Controlling core actions on older presses

If you are like Dick Benedict, you probably have a few older presses in your shop that are not exactly on the cutting edge of injection molding technology. Though an older press is not, by definition, deficient, it most likely lacks the contemporary electronic wizardry that makes new presses so efficient. Take, for instance, core control, a hassle for Benedict on some jobs.

Benedict is the plant manager at Frontier Tool in Phoenix, a 10-press injection molder with machines ranging in age from those built in the 1970s to 1997-Van Dorn, Fellows, Niigata, Newbury, and CMP. On his older presses-like the relay-logic-based 1982 Niigata-Benedict does not have the built-in engineering required to properly control core-pulling sequences. Because of this, he became dependent on maintenance personnel who had to "wire" a machine to perform a particular core sequence for some molds. "My basic problem was having to rely on our maintenance department to set this job up," he says.

"This job" is a cylindrical part about 14 inches long and 3.5 inches in diameter. It contains one main cored-out section down the center and two smaller holes along the side at the bottom of the part. Previously, the holes were drilled by hand in a postmold operation because the press didn't have the control required to core the holes in the mold. On top of that, Benedict says he was spending about one hour and $300 each time a maintenance employee set up a machine.

Benedict had worked in the past with Custom Automated Products to develop customized systems for his molding operations and again turned to engineer Russell Winnett. Benedict did not want to replace, overhaul, or retrofit his presses. He just wanted a way to program core sequences without a screwdriver and a degree in electrical engineering.

What Winnett came up with is the Integrated Core Controller (ICC), which, as its name suggests, allows molders to program, store, and retrieve specific core sequences through a relatively simple operator interface. It uses existing signals from the machine to control the core sequence by position or by time and sets on the inject or clamp close signal. It also controls core set and pull, clamp open and close, and inject forward. "The signals we're getting off the press are the most basic signals you can get. The controller gives the molder the ability to select a function based on the mode," says Winnett. "It gives them the ability to change over sequences on the run."

The PLC-based system consists of a terminal strip, fuses, and programming logic written by Winnett. It accepts up to 10 inputs from the press and generates up to eight outputs. "Someone could either attach it to the outside of the machine or patch it into the panel," says Winnett. Installation, he says, can be done in a couple of hours. For multiple-machine use, the system can be configured with a portable operator interface that can be carried from press to press, plugged in to a communication port, and used as needed.

Benedict installed the ICC on the Niigata molding the tube and now uses three cores in the mold-the main center core and two smaller side cores for the holes that were previously hand drilled. He says the cores on the part are actuated based on a timer and programmed via the ICC. In the few months he's had it, Benedict says he's not had to call for maintenance personnel once to set up the press.

On another part, a cam slide with one core in three parts, Benedict uses the ICC with limit switches to control core action. In this sequence, after the mold closes, the core sets before injection starts; after a set time-about 25 seconds-the core is pulled and has to make the back limit switch before the mold will open. All of that, he says, was most difficult to do before the ICC was installed.

Price is unlikely to be an object for most molders. Winnett says one unit will run about $1200 and multiple units with the portable controller interface will go for about $1050.

Says Benedict: "It's certainly affordable to me. I can see within a year it will pay for itself, especially when I used to pay a guy $200 or $300 to set it up."