A US manufacturer of pipe fittings and couplings casts these parts in sand molds. The automated process uses several pneumatic cylinders to put the molds into a properly “stacked” position. It is imperative that these molds are properly positioned so the front and back sides are aligned.
Non-contact laser distance sensors were selected to measure the position of the mold with each placement with the pneumatic arm. The installation puts the device several inches away from the moving mechanical parts. The glass optics of the unit are kept clean with a pressurized air knife.
Non-contact laser displacement sensors are used to measure the thickness of polystyrene foam-extruded insulation boards in a continuous manufacturing environment. The boards are composed of foam sandwiched between plastic film. The rigid boards are continuously produced and cut to length at subsequent stages in the process.
The manufacturer needs a reliable and accurate thickness profile of the foam insulation boards for quality control and material waste projects. The system is composed of two, opposing laser displacement sensors that act as non-contact calipers for thickness measurement. The integrator plans to install this measurement system on a motorized, traversing linear slide so surface profiles can be collected. They know that a full thickness profile will help them to tighten the manufacturing process inputs and save on expensive petroleum-based polystyrene. Their goal is to produce panels to more strict dimensional tolerances.
In the above video, a pair of Acuity AR700 laser sensors measure the thickness of polystyrene board as it passes by. The sensors interface with a smart Touch Panel Display which calculates the thickness at 100 Hz based on the individual sensor distance measurements. This calculated thickness is transmitted via RS485 to a nearby PC computer for archiving purposes.
Once the sensors were properly fixtured directly above each other, with their emitted laser spots aligned, the demo took only 10 minutes to begin. The customer plans to use the solution with a linear stage to profile the thickness of board material in sections measuring 4 X 16 feet.
Profilometers provide high-quality measurements of pavement deformations at highway speeds. The equipment measures the longitudinal and transverse road profiles, International Roughness Index (IRI), wheel path rut depth, Ride Number (RN) and macro texture of asphalt and concrete surfaces.
Road profilers use multiple laser sensors to measure longitudinal and transverse road profiles at highway speeds
Road profiling equipment can be installed on a variety of vehicles. The system has 5 or more laser distance meters installed in the front of the vehicle. Each laser sensor measures the height between the vehicle body and the pavement surface at rates up to 3,500 measurements per second with a precision superior to 0.06mm. Measurements are made at the current transit speeds on city and highway roads ranging from 25 up to 140 km/hr.
Two encoder sensors provide measurements of the distances traveled by the vehicle, two accelerometers measure the vertical body bounce that the vehicle and the lasers experience when going over the pavement deformations, and a GPS device collects the geographic coordinates of the route traveled by the vehicle. The computer inside the vehicle simultaneously collects the measurements of all lasers, distance linear chainage, accelerometers and georeference.
Each laser measurement is influenced by the instant vertical movement of each sensor when driving over the pavement. Because of this, the accelerometers measure this movement and the computer program removes its influence when generating reports with the longitudinal and transversal profile of the pavement.
Each laser meter obtains a longitudinal pavement profile composed by more than 40,000 measures on each kilometer, approximately one measurement for every 2.54cm of travel!
With the simultaneous measurement of the 5 or more lasers, a transvere profile is obtained, which is used to calculate the rut depth for both wheel paths. This value reflects the structural weakness of the pavement produced by the transit load.
The international standard ASTM E950-98 dictates this type of measurements and classifies these types of Road Profilers within Class 1, which corresponds to the greatest precision. The IRI is calculated in accordance to the World Bank requirements.
The Block Qualifier is a height measurement device, used in the concrete brick and block industry. The Block Qualifier, uses non-contact laser measuring sensor technology to gauge the size of concrete bricks.
The concrete wall or paver blocks are manufactured in a similar way. Large steel molds are filled with a moist concrete mix, similar to wet sand. The material is heavily compressed while the entire mold is heavily vibrated. The green blocks are slid onto a steel palette which moves along a conveyor system.
The Block Qualifier system is an archway that places several laser displacement sensors above the moving palette. As the bricks travel under the archway, the sensors profile the height of the empty palette surface and the centerline of the blocks. Measurement statistics are captured for each palette and alarms are set for acceptable MINIMUM / MAXIMUM dimensions.
