Optically, however, they are inferior to gas lasers. Because of this small aperture the light diffracts, or spreads strongly with distance; it also has two different spreading angles because the aperture is rectangular. If a good quality lens is placed such that its back focal length coincides with the laser diode emitting surface, the beam produced will be elliptical in cross section and suffer from astigmatism. Much effort is required to transform the light from a laser diode into a high quality collimated beam appropriate for use in precision alignment systems.
It is now possible to buy a laser diode with this lens inside the typical 9 mm diameter by 5 mm long laser diode case. Unless this lens is chosen carefully there still can be significant astigmatism is the optical system. External prism pairs can be used to circularize the laser beam, but it does not solve the astigmatism problem. By choosing different focal length lenses the laser beam can be of any diameter desired.
If a steel case is used, maximum drift can be as low at a few arc-seconds. Randomly polarized light is usually not a problem for an alignment target consisting of a lateral effect photodiode. In all laser measurement applications a question always arises as to how to mount the targets and laser sources. Usually commercial equipment vendors will supply their own proprietary mounting hardware. Figure x below shows a transparent Target and reference target using these tooling spheres.
A target placed at a reference station establishes one end of the LOS; the center of the laser beam is the other end of the LOS. High frequency disturbances such as vibration can not be corrected. If two targets are used the measurement becomes more accurate; the addition of a Reference target situated at the end of the LOS constantly monitors beam position.
If the two dimensional coordinates of the laser beam on the Reference and Alignment target are measured simultaneously the position of the Alignment target with respect to a line between the laser and the Reference target can be measured, independent of any pointing error of the laser.
Instead, the coordinates of the laser beam at both targets is used to compensate for any laser beam movement. In Figure x the line between the center of the Reference target and the center of the laser beam source defines the LOS, not the laser beam.
Subtracting this error from the measured beam position at the Alignment target results in a compensated C alignment measurement, or true position of the target in both the x and y axes:. Absolute target distances are required.
Because of how this technique uses geometric principles, it is called similar triangle compensation or passive pointing compensation. Perhaps the most recent method to compensate for steering of the laser beam due to thermal, mechanical or atmospheric effects is to actively steer the laser. One advantage of this method over that of the similar triangle method is that absolute or ratiometric distances are not needed. Since the laser is always on the Reference Target center, no mathematical compensation needs to be applied.
Any transparent Target placed in the beam at any distance from the laser simply determines beam position. In this method the laser beam is the LOS. Scanning systems can be simple single axis systems that are manually rotated, or have 3 axes with each axis motor driven.
For three axis systems, once level has been established the other two axes will sweep out vertical planes of light that are perpendicular to each other. Some even control the degree of "levelness" by servo correcting the source if it moves off of level. A simpler method uses a pendulum on which a light weight laser diode source is attached. For a manually rotated source the electronics are similar to 2D targets; the user must aim the beam by hand into the target's window.
For dynamic scanning the targets use very fast detector as the beam sweeps by in only a few microseconds if the target is located at some distance and the scan rate is 60 RPMs or higher.
Sometimes PSDs are used as the sensor. For very high speed systems a bi-cell sensor is used. A typical size would be 30 mm tall by 5 mm wide. But this sensor is split along its diagonal into two triangular shaped photodetectors.
When the time the laser beam spends on each segment is equal, the beam is exactly in the middle of the bi-cell. Deviations up are down produce a difference in timing that is exactly proportional to distance. It has a degree scanning window and is really designed for leveling applications. Accuracy is the same as for simple laser alignment and will be discussed in detail later.
Any laser alignment system has associated with it measurement errors. Even if active and passive pointing compensation is not employed, any transparent Target must not produce steering or deviation of the laser beam as it passes through it. Each window and the beam splitter possess a small amount of wedge error which acts to mis-steer the beam. Rotation adjustment of the wedge prisms on the transparent Target allows for the refractive error of the transparent Target to be adjusted to less than one arcsecond.
Figure 3 shows a two target system with the laser beam initially centered on the Alignment target. Inspection shows this error is zero when the alignment target is situated at a distance of 0 or D from the laser source. Deviation errors do not grow with distance as do pointing errors. Most modern position sensitive targets used in alignment contain dedicated microprocessors. Targets come in a variety of different sensing areas and virtually all use lateral photodiode detectors to sense laser beam position.
