Canadian Plastics

Turn, turn, turn: The long and short of unscrewing components

Like everyone else in today's plastics industry, moldmakers are looking for ways to shorten leadtimes while still maintaining quality. Although not exactly new, one timesaver continues to win over new converts: unscrewing components, which can...

April 30, 2011   Canadian Plastics

Like everyone else in today’s plastics industry, moldmakers are looking for ways to shorten leadtimes while still maintaining quality. Although not exactly new, one timesaver continues to win over new converts: unscrewing components, which can not only cut leadtimes but also reduce component costs and decrease cycles times – in other words, win-win-win.

The aim is simple: get rid of the need to constantly open and close a mold to adjust internal or external molded threads. According to Mike Hicks, North American sales manager with DMS (Canada) Ltd., unscrewing components were developed to rotate mechanically and unscrew internal or external molded threads by simply opening and closing the injection mold. “Nothing else is needed, including hydraulic or pneumatic drives, and the components are designed so that all other component parts are contained inside the mold base,” he said. DMS sells ExaFlow unscrewing components, and, according to Hicks, the system offers cost savings through ready-made CAD data, short procurement times, and an accurate and space-saving telescopic design. “In its standard version, ExaFlow’s innovative telescope-type thread unscrewing unit supports unscrewing lengths of up to 70 mm despite the unit’s low height of only about 180 mm,” he said. “Also, they need only minimum maintenance and are easily retrofittable on existing molds.”

A big plus to unscrewing components is that the unscrewing of a threaded part starts simultaneously with the opening of a mold, resulting in cycle time reductions. “Hasco’s components can be used to unscrew molded threads in both the core or cavity side of the injection mold, regardless of whether the thread is right- or left-handed,” said Louis Hebert, president of Hasco Canada Inc. 

And for mold applications with one to 16 cavities, Hebert continued, Hasco’s unscrewing components are very economical. “The system can accommodate molded thread sizes up to 70 mm,” he said. “Family molds also can be produced to unscrew molded threads of different sizes or different thread pitches, reducing the need and cost for separate molds.”

The company also stocks various standard sizes of core blanks and the rack material to handle larger cavitation molds. “The core blanks are supplied with the spur gear teeth already cut on the shaft and require heat-treating prior to finish thread grinding,” Hebert said. “Intermediate gears are available to change rotation or help in design of cavity spacing.”

MAKING A DIFFERENCE

For P.H. Mold Ltd., a Pitt Meadows, B.C.-based custom molder and PET bottle maker, Hasco’s unscrewing components came through with three big benefits. “The system gives us reduced cycle time, a smaller clamp machine, and it’s very simple to use,” said Gordon Menzies, a toolmaker and CNC programmer with the company. “There’s no hydraulic cylinders, no wear pads, and no stripper plate – in short, very little to go wrong. As the mold opens, a latch system grabs the stripper plate and pulls the part off.”

Installed in a mold last year, the unscrewing components have already made a big difference for the shop. “Before, we had to do a semi-automatic operation, with the operator physically unscrewing the nut from the core,” Menzies said. “We’ve now gone from a two-cavity semi-automatic operation to a four-cavity fully automatic operation on the application for which we use the system.” 

Are unscrewing components really a better mousetrap? Menzies seems thinks so. “We’ve built a lot of rack and pinion systems over the years, and they’re slow, complicated, and require a lot of maintenance,” he said. “The unscrewing style is fast and very simple – it’s an open-and-close process, and our operators definitely appreciate it.”


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