Laser Alignment Theory and Optical Tooling
Metrology is the science of measurement and one aspect of modern metrology utilises a technology known as optical tooling. Optical tooling is a relatively new development with a history of about 35 years, and over this time the systems used have matured to deliver an extremely precise method of measuring. Below is a lucid explanation of what optical tooling is and isn’t, why it is a preferred method and what variables will affect the precision of results.
Optical tooling is method of metrology which measures specifically alignment. This means OT is used to decipher geometric relationships such as linearity, parallelism, flatness and squareness and the like. It’s different from 3-D measuring in that it can’t give you indication of curvature, for example. Optical tooling is used in engineering and manufacturing to ensure that all parts of mechanism are of the right measurements so that they can fit together properly and the whole machine can work as intended. Since engineering can often involve a lot of very intricate parts it has to be (and is) extremely precise and accurate.
Optical tooling is far superior to mechanical measuring tools in terms of accuracy, delivering results with minimal margins of error because it follows on from the scientific fact that light travels in straight lines. The method establishes and then uses a “line of sight” in order to gauge four different things: straightness, squareness, plumb and levelness. In the past, measurements were taken by a human interpreting a scale or optical micrometer via an alignment telescope; nowadays lines are created by a laser, measurements are digital and no interpretation is required, further increasing accuracy.
The Four Big QuestionsIn aligning precision systems, or maintaining and calibrating industrial equipment optical tooling can be used to answer four key questions:
Is it straight?This one is pretty easy. Light travels in straight lines so a line of sight is used as a reference. Each piece of laser alignment equipment is created to maintain a straight line with extremely low margins of error (they can determine straightness within a thousandths of an inch). Since it is light the line isn’t susceptible to weight, sagging or any other kind of disturbance, instead providing an unvarying reference across potentially huge distances making it perfect for measuring both tiny pieces of equipment and gargantuan structures.
Is it level/flat?Spirit levels are great for around the house but if you need to check how level a big piece of equipment is you’re going to need something a little different. Optimal tooling allows for precision measuring of levelness by sweeping a line of sight back and forth creating a horizontal plane. This plane is then used to determine whether something is level or flat (the terms are used interchangeably).
Is it square?Precise squareness relates to whether two intersecting planes create a 90° angle. There are various methods used to create a precise right-angle via optical tooling, one being the use of a penta transparent prism in conjunction with an alignment laser. The beam is split into two parts as it shines through the prism; the two parts of the beam will be a right-angle to each other. An alternative is to use three laser beams which are orthogonal to each other.
Is it plumb?Similar to whether something is level, plumb relates to a vertical line or plane. Optical tooling sweeps a transit telescope to define a vertical reference plane. You can check parallelism by measuring the offset between the created plane and the surface you are measuring. Measurements can be made to within 0.001inches and even very large vertical areas can be made perfectly plumb.
Laser Alignment and optical tooling allow metrology new level of precision which radical alters engineering possibilities. The technology has advanced a lot over the last 3 to 4 decades and now necessary equipment is now readily available. SKF services offer SKF laser alignment technology for example, along with lots of other suppliers.