Quad-cells are almost never used due to their small sensing range. Since each lateral photodiode detector has slightly different linearity, manufacturers now calibrate each target on a precision motion platform. Stored within each target are corrections for its detector. A good rule of thumb for target accuracy is 1 part in of a target's sensor diameter. Scanning type targets have similar accuracies.
Much effort has been expended on describing how to make and interpret optical measurements and how such statistics as standard deviation is defined for an area target. For simple straightness applications a non-compensated laser alignment system is adequate.
For situations where high accuracy is required, active pointing compensation is ideal. Active pointing compensation of the alignment laser eliminates movement of the laser beam by maintaining precise alignment of the laser beam on the reference target. A propagating laser beam does not remain parallel as is frequently assumed.
All laser beams follow a prescribed propagation characteristic that depends on two conditions: how the beam was launched, and what type of disturbed it encounters along it path. For a given distance, a laser beam with a long wavelength will grow in diameter faster than a laser beam of a shorter wavelength.
A beam of light propagating in a vacuum obeys the laws of diffraction and is not affected by any other source. However, in an atmosphere the beam will behave differently. Much work has been conducted on the effects of atmospheric turbulence on propagating light. An expression for the index of refraction due to temperature, pressure and humidity is given by:.
It can be appreciated that it is a weak effect by the 10 -6 factor in front of the second term. This level projects three dots simultaneously to verify your installation is straight, level, and plumb.
Project accurate level references onto walls and ceilings when hanging light fixtures or installing pipe. Mark a dot up to feet across your plant for long-range applications such as laying out conveyors and positioning ventilation systems.
These lasers are also known as torpedo levels. Green lasers appear up to 10 times brighter than red lasers, so they remain visible from farther distances and in brightly lit areas, including outdoors. Use a leveling plate for mounting the laser to a tripod, or placing it on a surface.
The plate has three adjustable legs to level the laser. Dot - to - line converter changes the dot into a vertical or horizontal line. These kits include a laser, a beam splitter, and a leveling plate. Mark a dot up to 1, feet across your plant for long-range applications such as laying out conveyors and positioning ventilation systems. Use the leveling plate to steady lasers on uneven surfaces or to mount them to a tripod.
These plates have three adjustable legs that stabilize the laser. Add a leveling plate to steady lasers on uneven surfaces or to mount them to a tripod. Direct laser beams where you need them with components that turn or split your beam. They work with any dot laser. Mirror requires a holder to mount to a standoff. The splitter screws into a standoff.
Dot - to - line converter requires a holder to mount to a standoff. For additional lengths, see Stainless Steel Standoffs. Align rotary shafts with the help of a mobile app. These sensor kits are more accurate than straightedges and easier to use than dial indicators. Properly aligning shafts reduces vibration and protects couplings, bearings, and other parts from wear and damage. Use the included chain clamps to mount these sensors above your coupling, where they detect the degree of misalignment between the shafts.
The app shows live animations to give step-by-step instructions for repositioning your equipment. Once the shafts are aligned, the app saves a report documenting the process.
Good for extended use in industrial environments, these sensors last up to 18 hours between charges and are IP54 rated for protection from dust. They cannot be sold to California or Oregon due to energy efficiency requirements. Lay out machine tables and work stations at precise right angles. The laser lines are best viewed indoors. Align guide rails or lay pipe at specific angles from a flat surface.
The display shows the precise angle of the beam and rotates for overhead measurements. The audible level indicator tells you when the tool is level and plumb.
Use these precision posts to build mounts for optical components, such as those used in laser directing systems. Insert a rod in the through hole for leverage during tightening. Posts have good corrosion resistance and may be mildly magnetic. For technical drawings and 3-D models, click on a part number.
Build mounts for optical components, such as those in laser directing applications, with these precision posts. The pointed feet provide stability on grass, gravel, and dirt. Laser Shape. Laser Color. Power Source.
Laser Class. Overall Length. Dot Size. Number of Dots. Mount Type. Battery Size. Batteries Included. Line Size. Electrical Connection Type. Overall Diameter. Overall Height. Overall Width. For Maximum Pulley Spacing. Number of Mounting Holes. View catalog pages 8. Send Cancel. How can we improve? Laser and Optional Mount. Optional Plug-In Transformer Each Chuck-Mount Lasers.
