Mold Shrinkage — PET (Preform Grade)
Cavity dimension to cut for a target PET (Preform Grade) part size (nominal shrink 1.2%).
PET drying is the harshest in commodity molding: 160 °C, 4–6 hours, −40 °C dewpoint. IV (intrinsic viscosity) loss from wet drying shows up as weak, hazy bottles two machines downstream. Steel-safe practice: cut the cavity to the LOW end of the shrink range — adding steel later is welding; removing it is machining.
Formula
Note: Starting-point process values — the resin grade's datasheet and an in-mold study govern. Verify with a gate-seal study and a cooling-time ladder on the actual tool.
Cavity dimension to cut for a target PET (Preform Grade) part size (nominal shrink 1.2%). A free injection molding cycle & process tool — no sign-up, no upload, instant results in your browser.
About Mold Shrinkage — PET (Preform Grade)
Mold Shrinkage — PET (Preform Grade) computes the governing relationship L_cavity = L_part / (1 − s) live as you type. PET drying is the harshest in commodity molding: 160 °C, 4–6 hours, −40 °C dewpoint. IV (intrinsic viscosity) loss from wet drying shows up as weak, hazy bottles two machines downstream. Steel-safe practice: cut the cavity to the LOW end of the shrink range — adding steel later is welding; removing it is machining. Defaults are pre-filled with realistic values for this exact scenario, and the worked example substitutes your numbers step by step so the math is never a black box.
How to use Mold Shrinkage — PET (Preform Grade)
- 1Enter your values — Target part dimension, Shrinkage (sensible defaults are pre-filled).
- 2Read the live results: Cavity dimension, Steel oversize.
- 3Check the "with your numbers" line to see L_cavity = L_part / (1 − s) substituted step by step.
- 4Adjust inputs until the scenario matches yours, then copy or share the result.
Why use Mold Shrinkage — PET (Preform Grade)?
- ✓Instant, free and private — every calculation runs client-side in your browser; nothing is uploaded
- ✓Built on the stated formula L_cavity = L_part / (1 − s) with authoritative sources cited on the page (Resin supplier processing data sheets (per-grade values govern); Rosato, Injection Molding Handbook, 3rd ed.)
- ✓PET drying is the harshest in commodity molding: 160 °C, 4–6 hours, −40 °C dewpoint.
- ✓SI ⇄ Imperial toggle converts your inputs in place, so you can work in the units your drawings use
Frequently asked questions
What formula does the mold shrinkage — pet (preform grade) use?+
It evaluates L_cavity = L_part / (1 − s), exactly as published. Sources: Resin supplier processing data sheets (per-grade values govern); Rosato, Injection Molding Handbook, 3rd ed.. The substituted worked example on the page lets you verify every step against the textbook.
How should I read the result — and how far can I trust it?+
PET drying is the harshest in commodity molding: 160 °C, 4–6 hours, −40 °C dewpoint. Starting-point process values — the resin grade's datasheet and an in-mold study govern. Verify with a gate-seal study and a cooling-time ladder on the actual tool.
When is this calculator the right tool for the job?+
Cavity dimension to cut for a target PET (Preform Grade) part size (nominal shrink 1.2%). A free injection molding cycle & process tool. IV (intrinsic viscosity) loss from wet drying shows up as weak, hazy bottles two machines downstream. For neighbouring scenarios, the related tools below cover the same engine with different presets.
Does it support both metric and imperial units?+
Yes — the SI ⇄ Imperial toggle converts the values already in the fields, preserving the physical quantity, so you can flip mid-calculation without re-entering anything.
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