GOMACO World Index --- GOMACO World 39.2 - November 2011
3D paving is growing more popular on job sites around the world. How familiar are you with the stringless system? Please take our quiz and see how knowledgeable you are and also learn more information about GOMACO 3D.
GOMACO is still in the testing phase with 3D on our paving equipment.
FALSE Twelve years ago GOMACO first recognized the potential of 3D and began testing 3D on our equipment. Today, GOMACO equipment with 3D is being successfully used on projects all around the world and in a variety of applications, including grade trimming, curb and gutter tight radii, tunnel floors and walkways, airport runways and aprons, highways, interstates, concrete overlays, municipal projects, safety barriers, golf cart paths, and more.
GOMACO has been involved with 3D since it's inception, working closely with the major system developers, including Leica Geosystems, TOPCON Positioning Systems, Inc., and Trimble. Our Research and Development team is not adapting our controls to work with 3D like other paving manufacturers. We have developed our controllers along with 3D technology to offer the seamless 3D paving package that we have available for sale today.
3D may improve rideability on paving projects.
TRUE 3D eliminates the human error that can be involved with setting a physical stringline. 3D works from a digital model with a virtual stringline, which is a constant that cannot be physically changed.
"During paving, trucks or workers can accidentally hit the line causing stringline movement and errors in paving," Kevin Klein, Vice President of Research & Development/Engineering, said. "Conventional stringline is prone to displacement. Relying on a physical string measured and 'eye-balled' by workers for set up and accuracy can build error into the paving."
Potential error is also eliminated from other sources. For example, any potential error from the surveyor's grade control stakeouts is now gone.
3D is more difficult to set up than conventional stringline.
FALSE 3D technology is not more difficult to set up. Contractors no longer have to deal with the hardware of traditional stringline... the clamps, stakes, string, and the manpower necessary to set the stringline on both sides of the slab for the entire distance of the project. When working with stringline, workers are needed to monitor and maintain the line during the paving operation. Then, at the end of the day, a crew has to go out and gather and store all of the hardware.
Total stations should not exceed 250 feet (76 m) in distance apart when paving for rideability.
TRUE "For rideability, we'll set our total stations every 250 feet (76 m)," Kevin Ackley, GOMACO's 3D Support Specialist, said. "And for high production paving, we recommend four total stations on site."
Two total stations are always working with the paver, shooting at the two prisms mounted on the paver. This is the paver's elevation and alignment control. A third total station can be used to verify grade behind the paver. The fourth one is for leap-frogging, the process of switching from one total station to the next as the paver works forward and out of range.
Line of sight is very important for the total stations to the paver.
TRUE Obstacles, such as trucks or workers, between the line of sight of the total station and the prism on the paver will cause signal loss. It's not just physical objects that can affect that line of sight. Caution must also be taken when paving in fog or areas with poor air quality. Care must also be taken in regards to the sun. Total stations cannot be aimed directly into the sun. The resulting glare can cause signal loss. Strategically placing the total stations can lessen or eliminate the effects of fog or sun glare.
3D paving accuracy can be affected by high winds.
TRUE It's important on windy days to make sure the total stations are not set up so wind hits them broadside, and to anchor the tripods well, possibly add weight to the tripod with sandbags, and position the total stations at closer intervals.
The total stations, Leica's for example, have two subsystems that work to guarantee the accuracy of a measurement. One is the AutoTargetRecognition (ATR) lock threshold that monitors the quality of the ATR's prism following. It makes sure the prism is reliably locked onto and tracked. It helps prevent inaccuracy potentially caused by high winds pushing or vibrating the total stations, fog, dust or heavy rain.
A second feature, the dual-axis compensator, acts as a level and ensures the total stations haven't been shaken out of level or knocked over by wind or other things. If a total station is up to 0.1 degrees off vertical, it will compensate automatically in the measurements for that inaccuracy.
Some paving products require a "black box," but GOMACO equipment does not.
TRUE GOMACO has pioneered stringless paving and digital paver control systems. Our controls and programming software seamlessly interact with 3D. With the Leica Geosystems 3D, for example, a Leica computer is mounted to the paver. It is connected to the GOMACO controller by cable and the two work together to control the paver. The Leica computer computes the input from the total stations and prisms, compares that information to the project design model, and then outputs the elevation and steer commands to the GOMACO controller.
3D allows paving flexibility on the job site.
TRUE Not only does it increase flexibility, it also improves job-site logistics, such as not having to work around or be limited by stringline; no restrictions in getting concrete trucks in and out of the site; easier to pave in tight clearance conditions because extra room for stringline is not needed; and the contractor has the ability to pave anywhere on the project at any time.
"Another important advantage is a quicker move-in and move-out on construction projects," Klein noted. "For instance, if you're constructing a median barrier under traffic, and the contract only allows you to work during the evening from 9 p.m. until 5 a.m. before you are required to open the road for morning rush hour. This system saves time by not having to set stringline before the machine can start producing barrier. And you do not have to tear down stringline before opening up to traffic."
3D technology is still changing and progressing.
TRUE GOMACO is always striving to create a better paving system. And stringless technology is going to continue to change at a fast rate.
"Contractors need to expect that there is going to be continued advances in this technology," Klein explained. "I like to compare it to buying a cell phone. If you wait, you know you're going to get something newer and better six months from now. But you also can't wait forever, because you will get left behind in this competitive market. Despite the changing technology, our contractors tell us they wished they had made the move to stringless paving earlier than they did. They understand the industry is changing and they don't want to be left behind. They also understand that stringless is nothing to be afraid of or intimidated by. They just have to understand concrete paving..."
"It's also a matter of getting into the game, so to speak," said Ackley. "A contractor who has purchased a 3D system this year already has a season of 3D paving experience. He's used the system, is comfortable with it and can start next season with this experience. That's a huge advantage over someone who hasn't used 3D yet."
More features continue to be integrated into the system, too. For instance, 3D can now be used to control the firing of an accessory like sidebar inserters and IDBI. Different stringless systems are also available for placer/spreaders and texture/cure machines.
GOMACO has its own in-house 3D controls department.
TRUE GOMACO has been involved with the development of 3D machine controls for concrete paving since 1999. Our 3D controls department provides sales, service, and support of Topcon, Leica Geosystems, and Trimble concrete paving products on our equipment. GOMACO is committed to providing the leadership in 3D technology for the paving industry.
Select any photo to enlarge
A GOMACO paving train with 3D controls on both the PS-2600 placer/spreader and GHP-2800 at work near Cary, North Carolina.
Total stations set up on a 3D project.
Sonic sensors are being used on GOMACO texture/cure machines to eliminate the need for stringline on slipform paving projects.
A GOMACO 9500 trims with 3D on a new highway project near Reno, Nevada.
Continue Reading GOMACO World Vol. 39, No. 2