Injection molding involves two very different timelines: cycle time (how long one shot takes — typically 10–60 seconds) and mold build lead time (how long to manufacture the mold — typically 4–12 weeks). A single injection molding cycle producing a finished part takes less than a minute; building the mold that makes those parts takes weeks. Understanding both is essential for project planning.
Part 1: Injection Molding Cycle Time (Seconds to Minutes)
The injection molding cycle time is the time from one mold opening to the next — including closing, injection, packing, cooling, opening, and ejection. It determines how many parts the machine produces per hour.
| Part Type | Wall Thickness | Typical Cycle Time | Parts per Hour (1 cavity) |
|---|---|---|---|
| Thin-wall packaging | 0.5–1.0mm | 5–12 seconds | 300–720 |
| Small consumer part | 1.0–2.0mm | 10–20 seconds | 180–360 |
| Standard plastic part | 2.0–3.5mm | 20–45 seconds | 80–180 |
| Thick structural part | 3.5–6.0mm | 45–90 seconds | 40–80 |
| Very thick/large part | 6.0mm+ | 90–300 seconds | 12–40 |
What Controls Cycle Time?
Cooling time accounts for 60–70% of total cycle time and is the primary optimization target:
| Stage | Typical Duration | % of Cycle | Key Variables |
|---|---|---|---|
| Mold close | 0.5–3s | 5% | Clamp speed setting |
| Injection (fill) | 0.5–5s | 5% | Injection speed, gate size |
| Packing | 2–15s | 15% | Pack pressure, gate freeze time |
| Cooling | 5–60s | 65% | Wall thickness, mold temp, coolant |
| Mold open + eject | 1–4s | 10% | Machine speed, robot time |
How to Reduce Injection Molding Cycle Time
- Reduce wall thickness — Cooling time scales with the square of wall thickness. Reducing from 3mm to 2mm cuts cooling time by ~55%
- Lower mold temperature — Colder mold = faster cooling, but too cold causes surface defects and poor crystallinity in semi-crystalline materials
- Improve cooling circuit design — Channels closer to the cavity surface extract heat faster. Conformal cooling (3D-printed channels) reduces cycle time by 20–40% in complex molds
- Minimize pack time — Run a gate freeze study to find the minimum effective pack time. Every unnecessary second adds directly to cycle time
- Use hot runner systems — Eliminates runner cooling time; allows shorter overall cycles
- Automate part removal — Robots remove parts faster and more consistently than manual operators, reducing the mold-open time
Part 2: Mold Manufacturing Lead Time (Weeks)
Before any parts can be injection molded, the steel mold must be designed and built. This is a completely separate timeline:
| Mold Complexity | Description | Lead Time to T1 Sample |
|---|---|---|
| Simple | Single cavity, no sliders, standard steel | 4–6 weeks |
| Medium | 2–4 cavities, 1–2 sliders | 6–9 weeks |
| Complex | Hot runner, multiple sliders, complex geometry | 8–14 weeks |
| High precision | Medical/optical, tight tolerances, special steel | 10–18 weeks |
| Large automotive | Bumpers, large panels, multi-cavity | 14–24 weeks |
The mold build timeline includes: DFM analysis (3–5 days) → mold design (5–10 days) → steel procurement (5–14 days) → CNC machining and EDM (14–30 days) → fitting, polishing, assembly (5–10 days) → T1 trial (1–3 days).
Total Project Timeline: From Drawing to Production Parts
| Phase | Duration | Key Activities |
|---|---|---|
| RFQ and DFM review | 1–5 days | Submit drawing; receive DFM report and quotation |
| Mold design and approval | 5–14 days | 3D mold design; customer approval |
| Mold manufacture | 3–10 weeks | CNC, EDM, fitting, polishing |
| T1–T3 mold trials | 1–4 weeks | First shots, optimization, FAI |
| Production startup | 1–2 weeks | Process documentation, operator training |
| Total: simple mold | 6–10 weeks | Drawing to production parts |
| Total: complex mold | 12–20 weeks | Drawing to production parts |
How long does one injection molding shot take?
A single injection molding cycle (one shot) typically takes 10–60 seconds for standard thermoplastic parts. Thin-wall packaging can cycle in 5–12 seconds. Very thick or large parts may require 2–5 minutes. The cycle time determines parts-per-hour output.
How long does it take to build an injection mold?
A standard single-cavity injection mold takes 4–6 weeks from design approval to first sample (T1). Complex multi-cavity or hot runner molds take 8–14 weeks. High-precision medical or optical molds may require 12–18 weeks.
Can injection molding lead time be shortened?
Yes. Lead time can be reduced by: overlapping DFM and steel procurement (saves 1–2 weeks), choosing simpler gate designs, selecting in-stock steel grades, and working with suppliers who have dedicated capacity. Aluminum soft tooling can reduce lead time to 1–3 weeks but sacrifices tool life.
How many parts can injection molding produce per day?
A single-cavity mold cycling every 30 seconds produces ~2,880 parts per 24-hour day. An 8-cavity mold at the same cycle produces ~23,000 parts per day. High-speed thin-wall molds with 32+ cavities can produce hundreds of thousands of parts per day.
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