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Is It Time to Automate Your Insert Molding Job? Answer these questions first

By: Tony Deligio 25. February 2015

Wayne Gibson of automation system designer and manufacturer Pro Systems LLC, Churubusco, Ind., has consistently seen one problem area arise in automating insert molding operations, and he had some simple advice for his audience.

 

“Let a part be fed they way it wants to be fed,” Gibson said, “I’ve seen cell after cell where there are feeding issues.”

 

Gibson was a presenter at injection molding and automation supplier Engel’s recent symposium held at its Technical Center in Corona, Calif. Pro Systems has worked with the Austrian machine supplier on a number of installations, with more than a few of Engel’s vertical injection molding machines tasked with insert molding jobs domestically.

 

Prior to automating, Gibson offered up a list of project assessment questions molders should answer, including:

 

  • Production volume
  • Molding cycle time and overall cycle time
  • Mold cavity matrix/layout
  • Machine selection
  • Type of runner system

 

In addition, Gibson said molders looking to build a cell around an insert molding job should consider:

 

  • How are inserts presented to the cell (bulk, trays, conveyor, tubes, reel, bandolier)
  • Orientation requirements
  • Handling, feeding
  • Measurement/Inspection/Verification requirements

 

It’s during this process that molders should consider the preferred orientation of the insert and how it needs be positioned within the mold to make sure they’re not, “stepping over dollars to get to pennies.” If tool steel hasn’t been cut, for example, the mold could be designed around the insert’s preferred orientation.

 

Gibson also noted that some jobs are best suited for the original automation solution, human operators, who, in some instances, can save you some dollars vs. pennies. He recounted a recent job where the cell as required would have cost enough to hire on 10 new operators.

 

“I’ve been doing automated cells for a long time,” Gibson said, “but there are still a lot of things that only an operator can do.” 

Quoting a Job: the Good, the Bad, the Nonsensical

By: Tony Deligio 18. February 2015

On the short list of regular tasks that are difficult for processors, I’d guess quoting a job has to be up there pretty high. In a perfect world, the ideal design calls for the ideal material and the ideal process. Trials result in perfect product and the job seamlessly shifts into all-out production with zero scrap.

 

Reality, as I overheard it at last week’s agglomerated trade shows in Anaheim, is something quite different. As I ate lunch, the gentleman next to me tried to walk through a prospective job, repeating the potential client’s requests, which included a series of somewhat puzzling choices.

 

The part in question could be polyethylene or polycarbonate; machined or molded; with a preferred initial run of 100 pieces.

 

Not sure how that’s going to work out for either party. How about at your shop? What are some of the crazier/nonsensical quote requests you’ve gotten? What works in quoting, what doesn’t? I’d love to hear you stories, drop me a line or type them into the comments below. Maybe we can make quoting easier for everyone. 

For Repeatable Molding, Add Some Variability

By: Tony Deligio 18. February 2015

The contrast in the two images couldn’t be more stark. On the left, bars marking screw position run jagged, lengthening and shortening the whole way down. On the right, a perfectly straight line can be drawn down the corresponding short shots molded from those varied screw positions.

 

Joachim Kragl, director of advanced injection molding systems at injection molding and automation supplier Engel, explained the dichotomy between the images at Engel’s recent symposium at its Corona, Calif. technical center, but first he had a question for his audience.

 

“It’s 2015; all-electric injection molding machines offer precision, but we still get short shots, we still get flash—why?” Kragl asked.

 

Why indeed; if servo motors can ensure screws travel the virtually same path on every shot, down to the micron, how are different amounts of material injected into the mold?

 

To answer the question, Engel took an all-electric press and measured the repeatability of its stroke. It found variations of ± 3 µm on stop and ± 10 µm in start positions, which would theoretically result in a variation of .009g in part weight. In reality, however, the shot-to-shot weight variation ranged up to .011g.

 

Potential culprits are numerous—slippage of check ring on the machine side—with variations in material viscosity playing a role. Those viscosity changes could derive from multiple factors, ranging from inadequate material drying to the presence of regrind to lot-to-lot inconsistencies in resin.

 

Accepting some variation as an inevitability, Engel sought the best outcome by treating the symptoms of the malady, namely short shots and flash. The answer has been its iQ weight control software, which tracks the changes as they occur and varies the screw position in real time to get the closest to the desired shot volume. (You can read more about the software here).

 

In practice, the software looks at injection pressure vs. screw stroke, taking a reference pressure curve and splitting it into three areas:

 

  • Volume variation (as the check ring closes)
  • Changes in viscosity
  • Conformance of pressure profile

 

The result: molders have been able to reduce shot weight variation by up to 85%, according to Engel, with the biggest potential improvements coming in thin-wall parts. “We tackle the viscosity as well as the volume variation,” Kragl explained after his presentation, noting that dealing with both variables heightens iQ’s effectiveness and is possible because the machine maker can “grab data directly in the machine.”

