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Why Five-Axis Cartesian Robots Are a Hit With Molders

By: Matthew H. Naitove 21. January 2015

Why is five better than three—or six? At the recent Fakuma 2014 show in Germany, Sepro Robotique of France (U.S. office in Warrendale, Pa.; seproamerica.com) said it has seen sales of five-axis Cartesian robots take off. Such robots are more capable than standard three-axis linear robots and often are a more cost-effective choice than a six-axis articulated robot (which Sepro also offers).

Based on a standard three-axis Cartesian beam robot, Sepro’s 5X line adds a two-axis servo wrist developed in partnership with Staubli Robotics (U.S. office in Duncan, S.C.; staubli.us). In the two years since the 5X line was introduced at Fakuma 2012, Sepro says sales of these units have grown nine-fold and should double last year’s sales. It is by far the company’s fastest-growing new product line. According to CEO Jean-Michel Renaudeau, “We are seeing molders buying five-axis models even when they don’t have a need for them today, because they expect to in the future.”

 

There are several reasons for this popularity:

 

 •  Molders increasingly require high accuracy and flexibility in gripping and downstream positioning. Loading multiple inserts at high speeds, or multiple motions to demold complex parts in a tight mold space are facilitated by the extra axes. The same goes for secondary operations like passing the edge of a part past a flaming fixture or placing parts in trays in different positions. And unlike a pneumatic wrist, the servo wrist can grip parts at any angle and perform multiple servo motions in synchronization with other robot movements.

 

 •  Another benefit is adaptability to different molds and machines. Ability to reprogram servo motions in software is especially helpful for custom molders dealing with transfer tooling that they did not design, or that must run a given mold in different machines to meet scheduling requirements.

 

 •  The servo wrist boasts clean operation, suitable for medical and other applications that cannot tolerate particulates resulting from drive-belt wear or lubricant contamination.

 

 •  High accuracy and repeatability are afforded by servo wrist operation with a positional encoder that recognizes exactly where the drive shaft is at any moment. And the system control can integrate positional signals from all of the servo motors on all five axes so that it knows exactly where the gripper and part are in space at all times.

 

 •  Many of the complex part manipulation tasks mentioned above have historically been assigned to six-axis articulated-arm robots. But a linear Cartesian robot offers faster access to the mold space and simpler programming.

 

These capabilities were demonstrated at the booth of Billion, the French injection machine builder (billion.fr), where a Sepro 5X robot was mounted on a Billion Select 200 all-electric two-shot press. This demonstration of in-mold assembly involved multi-shot injection (a Billion specialty) encapsulates a liquid (water) inside a closed, cup-like container and with dice floating inside. The mold, built by MIHB in France (mihb.com), uses two rotating plates for a multi-step process (see it on YouTube here at youtube.com/watch?v=iXCqj6-EO9I):

  1. The machine injects the top and bottom of the container on opposite sides of the mold. One of the two rotating plates holds the lid of the cup and a finished part. The other rotating plate holds the body of the cup. One plate nests into the moving half of the mold and the other into the stationary half, but both are connected by a shaft to the moving half of the mold.
  2. The mold opens and the two rotating plates index forward and turn 180° so as to bring the two parts of the cup in line with each other. One plate retracts again into the stationary mold half, and the Sepro robot descends and removes the finished part and turns 180° to insert the dice into the body of the cup.
  3. The plate holding the bottom half of the cup retracts against the other plate, holding the two parts of the cup together with mild pressure. Meanwhile, the robot turns 90° moves laterally to insert the end of a long filling nozzle into a hole in the lid of the cup. Water is dispensed to fill the cup about two-thirds full.
  4. The robot retracts and the mold halves clamp together, and the second Billion injection unit overmolds the seam between the cup halves to create a water-tight seal.
  5. The mold opens so the finished part can be removed and the cycle repeats.

 

In this demo, the robot performs multiple functions: inserting the dice, filling the part with water, and removing the finished part. This involves several lateral motions and two rotations inside the mold area.

 

The material was Eastman’s Tritan clear copolyester for the lid and body and Tritan with color masterbatch for the overmolded seal.

