Unscrewing Components: One Good Turn Deserves Another

Although moldmakers are always on the lookout for ways to shorten leadtimes while still maintaining quality, dealing with external components and hydraulics can further complicate the mold design and build process, especially when building high-precision molds with internal or external molded threads. Combine that with the frustration that can occur on the molding end from constantly opening and closing the mold to make adjustments, and it becomes evident that a more simple process is needed.

One way to simplify this process is to use HASCO transmission range unscrewing components, which are manufactured by HASCO America (Arden, NC) - a manufacturer of mold bases and related components. According to Mark Cichy, a HASCO America technical sales representative, these 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 system is designed so that all other component parts are contained inside the mold base.

Operation Know-How

One advantage to using these components is that the unscrewing of a threaded part starts simultaneously with the opening of the mold - resulting in cycle time reductions. And, as Cichy explains, the system can be used to unscrew molded threads in both the core or cavity side of the injection mold. The molded thread can be right- or left-handed.

"During the mold opening cycle, the thread on the helical spindle drives a gear train, which in turn rotates the threaded steel core insert," Cichy continues. "This also can be achieved in the 'A' half or stationary side of the mold by simply splitting a separate parting line prior to opening the main parting line of the mold. The system also can be incorporated in the ejector plates of a mold and actuated by press knockout. The stationary side and ejector plate applications do limit the number of revolutions you can achieve."

When considered for mold applications with one to 16 cavities, Cichy notes that the system is "very economical," and adds that the company also stocks various standard sizes of core blanks and the rack material to accommodate 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," he notes. "Intermediate gears are available to change rotation or help in design of cavity spacing."

The system can accommodate molded thread sizes up to 70 mm. Family molds also can be produced to unscrew molded threads of different sizes or different thread pitches. This reduces the need and cost for separate molds, Cichy states.

Real-World Applications

For Accumold Corp. (Ankeny, IA) - a producer of very precise, small plastic injection molds for the electronics industry - the unscrewing components allowed the company to expand its customer base. "Basically, we 'no quoted' a lot of unscrewing applications in the past because we just didn't have anything we thought would work that well," recalls Greg Peterson, engineering and design manager for Accumold. "Then we ran across HASCO's components and I noticed the system is completely mechanical and driven by the mold opening. It is, without a doubt, the most reliable and the easiest to install."

Peterson adds that the mechanism starts to unscrew as soon as the mold starts to open and, depending on what components are used, a lot of turns can be achieved quickly. "It is great not to have to use any hydraulics, air cylinders, or rack and pinions externally on the mold," he notes. In addition, Peterson has found that the components are so sturdy they will not break, and there is no wear and tear.

For Erich Fiedler, president of Wheeling, IL-based Fiedler Tool & Mold, Inc. - a producer of high-precision hot runner, unscrewing and gear molds for the automotive, consumer products and medical industries - it was a matter of finding new ways to cut cycle times for his customers. "Where the application suits it, the unscrewing components are a perfect fit," Fiedler notes. "It is really a positive system because it cuts the cycle time for the molders since they don't need to open up the mold."

Thus Fiedler Tool was able to reap more benefits. "The system cut the cost of having to build more components for the mold, which in turn shortened the leadtime," he states. "We've built a lot of molds over the years with all types of hydraulic action and racks and pinion and different components for unscrewing - even side ones. If somebody has a part for a straight open and shut mold, this is really the perfect action, because it saves time and money with the component costs."

Jon Granger, design manager of Hugo, MN-based Imperial Tool, Inc. - another plastic injection moldmaker for the automotive, consumer products and medical industries - feels the timesavings are the best aspect to using the unscrewing components. "With the old rack and gear systems, you have to somehow get your unscrewing core to be timed with the rack and pinion, and it takes a lot of time to set up a mold and get everything ground in to size," he explains. "With the unscrewing components, there is probably 25 percent less time spent fitting."

Granger adds that since rack and pinion systems are external, the mold is more awkward to handle. "With the unscrewing system, there's no components that can get banged up during shipping," he explains. "This is a huge benefit on both ends - we know that nothing will happen during shipping; and it is very easy for our customers to set up since it is internally mounted. Plus, with the rack and pinion, close to 75 percent of the molds come back for tweaks with the rack because of binding problems or the gears didn't mesh right. We don't have these problems with the unscrewing components - we haven't received one complaint from customers who have received molds with unscrewing components. We bank on the saying, 'No news is good news.'"