Ask a senior technician if computers can fix cars, and he’ll likely laugh out loud. Extremely accurate repairs require a talented technician to perform the work. But ask that same technician what his favorite measuring system is and he’ll likely mention one of the more sophisticated systems available. The smart technician always wants the most efficient tool available.
Like any good tool used to repair vehicles in the collision repair industry, the measuring systems in use today have gradually evolved. Carpentry, coach and boat building tools were used when cars were first mass-produced because they were available and fit the needs of repairers. Tools designed specifically for use in “frame” shops were developed to make the job easier as cars evolved. Centerline gauges were invented to repair full-frame vehicles, which had larger build tolerances.
Mechanical, three-dimensional (3-D) measuring systems were introduced decades ago to provide three-axis measuring accurate to a millimeter or so. This was necessary as the automotive industry moved toward unibody construction with tighter build tolerances. The next step was applying technology to the problem of accuracy and efficiency.
Engineers have applied three types of technology solutions to enhance the capabilities of measuring systems. These types include lasers, ultrasound and positioning sensors such as those used in robotics.
Laser Measuring
Lasers first competed directly with centerline gauges and then 3-D mechanical measuring systems. The laser provided a very accurate straight line of light, sort of like a string that is not affected by wind or gravity. For the same reasons, lasers have been adapted to survey and construction work. Today, lasers can automatically control the height of a bulldozer blade or make it possible to install acres of suspended ceiling and shelving at the local shopping mall completely level.
The first application for collision repair was two lasers shining their red lines parallel down both sides of the car.
Measurements could be taken in to any point on the structure. This gave very accurate centerline information and proved quite useful for side hits. Length was still taken with conventional tools. Using the laser light in the X and Y axes, parallel to the datum of the car, provided true 3-D information. The laser could be intercepted with a clear target hung from a location to be measured, indicating the exact position of that point. The technician was still required to look at the targets to determine the position. Replacing the clear targets with reflective, bar-coded targets made it possible for a central sensor array to collect all the data. This makes it possible for the technician to have real time information on all the measurement points on the vehicle right on the computer screen beside the car.
Ultrasound
Ultrasound was popularized as the gold circle on the front of all those Polaroid cameras. Sound waves were used to measure distance to the subject and set focus. Sonar on submarines works much the same way. Sound takes time to travel through a medium, such as air. All that is required to measure a distance is to see how long it takes sound to travel across that distance and divide it by the speed of that sound. A central sensor is positioned and ultrasound transducers are attached to any location to be measured. Because of the short distances being measured on vehicles, it took some time before this technology was accurate enough, at an affordable price, for use in the collision repair industry. Those Polaroid cameras only needed to be accurate to a few inches. Obviously, vehicle measuring systems need to be accurate to much closer tolerances.
Positioning Sensors
Positioning sensors are widely used in robotics. For a computer to control a robot, it must have extremely accurate position information. At every joint on a robot’s “arm,” a sensor measures travel. These rotational measurements, along with the known distance between each joint, are used to calculate precise position. A mechanism much like a robotic arm, sliding along a ladder under a vehicle, can give very accurate measurements. This technology is somewhat parallel to the mechanical measuring systems and was easily adapted for use with them.
Computers, Sensors and Data
What made these systems possible and practical were computers, sensor technology and data management technology from other industrial applications. High-quality lasers, ultrasound transducers, position sensors, and CNC (computer numeric control) machining capability made these systems affordable. Relatively cheap computing power made it possible to do all the complex math involved in calculating positions. Computers also simplify the task of getting the correct data sheets for the vehicle. Regularly updated data files keep all the data right at the frame machine.
Choosing the Right System
Making a choice among the different computerized measuring systems involves several variables. The frame equipment the shop has may greatly influence the decision. If the maker of the frame equipment also has a system, it is a little simpler to buy that system and have one point of support. Some systems are designed to work with specific frame equipment.
Systems using robotic arms are different in one important way from laser and ultrasound systems: They measure only one point at a time. This presents both advantages and disadvantages. One advantage is a quick setup for a few fast measurements. A disadvantage is that only one measurement can be monitored in real time during pulling operations, while other systems can monitor multiple points simultaneously.
Some common and inaccurate comments heard around shops are that wind and noise make these systems inaccurate. Any mechanical system can be affected by outside forces. High-pitched sound, such as that from a hammer striking metal, could disrupt the sensors on measuring systems using ultrasound. Wind in the shop can swing a target momentarily out of alignment. However, the systems remeasure the vehicle every few seconds, so it’s not an important consideration. If the ladder is bumped on a robotic-type system, the zero point calibration could be moved, resulting in inaccurate measurements. Checking a known reference point is easily done to confirm the position of the system. In general, all the computerized measuring systems are reliable and highly accurate.
Documentation
One of the best advantages in the development of computerized measuring systems is the ability to accurately record data. Suspension alignment systems have developed to the point that a printout of the before and after measurements is expected. These data clearly indicate what was wrong and what has been corrected. This practice, applied to structural repairs, also clearly documents all damage and repairs. One maker of computerized measuring equipment markets the product exclusively as a diagnostic tool, preferring to repair vehicles with a fixture system. Other vendors also promote the measuring systems as excellent diagnostic tools, offering packages more easily used under a post lift in the estimating bay.
