Small precision plastic parts weigh less than 5g with dimensional tolerances between 0.01mm and 0.05mm, covering electronic connectors, miniature gears, medical micro fittings and watch internal components. They impose strict demands on dimensional stability, surface finish and low deformation, so ordinary two-plate molds cannot meet production standards. Different mold structures are selected based on product complexity, precision grade and output volume.
Precision Two-Plate Molds: Basic Choice for Simple Small-Batch Precision PartsThis basic mold consists of only moving and fixed plates with standardized precision mold bases and ball bearing guide sets to eliminate mold closing offset. Point gates and mini runners are matched for regular thin-wall parts without undercuts. Its parting surface flatness is controlled within 0.01mm, with repeat positioning error under 0.02mm. With low manufacturing cost and easy debugging, it fits monthly output below 100,000 pieces. The shortcoming is manual gate trimming, making it unsuitable for fully automated lines and products with deep ribs or inner undercuts.
Three-Plate Fine Gate Precision Molds: For High-Appearance Mini ComponentsA runner stripper plate is added to realize automatic gate separation, leaving invisible marks on product surfaces. Tiny pins and micro holes are split into independent inserts for easy polishing and size adjustment, paired with four sets of ball guides and secondary positioning pins. Most adopt 2 to 4 cavity layout to guarantee even melt pressure, suitable for medium batch products with monthly output 100,000 to 500,000 like connector plastic shells and medical sealing gaskets. Its thicker mold body requires dedicated small precision injection machines, and the production cycle is slightly longer than two-plate molds.
Hot Runner Micro Precision Molds: Mass Production High-Precision SolutionHot runner molds cancel cold runners and use micro needle valves as small as 0.3mm to deliver melt directly into cavities, cutting material waste and pressure loss. Spiral cooling channels and baffle inserts balance cooling speed to reduce shrinkage deformation. It controls product weight fluctuation within ±0.002g, ideal for monthly output over 500,000 such as miniature mobile connectors and sensor bases. Despite stable long-term production performance, high hot runner costs limit its use to mature mass production rather than prototype trials.