The manufacturing environment is particularly rough for precision sensors due to the heavy vibrations from the casting machine. The Block Qualifier design insulates the sensors from measurement noise created by the floor vibrations.
For more information about the Block Qualifier system for measuring concrete brick and block heights, please contact Rampf Molds, Inc.
A major North American propeller manufacturer and service company selected a long-range triangulation sensor to measure the profile of its propellers and controllable tip blades during the manufacturing process. Non-contact measuring, like that afforded by laser sensors, is desirable in propeller manufacturing because the fixed measuring device can be installed with a large standoff away from bulky and/or moving parts.
Propeller profiling using laser sensors
In this case, the customer chose a laser sensor that had the best resolution while allowing them to measure the greatest pitch of the largest propellers and blades (difference in height between the leading and trailing edge). The typical surface finish of the propellers was a shiny, ground appearance, and was no problem for the Acuity AR700 sensor with its highly-sensitive, digital CMOS detector array technology.
A recent journey to India brings us a novel application for a laser distance sensor. Even in a part of the world that tends to value the manual efforts of its laborforce, there is a strong recognition for precision, non-contact measurements afforded by the latest in sensor technology.
The Center for Rural Development and Technology at the Indian Institute of Technology Delhi thoroughly investigated the use of laser displacement sensors to measure the strain of samples during a particular materials testing experiment. Specifically, the Center was tasked with the evaluation of bamboo as a primary construction support material for use in projects in the most rural parts of India. Students within the Mechanical Engineering Department devised an experiment to test the compressive strength of bamboo.
Currently in their setup, they were using dial gauges which tended to “jump” as the force was increased during the experiment. The group investigated the laser sensor (Acuity model AR700) to measure the relative movement of two plates that moved together as the sample became compressed. They required a laser sensor with a long standoff so that it would not get harmed if the bamboo failed and shattered. The optoelectronic laser sensor with its analog output permitted the continuous acquisition of the distance output relative to other experimental variables.
Below is a video that shows the setup of the experiment. In the footage, the engineer adjusts the load by controlling the speed of a hydraulic piston controlled by an electric motor. The instantaneous position of the sample chuck is indicated on the visual Touch Panel Display.
Although now discountinued and replaced by the AR700 series, Michigan state selected the AR600-6 with a 150 mm measurement range. The laser has a 5mW visible laser spot and has excellent sensitivity for measuring to shiny targets. The sensor was mounted to dual rotational stages to allow two degrees of freedom. Their system swept the laser spot across the target surface to create polar cordinates for a 3D profile.
Acuity sensor on dual rotational stages
Graduate students developed software to control the laser, scan edges with specified step sizes. Output is distance, theta’, and phi’; convert laser coordinates to spherical coordinates; correct position for off axis rotation; and combine different reference systems; convert positions to final lab reference frame of choice. For each 0.01° step in angle, the position resolution was ~0.2mm.
A major car audio speaker manufacturer contacted Acuity to help solve a challenging measurement application. The company’s Research and Development Department chose the AR200 laser measurement sensor to measure the positional changes of a subwoofer cone.
Application requirements
Fast-moving targets demand a laser sensor with a fast sampling speeds. As the sales engineer in the video explains, the sensor must have a fast frequency response to profile the entire amplitude of cone movement which is moving at 60 Hz.
The engineer required an analog output whose resolution was as good as that of the measurement resolution
Finally, the speaker manufacturer needed a laser sensor with performance that would not suffer when measuring to a black target. The AR200 with its CMOS detector array performs well on light and dark targets alike.
The USGS Volcano Hazards Program studies debris flow and landslides at their facility in Washington state. They chose several Acuity laser displacement sensors to profile the height profile of material as it passed beneath archways in their test flume. The distance sensors take over 9000 distance readings per second and provide important metrics for the scientific studies.
The extreme “texture” of the debris flow created situations of occlusion whereby the detector in the triangulation could not “see” the reflection of the laser spot because the geometry of the debris occluded its view. This was minimized by orienting the laser sensor 90° to the direction of flow.
Posted on April 18th, 2012 by admin
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