or die section. This is a common misconception of the function of an ELS. Its purpose is to match the position of the image on the cylinder to the image ors the web. Therefore, if the printed image and the cylinder image is of equal size, when the web, being moved by the pull rolls.001 ", the ELS moves the cylinder such that its circumference moves. 001". As the speed of the press and hence the web changes, the speed of the cylinder must exactly follow the web, no acceleration or deceleration differences are permitted. And differences would introduce error between the two images. The servo or stepper motor drive is operated in the pulse mode with no acceleration or deceleration profile. This means that for each pulse received by the drive, the motor is immediately incremented by a pulse. Usually the rate of change in speed of the press (acceleration or deceleration) is slow enough the drive can follow the speed change and hence the position of the web.

Usually, a 2500 line (2500 pulses/rev) incremental encoder is used. In quadrature mode, this is equivalent to 10,000 pulses/rev. If the pull roll has a circumference of 8.250", the resolution of the ELS system is .000825". If the servo or stepper drive is set to 10,000 pulses/rev, the cylinder would move .000825" circumferentially for each .000825" movement of the web. Theoretically, the motor moves in 10,000 discrete steps. These discrete steps can be seen when the press is operated at very low speeds, usually below jog speed. However, due to the mass of the cylinder and motor, these discrete steps tend to become invisible at normal press speed.

The ELS control system processes the pulses from the encoder and allows the operator, through the operator's control station, to monitor and adjust the printing process. Advance and retard functions are provided to allow the operator to adjust the relative position of the cylinder to the web. This is accomplished by adding or subtracting pulses going to the motor drive. If the motor moves one pulse for each encoder pulses, advancing its relative position is not possible. In order to overcome this problem, the ELS divide the encoder pulses by a factor, usually two. This means that for every two pulses received from the encoder, the system transmits one pulse to the drive. This means that the drive must be set to 5000 pulses/rev to maintain a matched position. When the operator advances the cylinder position, the system allows more pulses to pass through to the drive. To retard position it reduces the number. A rate multiplier provides the means to control advance, retard and match positions. When operating at matched position, the rate multiplier is set to .500000 (divide by two). To advance position, the multiplier is set to .0500500 (as an example) allowing 5 more pulses per revolution to the motor. This is equivalent to a .00825" increase in relative position. Likewise, to retard relative position, the rate multiplier is set to 499500, which subtracts 5 pulses/rev or a decrease of .00825". The values of the increase and decrease rate multipliers are adjustable within the system by the operator and can, be changed to provide proper operation of a particular press or a specific job. Advance and retard keys are provided on the operator's control station.

Rate Multiplier Matches Cylinder Circumference to Web Repeat
The ELS control system also provides a means of matching the effective circumference of the cylinder to the image on the web. If the apparent circumference of the cylinder is slightly larger than the web, the cylinder must move slightly farther to provide a match. To accomplish this, the base rate of the multiplier must be set slightly larger. This value may be as small as .500010 which adds .000165"/rev. The need for this adjustment may be necessary because of undercutting on cylinders or rollers or because of tension differences between stations. Adjust of the rate multiplier is available to the operator through keys on the operator's control. Registration of the station to the web can be accomplished by the "advance" and "retard" keys and by adjusting the base rate multiplier and can be done during make ready or run modes of the press.

Automatic Registration
Automatic control of registration is easily added to the ELS system. Two color registration scanners are normally used: one sensing the position of the image on the web and the other sensing the position of the cylinder. 'typically, a registration. mark is printed on the web by the first station. This mark is then sensed by a scanner just before or just after the station and is used to "register" the station cylinder to the web. A mark on the cylinder senses the relative position of the cylinder. The system measures the distance between the mark on the cylinder and the mark on the web. In " make-ready"' this distance is displayed on the operator's control in inches. The operator uses the advance/retard keys to move the cylinder into registration. Once in registration the operator can charge the mode of the ELS to "manual". In this mode, the system displays the plus or minus error from the position set by the operator in make ready. The operator can manually advance or retard the cylinder position to correct for any accumulated error or to change registration. In "automatic" mode, the system displays the error from desired registration. In this mode, any error, over a preset dead band, will cause the system to advance or retard the cylinder position to compensate and bring the station into "registration:. Manual registration adjustment is disabled in this mode. However, adjustment of the base rate multiplier can be made.

Print in Print
"Print in print" registration control is available with the ELS system. If a feature within the printed image is distinguishable with a clear area before it and if it is perpendicular to the web, this feature may be used as the station mark instead of a printed mark in the margin. Features at the top or bottom of the image are usually effective as are marks printed in the chip gaps.

Pre-Printed Webs
The versatility of the ELS system is especially useful when printing or die cutting "pre-printed" webs. Whether the web was printed on the same press or whether it was printed on another or whether or not it was printed by the same printing process, variances in image length may require constant adjustment. This is due to changes in tension throughout the preprinted web and can be aggravated by changes in temperature or humidity, Usually, the image length constantly increases or constantly decreases (trending) as the preprint moves through the press. This means that the operator would have to constantly adjust the station in manual mode in order to maintain registration.

In automatic mode, the system would have to constantly correct in the advance direction or the retard direction. The effect would be a sluggish control in one direction and an overly sensitive control in the other. Ideally, the amount and direction of the error and the amount and direction of the correction should balanced around "zero". This would provide the most effective and accurate control. The ELS system includes an "auto rate" feature that monitors the amount and direction of the error. The system then averages this error over a number of repeats and re-calculates and adjusts the rate multiplier to a value that matches the image length of the web to the image of the cylinder.

Other Applications of ELS
In addition to controlling print or die stations, the ELS system can be applied to metered indeed systems, board length control, screen printing, flat plate die cutting and step and repeat stations. With the development of more economical PES system, production and job management arid quality control features and interfaces to a local area network (LAN) and mainframe systems are easily accomplished.