E-shots Web Exclusive: Mold, press, and automation coming together

CBW Automation is building four customized automation systems for a four-level stack mold, used by a major housewares molder to make shallow lids. It’s the only automation that the moldmaker, Tradesco/StackTeck, knows of that can accommodate such a large-cavitation mold, according to Jim Swim, executive account manager at CBW Automation. A Husky Hylectric 1000, a 1000-ton hydraulic press, completes the automation/mold/press team.

The robot is called a Retrieval Transfer Stacking System (RTS). The first system was shipped in December of 2002, and was up and running in only 72 hours. According to CBW, 22 other customers are interested in this particular robot/automation system.

The robot is side-entry instead of top entry—carbon arms move into the open mold horizontally, take the parts out, then a linear transfer takes the parts over to a stacker, which in turn lays them on a conveyor. The conveyor is also part of the automation. The robot has 14 servos. The retrieval and transfer functions run on the x-axis, and the stacking function runs on the y-axis with a rotating motion from vertical to horizontal. The stacker is a two axis, cam robot.

The carbon arms that form the Retrieval part of the RTS system include receivers for a particular part (made on a thermoformer in the CBW plant). The receiver is made of HPDE or teflon-coated, depending on the part. The arms can also change with different molds or receptacles. The carbon arms shoot out into the mold at 18G, but can do 28G. The receivers use vacuum suction to grab the part and hold it.

The second part of the system, Transfer, uses an array compressor. The EOAT consists of suction cups on a transfer plate, which accordions down to size to fit the conveyor. The linear transfer does a double pick—it waits for two cycles of the carbon arms, then moves to the stacker. The tooling is programmed to automatically adjust to different molds.

The third part of the system, Stacking, includes the conveyor. Stacking height is predetermined—on this system the parts are stacked 10 high, then the conveyer moves down to allow for a new stack to start.

The automation was designed to remove multiple kinds of parts if the mold is changed. Vacuum Teach, a feature included in the debugging and installation process, tells how much vacuum is needed to retrieve a part. A vacuum transducer senses if a receptor is missing a part (the part didn’t come out of the mold), and the carbon arm won’t leave the mold until an operator checks the problem. This protects the mold.

Once shipped, there is an installation phase during which the system is retrained to remove hot parts and reset to the actual mold, so, the 72-hour installation time for the first system was very fast.

Polypropelene is being molded on this particular mold, but most any material would work, according to CBW.

The automation and press runs a 7.5-second cycle time, though the automation is capable of a six-second cycle. The mold is only open 900 milliseconds.

The TCP (Total Control Products) control lets the operator enter a code and get measurements for the mold setup. The TCP won’t let the robot run until the setup is correct. The robot’s 14 servos are programmed through the TCP. The HMI (Human-Machine Interface) can view the different robot functions and also communicates between the machine and the robot. CBW can send replacement programs out to the customer if one corrupts at the site.

The carbon arms run on UHMW (ultra-high molecular weight) tape. The tape acts as bearings for the arms to slide on. The tape needs no maintenance or lubrication, and doesn’t wear out. CBW has had many automation systems running for five or more years without replacing the tape.

The guarding around the automation is independent of the automation frame, and can be adjusted per plant specifications.

CBW’s plant is lean. The production area is set up in stations, and all the parts needed for each stage are waiting at the station.

Stackteck's Four-Level Mold
A four-level stack mold yields increased capacity with less machine—allowing a 1000-ton press to produce as much as two machines would—saving overhead costs and floor space.

"StackTeck is the only company that supplies a complete four-level mold. We built the first in 1991, and throughout the 90s built five per year," said Jordan Robertson, general sales manager at StackTeck Systems Limited. The company built 10 molds in 2002. The growth in the industry is partly because of the new availability of a four-level robotic solution—prior to 2002, the molds were limited to a free-drop part release solution. Among the systems sold last year, 60 percent were configured to run with a robotic system.

The partnership between StackTeck, CBW Automation, and Husky has been beneficial to the companies and their customers. The companies team up for big applications, and offer a system integration of the machine, mold, and robot. The team does the installation, there are service technicians who carry pagers and are on call, and customer phone support is available 24 hours a day.

One related trend that has emerged recently is the increased use of Quick Product Change (QPC) module sets that allow a changeover from one plastic part to another in less than an hour, even for these large molds. Faster mold changeovers allow greater flexibility in a molder's manufacturing schedule, as well as a reduction of inventory held.

The highest cavitation four-level mold is a 4- by 24-lid mold that produces 75,000 parts per hour. StackTeck's four-level mold is said to be proven, reliable, and fully balanced, with an equal length of flow to all cavities in the mold. The mold design also includes a Valveless Melt Transfer System (VMTS), a patented technology that allows decompression of the resin in the hot runner during mold opening.

A few recent developments in three- and four-level stack molds include container applications. For 500-ton machines, StackTeck has recently supplied three-level molds for containers that are over 6 inches in height. For 1000-ton machines, four-level molds are now available for container heights up to 4 inches. As mold and machine designs change to suit a broader range of plastic parts, it is anticipated that the rate of growth in the population of large stack molds will increase further.

The four-face stack mold is essentially two stack molds placed back to back. Due to increased mold shut height and plasticizing requirements, it is suited for the high volume production of shallow parts such as thin wall lids for the packaging industry.

Jim Swim, Executive Account Manager
Sales and Engineering Group, CBW Automation
Fort Collins, CO
(970) 229-9500; [email protected]

Darrell Johnson, Engineering ManagerCBW Automation, Fort Collins, CO (970) 229-9500; [email protected]

Jordan Robertson, General Sales ManagerStackTeck Systems Ltd., Brampton, ON (416) 749-1698 ext. 334; [email protected]