Porter International, a subsidiary of residential furnishings maker Leggett & Platt Inc., designs and manufactures mattress machinery systems that streamline manufacturing processes. Fifty years ago, two men founded Porter International as an apparel and footwear manufacturer. But in the early 1970s, Porter developed a technology that changed the company's course: a compound feeding mechanism for bringing extremely thick material, such as quilted bedding, uniformly through the sewing machine. This technique, which is still unique today, was of little use in the garment industry. It was however, a lucrative tool for bedding and furniture manufacture so Porter shifted to this market and has been dedicated to making machines for bedding and furniture since the late 1980s.

In 1997, Leggett & Platt bought Porter International to build Leggett & Platt's bedding manufacturing business, which now includes eight companies located across the U.S. and England. The move strengthened Leggett & Platt's position in Europe, where plants prefer to buy all of their equipment from one company. Today, Porter has installations in Europe, South America, and the Far East. To support Porter's global installed base efficiently, remote diagnostics are essential. Fortunately, Porter uses controllers from Control Technology Corporation in many of its machines, which Steve Marcangelo, Porter's Manager of R&D (right), can access via modem or network connection. This proved to be an extremely powerful tool recently for an installation in Argentina. When the customer called, support staff at Porter had no idea what the problem was. However, Steve Marcangelo reports, "By going through the program, we identified the problem. For the cost of a phone call, the customer saved a lot of time and we saved a trip half-way around the world." By April, Porter plans to install remote connectivity capability on all of its new machines. From their home office, Steve Marcangelo can access the CTC controller and work with the on-site technician to solve the problem faster.

CTC automation controllers control three machine models built at Porter's new Rowley, MA headquarters:

• the PHH-600, which measures and cuts mattress side panels to length and stitches handles onto them
• the PAV-500, which applies the metal breather units to the side panels
• the ATA Flangemaster, which trims and finishes the raw edge of the top and bottom mattress panels.

The PHH-600
The PHH-600 automatically measures and cuts the mattress side panels, dispenses and folds the handle material, and stitches the handles in place. From the CTC touchscreen, the operator can select one of seven mattress sizes and specify the location of the handles on the mattress. If necessary, the operator can enter a correction factor unique to each type of border material, which compensates for length errors due to the material's stretching. The operator then pushes the Start button and walks away. The machine feeds the border material from the roll, cuts, folds and stitches each handle in place, and then cuts the border to the right length for that particular mattress size. One minute and 45 seconds later, the panel is ready for the next step in production — and the only operator intervention required is the initial machine set-up. Using previously available manual techniques, two people needed seven to nine minutes to do the same task.

The PHH uses a CTC controller with three axes of motion control: one servo and two steppers. It also coordinates additional I/O. Steve Marcangelo has used Quickstep™, CTC's programming language, since 1982 and did the programming for the PHH in about six weeks "off and on," he said. He prefers Quickstep to ladder logic, explaining, "They've done some nice things for the motion control world to make it easier to develop programs. It's a powerful system."

PAV-500 Vent Machine
The PAV-500 applies the "breather vent" hardware to the mattress side panels. It automatically punches a hole in the mattress and then feeds the vent cap from the top and a backing washer from the panel's underside. The PAV-500 pushes the cap through the holes in the mattress and the washer, then crimps the cap so it locks in place within the washer. The PAV-500 is twice as fast and safer than the previously available equipment. While this application is relatively simple for the CTC controller, Porter selected this controller to provide for possible future integration with the PHH-600.

ATA Flangemaster
The ATA Flangemaster receives a rectangular piece of quilted fabric with raw edges. It trims the fabric to size for the designated top and bottom mattress panel, and simultaneously finishes off the raw edge with stitching. This trimming and finishing process, called serging, ensures that all three layers - top layer, quilted batting, and bottom layer - are bound together smoothly and securely by a single row of stitching. The serging step also rounds the panel's corners into the shape consumers are familiar with in a completed mattress. Serging not only prevents the fabric from raveling, but also stabilizes and compresses the thick, quilted material so it is easier to manipulate when binding to the side panels. A second needle adjacent to the serger stitches a row of safety stitching about 1/2" inside the outer edge. This reinforces the first row of stitching and flattens the panel's perimeter, which also makes it easier to apply binding later. The ATA uses six axes of motion control: four servo and two stepper. For this application, Steve Marcangelo selected a rack-style CTC controller with one I/O, two servo, one dual-axis stepper, one high-speed counting module, and one analog control module. Porter may add a communications module in the future. The company built this machine by using an existing Porter sewing machine model and integrating it with the CTC controller, which controls the sewing machine.

One of the most difficult parts of this application was turning the panels when the sewing unit reaches the corner. The stitching for the inner and outer needles must work well in tandem, despite the fact that the radius for the inner stitching is a shorter path than the outer one. To solve this problem, the CTC controller takes a snapshot of data for the first few stitches that the machine runs and then uses that data to adjust the speed as the sewing head reaches the corner. By controlling the rates at which the panel turns and the needles stitch, the two needles stay synchronized, so the two rows of stitching are even and unpuckered.

But this solution alone did not assure success. While many manufacturing applications deal with rigid materials, such as metal or plastic, fabric is pliable. When a thick, five-foot by six-foot piece of material rotates, it's likely to wrinkle and shift out of position, potentially causing the machine to trim the panel irregularly or stitch a fold in what should be a flat panel. To make sure the panel stays flat, the CTC controller uses two techniques. First, it gauges how thick the mattress panel is and makes the turning arm, which actually rotates the fabric, clamp it down to exactly half that thickness. Second, the panel sits on a ventilated air flotation table, which has hundreds of perforations through which forced air floats the panel enough to neutralize the drag caused by friction. The panel turns smoothly and remains flat as it is turned around. A pair of electromechanical pneumatically powered sled clamps pull and guide the material through the serger and feed data back to the CTC controller on their positions; the controller uses this data to calculate the length the serger has traveled, and when to start turning the panel to make the corner.

Like the PHH-600, the ATA can run largely unattended. After loading the panel into the machine's sewing head, the operator runs a few stitches to start the panel and then presses the Start button. The ATA finishes and ejects the panel, which is ready for the next production step. Like the PHH-600, it can run any standard-sized mattress automatically.

What are the benefits of this machine over manual methods? "It takes a few months to train someone to sew the panel manually," says Steve Marcangelo. The machine reduces training and frees up the operator to run other equipment. Sewing the mattress panels by hand is a labor-intensive, tedious job, and as fatigue sets in, product consistency may suffer. The ATA Flangemaster, on the other hand, turns out consistent product every time.

With CTC's remote access, Porter International's technicians can spend more time sleeping on mattresses — at home — and less time troubleshooting them. Using CTC controllers, Porter's automated mattress manufacturing machines have helped Leggett & Platt become an industry leader in engineering for residential furnishings. Control Technology Corp. is delighted to contribute to Porter International's success.