Rotary welding systems built by Contour-Arc.

Robert H. Peterson Co. (www.rhpeterson.com), City of Industry, Calif. produces premium-quality Fire Magic gas grills and Real-Fyre gas logs that are sold domestically and internationally at specialty dealers of patio, barbeque and fireplace fixtures and furnishings.

The company has grown steadily since 1937 and its commitment to quality and craftsmanship has remained unchanged, despite foreign and domestic competition, changing demands in public taste and the constant challenge of product innovations.

What has changed is its approach to manufacturing, moving from single station operations with one man/one machine orientation, to more automation, both in its fabrication and assembly.

The company’s main facility has nearly 230,000 sq. ft. of manufacturing space, and houses every facet of its manufacturing, including sheet metal fabrication, laser cutting, robotic welding, die and press brake forming, grinding, polishing, assembly, testing, packaging, and distribution.

Recently, as part of the continuous flow manufacturing line for its new Echelon and Aurora gas grills, R.H. Peterson used Contour-Arc, Inc., a local integrator of robotic and automated welding systems to develop a custom, CNC Controlled Spot Welding System.

This new machine was needed to automate the precise and challenging welding of large, cumbersome stainless steel grill firebox assemblies, and integrated directly into the company’s continuous flow line of fabrication, assembly, test and packaging operations.

Contour-Arc reviewed the company’s requirements and brought its 30 years of expertise in automated welding and factory automation to the task.

The CNC Spot Welding System Contour developed consists of several major components, built around the Siemens Sinumerik 802D CNC control, using three axes, X, Y, and C, of coordinated motion, and the Miyachi Unitek IS-120B Inverter Spot Welding Power Supply.

Controls help Robert H. Peterson manufacture steel barbeque grills.

The system was designed with four independent welding stations attached to two oscillating rotary index tables placed side-by-side.

Steven Pfahl, president of Contour Arc, said that configuration allows the operator to safely load the fixtures on one side of the index tables while the machine is welding on the other side, maximizing production time and minimizing machine idle time.

In addition to the three motion axes and the two rotary index tables, the Siemens CNC controls and monitors all functions of the machine, including the spot welding process.

The CNC interfaces seamlessly with the Miyachi IS-120B power supply to allow the programmer to call up any number of pre-programmed weld schedules stored in the weld controller and use them wherever they are needed. That allows the machine to deal with the different material thicknesses for the firebox assemblies.

A typical Fire Magic Grill firebox assembly has 50 spot-welds on each side. Fixtures that hold the parts in assembly hold both sides of the fireboxes simultaneously.

The typical welding program for these assemblies can be written in less than one hour, Pfahl said.

Siemens provided on-site training at the manufacturing facility to train the company’s operators on how to write specific programs using the CNC’s control panel and a remote pendant, and how to back up and store machine data. Data is stored on a compact flash card or on the company’s server through the control’s Ethernet port. Training provided by Siemens included hands-on programming of the CNC’s servo motor drives, internal programmable logic control, and in-put/out-put control.

Contour-Arc robotic welding and cutting stations use state-of-the-art computerized numerical control.

Pfahl said the Siemens CNC was the right choice as an integrated control.

“Due to the nature of custom machine building, we needed a complete single-source CNC package, including the hardware, drives, motors and programming software,” he said. The Siemens CNC provided those features and was versatile and easy to integrate, he added.

In addition, Pfahl said the Siemens CNC has a software package that is easy to learn and to navigate.

“The 802D control had everything we needed for this project, including Profibus connection between the CNC and I/O boards, as well as the Siemens mini-handheld, a portable remote programming pendant,” Pfahl said.

The machine’s X-axis has 120 in. of linear travel, and the programming pendant allows the programmer to write the program point-to-point by jogging the various axes into position then recording those locations with the pendant rather than at the control panel. That saves the programmer time and motion.

The machine’s large footprint also required that a remote operator station was placed at a considerable distance away from the CNC cabinet and closer to where the operator runs the machine in production.

The operator start station is a pedestal-mounted console with a series of pushbuttons, rotary switches and pilot lamps that are connected to the CNC’s I/O board. The CNC’S buss connection allowed a remotely mounted, second I/O board to be placed inside the operator console and to be connected to the machine controls, rather than running wiring back to the main control cabinet.

Pfahl said that set-up reduced the amount of wiring between the control and operator station by more than 90 percent.

To complete this turnkey system, Contour-Arc designed and built custom part-holding fixtures to assure the combined time of part loading and unloading would be less than the weld cycle time.

The firebox assembly comprises several irregular shaped sheet metal components, and welding is done around the perimeter of the assembly.

Because the shape of the assembly is such that mechanical clamps would interfere with either the welding head or loading and removing the finished assembly from the fixture, vacuum clamping was chosen to hold components in the fixtures.

”The advantage of the vacuum clamping system is that the operator can load and unload the fixtures in a matter of seconds and nothing gets in the way of the machine’s welding head and electrode. This allows us to run the machine at its maximum speed. We also programmed the CNC to monitor vacuum sensors placed in the fixtures, so if the vacuum level falls below the minimum set-point, machine motion will stop and an alarm will display on the control panel,” Pfahl said.

All the fixtures on the machine are quick-change style and have locating pins and quick disconnect electrical and vacuum fittings. The system’s configuration allows the fixtures to be changed on one index table while the robot is welding on the other index table, to reduce system idle time and to maximize production on each shift.

R.H. Peterson has reported time savings of as much as 30 percent.

Jon Bridgwater, senior vice president of R.H. Peterson, said his company runs eight different grill sizes for three different models in production.

“Once we set up the four programs needed, no additional programming must be performed. After we program the CNC, it is fully automated in process,” Bridgwater said.

He said his company also spent a considerable amount of design time on standardizing part holding fixtures, so that minimal or no changeover would be needed, when going from one size to another.

“As a result, the fixtures have no moving parts or mechanical clamping devices that might interfere with the spot welding head. This system has allowed us complete flexibility in the models, sizes, and quantities we can run at any time. This is the ultimate in lean manufacturing,” Bridgwater said.

He added that he believes the Siemens CNC is the key component for the system’s performance.

“Regardless of the components run in any cycle, the CNC is able to determine and execute the angle and depth of the welding arm’s articulation, resulting in non-stop production with no compromise of quality,” Bridgwater said.

The company has a historical commitment to vertical integration in its manufacturing and Bridgwater said that commitment gives it more control over its destiny.

In addition to Fire Magic gas grills, R.H. Peterson produces the American Outdoor Grill line and Real-Fyre line of vented and unvented gas logs for home fireplaces.

To maintain its competitive advantage, the company has integrated manufacturing capability on its factory floor, including cutting and marking lasers, punch presses, CNC press brakes and folders, Robotic MIG and TIG welding, CNC spot welders, manual MIG and TIG welding, grinding, polishing, plus concrete pouring and mixing equipment used for the production of its more exotic outdoor fireplace bases.

Contour-Arc, Inc. (www.contour-arc.com), Laguna Hills, Calif. produces a pre-engineered or custom built stand-alone or in-line robotic welding systems, and computer-numeric controlled and programmable logic controlled rotary and linear welding systems for MIG, TIG and plasma welding processes. The company also builds welding system components that include heavy-duty precision floor-mounted and table-top rotary positioners, welding process controllers, TIG cold wire feeders with wire guide positioners, a variety of aluminum cross/rotary/compound slides, plus rotary and purge live center tail stocks.