 

‘No flipping way!’
Nearly three years since its launch, the technology has seen increasing adoption, according to Kragl, albeit more so in Europe than North America. The fact that it creates a repeatable process by varying that process shot to shot has met some resistance, however.

 

“If you tell someone your cutover point will not be constant and you don’t want it to be constant, they’d just be shocked because that’s what they point the process toward,” Kragl explained. “It’s got to be a repeatable process and position. We say, ‘You know what? Forget that. In order to make your part consistent, this will move,’ and that scares a lot of people.”

 

In particular, it scares quality folks in industries like automotive and medical, where meticulous documentation of set-in-stone processes is mandatory. “In most of these discussions, first with the processing guys, they’re like, ‘That’s pretty cool and then next we talk to the quality manager, and they’re like, ‘Hey, no flipping way!’” Kragl said with a laugh. “Part of it is actually finding means to kind of make them feel comfortable, let them know if [the process] changes you get a higher quality part.”

 

One molder, one shot at a time, it seems Kragl and Engel are winning converts.

Nine “Shots” Plus One Machine Equals a Very Unique LSR Molding Technology

By: Tony Deligio 11. February 2015

How did this part come out of that machine? Visitors to liquid silicone rubber (LSR) molder Silcotech’s MD&M West booth were genuinely perplexed by the nine-shot iPhone cover molded on a by-all-appearances single-shot Arburg Allrounder 370A. Eying the material-feeding system, featuring the standard two barrels of LSR ingredients, a visitor pushed Silcotech President Michael Maloney on the “how” of his novel display, and he coyly replied, “That’s the magic.”

 

The magic result? An LSR iPhone cover composed of nine distinct LSRs, with eight different shades of LSR down the back, and each of those different colors featuring a unique durometer from 20 to 75 Shore A, plus another LSR for the phone case’s housing.

 

Maloney said Silcotech has been developing the technology it’s codenamed “Canvas” for the last 18 months, collaborating closely with LSR supplier Dow Corning. That company’s QP1-2XX series LSR was applied, with it also making its debut at the show, according to Gary Lord, Dow Corning’s global strategic marketing director for healthcare. The high-flow LSR also features a low compression set and good green strength allowing it to demold without damage, as well as having the ability to create intricate parts.

 

In operation, the mold’s “B” side featured a rotary plate, with the eight discrete durometer/color strips molded in the first “shot” on the bottom half of the tool, which then rotates 180 degrees for the housing to be molded in the second shot. An Allrounder 370A molds the 20.5g part in a cycle time of 57 seconds from a 1+8 cavity tool.

 

Maloney said Silcotech designed the specialized material handling, injection systems and cold deck on the cell. Going forward, the company will keep the technology as a closely held trade secret, with the goal being to keep the novel concept under its own roof while using it to make parts for customers.

 

“We’re working on a number of projects right now that use 3, 4, or 5 shots,” Maloney said, adding that the technology creates a “larger canvas” for designers. “It’s demonstrating the possibility of integrating shots, breaking down the perceived barriers. There’s not a single LSR device that couldn’t benefit.”

 

The same cell will be on display at NPE2015 at Silcotech’s booth (W7253; pictured below, Michael Maloney with the 9-shot LSR iPhone case).

 

More Korean Injection Molding Technology Coming Stateside

By: Tony Deligio 11. February 2015

The launch of LS Mtron all-electric injection molding machines in the U.S. is actually a reintroduction of the former LG brand presses. Debuting at Plastec West 2015 in Anaheim, Calif., the LS Mtron machine was running in the booth of Hirate America Inc., Diamond Bar, Calif., a distributor of plastics machinery that brought another Korean press, Hyundai Injection Machinery, stateside at last year’s Plastec.

 

Shingo Hirate told Plastics Technology that the LS Mtron line offers molders an all-electric option, with his company stocking machines from 90 to 500 tons. At the show, Hirate America featured a 240-ton LS Mtron running a 16-cavity mold from Dauntless Industries, Covina, Calif. Ron Wierzbowski, technical sales engineer at Dauntless, noted that the hot runner mold—Gammaflux supplied—was shooting optical parts and featured a stripper eject.

 

Hirate said this was the first U.S. show for the LS Mtron but the machines are already running stateside in Alabama in support of Korean automakers like Kia and Hyundai, as well as in Tijuana molding parts for Samsung. Hirate, who said his company sold more than $10 million in equipment last year, has seen business pick up thanks to molding jobs returning to the U.S.

 

“We have seen a lot of reshoring happening,” Hirate said. “We’ve had a lot of customers that wanted to start doing their own molding out of the blue, and we’ve been able to set up their entire plant.” 




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