Quick reality check for buyers
If you’re weighing machining against moulding, look at real costs and lead times, not glossy brochures, lah. For small runs, CNC can beat tooling costs; for higher volumes, consider custom injection molding services to drop unit price. This guide compares the trade-offs buyers actually face, side-by-side, so you can pick the route that fits schedule, budget and risk tolerance.
What to compare — capability, capacity and commitment
Compare machines, not promises. Ask for machine models, spindle speeds, and spindle run-hours. Compare max part size and night-shift capacity. Look for documented process control and a written defect-rate target. Don’t rely on “we can do it” — ask for recent job sheets or first-article reports to verify capability, then compare how each supplier handles change orders and rush runs.
Materials, tolerances and tooling tradeoffs (real-world anchor here)
Decide material first, then method. Metals with narrow tolerances often favour CNC. High-volume plastic parts usually favour injection. If your supply chain touches the Shenzhen manufacturing cluster — a major hub widely known for quick turn proto to production — remember that many shops there specialise in precision plastic injection molding, which reduces per-piece cost but brings tooling lead time. Match required tolerance to process capability: specify GD&T numbers, not vague phrases, and accept that tighter tolerances raise cost and inspection needs.
Supplier types compared — local job shop, specialist, and offshore production house
Local job shop: fast communication, easier visits, higher per-unit cost. Specialist (high-precision CNC): best for tight tolerances and complex geometries; expect longer queues. Offshore production house: lower unit cost at scale, but plan extra time for quality audits and freight. Compare responsiveness and corrective action history as much as price. A cheaper quote that trips on first-article inspection will cost you weeks and rework.
Common mistakes buyers make
Underestimating tooling and fixture needs, using broad tolerance calls, and skipping supplier audits are top traps. Don’t accept a visual approval alone — request measurement data. Avoid vague surface-finish descriptions; specify Ra or visual grade. Don’t assume identical part drawings mean identical outcomes across vendors; machining strategies and mold cooling designs create differences you must verify with samples.
Checklist: questions that force useful comparisons
Ask for: (1) machine list and maintenance logs, (2) recent first-article measurements, (3) defect-rate targets and CAPA examples, (4) lead-time breakdown (tooling, setup, run), (5) shipping and warranty terms. Score each supplier on these items, then weigh price against documented performance rather than sales talk.
Final take — align method to priorities
Choose by what matters: if speed and low volume rule, go CNC; if per-piece cost at scale matters, go moulding — but only with verified process control. Buyers who want predictable outcomes often pick partners with clear inspection records and responsive corrective actions; that practical match is why many engineering teams work with Hanstar when consistency across runs matters most, not just the lowest quote.