Controllers Reduce Start-Up Time By 50%

A.L. Hyde Co. doesn't believe in throwing the baby out with the bath water. The Grenloch, NJ, company's philosophy is illustrated by its decision regarding how to achieve better control of its plastics injection-molding process.

A.L. Hyde produces a wide range of products, specializing in short-order runs and heavy-wall parts such as gas-pipe fittings with wall thicknesses of 1 in. These wall thicknesses are regularly produced to between 0.010 in. and 0.015 in. of a customer's specifications.

Attaining these tolerances with molding machines that are equipped with two solenoid-operated, flow-control valves, controlled by manual thumbwheels, is very labor intensive. This is especially true in a two-stage control cycle configuration, which works like this: one valve begins the injection process with a slow fill. After a certain amount of time, the second valve takes over and increases or decreases the flow speed.

This method requires a great deal of trial and error, sometimes as long as 8 hours to determine the proper two stage, injection velocity profile. Although this technique makes it fairly easy to attain the proper aesthetics, obtaining the correct size is more difficult because decreasing the speed to prevent flashing (spillage out of the mold) also decreases the injection pressure. This pressure decrease can cause a problem because high injection pressure is needed to properly fill the part.

The process also requires a lengthy trial and error process for the operator to determine the amount of time that should be added to holding. This is because the viscosity of the material differs from job to job, said Gerald Riley, technical development training manager.

A.L. Hyde's solution was to add controllers to 18 of its 36 existing injection molding machines, which have an average age of more than 20 years. The Scoremaker controllers, from Solid Controls, Inc., Hopkins, MN, were first installed in the mid-1980s. "Switching to a six-stage, closed-loop controller, which gives commands to the machine and monitors the molding process, made it possible to supply materials at a higher level of pressure that remains constant regardless of the injection speed," Riley said. The controllers also provide injection-velocity control profiles; a graphic display of the actual velocity; and digital control of molding parameters such as time, injection pressures, and injection speeds.

A.L. Hyde has reaped numerous benefits since the controllers were installed. Customer satisfaction is up because flashing and the subsequent trimming have been virtually eliminated. "Customers are happier with the aesthetics of the parts. They liked them before but now they love them," Riley said. Most of this is due to the controllers' ability to first inject a part slowly so gates don't freeze off, then pick up speed to prevent flashing. The controllers also can reduce injection speed without creating a corresponding decrease in pressure.

Within the company, the foreman and molding technicians have used the additional data the controllers provide to improve parts. Also, start-up time on a normal job has dropped 50% from approximately an hour to about 30 minutes and cycle time has gone down 13% from 60 seconds to 52 seconds.

BENEFITS:

• Start-up time down by 50%.
• Cycle time down by 13%.
• Flashing and trimming virtually eliminated.
• Greater customer satisfaction.

Solid Controls, Inc., 820 South 5th Street. Tel: 952-933-9053; Fax: .