Insert molding: Ripe for automation

Automation can lead to faster cycle times, improved quality, enhanced production efficiencies, and in the end, new business opportunities-all of which two Connecticut companies were banking on when they recently took on the daunting task of completely automating insert molding.

"Quality. That is the biggest improvement we anticipate from automation," says Michael Sansoucy, program manager at Seitz Corp. (Torrington, CT). "And it increases the volume potential of our machines by eliminating human error and inefficiencies, so now we can go after projects involving higher volumes. Automation does all this by stabilizing the insert molding process."

For Plastic Molding Technology (PMT) of Seymour, CT, the driving force was not necessarily fostering new business opportunities, but keeping its existing customers happy. "Our customer needed output and wanted the piece price down, too," says Gordon B. Sanford, PMT's plastic process engineer. "We had one part running with two operators. Cycle times were around 50 seconds. With automation, the cycles now are around 21 seconds. We doubled the output by automating. Otherwise, we would have had to buy more molds and more machines."

To get to where they are today, both companies worked closely with systems integration specialist Injectech Engineering LLC, also based in Connecticut.

Creating New Sales Opportunities
For Seitz Corp. the goal was to automate the production of nylon parts for a bill validation device that involved the insert molding of manually loaded metal shafts in a 30-ton Newbury shuttle press. Seitz, a custom molder and moldmaker, operates 40 molding machines from 28 to 400 tons at its plant in Torrington, and six presses up to 770 tons at its Rockford, IL facility. Though the company has considerable experience with parts removal robots, it relied on Injectech's expertise to help it automate the insert molding operation.

"The robot itself is not the key thing in this kind of cell," says Sansoucy. "The interfacing-that's the big thing." Injectech and Seitz Corp. worked closely to design the gear shaft production cell. Currently, the insert molded gear shafts are running around the clock, unattended.

Shafts are bowl-fed over the cell guard to a Scara robot. It places a shaft in the mold where its presence is sensed. The table shuttles the mold under the shooter as the Scara rotates on its vertical axis to unload finished gear shafts from the other side of the table.

Injectech Engineering specializes in vertical injection molding and supplies custom-built vertical presses to a select customer base. The company is also an authorized integrator for Intelligent Actuator's Scara robots. Ken Heyse, Injec-tech's president and general manager, sees the auto-mation of insert molding as a niche with great potential. Because of the Scara robot's programmable versatility in a nearly hemispheric, horizontal-axis work envelope, Heyse feels these units are ideal for handling inserts and parts molded on vertical presses that are equipped with rotary or shuttle tables.

Sansoucy, for his part, expects that the higher-quality yields at higher-volume throughputs, which automation provides, will foster new high-volume business opportunities for Seitz. And Seitz is using the building blocks of the cell to benchmark new standards for future automation projects since the Scara can be easily reprogrammed and retooled for other insert molding jobs.

High-speed Automation
Many of the benefits from automation have already been seen by PMT, which has long been a proponent of advanced automation. In fact, PMT was one of the first companies to use digital vision sensing technology from DVT (Norcross, GA) to verify accurately that its extremely small inserts are properly loaded (see January 1998 IMM, pp. 93-94). Digital imaging is designed to help further reduce insert molding costs by automatically verifying the accuracy of insert loading.

PMT, which runs 30 machines up to 110 tons in Connecticut and a full-service molding venture in Slovakia, has now taken the next step by working with DVT and Injectech to automate insert molding. It has completely automated a rotary-table Autojectors press that insert molds Noryl GTX automotive E/E parts for braking systems in four-cavity tooling. Twelve small metal inserts are loaded during each shot-three in each cavity. The cell can run unattended with three or four mold stations, 24/7, and now produces parts in a 21-second cycle, down from 50 seconds.

Inserts from a vibratory bowl are transferred into a mold loading bar. Fixed-axis slide robotics are used. Highly accurate linear servomotors drive the slide robot arms.

Strategically located load sensors and fiber optics support automated insert handling. DVT cameras, one for each cavity, ensure proper insert loading. If inserts are improperly placed the process is not allowed to continue. Plastic would shoot into the mold where the insert should be, causing mold cleaning downtime.

Another linear servo robot removes finished insert molded parts and deposits them by cavity into individual Lexan tubes for traceable packaging. Rejects, based on eight key machine setting parameters, are automatically segregated.

Safety standards and communication protocols
for insert molding machines

Now is a good time to review and comment on the final version of a proposed American National Standard for Vertical Clamp Injection Molding Machines. The Machinery Div. of the SPI has recently completed the document, and wants input from the molding community before the standard is submitted to the American National Standards Institute for approval.

To obtain a copy of the proposed standard, contact SPI's Betty Drake at (202) 974-5340, or e-mail [email protected]. There is no charge for copies. The committee working on the standard is eager for input as soon as possible, before the final draft is sent out for balloting.

On the protocol issue, Ken Heyse of Injectech is working with the SPI to develop a communications protocol between vertical insert molding machines and automation support systems. "You are always making a part in automated insert molding. There is no dwell time, as there is with horizontal machines. There are enough subtle differences in the processes that call for a different communications protocol," Heyse says.