Custom Injection Molding Services — From First Sample to Mass Production

Injection molding melts thermoplastic pellets to a controlled melt temperature, then injects the molten material at high pressure (10,000–30,000 PSI) into a precision steel or aluminum mold cavity. The plastic cools in 15–60 seconds, the mold opens, and ejector pins push out the solidified part. The cycle repeats with exceptional repeatability — often holding ±0.1mm dimensional consistency across thousands of shots. Great Light manages the entire workflow: DFM review, mold design, T1 sample validation, and mass production.

Injection molding costs consist of: (1) tooling cost, one-time — aluminum prototype molds $500–$5,000; hardened steel production molds $3,000–$30,000+; (2) per-part cost — drops significantly with volume, typically $0.10–$5.00 for volumes above 1,000 units. Great Light provides fully itemized transparent quotes covering tooling, material, processing, finishing, and logistics — with no hidden fees. The break-even point versus CNC machining typically occurs between 300 and 1,000 parts depending on complexity.

Great Light supports 100+ injection molding materials: rigid thermoplastics (ABS, PP, PC, POM, PA6/PA66, PEEK, PET, HDPE, PS, PMMA), flexible elastomers (TPE, TPU, LDPE, silicone via LSR molding), engineered blends (PC-ABS, PS-PPE), and glass or carbon-filled composites for structural applications. We source specialty compounds and mix custom color masterbatch. Material selection guidance is included in our free DFM review.

DFM (Design for Manufacturability) is an engineering review of your CAD design before any tooling is ordered. Great Light’s injection molding DFM covers: wall thickness uniformity (target 2–4mm; thick-thin transitions cause sink marks), draft angles (min 1–3° on vertical walls for clean ejection), rib design (width ≤60% of adjacent wall to prevent sink), gate placement for balanced fill with minimal weld lines, parting line position, and undercut identification. We provide free DFM feedback with every quote — within 24 hours.

Overmolding is a two-shot injection molding process where a second material — typically TPE or TPU — is molded directly over a rigid plastic substrate, producing mechanically bonded multi-material parts. Use it when you need: soft-touch grips on rigid structural housings, watertight seals integrated into the part body, vibration damping layers, or improved ergonomics without a separate assembly step. Overmolding eliminates adhesive bonding failure risk and reduces labor cost versus assembled multi-material parts. Common applications: medical device handles, power tool grips, consumer electronics housings, wearable device enclosures.

Insert molding encapsulates a non-plastic component — typically a brass threaded insert, a metal blade, or an electrical contact — within the plastic mold shot. The insert is placed in the mold before injection; molten plastic flows around it, creating a mechanically integrated assembly with 3–5× higher pull-out strength versus post-molded press-in inserts. Unlike overmolding (which bonds plastic-to-plastic), insert molding bonds plastic to metal or other rigid substrates. It is the preferred method for threaded features in plastic housings that must withstand repeated assembly cycles.

Standard injection molding follows ISO 2768-m or DIN 16742, achieving ±0.1mm to ±0.3mm for general features. Tight-tolerance precision injection molding can achieve ±0.05mm on critical features with hardened steel tooling and controlled process parameters. The primary variables affecting tolerance are: material shrinkage rate (0.3–2.0% depending on polymer), wall thickness uniformity, gate placement, and cooling channel design. Great Light’s DFM review addresses all of these before mold fabrication begins.

Aluminum prototype tooling + T1 samples: 7–15 business days. Hardened steel production mold fabrication: 15–25 business days. Production batch (post-tooling): 5–10 business days depending on volume and complexity. Express tooling services available for critical timelines — specify your hard deadline at the quote stage. Great Light provides confirmed lead times at quote approval — not estimates that slip during production.

Yes — and this is one of our core structural advantages. We offer a seamless prototype-to-production pathway: aluminum soft tooling for T1 sample validation (7–15 days, 50–10,000 parts), followed by hardened P20 or H13 steel tooling for 100,000–1,000,000+ production cycles. The same engineering team designs and manages both tooling phases — ensuring zero design changes or dimensional drift are introduced at the transition to mass production. CNC machining for secondary operations is also available in-house.