Plasma/oxyfuel system with 3D scanning automates challenging dome cutting operations

With more than 70 employees, Waterford Tank and Fabrication manufactures above-ground storage tanks and custom ASME pressure vessels in Beverly, Ohio. The company’s 90,000-sq.-ft. fabrication facility houses equipment including a plasma table; combination plasma/oxyfuel table; large, medium, and vertical ring rollers; a press brake; and 10 overhead cranes.

Waterford has a steady stream of work, but the volume of these jobs, coupled with complex fabrications and a limited ability to process thicker metals, had become a roadblock to growth.

“In the past, we manually transferred measurements from drawings onto the dome and made cuts with a hand-held plasma torch. The edges were then prepared for welding using a grinder,” said President Matt Brook. “Typically, processing a single dome would take anywhere from eight to 10 hours.”

Like many manufacturers, Waterford faces a shortage of skilled labor. The prolonged fabrication process was consuming resources and limiting opportunities to take on more work and expand the business. The company needed a more flexible and automated system to expedite production and expand the company’s offerings by accommodating thicker plate cutting.

While investigating the alternatives, Brook was introduced to United Precision Services, the exclusive North American partner for MicroStep cutting equipment.

Waterford Tank and Fabrication selected the MicroStep model DRM plasma/oxyfuel machine for making straight and bevel cuts on flat plate and cutting hole penetrations into vessel heads with plasma. This multifunctional system has one working zone with a 15- by 45-ft. table and a second working zone with a pit in the floor to process large dome heads.

The machine not only processes thicker metals to expand the fabricator’s cutting services, but it also automates most dome cutting applications, including trimming, separation cuts, cutting diverse openings, weld edge preparation, and cutting inverted domes.

To help ensure that contours and openings are precise and compliant with production requirements, MicroStep’s mScan, a 3D laser scanning process and corresponding point cloud mapping software, allows the machine to measure the true shape of a dome and use this information to guide the cutting process.

According to John Prevish, United Precision Services national sales manager, this has a significant impact on dome cutting accuracy.

“The actual dimension of a dome can lay within allowed tolerances, which in fact means that the real and ideal shapes of domes sometimes differ by inches, and conventional 2D methods of positioning corrections via control of plasma arc voltage do not apply to 3D cutting,” Prevish said. “The MicroStep scanner creates a model of the actual dome surface within the coordinate system of the cutting machine. This model can be used to analyze the shape of the dome, identify its center, and define the exact toolpath above the surface.”

Data received from the scanner is paired with positions of the machine’s motion axes. These positions are adjusted by applying displacement corrections based on the measurement of machine kinematics by a laser interferometer, as well as the calibration data of the bevel head and 3D scanner itself. This provides the control system with information regarding the exact position of the scanned object with respect to the cutting tool, enabling exact scanning of the object within the coordinate system of the cutting machine. The software then creates a detailed 3D model of the object while describing its parameters and any deviations from ideal shape.

Armed with new capabilities, Waterford has experienced a measurable improvement in cutting time and efficiency. A more automated and lean fabrication process is simplifying dome cutting and allowing the company to take on more jobs without added headcount. Workers can be allocated away from manual dome cutting to other areas on the shop floor or to tasks such as estimating and sales support.

“For years we were limited in terms of the volume and scope of jobs we could take on,” said Rocky Roberts, vice president of sales and marketing. “With MicroStep, we’ve greatly expanded our capabilities and today we’re able to process domes up to 14 ft. in diameter and 55 in. high. This allows us to offer even more value-added services to our customers. Now, instead of them spending hours manually figuring out dome hole penetrants, we can make the cuts and return the dome to them at a fraction of the time.”