Standard Injection Molding

Standard injection molding forms high-volume plastic parts by injecting molten resin into a steel or aluminum mold, delivering repeatable dimensions and fast cycle times.

Overview

Standard injection molding produces thermoplastic parts by injecting molten resin into a closed mold, cooling, and ejecting the part. It excels at consistent, near-net-shape components with molded-in features like ribs, bosses, snaps, and textures. Once the tool is built, piece price is low and repeatability is strong across large production runs.

Choose it for production quantities where tooling cost and lead time are justified, and where part geometry can be designed around draft, uniform walls, and predictable shrink. Typical tradeoffs: higher upfront cost (tooling, DFM, sampling), longer setup time than prototype methods, and constraints on undercuts, wall transitions, and cosmetic requirements without careful gate/vent/ejector planning. Material selection, gate location, and mold temperature control drive warpage, sink, weld lines, and dimensional stability.

Common Materials

  • ABS
  • Polycarbonate (PC)
  • Polypropylene (PP)
  • Nylon 6/6 (PA66)
  • Acetal (POM)
  • HDPE

Tolerances

±0.005" to ±0.010" (tighter on small features with stable materials and controlled tooling)

Applications

  • Electronics enclosures
  • Automotive interior trim clips
  • Appliance knobs and bezels
  • Medical device housings (non-implant)
  • Consumer product covers and handles
  • Cable management clips

When to Choose Standard Injection Molding

Standard injection molding fits parts that can be designed with draft and largely uniform wall thickness, and that need consistent quality over hundreds to millions of cycles. It’s a strong choice when unit cost, repeatability, and molded-in features matter more than avoiding tooling lead time. It works best when material, shrink, and cosmetic requirements are defined early enough to lock gate location and tooling details.

vs Overmolding

Choose standard injection molding when the part can be a single material and you don’t need a soft-touch grip, gasket, or multi-material bond. It keeps tooling simpler, reduces cycle complexity, and avoids adhesion/compatibility risks between resins.

vs Insert Molding

Choose standard injection molding when you don’t need metal bushings, threaded inserts, contacts, or reinforcement molded in during the shot. It avoids insert handling, fixturing, and scrap risk from insert misload or movement.

vs Thin Wall Molding

Choose standard injection molding when walls can be thicker and flow length-to-thickness ratios are moderate. It reduces the need for specialized high-speed tooling, aggressive venting, and tight process windows required to fill very thin sections.

vs Compression Molding

Choose standard injection molding when you want higher feature detail, tighter repeatability on complex geometries, and faster cycles for thermoplastics. It also supports more intricate ribs, bosses, and snaps without post-trim labor.

vs Blow Molding

Choose standard injection molding when the part is not a hollow vessel and needs accurate internal features, threads, bosses, and controlled wall placement. It delivers better definition for structural details and assembly interfaces than hollow-form processes.

Design Considerations

  • Hold nominal wall thickness as uniform as possible and use ribs/gussets instead of thick sections to limit sink and warpage
  • Add draft on all faces that contact the mold, and increase draft for textured surfaces
  • Place gates on non-cosmetic faces when possible and expect knit lines opposite gates or around holes
  • Use generous radii at wall intersections and avoid sharp internal corners to improve flow and reduce stress
  • Avoid unnecessary undercuts; if required, call them out early so slides/lifters can be quoted correctly
  • Specify critical dimensions with realistic tolerances and include resin, color, and finish requirements to prevent tool changes after sampling