 The Johnson Atelier Technical Institute of Sculpture has eliminated four weeks from the time needed to produce a full-size sculpture from a scale model by replacing traditional copying tools such as a pantograph with a laser scanner and CNC capabilities. When using traditional implements, Johnson Atelier staff followed the conventional process of capturing the coordinates of the scale model and adjusting them to the desired size, then building a wood and lath armature, adding clay to the armature, and doing the final surfacing of the piece. This process took about six weeks. With the laser scanner, they capture the coordinates digitally and use the digital model as the basis for programming a CNC machining center or lath. These machines cut the piece automatically from foam or stone. Although some handwork is still required, the process takes only two-and-a-half weeks.
The Johnson Atelier is a full-service, non-profit, art casting-fabrication and educational facility whose production of sculpture has earned it a place among the world's leading fine art foundries. Founded in 1974 by sculptor J. Seward Johnson, Jr., the Atelier serves professional artists who need a foundry to cast their work, art students seeking a facility to enhance their skills, municipalities looking to restore their statuary, and architects hunting for the perfect sculpture to crown a winning design. Located in central New Jersey between New York and Philadelphia, the Atelier's 75,000 square-foot facility houses a technical school for sculpture, a library specializing in technical literature relating to sculpture casting, a 1,400 square-foot exhibit area, and a full-service, state-of-the-art casting and fabrication facility. This facility provides custom art services for artists, architects, designers, preservation organizations, and private foundations. It offers ceramic shell castings of the highest quality, produced either from wax patterns or organic materials. The staff can build shells to receive more than six hundred pounds of bronze in a single pour. The Atelier also has a sand-molding department. Using a variety of sand additives, the sand molding staff can enhance a finished casting based on the particular metal chosen. In addition, there is a 12,000 square foot stone cutting and finishing department.
Enlarging models
Often an artist who comes to the Atelier for fabrication services has a scale model of their work. The scale model may have been used to present the idea to a selection committee and after winning the contract, the artist wants the Atelier to produce the piece full-size. In the past, a staff member would have used a pantograph to capture the shape of the scale model and resize it. A pantograph, an instrument for copying a figure to any desired scale, consists of styluses for tracing and copying mounted on four jointed rods in the form of a parallelogram with extended sides.
This method is slow because the user must touch the stylus to hundred of points on the model. It is also inaccurate when the enlarged piece was more than four times the size of the model. It is possible to get around this problem by creating an enlargement in stages, creating intermediate models that are less than four times the size of the original. This slows the process even more, and the end result is still off by several percent. Another drawback to using a pantograph is that it must physically touch the object. For scale models, this is not usually a problem. But the Atelier is often asked to work on very valuable objects, such as stone figures more than 400 years old, that the owners do not want touched. An alternative to the pantograph is Cartesian box, but it has similar drawbacks. This technique requires that an actual box be built around the object. A technician then measures the distance between the walls of the box and various points on the object. Like the pantograph, this method is slow and not highly accurate and it requires that the object be touched, as well as allowing an objective response from the craftsman.
The Atelier needed a more advanced measurement tool that could capture existing shapes quickly and accurately without touching them. The last requirement ruled out a mechanical digitizer, which requires the user to touch the object to record the x, y, z coordinate location of each point. After researching the issue, Jim Barton, President, and Jon Lash, Director of Special Projects, came to the conclusion that laser scanners were the better option because they do not touch the model, yet are fast and accurate. After evaluating the products on the market, they decided that the system that best fit Atelier's needs was the
HandHeld scanner from NVision, Dallas, Texas. The major components of the system are a 3D laser sensor, a mechanical digitizer on which the sensor is attached, a PC, and software that extracts, displays, and manipulates the data.
Faster process
The data is exported from the PC that runs scanner in ASCII format and imported into a surface-modeling program. This software is used to create a high-quality CAD model from the coordinate data. This program is also where the model is enlarged if necessary. A benefit of using the laser scanner is that it enables the Atelier to resize scale models with greater accuracy than they could when using a pantograph. When enlarging a 10-inch model to a 20-foot statue, for instance, the pantograph could be off by several inches even when care was taken to produce intermediate models. Capturing a 10-inch model's shape with the scanner and enlarging it in a CAD system ensures accuracy to within several thousands of an inch on a 20-foot piece.
When the CAD model is finished, it is transferred to a computer-assisted manufacturing (CAM) program that creates the
tool path for the production machine. The Atelier has a custom built CNC milling machine that can cut models out of foam, wood and non-ferrous metals. This machine has a 10-foot by 10-foot cutting table with a 16-inch z-axis. Foam pieces are used as armatures onto which the artist may apply an additional texture or "skin". Wax pieces are used when the artist wants the final sculpture to be cast in metal. The wax model forms the molds for the metal casting process. The Atelier also has the option of using the CAD data to drive an Omag CNC lath. This machine, the only one of its kind in use in the U.S., can mill pieces out of a 5-foot by 5-foot by 10-foot block of stone.
By using the data captured by the scanner as the basis for the production of a sculpture, the Atelier is taking advantage of the same efficiencies that other industries obtain from CAD/CAM. When the Atelier takes the digital approach-scanning a model and producing it on one of the CNC machines-they need four days at most. It takes one or two days to scan the model. Another day is needed to prepare the tool path, and another day is needed to cut the piece. The artist may still want to do some final surface modeling, which takes up to two weeks. This is much faster than the manual approach, which required two weeks to build the armature of wood and lath, two weeks to shape the clay around the armature, and then two weeks of surface modeling.
Due to the increased speed of the digital approach, the Atelier has been able to produce more projects. In the first six months after installing the laser scanner, the Atelier increased its stonework by 30 percent. Many museums in particular have expressed interest in the Atelier's services now that they do not have to touch objects to capture their shape. Atelier management expects to double or possibly triple sales next year. In addition, some of the organization's expenses have dropped since installing the laser scanner.
Barton and Lash believe that their organization is the first art foundry to offer a completely digital sculpting process. Others have some of the components, such as a data collection device or a CNC machine, but none has devised a method that both captures shape information digitally and runs machines from the digital data. For the Atelier, the use of this technology is a logical step because it permits a sculpture-making process that is faster, more accurate, and less expensive. Their experiences have been so positive that they believe the rest of the art world will also evolve toward the digital Atelier approach.
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