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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.

At NPE, Tap Into the PT Knowledge Network

By: James Callari 16. February 2015

That booth is in a prominent spot in the West Hall of the Orlando Convention Center in Orlando, Fla., which will be hosting NPE2015 from March 23 to 27. Yes, we’ll be giving out T-shirts; we’ll have a number of contests; we’ll be talking about some new things we have going on (such as conferences, databases, and even a new benchmarking study); and we’ll even be serving a beverage or two.

 

In addition, like in 2012, our booth will have a theme. We’re calling it the PT Knowledge Network, and that theme is consistent with our mission each time we visit a processing plant, write or edit an article, update our website, send out an e-newsletter, or host a webinar: To provide useful knowledge to our audience of plastics processors by acting as a conduit between them and the experts in the field.

 

So how do we do this at a trade show? By bringing to life the pages of the magazine and exposing show attendees to the depth and breadth of product offerings of Plastics Technology and our related sister publications.

 

The main way we’re doing this by holding a series of short seminars at our booth throughout the show. No charge. Most of our speakers will be the same columnists and insiders who provide the technical tips, insights, and know-how you’ve come to expect from Plastics Technology. Expert minds in materials science, injection molding, extrusion, tooling, additive manufacturing, and more. Right there for you … not only to listen to, but to engage with.

 

My suggestion: Get there early. As in 2012, our booth will fill up with attendees for many of our presentations. Our agenda is just about locked up. Here’s what we have going on: 

 

MONDAY, March 23
3:00-3:45  How to Calculate Shot Size vs Barrel Capacity
John Bozzelli, Injection Molding Solutions (Scientific Molding)

 

TUESDAY March 24
10:30-11:15  The Importance of Gate Geometry
Randy Kerkstra, Nanoplas, Inc.

3:00-3:45  Drying PET for Rigid Container Applications
Pete Stoughton, consultant

 

WEDNESDAY March 25
10:30-11:15  5 Common Extrusion Problems, and How to Solve Them,                       Jim Frankland, Frankland Plastics Consulting LLC

1:00-1:45  The Three Ts of Growing Your Own Talent
Rich Stueber, Mold Design Manager, NyproMold, Inc

3:00-3:45  Trying to Solve Molding Problems? Think in Plastic, Not Steel,                 Rich Oles, Tooling Manager, Stone Plastics

 

THURSDAY March 26
10:30-11:15  Big-Area Additive Manufacturing
Chad E. Duty, Ph.D., Oak Ridge National Laboratory

3:00-3:45  Resin Drying: Separating the Science from the Myth, 
Mike Sepe, Michael Sepe LLC

 

Check out a special page on our website for updates: PTonline.com/network.

 

See you at the show.

 

Engineered PP Compounds, TPO, Key In Grand Award Winner Of SPE Auto Innovation Awards

By: Lilli Manolis Sherman 13. February 2015

With tough competition on its heels, the Grand Award winner and winner of the Safety category of the 2014 SPE Automotive Innovation Awards was the Integrated Glove-Box Door & Airbag---an injection molded “active glove box” and integrated knee airbag system on the 2015 Ford Mustang. In fact, this integrated design is now standard on the mass-produced 2015 LHD Mustang and on 2016 Europe LHD and RHD Mustang.

 

It is produced by Faurecia Interior Systems, Auburn Hills, Mich., using engineered PP compounds from Advanced Composites, Sidney, Ohio: ADX 5028 a 20% talc-filled PP with high rubber content for cold ductility and ADX 5017, a20% talc-filled PP stiffer than 5028 to provide a reaction surface.

 

A third material used is a TPO from Mitsubishi Chemical Performance Polymers, Greer, S.C.  Developed for airbag doors, TT850N TPO performs well at high-strain rates in hot and cold temperatures.

 

Want to find or compare materials data for different resins, grades, or suppliers? Check out Plastic Technology’s Plaspec Global materials database.

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).

 

Big Presses Get Their Mojo Back with Control Retrofits

By: Matthew H. Naitove 11. February 2015

 

One of the largest injection machines in North America gained new life last year from a “brain transplant”—a controls upgrade that converted it from a constant headache to trouble-free operation. The press was a one-of-a-kind machine (photo) built in 1999 with an 8800-ton clamp having eight tiebars, three of which retract for mold changes; a plunger/shot-pot injection unit fed by a reciprocating extruder; and a seven-axis, side-entry robot. The machine had been acquired along with a defunct molding plant in Shelbyville, Ky., by Macro Plastics of Fairfield, Calif., a producer of reusable bulk containers. Unfortunately, the giant machine, originally built for Chrysler, had problems with its control system. “We could never depend on the press to run for more than a few hours without a cycle stoppage,” says plant manager Jonathan Kitchen. “We have another machine capable of handling the largest jobs. Moving the 77,000-lb mold back and forth between machines each time we had a problem was an arduous job, requiring two days of downtime.”

 

Macro called in Cincinnati Process Technologies (CPT), Cincinnati, a provider of injection machinery upgrades and other services. Sales manager Dane Bales says CPT has concentrated lately on upgrading large machines because “it’s easier to see the benefit of preserving that big capital investment with a retrofit.” The Macro case “was the largest and most complex control system replacement we’ve done to date,” says CPT application engineer Jim O’Bryan. CPT installed control hardware from Atlanta-based B&R Industrial Automation (which it uses exclusively), along with CPT’s own software. Says Macro’s Kitchen, “Now we can start it up and it will run continuously without so much as a glitch.”

 

CPT accomplished other big projects in 2014. It also outfitted new controls on one of the largest low-pressure structural-foam machines in the world for Infiltrator Systems to produce large septic ad potable-water tanks in Winchester, Ky. Each PP tank measures up to 15 ft long and weighs 245 lb. They are molded on a mammoth press that Infiltrator constructed by joining together the clamps from two 1990s-era foam presses, for a total of 6000 tons of clamp force. The two injection units, plus a third, were mounted on this custom machine. For the control, CPT used B&R’s Panel PC with 15-in. touchscreen (photo). Due to the machine size, four I/O racks were located closest to their points of use, which drastically reduced the amount of wire and assembly time.

 

Last year, CPT also retrofitted two 750-ton structural-foam presses from the 1990s at Buckhorn Industries in Bluffton, Ind., and will do a third at the firm’s Springfield, Mo., facility. Buckhorn molds large reusable bulk containers weighing up to 150 lb. Buckhorn aimed to install sequential valve gating (SVG) on these machines to cut material loss by reducing overfilling and improve part quality through tighter knit-line control and consistent cavity filling in molds with high length-to-thickness ratios. With SVG and new controls from CPT, Buckhorn saw better fills, shorter cycles, and more than 20% reduction in clamp tonnage. Rex Reynolds, Buckhorn maintenance manager at Bluffton, says the upgrade will extend machine life and provide energy and material savings well beyond the estimated two-year ROI for the project.

 

CPT, which will exhibit at NPE2015 this month in Orlando, Fla., also supplies Asian Plastic Machinery and Borche injection presses, Wetec robots and automation systems, new and remanufactured parts, screws and barrels, variable-speed drives, and energy-efficient lighting.




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