Got An Old Open Loop Machine? Don't Quit: Refit!
This is the story of how one molder cut scrap 15 percent and boosted productivity 20 percent by retrofitting with closed loo
This is the story of how one molder cut scrap 15 percent and boosted productivity 20 percent by retrofitting with closed loop controllers. It's an old story, one you're sure to have heard before: faced with the cost of buying brand new molding machines, a molder decided instead to upgrade existing machines with new controllers. An old story sure, but one that needs to be repeated again and again these days, not only because of the competitive climate out there, but because today's retrofit controllers can do so much more to help molders meet today's challenges - SPC data collection, for instance.
Advanced Auto Trends (AAT-Oxford, MI) specializes in small automotive parts, like body side rocker panel brackets for the Ford Explorer. It employs 95 people and runs 32 presses, 55 to 700 Tons. Its machines were old and they were open loop. Being open loop, there was no way for the controllers to verify that commands were being properly carried out, that makes it kind of tough to repeatedly mold tightly toleranced parts. That also meant machines had to rely on malfunction prone electromechanical relays and limit switches and such. And that also meant AAT was limited to relatively simple control cycles, such as a flat velocity profile.
Rather than buy new machines, AAT upgraded with Scoremaster closed loop controllers from Solid Controls Inc. (SCI). Michigan Plastic Machinery Rebuilders (Auburn Hills, MI) installed the SCI controls, and also improved some hydraulic and mechanical systems on machines where required. The Scoremasters keep a close eye on all molding variables, and make subtle adjustments for changes in materials or hydraulic oil viscosity. They can be programmed to sound an alarm or shut down a machine if parameters stray outside control limits. And all parameters are set up digitally, no need to worry about failure of electromechanical components. Repeatable production of quality parts is the result.
Case in point: seat belt adjustment knobs. They're tough to mold because the small gate can cause splay. Previously, about 15 percent of AAT's knob production had to be scrapped. After it installed a new Scoremaster on its 200-ton Van Dorn, profiling became possible. Injection speed is held low until the material passes through the gate, then it's high speed for filling. The scrap rate is now around 2 percent for this part. Here's another: difficult to fill clips with a thin disk. Scrap from short shots and flash on a 330-tonner also was 15 percent. The Scoremaster now monitors the cushion. It turns the machine off if the cushion distance is ñ.010 inch off the preset 1/2-inch position. Scrap is down to 1 percent on this job.
Its controllers also are opening the doors to new opportunities for AAT. Automatically, they gather, compute, and print out SPC data for all important parameters, a good first step to ISO certification, which is now in the game plan. Elimination of things like limit switches and thumbwheels on the old open loopers means set ups are faster now, one hour versus two or more. And the controllers remember those set ups. All but five of its molding machines had been upgraded at this writing. Faster set ups and less downtime have improved AAT's productivity by 20 percent, according to its own estimates.
Solid Controls, Inc., 820 South 5th Street. Tel: 952-933-9053; Fax: .