Industrial engineering team helps improve output at Springs Window Fashions
The process- improvement team, pictured with a pleater (clockwise from left): Springs Quality Engineer Dave Murn, PhD student René Valverde-Ventura, Springs associates Brad Olson and Reggie Shrader, and IE Assistant Professor Harriet Black Nembhard. (Photo by Greg Anderson)
A leading manufacturer of home furnishings, Ft. Mill, South Carolina-based Springs Industries sets and maintains rigid requirements for its products' quality. Associates at the Middleton, Wisconsin, headquarters of Springs Window Fashions Division also embrace high standards: A window blind that's just a quarter-inch off won't leave the plant. Neither will a pleated shade with an almost invisible fabric flaw.
Given this philosophy of excellence, the Middleton plant places a priority on making sure its newest fabrics perform consistently. The plant uses one especially important new fabric "family" to make its Crystal Pleat cellular window shades.
Because of their hearty honeycomb-style configuration, cellular shades look as elegant as traditional pleated blinds but offer extra insulation. At the Middleton plant, which houses several cellular-pleating machines the size of small busses, cellular shades start life as 3,000-yard rolls of horizontally striped fabric. On the machine, the fabric winds over, under and through several rollers, then a motorized arm whisks a thin layer of glue across it and a pleater curls it into a cell.
When the process goes as planned, the crest of the pleat is in the center of the stripe and the finished product is white on back and colored on front. When something goes wrong, defects can include a color that bleeds through to the other side, "twist," misshapen cells or bows and ripples in the fabric. Industrywide, about 80 percent of the final pleated product makes the cut. Since products containing such defects never leave the Middleton plant, Springs hoped to beat that number.
With funding from Springs and a University-Industry Relations grant, the plant formed a team that studied how to make the company's pleating and gluing process even better. Its members included pleater operators, machinists, quality engineer Dave Murn, industrial engineering PhD student René Valverde-Ventura and Professor Harriet Black Nembhard.
With Nembhard's help, the group used a statistically efficient method called a design of experiment (DOE) to identify what factors would cause flaws in the finished pleated fabric. "We were able to, through our design of experiment work, identify regions of preferred operation," says Murn.
The group learned which pleater parts could contribute to product variance. While previously operators adjusted those areas "by feel," says Murn, the group eliminated many variables by calibrating all of the plant's pleating machines and installing permanent measurement scales. "When we went through and calibrated machines, we found machines that were more than an inch off because the operators didn't know where they were," he says. "Now they know that the closer to the zero baseline setting they run, the better off they are." In addition, operators now record how, when and why they've adjusted their machines.
After he collected data from the system and modeled fabric performance, Valverde-Ventura updated the formula a computer-driven camera uses to target a pleat in the center of the fabric's colored stripe. "The computer program originally written for that was written for a specific family of fabric that performs differently than the newer fabrics we are currently running," says Murn. Valverde-Ventura also added a Cuscore monitoring chart to detect the smallest changes in the stripe's width.
In all, the DOE revealed nearly 60 variables per machine, and helped the team identify six key variables the Middleton plant needs to control. Improvements are ongoing. "One of the absolute benefits of this work was to identify all of the variability and to bring some sense of order to it," says Murn. "This has allowed us to take certain aspects of the quality engineering body of knowledge and show that we're applying it in the workplace."