Extension rods: Extension rods are used to align shafts with large couplings, so laser paths remain unobstructed. Sensors slide directly onto the rods. Display unit: The display unit shows alignment data in real time as the laser alignment tool takes readings.
Most display units have built-in software, LCD screens, rechargeable batteries, memory storage, wireless connectivity and more. Many laser alignment tools come with mobile apps that connect to the tool using Bluetooth and display data in real time on mobile devices. Measurement methods include the Express method, the Tripoint method and the Clock method. Modern laser alignment tools come with inclinometers built into the sensors, making the first two methods the best options.
In the Express method , alignment is calculated by recording three points while rotating the shafts at least 60 degrees. Once you record the first point, the other two points are automatically recorded when the shaft is rotated to a new position and is held there for more than two seconds.
Mounting distance is highly adjustable, ranging from the sensors nearly touching to around 35 feet 10 meters apart. Angular relationship refers to the ability of taking multiple measurements around the shaft. Most modern laser alignment tools have inclinometers built into the sensors.
Inclinometers measure the radial position of the sensors. Inclinometer values are used in the calculation of misalignment. This lets you take measurements at any position around the shaft. Inclinometer values are shown on your display. Setting up a Laser Alignment Tool When you purchase a laser alignment tool, it generally comes in a case with all the components you'll need, such as the display, extension rods, chains, sensors, brackets and user guide.
Use the chains to secure the brackets to the shaft, adjusting for the diameter. Next, place your sensors on the brackets. Make sure the correct sensor is mounted on the correct side. Sensors will have some way of denoting the appropriate side. For example, an "M" sensor should go on the motor side, while the "S" sensor should be mounted on the stationary side.
Once on the correct side, tighten the sensors onto the rods. Once you've mounted the sensors, you can turn on each one and verify that they are aligned.
Modern laser alignment tools are very user friendly and perform nearly all the work for you with built-in software. When setting a new alignment, the software walks you through what to do, starting with getting a few measurements. You'll need to measure from the "S" unit bracket to the center of the coupling, from the center of the coupling to the center of the "M" unit bracket, the horizontal distance from the center of the "M" unit bracket to the first bolt on the motor, and the horizontal distance from the front bolt on the motor to the back bolt.
All of these measurements will be plugged into the software. Next, you'll be asked to enter the machine's tolerances. You can determine these by using the machine and coupling type or by looking at the speed of your machine's motor and comparing it to a pre-loaded or pre-installed tolerances chart. Match the speed of the motor to the corresponding tolerance.
Most modern laser alignment tool software comes with a tolerance chart for reference. Below is an example of a shaft alignment tolerances table for direct-couple shafts. Source: Alan Luedeking, Ludeca, Inc. Department of Energy After these numbers are entered, it's time to perform vertical correction of the motor. Checking for what is known as soft foot is a key part of this step.
This is done using the provided shims and placing them under the "feet" of the motor. A soft foot check can be done in the pre-alignment phase, which we'll discuss later, or after you've taken measurements if you are showing misalignment. Now, you can connect your sensors to the display using a Bluetooth or wireless connection.
This allows you to see real-time data as the sensors work. It also shows you if you need to adjust the sensors. If the angle difference is more than 2 degrees, you should adjust one sensor manually to correct it. Tighten the "M" sensor on the rods and adjust the position of the "S" sensor on the rods until the laser is aligned with the centerline of the "M" sensor. You'll then adjust the "M" unit laser line to match the centerline of the "S" sensor. Single vs.
Dual Laser Alignment Probably the most common type of laser alignment tool on the market, dual laser alignment tools require you to adjust both lasers so they hit the opposite detector. Uncoupled Shaft Alignment Even though it's quicker and more accurate to align the shaft while the machines are coupled together, sometimes the coupling might need be separated.
These problems include: Increased shaft and bearing loading Increased wear of the sheaves leading to reduced sheave life Increased noise and vibration due to belt wear Belt or sheave alignment tools help detect three types of misalignment: radial runout of the shaft, radial runout of the sheave and axial runout of the sheave. Preparation: Preparation involves inspecting the machine you intend to align.
This includes examining the coupling's insert and lubrication; checking for loose bolting, most notably the feet of the machine; and inspecting for obvious pipe strain.
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