New automation helps established molder learn new market opportunities

Custom injection molder and mold builder ABA-PGT (www.abapgt.com; Manchester, CT) has long specialized in molding of plastic gears and precision motion transfer components. For many years ABA-PGT survived molding standard plastic parts and shipping them out bulk packed. But over time, more of the products molded by ABA-PGT required insert molding, tray packaging or both, and these new projects began to raise the firm’s labor costs to an uncomfortable degree.

With each new part comes the decision whether to automate or not to automate. For high volume work where a machine is going to be fully utilized the decision to automate is an easy one. For lower volume work, where the part may run for just 10–20% of the time, the decision becomes more difficult. In the past, for low volume insert molding work, jobs were either “no quoted” or quoted with manual labor. With manual labor, jobs were often not awarded because ABA-PGT was competing against lower labor cost areas of the country or world. When jobs did get awarded, there were often hidden or difficult-to-predict costs associated with manual labor that hurt profitability.

Tim Vale, director of R&D at ABA-PGT, decided that flexible automation cells might be the best chance to successfully compete for this ’value added’ work. He reasoned that the automation cell had to be flexible enough to allow for molding of one product with one type of insert and/or packaging tray and then switch over to a completely different product within a few hours. Additionally, the upfront costs to the customer needed to be low enough to provide them with payback over the span of a few hundred thousand pieces as opposed to a few million pieces.

The ’Flex Cell’ concept, which includes the molding machine, robot, automation system for inserts, and a similar system for handling finished product (tray pack or bulk pack), is owned by ABA-PGT. The only costs to the customer are for the product specific components. This includes the end-of-arm-tooling (EOAT), trays, and insert pallets for presenting inserts to the robot. An operator is still required to place the inserts on the pallets but this requires less than 15-30 minutes every 2 hours. As a result, the labor content can be significantly reduced to only a few times per shift, allowing operators to perform other functions.

The molder decided to work with robot and auxiliary equipment supplier Wittmann www.robot-wittmann.at and www.wittmann-ct.com; Vienna, Austria) as the two had already successfully partnered on other projects. Vale presented his concept for the ’Flex Cell’ to Wittmann along with all of the required design parameters for the various parts. “Coming up with the parameters was a challenge because you were making an educated guess on what type of parts you might see in the future based on what was quoted in the past.” recalls Vale. “Designing an automation cell around a clearly defined product is not always that easy, but it is certainly a degree or two easier than trying to design an automation cell around a bunch of parts that don’t exist yet.” Some of the expected parts might be relatively small while others could be up to four inches (10.16 cm) in diameter. The inserts might be screw machined shafts, stamped metal inserts or some other intricate shape. In most cases they would be within a specified size range but all would have tight tolerances. Product changeovers would typically be required every 2-3 weeks but could be of shorter or longer intervals. And lastly, the automation had to be designed for a 110-ton molding machine and the capital investment kept to a minimum.

Vale requested that Wittmann work with ABA-PGT’s existing conveyor supplier, TEC Engineering, which had worked with the processor on the design of a custom dual conveyor system that could handle both presentation of the inserts and movement of the finished product.

Wittmann’s W631 servo robot, a 3-axis linear robot with a pneumatic wrist flip (c-axis), was chosen as the workhorse for the cell. The robot was supplied with a quick release system for the EOAT to allow for product changeover in less than five minutes. Vale says, “We had to make a lot happen in a very limited amount of space with these EOATs. The constraints were not just between the mold plates but also on the conveyor side of the system, where floor space is at a premium.”

The ’Flex Cell’ was set up and molding parts within two days of arrival at ABA-PGT. It was delivered pre-loaded with the first EOAT for a two-cavity gear mold with a screw machined shaft insert. The ’Flex Cell’ utilized an existing mold that had previously required hand loading of inserts and hand packing of trays. The cost savings are shown below; payback was swift as a typical EOAT for the ’Flex Cell’ costs from $15,000 to $25,000, depending on the complexity and number of cavities in the mold. The total cost of the pallets for the inserts is about $6,000; this includes 8 to 10 pallets.

Capital equipment costs are not the only ones that need to be considered when weighing payback/return on investment of such a cell. While the hourly costs of permanent employees are higher than that for temporary employees, temporary employees can be a risk, for instance when a temp doesn’t show up for a job and a machine sits idle because of the lack of available labor. “Another thing to mention is that on weekends and holidays we would normally shutdown a job as it is difficult to find people willing to work. Now, with the ’Flex Cell’ we can keep molding parts until the inserts run out,” adds Vale.

Another concern is mold damage due to operator error, which in the case of temporary employees can be more frequent because of their limited knowledge and experience of a particular operation. “In some cases, the cost of tooling repairs alone could justify the cost of automation, especially when the tool for example has expensive, hard-to-make inserts, which is usually the case with the type of work we do,” Vale says.

Vale adds, “Outside of these cost savings, there are product quality improvements to consider as well. The more repeatable automated process results in better dimensional and material property consistencies compared to a manual process. Also, the automated process reduces the chance of part damage during handling.”

The success of the first product to run on the ’Flex Cell’ gave ABA-PGT the confidence to quote additional jobs for the automation work cell. “Even the quoting process is easier and less stressful considering you can quote the job much more accurately when you know the exact cost of the process,” Vale says. He adds that both the molder and the customer benefit from the new cell: “All of the savings are passed on to the customer. ABA-PGT simply adds about $2.00 more per hour to the machine rate to cover the added cost of the automation portion owned by ABA-PGT….The design of the flexible automation cell has allowed us to share our total investment over several jobs, making the individual cost to each customer much less than that for a dedicated system for each specific part.”

Currently there are five jobs sharing time on the ’Flex Cell’ line, resulting in about 80% utilization. “There is capacity to probably run one more job on the ’Flex Cell’ and then it’s time for ’Flex Cell #2’,” Vale says.