TINKER, TEST, REFINE
At UMASS, Point Clouds Keep a Job on Track
BOSTON 03.03.14, 10:13Am by Les Holland
The University of Massachusetts Lowell campus has grown steadily for years, but the brightest jewel in their crown is being finished this year. University Crossing, a 230,000 square-foot, $96.5 million structure, will function as a hub between three UMASS campuses, linking the school to Lowell’s business and cultural centers. The space will function as a student center with campus offices, dining facilities, a bookstore and an event space. Within it, a three-story wood and metal sculpture called The Lantern appears to float in midair, casting both reflected and diffused natural light throughout University Crossing’s main room, The Atrium. It’s a feat that would have been nearly impossible without 3D scanning and point cloud modeling to facilitate the engineering and building processes.
Using more than 3,600 parts and weighing in at more than 12,000 pounds, The Lantern encases a stairway and three levels of balconies inside The Atrium. With a tight schedule and multiple trades depending on everyone working to meet the client’s deadline, there was no room for error. By creating point cloud models throughout the course of the project, CW Keller + Associates helped keep all of the trades working on the project on, and even ahead, of schedule. “We work hard to extend the capabilities of design and engineering firms by providing them with robust digital engineering tools and resources.” said Shawn Keller, principal at CW Keller + Associates, a New Hampshire engineering and fabrication firm that specializes in architectural millwork as well as complex pre-cast and cast in place concrete forms.
The Lantern is a functional feature element made of clear finished solid ash and powder-coated steel. This multifaceted structure diffuses light that floods in through the skylight in the roof and off a 9 by 62 foot reflector bringing natural light deep into the four-story Atrium.
“Building forms are often driven by conditions that challenge the ideal geometries of daylighting design. The depth of a building’s floor plate, the orientation of the site, the shadowing of adjacent structures and other factors inform decisions that create unique design challenges,” said Patrick Cunningham, a senior associate at the Boston office of Perkins + Will architects. Patrick is the design leader of a multidisciplinary team of contributing people noting that The Lantern is a true product of design collaboration. “Developing new design methodologies are crucial to effectively designing day-lit spaces in less than ideal orientations.”
The Atrium uses two primary natural lighting techniques, a large north-facing glazed window for diffused general illumination combined with the south-facing reflector hung within The Atrium’s skylight, which creates a play of light off of The Lantern. “With its wooden slats acting like baffles, The Lantern creates a play of intense and animated daylight on what would normally be a simple, artificially lit surface,” says Cunningham. “To make it work, these new design methodologies require the cultivation of strategic partnerships, the exploration of forward-thinking computational tools as well as new construction processes.” Conceiving and executing The Lantern was the fruit of a coalition between Perkins + Will along with Cambridge, MA lighting design firm Lam Partners Lighting and CW Keller.
Once the concept was established, CW Keller—the firm tasked with fabricating The Lantern developed a Rhino model of the entire assembly that would be used to guide the process of fabrication. Linking this model with the point cloud geometry collected by CW Keller’s Faro Focus3D scanner enabled parallel paths of shop and field fabrication to take place.
From outward appearances The Lantern is elegant in its simplicity. Solid ash slats are linked with folded steel plates. Behind this simplicity were the challenges of creating the geometry, working within the great vertical height of The Atrium, coordination with the structural steel and other trades that interacted with the structure frame and meeting an extremely tight deadline. All of these challenges reaffirmed the decision to go with the 3D scanning approach. At its highest point, the Lantern reaches 63 feet above the floor. Four main connecting points range from just below 18 feet to nearly 60 feet high. Documenting the specific fixing points on the steel girders using a traditional method of lasers, datum lines and tape measures would have been impossible.
Using their FARO Focus3D, the Keller team made a series of scans from several points within The Atrium. Back in their office, those scans were imported into FARO’s SCENE software, which used registration spheres placed on The Atrium walls to create the master 3D point cloud. This allowed the engineers to focus on model development rather than the tedious and time-consuming task of manual registration. More importantly, the Keller team was able to overlay their model for The Lantern on top of the point cloud, ensuring that all of the connecting points in the model matched what was built. This simple step of checking the work that had already been done allowed them to virtually install the fixture and make or request adjustments ahead of time, avoiding costly adjustments during the actual installation.
SCENE also offers the ability to colorize the scans, providing additional clarity to a point cloud. Color allows project engineers to clearly see the difference between elements such as plywood and steel. In The Atrium, the structural members were sprayed with a rough-textured fireproofing material. On the scan, those exposed steel spaces where the fireproofing was removed to mount the outriggers revealed the crimson red surface of the beams making isolating those areas in the model much easier. Once The Lantern’s support structure was installed in December 2013, CW Keller scanned the site again at a high resolution (.11 inch between scan points
at 30 feet). This was done to confirm the locations of the 76 hanging points had been welded to the structural steel at the precise angle and height needed to receive the prefabricated Lantern facets. The Lantern’s undulating surface also required that every fixing point be situated in a unique location. This meant that each facet sat at a unique angle and each structural steel outrigger had to be parallel to the face of each facet. Similarly, the saddle plates that the structural support rods rested on needed to match the angle of each ash plank. With only a few inches between planks, the placement of the steel saddle plates had to be exact.
The Keller engineering team created custom scripts to imbed logic and information to each part within the modeling software. Since its inception this project was a result of collaborative digital manufacturing. CW Keller has been at the forefront of this discipline for years recognizing early on the level of clarity that this can bring to projects regardless of their scale. In January 2014 the machining and assembly of The Lantern began on the shop floor. A cutlist of 865 individual ash boards was automatically generated from the model and CNC programs for each part were developed. Due to the large size and weight of each component of The Lantern, a crane was required to lift the individual facets into the air so they could be attached in their specific hanging location. There was no quick fix available if something did not fit and any modifications cost every team involved time and money. The development of the model within the context of the point cloud of the existing space allowed us to move forward with confidence.
“I think we’ve just begun to scratch the surface of how scanning technology can influence our industry,” says CW Keller principal, Shawn Keller. “We’ve begun using our scanner to document intricate carvings in a historic restoration project for Yale University. Soon we will be using it for our work on the new Miami Science Center’s Gulf Stream tank concrete formwork that we are developing for Baker Concrete. The ability for one person to bring the scanner to site and return to the office with a comprehensive virtual model affords us the ability to now take on more complex projects anywhere in the world.”