Laser alignment hits the mark

Machinery and equipment with moving parts rely on mechanical alignment between these moving parts to run smoothly and efficiently. Often, machinery alignment is checked, deemed OK for manufacturing, and then forgotten -- at least until some event catches the attention of plant engineers. These events might be a slight decrease in production output, an unfamiliar noise or squeak, or some dramati...

03/10/2005


Key Concepts

 

  • Laser alignment has replaced optical and wire methods.

  • Lasers can determine parallelism and squareness.

  • Roller crowns or profiles can easily be checked using a laser.

    Sections:
    Systems
    Equipment
    Roll alignment
    More Info:

    Machinery and equipment with moving parts rely on mechanical alignment between these moving parts to run smoothly and efficiently. Often, machinery alignment is checked, deemed OK for manufacturing, and then forgotten -- at least until some event catches the attention of plant engineers. These events might be a slight decrease in production output, an unfamiliar noise or squeak, or some dramatic event such as black smoke pouring from a motor housing or grinding gears.

    Before laser alignment, mechanical systems were typically aligned using optical transits or piano wire pulled between two ends of a machine. Plant personnel know the frustration of trying to make precise alignments with a ruler and a piece of sagging wire swinging in the breeze. In the past, the tools available for accurate alignment have been limited and technically challenging to use.

    Laser alignment provides a highly precise and efficient means of checking machinery. These products are easy and simple to use by plant or production personnel on the factory floor (Fig. 1).

    Much of the guesswork and subjectivity of traditional alignment techniques is eliminated because the laser now delivers precise, quantitative data, and in some instances, complete instructions on how to correct machinery flaws. Consequently, lasers are finding their way into many industrial plants.

    Systems

    A typical laser alignment system has a laser transmitter that emits a collimated beam of light that is of one color or specific wavelength. Because this beam is a single wavelength, the light is very organized and can be focused into a long, thin, reference beam.

    Many laser systems use a visible laser beam, typically red in color, or an invisible laser that may operate in either the infrared or ultra-violet wavelengths. In each case, the laser becomes the reference line in the same way piano wire has been used in the past.

    The laser is aligned and projected from a machined housing that has defined flat reference surfaces and mounting points on its exterior. The laser beam is an extension of the machined housing and is ideal for measuring and alignment.

    Projecting the laser onto a ruler or a target is fine for visual alignment, but true accuracy comes with the use of an optical detector. This detector is a long, light sensitive device that digitally determines the location of the laser beam along its length. This detector is also mounted inside a housing with defined surfaces and mounting points.

    Equipment

    If the laser transmitter and receiver are placed onto a flat surface, the display will read zero. When the laser beam is elevated or the receiver is moved, the new position of the laser beam on the detector is displayed in digital format to an accuracy of 1/10,000th of an inch. This digital information can also be used for calculating surface flatness, runout, straightness, parallelism, and other geometric parameters.

    By combining the laser transmitter, receiver, and display with various mounting fixtures, the laser system can be used for checking the alignment of roll systems, moving stages, gantries, and other applications.

    The laser is placed on a precision rotating base and the beam defines a flat plane. The orientation of this laser plane can be adjusted to match three or more reference points in the machine plane, and additional measurements taken to verify equipment alignment The laser transmitter may also be equipped with a precision leveling vial to level the laser plane.

    The laser system can check parallelism and squareness by adding a precise right angle attachment, a penta-prism that redirects the laser beam (Fig. 2). This accessory is useful for checking mechanical alignment of moving actuators, robotic systems, milling and cutting machines, as well as a variety of roll and web systems. The penta-prism is self-aligning so the operator can place the right angle attachment arbitrarily along the laser path and create many repeatable, right-angle reference lines.

    If the equipment has two or more parallel tracks or rails, checking parallelism is easy with a laser alignment system (Fig. 3). The laser is aimed across the ends of the rails and the right angle attachment is inserted to redirect the laser beam so it is parallel to the side of the first rail. The right angle attachment is then moved until the laser beam passes down the edge of the second rail surface and a pair of readings are taken.

    If the difference between these readings matches the difference between the first readings, then the two rails are parallel to one another. If the differential readings are not the same you then know by how much the rails are out of parallelism and which way the rails must be adjusted. Combining various mounts and fixtures with a laser system makes it possible to align bores, drive shafts, gear boxes, monitor gantry travel, and many other alignment applications.

    Roll alignment

    Verifying the position and alignment of rolls and web handling equipment is another common application. Typically, materials pass over many rollers while moving through the manufacturing process. Misalignment of rolls through the machine may stretch the material excessively on one side so when the material is wound up on a large take-up spool it is uneven and likely to be rejected for poor quality.

    Roll alignment has three basic components; roll straightness and parallelism in the vertical and horizontal directions. Straightness is simply a measure of each roll in a system to see if it is sagging or deflecting under its own weight.

    In many cases, manufacturing firms use crowned rollers, which are thicker in the middle and taper slightly toward the ends. As the roller sags under its own weight the top surface under the web or sheet will remain flat.

    The crown or profile of a roller is easily checked with a laser alignment system. The laser is projected across the top of the roll surface and adjusted so the receiver readings are matched at each end. The receiver is then moved along the roller to record height or surface deflections.

    A roller with a straight surface will produce consistent readings all the way across while a crowned roller will show different readings in the middle from those at the ends. A damaged roller will show surface deflections caused by uneven wear or high loading.

    Roll parallelism is typically defined in two planes; vertical and horizontal. Vertical parallelism can be checked with a precision bubble level, but often a manufacturing line may have settled and is no longer level across its width. Crowned rollers also present an uneven surface for checking with a level.

    The laser is well suited for this task and a plane of laser light is directed across the top of the rollers (Fig. 4). The display provides readings of the vertical roller position, relative to the plane of laser light. When adjusting rollers, the laser is also used to monitor the process.

    Roll position in the horizontal plane is equally important and the laser alignment system utilizes a penta-prism to create precise, right angle laser reference beams. Introducing the right-angle attachment redirects the laser into the machine and across the face of a roller. A pair of readings is taken and the difference between these readings shows the position of the roller relative to the laser reference beam.

    As the right angle attachment moves along the laser beam it provides precise, repeatable laser reference lines for other rollers. The laser system allows plant personnel to optimize their roll and web systems on a regular basis and ultimately reduce machine wear, breakdowns, and lost production time.

    More Info:

    Questions about laser alignment can be directed to Mory Creighton at 978-462-8056 x202 or mcreighton@pinlaser.com . Article edited by Joseph L. Foszcz, Senior Editor, 630-288-8776, jfoszcz@reedbusiness.com .





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