Multishot molding: It's not just about toothbrushes anymore.
At NPE 2003, machinery executives vowed to push the technology beyond specialty molding houses, to a broader custom molding world. Several companies introduced bolt-on injection units to convert a straight injection press to multishot at a fairly low price.
They touted multishot as a way to cut out a post-molding assembly step and - in what seemed to the buzz-phrase of this year's NPE - keep molding work in North America by ``adding value'' to customers through higher technology.
Multishot molding, also called multicomponent or multicolor molding, revolutionized toothbrushes. Those hard-plastic, single-color toothbrushes of a decade ago seem boring by today's standards, when molders turn out soft-grip models in a bewildering array of designs and colors.
Today, multishot products continue to proliferate. Just look around. The handles on your washing machine. Your screwdriver. The lid for your shampoo bottle. Ink pens. Garden tools.
NPE visitors could learn about lots of different systems - spinning molds, rotating platens, machines set up like a double-barrel shotgun with two parallel barrels, or with two injection units facing each other in a straight line. Or L-shaped. Or T-shaped, with the second injection unit coming in from the top. Some systems actually move the part into a second mold before the second shot.
Multicomponent molding is more common in Europe; in the United States it's still relatively rare. Injection press manufacturers want to change that, and at NPE, they played the China card - promoting multi-shot as a way to stem the flight of plastics work overseas.
``If you eliminate the manual operations on something, then yes, you can keep ahead of China,'' said John Hahn, vice president of engineering at MGS Manufacturing Group. MGS of Germantown, Wis., makes rotating platens and molds for multishot molding for sale to molders and machinery makers.
At NPE, held June 23-27 in Chicago, Toshiba Machine Co. America and Krauss-Maffei Corp. displayed MGS-made rotary platens and molds that ran parts.
MGS also builds portable injection units. MGS has sold nearly 100 Universal Multi-Shot bolt-ons worldwide since the company commercialized the portable injection units five years ago, said John Berg, marketing director.
Several machinery companies showed bolt-on injection units at NPE, and the reason is simple: Molders in today's cash-strapped economy can try out multishot with a bolt-on, instead of jumping in right away with a complete molding machine that comes fully equipped with two or more injection units.
Milacron introduced its Baby Plast, a small, self-contained injection unit that goes into the mold from the side. An extruder screw melts the shot, and a plunger injects it.
Like its namesake suggests, the Baby Plast just injects a small amount of plastic.
``I would say 90 percent of the time, the second shot is so small that you don't need a large screw and barrel,'' said Tony Minock, business development manager for Tech Group Inc. The Scottsdale, Ariz.-based custom molder bought one of the Baby Plasts to make a disposable baby bottle.
Minock was stationed at Milacron's NPE booth to explain the concept of a portable injection unit. Multishot molding still needs special tooling. ``But this way, you're not married to a machine,'' he said.
Minock said technologies such as spinning molds have more advantages than simply molding two materials in one part.
``Here in the U.S., people think of multicomponent two-shot as multicolor, or sealing surfaces and gasketing,'' he said. ``But in Europe they're using it a lot more for in-mold assembly, because of the spinning mold technology. Spin it, and you have time to do other things. They're using it not just for the traditional soft-touch, sealing and colors. They're using it for a lot of in-mold assembly, in-mold decorating, painting, UV curing. They're using it for a lot more applications because you have that extra time.''
MSG's Hahn agreed that Europeans look at the technology differently. He said they have a longer-term outlook than Americans. ``The American philosophy is, send it to the cheapest labor source, whether it's in the southern United States or Mexico or Asia,'' he said.
But Hahn said that as the parts become more common, U.S. molders are getting the picture. ``The technology is being so widely embraced that you can't miss it.'' Nearly every potential customer that contacts MSG already knows about multishot. They want to reduce labor costs and boost quality by taking out an assembly step, he said.
At NPE, Toshiba used one of its new ECN all-electric presses to mold a two-shot, blue, polypropylene cap with black thermoplastic elastomers, in a 16-cavity mold with a spinning central stack.
Tim Glassburn, vice president of the company in Elk Grove Village, Ill., said molders are interested in reducing assembly costs and turning out a good-looking product. ``If you spend the money, you can now take labor totally out of the picture,'' he said.
For Krauss-Maffei of Florence, Ky., NPE 2003 was the first showing of the Revolution. The press, available with two or more injection units, uses a rotating mold carrier on models under 800 tons. On bigger Revolution machines, the entire middle platen swivels.
``Instead of a rotary platen actually set in the vertical position on the stationary platen, we are now taking that table and putting it between the two platens. And the second injection unit is coming where you would normally have the ejector box,'' said Paul Caprio, executive vice president. ``The purpose of this is to double the productivity on the same size machine.''
KM also introduced a bolt-on injection unit, which Caprio said helps a company get into multicomponent molding quickly. Molders, he said, face a ``chicken-and-egg'' dilemma: They can't afford to buy two-component machines unless they first have the work, but they can't get the jobs unless they have the equipment.
Van Dorn Demag, part of Demag Plastics Group, introduced its bolt-on injection unit, called Multi-plug, on an 85-ton HT toggle press to make artificial fingernails from two grades of ABS, in a 24-cavity mold. Available in seven sizes, the Multi-plug can be fitted in the hotizontal L position or the vertical V position, according to the firm in Strongsville, Ohio.
Demag Plastics Group also demonstrated an El-Exis Multi press molding bottle caps using two types of polypropylene, with two injection units set up with a mold on a rotary platen.
In other multicomponent news from NPE 2003:
* Mold-maker Foboha GmbH demonstrated turning stack molding at its booth, on a Ferromatik Milacron K-TEC press.
* Arburg Inc. molded small suitcases with two colors on a 440-ton press. A second injection unit molded a white Arburg logo onto both sides. Arburg of Newington, Conn., said NPE marked the first time it demonstrated two-component molding at a trade show on its largest press.
* Engel Machinery Inc. of Guelph, Ontario, molded a reflective disc from polycarbonate and thermoplastic poluyrethane on a 300-ton Combimelt press. The second injection unit rides piggyback, coming in at an angle from the top.
* Norcross, Ga.-based Sumitomo Plastics Machinery of America LLC said it now is building all-electric, multishot machines at its factory in Jefferson, Ga.
* The HPM Division of Taylor's Industrial Services LLC introduced its Freedom Rotator, a two-platen press with a movable platen that swings out 180 degrees. HPM of Mount Gilead, Ohio, said the press can do multicomponent molding and insert molding on large parts for markets such as automotive, appliance, housewares. The moving platen rotates on its center.