Birdsall Earthworks Ltd
Laser Guidance
Laser Guided Excavators
All excavators in the Birdsall Earthworks fleet are laser guided.
Highly accurate angular sensors are installed on the excavator boom, stick and bucket. These sensors are connected to a computer which uses the length and angle of each component to calculate the position of the bucket relative to a datum. A screen in the operators cab provides a visual display of the bucket position relative to the cut level shown in blue (as shown above).
A datum can be set using two methods. The first method is to simply touch the excavator bucket on a known point and then simply enter the difference up or down you would like to dig into the computer (including a fall if required). Each time the machine is moved the datum or new cut can be used to reset the machine. This method does not require a laser but inaccuracies can be cumulative on a larger excavation.
The second method is to use a laser for reference. This provides high accuracy (+/- 1.0mm over 300m) and the laser can be set level or to a single or dual slope. Each time the excavator is moved it is simple to reset the datum by simply moving the stick mounted sensor through the laser plane.
CTL with Bucket Receiver
A proportional laser receiver is fitted to a pole which is bolted to the CTL bucket. The receiver gives a visual reference to the operator and the bucket is manually adjusted to the datum.
Accuracy and speed is less than with a box grader but level checks are not required which saves labour and the operator has a constant reference working to a level or sloping datum.
The machine can still be operated as a normal loader so material can be moved around site using the bucket.
CTL with Automatic Box Grader
A laser guided box grader is fitted to a Cat compact track loader (CTL). The CTL is a 3.5 tonne powerful, compact and manoeuvrable machine with the tracks providing a more stable operation than wheels.
The grader blade is located within the box and is automatically moved up and down by a hydraulic ram on each side. Sensors located on the two laser poles pick up the laser and move each side of the blade to follow a datum. The CTL is simply driven while pushing fill and the blade automatically adjusts leaving an accurate level with one pass. Accuracy is +/- 10mm on roughing passes and +/- 2mm with a finishing pass.
A CTL and automatic box grader can prep a slab or small carpark many times faster, and more accurately, than traditional freehand preps with manual height checks.
Laser Advantages
A laser guided machine can dig, trench or fill anywhere on site to the specified level without the need for an extra man doing level checks.
The computer can simply be inputted with a new height and steps in footings or benches are instantly achieved.
The base laser can be set to a single or dual slope, which provides very accurate falls to carparks, lawns or drainage trenches.
Base lasers in use are Leica Rugby 880 units which provide high accuracy of +/- 2mm out to a range of 300m and can provide slope accuracy down to 0.001%.