Lower Prices for Recycled Resins: A Mixed Blessing?

By: Matthew H. Naitove 7. January 2015

As reported this month by Contributing Editor Debbie Galante Block, prices for recycled resins are down sharply across the board, as a result of plunging oil prices and the resulting decline in prices of chemical feedstocks and virgin resins. Good news for resin buyers? Yes, in the short term. But, as Debbie’s sources note, a prolonged slump in recycle prices is apt to depress efforts at collecting plastic waste for recycling.  The year 2014 proved to be a “so-so” year for recycled material markets, with maybe a bit of a bright spot in PP. While recycled resin prices were up and down, the oil-price slide at the end of the year almost immediately affected recycled resin pricing as well. While that may be good news for processors, who can now get virgin materials for the same prices as recycled materials, the environmentally conscious resin buyer may suffer in the end, as lower prices affect enthusiasm for collecting materials to be recycled. As one recycler puts it, “Why recycle HDPE if virgin prices are equal?”

 

In the case of recycled PP, the return to earth of formerly stratospheric prices is a source of optimism for at least one recycler. “Natural bales were at 57¢, now they are at 35¢. That’s only in five weeks,” this source commented.”I think it will be a healthier market, once there is a price adjustment. I like it when prices are more realistic.”

 

Much of the growth in recycled PP is coming from Walmart’s call for recycled materials in its products. Much R-PP is generated from yogurt containers, apple-juice bottles, etc. Because of Walmart’s interest, “We are able to spark growth in collection,” says one reprocessor. “That’s how the cap and lid market was developed. It’s exciting to see the whole supply chain working for a common goal and seeing results.”

Something New for PET: Injection-Compression-Stretch-Blow Molding

By: Matthew H. Naitove 17. December 2014

At November’s BrauBeviale show in Nuremberg, Germany, SIPA of Italy (U.S. office in Atlanta) has launched Xtreme Syncro, billed as the world’s first injection-compression-stretch-blow molding (ICSBM) system. It brings together SIPA’s Xtreme preform compression molding system with a high-speed stretch-blow unit.

 

As reported in our K 2013 show wrap-up last February, the Xtreme continuous, rotary injection-compression system reportedly produces preforms up to 10% lighter than any made by conventional injection molding, but without sacrificing key properties. Before now, the maximum length-to-wall-thickness ration (L/t) of a preform was little more than 45; but Xtreme technology is claimed to make an 80 L/t ratio a commercial reality.

 

Injection-compression simplifies thin-wall molding by having the molds slightly open when injection starts, then closing them as dosing finishes. This means lower injection pressure, lower clamp force, and less stress on the melt, which means less acetaldehyde (AA) generation and less reduction in IV.

 

Xtreme’s mechanical layout is similar to rotary stretch-blow machines. It is all-pneumatic, with no hydraulics. Molds are mounted in blocks of three on a high-speed carousel fed by an extruder that runs continuously. It delivers melt to dosing devices directly under the preform molds.

 

In the new system, preform molding is directly coupled to SIPA’s latest SFR EVO3 rotary reheat stretch-blow unit (also discussed last February), which can put out 2250 bottles/hr per cavity. The Xtreme portion alone is said to cut energy use around 10% through lower temperatures and pressures. And integration with the bottle blowing system eliminates most of the need to reheat the preforms. Conventional IR ovens are replaced by small ovens that use highly efficient induction heating directed only at areas of the preforms just below the neck. The system can also be connected directly to SIPA’s bottle filling system.

Additive Manufacturing Is the New ‘Normal’

By: Matthew H. Naitove 4. December 2014

Normal founder Nikki Kaufman, wearing her product.

 

Leaders of large and small businesses are constantly asking the question of how to attract young talent to careers in industry: How do we make manufacturing ‘cool’ again?

 

Nikki Kaufman has found an answer. Her brand-new company, which launched just last July, has a cool, intriguing name, Normal. It’s located in the hip, artsy Chelsea district of Manhattan’s West Side. Her company makes a product desired by almost any user of a smart phone or digital music player. And Normal makes the product better, faster, and cheaper than anyone else in the world by using the newest, “greenest,” and, some might say, coolest industrial technology—3D printing.

