Preaching what it practices: the benefits of micromolding machines

Formative Tech, the Southeast Asian distributors for the Spanish-built Babyplast double plunger-type micro-injection molding machine is one company that practices what it preaches. Its sister company LNE is a Shanghai, China-based processor that operates nine Babyplast presses plus three "autonomous injection units," or UAIs in Babyplast parlance, that can be clipped onto larger machines to enable multi-shot molding.

These machines operate alongside a stable of 50 Sumitomo and Demag injection molding presses, but LNE often discovers that conventional machines have too large shot weight for the micro-parts it sometimes molds, and consume much more energy than a micromolding machine despite the former sometimes being an all-electric machine.

Relating one such case to PlasticsToday at the recent Interplas show in Bangkok, Thailand, Lily Lee, Business Development Manager at Formative Tech noted that the 6-tonne Babyplast 6/10p micromolding press consumed just one-sixteenth of the energy used by a 50-tonne all-electric press. Further, the 6/10p molded the 0.053-g PBT parts in a 32-cavity tool versus 16-cavity for the 50-tonne all-electric in a cycle time of 12 seconds versus 15 seconds. "While the runner weight is higher for the micro-molder, we were able to save $3,290 on a run of 500,000 parts," notes Lee. "The 500,000 parts were produced in just over 50 hours versus just over 130 hours for the 50-tonne all-electric," she adds. "The reject rate is only around 0.4%, which is much less than you'd expect for a standard machine molding very small parts.

Lee also highlighted a trend among processors in Asia to employ UAIs, which weigh in at 30 kg, on standard size machines for multi-shot molding. "In many instances of 2K molding, the second shot is substantially smaller than the main shot, meaning the resin used for the second shot tends to endure an extended residence time in the injection unit." She adds: "The double plunger unit minimizes residence time and also suppresses reinforcing fiber damage in composites."

One example of such utilization of an UAI on a standard machine is for molding a powertool housing. A standard two-shot machine is employed to mold the larger polyamide and thermoplastic elastomer components, while a Babyplast UAI is used to mold the product logo. "This part is now shifting to a four-shot process," notes Lee.

In fact, some processors are reported to have shut down the main injection unit on their standard horizontal presses completely and opted to use one or more UAIs in conjuction with the larger machine's clamping unit in order to better handle micro-molding jobs without having to invest in a complete micro-molding injection press. "Up to three UAIs can be mounted on the fixed platen/mold side, while additional UAIs can be mounted on the moving side. Formative Tech plans to demonstrate the concept by mounting two UAIs on a large rotary mold clamping unit at the upcoming Indoplas show in Jakarta, Indonesia in September this year.

"UAIs can also be used in conjuction with stack molds," says Lee. "And we've also been working on converting standard-sized molds with cavity-core inserts into 120 x 120-mm molds for use with micro-molding machines." The flexibility of these UAIs is sure to uncover many more applications moving forward.