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Optical Methodology

Introduction

Alignment of web handling equipment such as paper machines, corrugators, printing presses, converting equipment, film lines and roofing lines is a critical part of maintenance and is also key to producing quality product. The use of optical tooling is the most effective way of achieving proper alignment for most applications.

Alignment

The reason for aligning web handing and other similar production lines is to eliminate machine problems, increase efficiency, and improve the quality of the product. The precise and efficient alignment of web handling equipment requires a stable and accurate datum. The best datum for aligning production lines is a machine centerline reference. The design of the machine and its structural supports must be considered when determining the type of datum reference: an offset machine centerline (baseline), or a cross-machine baseline.

Proper alignment of machine components can solve many problems that cause product conditions such as:

• Poor Web Tracking
• Web Breaks
• Baggy Edges
• Decreased Trim Width
• Uneven Caliper (thickness)

• Static Electricity
• Misregistration
• Twist Warp
• Delamination
• Defective Flutes

Optical Tooling

The term "optical tooling" refers to optical instruments and the auxiliary tooling that accompanies them to perform the measuring tasks. The use of tight wires, tapes, plumb bobs, and spirit levels is not adequate for today's needs. Optical tooling applied to web handling equipment can assure the alignment of rolls with efficiency, flexibility, and accuracy not obtainable with other methods. The use of optical tooling for alignment is the accepted method today.

The development of optical tooling for aligning web handling equipment has made alignment accurate, efficient, and cost effective. Alignment with the use of optical instruments is based on planes or Lines Of Sight (LOS) that are formed by the use of these instruments. These planes are established forming 90 degree LOS’s in both the vertical and horizontal directions. Accurate readings are taken from these LOS’s depicting the exact location of the components. The readings are taken through the use of auxiliary tooling that makes direct contact with the component being measured. This location is reported in direct relationship to the datum.

Offset Centerline (Baseline)

The best datum for aligning web handling equipment is an offset machine centerline reference (baseline). A baseline is identified by a series of monuments mounted in the floor. Using a baseline with optical tooling allows each component to be measured relative to the same datum, eliminating the accumulation of errors that can occur in roll to roll alignment. The use of an offset baseline also allows the flexibility of relating one component to another component that is a distance away, or to a component that is not installed at that time. Two or more components that are aligned to a datum will be aligned to each other.

Cross-Machine Baseline

Machines designed as "freestanding" add extra considerations that compromise the accuracy of alignment readings. Freestanding machines are those that stand on foundations in the basement and are not connected to the operating room floor.

These machines move independently from the operating room as the machine temperature changes. Readings taken from monuments installed in the operating room floor of a "freestanding" machine will change with the movement of the building and machine as they cool down and heat up. The operating room floor cannot be considered a proper location for setting a reference to the machine centerline in these cases.

A reliable method for obtaining accurate data on a machine of this design is to place centerline references in the baseplates or sill beams across the machine: a baseline that is perpendicular to the machine centerline. In other words, a "Cross-Machine" baseline.

The rolls, frames and baseplates move as a unit as the machine experiences thermal changes. By placing the monuments in the baseplates, the movement of the rolls is tracked through the cool down period and the readings accurately recorded. It is critical to take as-built dimensions on these monuments with the machine and building at operating temperature.

Establishing a Baseline

The placement of the baseline is critical to efficient and accurate alignment. It must be a true representation of the machine centerline. Consideration must be given to machine movements caused by the shift of the building as temperatures change from an operating to a shutdown machine. The Stainless Steel Target Bushings (SSTBs) representing the baseline must be properly positioned to ensure the accurate tracking of the machine.

The SSTBs must be securely attached to the machine or located on the building steel to ensure they move with both the building and the machine. The procedure for installing a baseline cannot usually be performed with the machine running. It requires taking readings to identify the centerline of each section of the machine. This data is then studied to determine the optimum placement of the baseline. Holes are then drilled into the operating room floor or the soleplates, and the SSTBs grouted or pressed in place.

Instrument Calibration

OASIS calibrates its optical instruments regularly. Critical points are calibrated after each use and field verified as required.

The calibration tolerances for optical instruments used by OASIS are:
Level--one arc second (0.001" over a distance of seventeen feet).
Micrometer--0.001" through its full range of 0.200".
Cross Telescope--two arc seconds.

Inspection for Perpendicularity

A Telescopic Transit Square (TTS), called the control instrument, is bucked-in to the SSTBs on the baseline. A second TTS is positioned so its cross telescope can be collimated to the main telescope of the control instrument. This creates a line of sight (LOS) which is perpendicular to the baseline. A measuring device (optical scale or target) is placed on the side of the component and leveled to locate the horizontal tangent. Readings are taken at each end of the component and mathematically compared to determine the amount and direction the component is out of perpendicularity.

Inspection for Level

A TTS or a Sight Level (SL) is positioned to obtain a clear LOS to both ends of a component and then leveled to earth. A measuring device is placed on either the top or bottom of the component, depending upon instrument placement, and leveled to locate the vertical tangent. Readings are taken at each end of the component and mathematically compared to indicate the amount and direction the component is out of level to earth.

Inspection of Lineshafts and Drives

Because of the differing lineshaft and drive designs, several methods are used to establish a reference line. Whenever possible the machine baseline is used as the reference. The drives should be aligned to the driven component, which could be out of perpendicularity to the baseline. If this is the case, the component is bucked-in to and the drive is aligned to this established LOS.

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