 

Kaufman, 29, started her company out of a quest for earphones that aren’t uncomfortable to wear for extended periods. She tried dozens of commercial earbuds without success and considered having a custom pair made. But she learned that would involve a visit to a doctor’s office, would take three to six weeks, and cost up to $2000. She decided she could do better on her own.

 

Last summer, Kaufman launched her brainchild based on the idea of making custom earbuds with a personalized fit in as little as 48 hr and for $199, including shipping and tax. And all you need is a free iTunes or Android app that walks you through steps of photographing your ears, choosing among several color options, and ordering the earphones.

 

And about her company’s name: “What is a normal ear shape? There’s no such thing. Everyone’s is different,” Kaufman explains. “Even your left and right ears can differ by up to 20%.”

 

Kaufman in front of two of her 10 Stratasts 3D printers.

 

Normal has joined the small handful of companies today (apart from service bureaus) whose business model is based on making proprietary products with additive manufacturing, or 3D printing as it’s commonly known. Standing in the store, you probably won’t immediately notice (this reporter didn’t) that you’re also in the factory area. Set flush into the walls are eight Fortus 250mc 3D printers from Stratasys, Ltd., Eden Prairie, Minn. There are two more of these printers on another floor, along with two Stratasys smoothing stations, two paint booths, two cleaning stations, and one laser cutter.

 

The 3D printers use the Fused Deposition Modeling (FDM) technology, which extrudes fine molten strands of thermoplastic—ABS, in this case—in thin layers according to a “sliced” CAD model of the part.

 

FDM is used to produce the earpiece that fits your ear cavity. Seven colors are available. It is soft-touch coated and assembled with a handful of purchased components, including an injection molded and UV-coated ABS/PC “inner cabinet,” the 14-mm audio speaker, CNC anodized aluminum “outer cabinet,” a brass tube, coaxial connector, and 360° rotating CNC anodized aluminum cable housing.

 

Normal has another use for FDM—to make tools like jigs and fixtures for its own internal manufacturing needs. That’s in line with what Stratasys CEO David Reis sees as the main near-term market opportunity for FDM—jigs, fixtures, and molds, also referred to as “augmented manufacturing”—rather than “direct digital manufacturing” (DDM) of end products, as Normal is doing.

 

(More details on Normal’s use of FDM will appear in a special supplement on Additive Manufacturing to accompany the February issues of Plastics Technology, MoldMaking Technology, and Modern Machine Shop magazines.)

Amcor Wins Race for Hot-Fill PET with Metal Lug Closure

By: Matthew H. Naitove 3. December 2014

Amcor Rigid Plastics, Ann Arbor, Mich., claims to be the first to achieve a hotly pursued goal of using metal lug closures on hot-fill PET jars and bottles. The company recently launched a stock 24-oz PET jar with 63-mm neck opening designed for pasta sauces. It’s designed for easy conversion from glass because it uses the same type of capping machinery as hot-fill glass jars with metal lug closures, saving the need for new investment to utilize plastic. According to Bunlim Ly, Amcor senior marketing manager, metal lug closures are also less costly than some alternatives available for capping hot-fill PET containers. For consumers, the benefit of using familiar metal lug closures is the “pop” of the tamper-evident indicator button on the closure when the hermetic seal is broken. Consumers associate that “pop” with freshness and quality, Ly notes. He said Amcor’s next targets for hot-fill PET with metal lug closures will be 82-mm salsa jars and 38-mm bottles for hot-fill juice and tea beverages.

 

The “enabling technology” for this development is a patent-pending system Amcor calls A-PEX. It involves special engineering of the PET container and slight modification of the lug closure. Ly calls it a breakthrough technology because it’s the first to overcome obstacles of deformation of the PET container neck to achieve proper sealing necessary for the “pop” on first opening the container. Ly says the A-PEX63 containers are within the industry average range in weight—neither extra-heavy nor extra-light—and meet the industry average for opening torque. The pasta-sauce jar is made by reheat stretch-blow molding using a blow-trim process whereby a “dome” of extra material is cut off the neck of the container after blowing.




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