In November 2020, a pivotal discussion on the state of injection molding machines during Plastics Technology's Tech Days webinar highlighted a critical aspect of the industryscrew design and its impact on melt uniformity. Esteemed industry innovator Mike Durina, of MD Plastics, emphasized that despite decades of technological advancements in equipment, the adoption of 'general-purpose' screws persists. These screws, originally dubbed 'no-purpose' by renowned designer Bob Dray, fail to achieve uniform melting of plastics, impeding optimal molding processes.
Melt uniformity is a fundamental requirement in aerospace injection molding, influencing everything from material performance to the aesthetics of the final product. Discrepancies in melt uniformity can lead to numerous issues including weak weld lines, part failures, warping, inconsistent filling, and color marbling. Moreover, non-uniform melting can cause resin degradation and frequent necessity for screw cleaning, which in turn, extends color change times and impacts cycle efficiency.
The traditional solution frequently offered by machine suppliers has been barrier screws, which unfortunately still retain unmelted polymers even after purging, as depicted in anecdotal evidence from purged barrier screws showing residual green polymer. To address these challenges, a novel 'melt uniformity' screw was developed, veering away from barrier designs. This screw was rigorously tested and proven to enhance color distribution and, importantly, melt uniformity across different production settings. This innovation facilitated smoother operations with reduced temperatures and back pressure, halving the cycle times, and ultimately leading to significant cost savings and operational efficiency.
Despite the proven benefits of melt-uniformity screws, they remain underutilized, partly due to production challenges. The difficulty in finding manufacturers capable of producing these designs professionally points to a larger issue within the industryresistance to adopting advanced technologies that fundamentally alter performance outcomes.
It's time for a broader recognition of the need for specialized screw designs that align with the advanced technical demands of aerospace injection molding. The aerospace industry, known for its stringent standards and continuous push for optimal performance, stands to benefit immensely from embracing these engineering advancements in injection molding technology.
For professionals eager to maximize efficiency and performance in their molding operations, investing in next-generation screw designs is not merely an option but a necessity. These advancements not only streamline production but also drastically reduce the 'material and processing problems' that many assume are simply part of the job.
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