IMM Magazine Article Archive
E-shots Web Exclusive: Hot runner molding without a hot runner moldBy: Robert Neilley
The incorporated hot runner system allows direct injection into the cavity or cavities without the need for hot runners in the mold. You buy the hot runners once, rather than every time a mold is made, reducing the overall cost of tooling. The rotary table concept is not new, but its use is generally limited to certain applications and industries. Among its other benefits, a rotary table machine becomes more efficient and economical as inmold cooling time increases.
The Indestep machine’s rotary table has eight stations, one or two of which can be fitted with injection units. David Brent, chief executive of Indestep, told IMM that the two-component capability will make the machine competitive in applications such as two-component bottle or package closures. Both two- and single-component closures, which are usually made using multicavity hot runner molds in horizontal machines, are one of the company’s first target markets.
The integrated hot runner systems have been designed and will be built by the Plasthing Group. Plasthing’s injection molding specialists also contributed some of the machine’s design features. The hot runner system can be fitted with any of Plasthing’s range of injection bushings, including valve gate, edge gate, 240V externally heated open flow, and 24V thermocouple cartridge bushings. Also available are IC multitip bushings that can have up to four independently controlled tips/feed gates within a single bushing body and feed centers down to 9 mm. This allows, for example, valve gate bushings to be fitted at the station molding TPE for soft-touch or sealing applications, while conventional thermal break bushings are used at the station molding the base material.
WHERE IT FITS
Indestep’s target applications, according to Brent, are technical parts and/or value-added moldings such as automated insert molding. The first of the eight stations can be easily fitted with insert placement robotics. Likewise, the last station is easily accessible for robotic parts removal, and it is feasible to use one robot for both insert setting and parts removal, given the correct design and end-of-arm tooling. Whether the technical parts have inserts or not, the hot runner system can have standard Plasthing titanium nitride-treated injection bushings to avoid the wear problems associated with reinforced engineering thermoplastics.
The Indestep molding system, says Brent, has been in development for more than five years. An earlier version without integrated hot runners was scrapped in favor of the present, higher-performing configuration. Moreover, the company’s strategy for entering the technical parts market is not based solely on the integrated hot runner system. Though much depends on the application, company sources say a 50-ton Indestep machine with eight tooling sets can yield greater productivity than a 200-ton conventional molding machine with a 32-cavity hot-runner mold. Using standard baseplates on the rotary table allows interchangeable cavities, thus further reducing the tooling cost. Quick mold change is possible where there are numerous short runs. There is a central rotating cooling system in the machine and table indexing is said to be fast. Brent says the machine is built to cycle rapidly enough to compete with the shortest cycle times of high-speed horizontal molding systems.
Indestep’s initial models will be in the range of 50 to 100 tons. System design is modular, allowing both standard and custom machines. In either case, says Brent, the cost should be lower than traditional alternatives. A key to understanding rotary table production economics is that the stations are performing their functions at the same time. Insertion, clamping/injection/holding, cooling, and extraction happen simultaneously in the various stations, and recharging takes place while holding. The stations can also be used for secondary functions such as printing, labeling, or a press-fit outsert. On the front end, inmold decorating can be done, for example using a robotically placed preprinted film or foil. Brent pointed to the decoration currently in vogue on mobile phone housings as an application perfect for Indestep.
Indestep systems are slated for market introduction in Q1 2004. Brent says the company is already developing specific variations for molders who want the system. Indestep plans to manufacture the machines in the U.K. and the U.S., and is finalizing support and technical service. Brent says there are a number of companies interested in being strategic partners, and working with them will provide the resources for a faster startup and subsequent growth.
Indestep International Ltd.
IMM - December 2003