When you're quoting a new project, the first question is rarely about the part—it's about the process. Injection molding remains the go-to for high-volume, tight-tolerance parts. A typical mold runs 304 stainless or P20 steel, handles 200–800 ton clamping forces, and cycles in 20–60 seconds depending on wall thickness. You're looking at $15k–$80k for a simple two-plate mold, but the payoff is millions of cycles with shot-to-shot repeatability under 0.1%. For engineering resins like PC/ABS or glass-filled nylon, injection is often the only viable route because you need consistent melt viscosity and packing pressure.

Blow molding splits into extrusion and injection-stretch variants. Extrusion blow molding uses a parison dropped between two halves of a water-cooled aluminum mold—cycle times run 30–90 seconds for HDPE bottles, and tooling costs sit around $5k–$25k. Injection-stretch blow molding (ISBM) for PET water bottles is a two-stage animal: first you injection mold a preform (16–32 cavities, 15–20 second cycles), then reheat and stretch-blow it. That preform mold alone can cost $30k–$60k, but you get biaxial orientation and barrier properties you can't touch with extrusion. Key detail: blow molds need venting at the pinch-off to avoid trapped gas and weak weld lines.

Vacuum forming is the low-cost cousin—think $1k–$8k for a single-cavity aluminum tool. You clamp a thermoplastic sheet (ABS, PETG, HIPS) over the mold, heat it to 150–200°C, and pull vacuum. Cycle times are 30–120 seconds, but wall thickness varies 20–30% across deep draws, and you can't hold ±0.005" tolerances like injection. It's fine for packaging trays, prototype enclosures, and low-volume runs under 5,000 parts. If you're sourcing any of these tools, visiting MoldWorld (www.moldw.com) gives you direct access to vetted moldmakers and process data before you commit to steel.