Working closely with Sage Woods, the System Integrator focused on solving their pain points and optimizing these three areas: Primary Breakdown, edging and trimming, and finally, grading. They agreed on rolling out the changes in stages to allow time for system tuning and operator training and make adjustments when necessary.
Disclaimer: This story is based on actual events. In certain incidents, characters and timelines have been changed for dramatic purposes. Certain characters may be composites, or entirely fictitious. For more details on how Sage Woods found the perfect System Integrator (SI) partner to automate, click here.
Primary Breakdown Optimization
Before an optimal sawing pattern can be applied to a log, each full-length stem is bucked (sawn) into product-length logs. During traditional Primary Breakdown, operators manually cut the bucked logs into rough lumber based on a sawing pattern the management deemed most profitable. As examined in this article, this manual process was overly subjective, and most of the time, wasting precious raw material as a result.
The proposed Primary Optimizer would calculate an objective, precise assessment to maximize sales revenue for the sawmill. The System Integrator employs a non-contact laser scanning technique that would scan bucked logs for shape and provide very precise digital 3D images. These images are a 3D representation of the log’s geometric measurements in a point cloud format. A computer then runs the captured point cloud data through proprietary optimization algorithms to calculate the best sawing breakdown.
Typically, sawlogs are from 2.5 to 7 meters (8 to 24 feet) with diameters ranging from 10 cm (4 inches) up to 60 cm (24 inches). To take complete measurements of a log, the System Integrator used a 4-head scanner configuration with each scanner mounted on the four corners of a metal frame. The scanner emits a Class-2 fanned laser beam pointed at the conveyor transporting the logs. Each scanner has a resolution of approximately 0.254 mm (0.1 inches) at a scan rate of 10 milliseconds (100 Hz). The scanners are Time-division Multiplexed to avoid crosstalk, so when activated, the scanner’s reference beams would not interfere with each other. With four scanners in a ring around the log, a cross-sectional scan roughly every 1 inch along the log can be captured.
Laser triangulation and 3D scanning
3D laser triangulation works by illuminating a single point or a linear line on the log’s surface. A camera sensor then observes the laser projections at a known, pre-calibrated angle to the laser illuminator. The System Integrator chose to use laser triangulation as it has characteristics such as speed, range, and accuracy that make it the most suitable and safest for many industrial applications.
Processing the 3D data
Each laser point/profile observed by the imager becomes a point cloud or a series of point clouds. The data is represented by a list (row) of X, Y, and Z coordinates that each set of values corresponds to a location in 3D space. Before the optimization software can process the data, the data is filtered of any unwanted data. This commonly constitutes noise from bark or branches on the log or parts of the log transport mechanism such as flights or chains.
The next step after filtering the data is to combine datasets from multiple scanners to create an accurate representation, a process known as point cloud stitching. In principle, it converts each scanner’s dataset from referencing “local coordinates” into a common, single base coordinate system. Keep in mind that each of the four devices is taking 100 scans per second, the result is the log’s complete 3D profile at any given moment.
With the primary breakdown digitally aided by machine vision and optimization software, the most critical part of the sawing process now exceeds 150 meters (500 feet) versus the earlier speed of 120 meters (400 feet) per minute. Using a 3D computer program also meant that the optimal sawing model was objectively calculated based on the log’s actual measurements, eliminating any guesswork. Sage Woods was able to saw more sellable dimension lumber from each log, significantly increase their production volume and shortening the lead time. They reached an unprecedented level of throughput, which became vital to Sage Woods’ profits. A study later conducted by West Virginia University and the USDA Forest Service also proved that 3D sawing optimization systems help small sawmills recover lumber volume by 4.1% and value by at least 14%.
The unexpected outcome
Digitizing the process and data also gave the sawmill unrivaled flexibility and responsiveness to different economic opportunities. In many cases, Sage Woods was able to quickly reconfigure the production lines to meet customers’ demands with simple computer commands.
In addition, aided by optimization algorithms that calculate the maximum value, they prioritized cutting the lumber types that would deliver the highest yield. Sage Woods also lowered their inventory level, which freed up storage space, cut down on waste, and reduced operational costs.
Economic uncertainties in the following years left many of their competitors stranded for cash. On the contrary, the revenue gain from Sage Woods’ capital investment was starting to pay off. They were able to integrate vertically and horizontally, acquiring nearby timberlands and sawmills.
Early in the planning stage, Sage Woods had devised training programs that would help transition their workers into digital manufacturing. Thanks to such programs, they expanded the business with talent ready to operate these automation systems. Eventually, they acquired the sawmill that stood across from them for almost a century, the Brown Brothers.
Sage Woods’ success in transforming the sawmill into a technologically advanced workplace laid the groundwork for its process upgrades throughout the following decade. They would go on to revolutionize the industry with ground-breaking automation like Edger and Trimmer Optimization, log rotation, and real-time dimension monitoring. The third and final article of A Tale of Two Sawmills will look at how modern manufacturers can learn from Sage Woods’ journey, as digitally transforming factory processes is imminent and inevitable. Click here to continue reading.
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