Injection Molding Calculators & OEM Engineering Tools

Calculators and selectors built on 29 years of OEM injection molding experience. No sign-up and no sales call: these are the same numbers we use when reviewing real RFQs.

3 Cost Tools
3 Material Tools
3 Process Tools
Home›Resources›Tools
9
Free Tools, No Sign-Up
29
Years of OEM Data Behind Them
100%
Built by the Owner, Not an Agency
24h
Human Reply on Real RFQs

Pick the Tool You Need

Every tool here was built to answer a real question we get from procurement and design engineers. Use the one that fits your stage — quoting, materials, or DFM.

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Cost Estimation

3 Tools
🧮

Injection Molding Cost Calculator

Estimate mold cost, per-part cost, and Year 1 totals from your annual volume and part complexity.

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⚖️

Aluminum vs. Steel Break-Even

Find the volume at which steel tooling pays back compared to aluminum — for short-run vs. long-run programs.

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📐

Tolerance Cost Multiplier

See how tightening tolerance from ±0.05mm to ±0.02mm changes mold and inspection cost.

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Material Selection

3 Tools
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Plastic Material Selector

Match application, temperature, strength, and cost requirements to the right resin from PP, PC, ABS, PA66, POM, and more.

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Overmolding Bond Matrix

Check substrate-to-overmold compatibility before you commit. Rated by chemical and mechanical bond strength.

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Clear Resin Selector

Pick between PC, PMMA, COC, SAN, or clear ABS based on optical clarity, temperature, and impact needs.

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Process & Geometry

3 Tools
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Cavity Size & Shrinkage Calc

Get cavity dimensions corrected for material shrinkage. Covers PP, PC, ABS, PA, POM, and engineering blends.

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Vent Depth Calculator

Get the recommended vent depth for your material — a small number that prevents short shots and burn marks.

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Gate Type Selector

Pick the right gate (edge, sub, hot tip, fan, tunnel) based on part shape, material, and surface requirements.

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What These Tools Are and Aren't

We'd rather be useful and honest than impressive and vague.

✓ What They Are
  • Rough estimates: within ±25% of a real Weilin quote on most projects
  • Starting points for RFQ conversations: bring the numbers and we'll refine them
  • Engineering reference: vent depths, shrinkage rates, and bond matrices come from real production data
  • Built by an owner-operator who quotes real projects with the same math
  • Free, with no email gate: use them, share them, bookmark them
✕ What They Aren't
  • Real quotes: actual pricing depends on geometry, finish, packaging, and tooling complexity
  • CAE simulation: we don't run simulation software; these estimates and our DFM feedback come from CAD review and production experience
  • A replacement for human review: every Weilin RFQ gets owner review within 24 hours
  • Valid for Class II/III medical devices: we don't make those, and these tools don't cover them
For a real quote

Ready to send your CAD file?

Frank personally reviews every project within 24 hours. No middlemen, no translation layer — just direct CAD conversations with the owner of a 29-year OEM workshop.

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Need a custom calculation?

Have a calculation we don't cover?

If you're working on something these tools can't answer — multi-shot tooling, gas-assist, complex insert overmolding — message us with the question. We may build a tool for it.

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Explore More

Capabilities

What We Can Mold

5 in-house machines (100T-150T), 15+ engineering resins, partner facility up to 1,000T. Honest scope, no overpromise.
Medical OEM

Medical Plastic Parts

Dental and respiratory consumables since 1996. Class I components only, and we say so up front.
Engineering Guide

Material Selection Guide

Full reference for picking the right resin: thermal, mechanical, chemical, and cost considerations side-by-side.

Contact

FAQ

How much does plastic injection molding cost?
Injection molding cost has three components: tooling (one-time), per-part cost (recurring), and setup. For a typical small to medium part, mold tooling runs $3,000 to $25,000 depending on cavity count and steel grade, and per-part cost runs $0.05 to $5.00 based on material, weight, and volume. The Cost Calculator gives you a project-specific estimate.
How do I estimate the cost of an injection molded part?
You need four inputs: annual volume, part weight in grams, resin choice, and tolerance grade. Multiply material cost by shot weight, add the machine hourly rate divided by parts per hour, then add a margin for finishing and packaging. The Cost Calculator automates this and returns mold cost, per-part cost, and first-year total.
What calculations are these tools based on?
The nine tools cover the calculations that come up most in production: mold cost estimation, material shrinkage (typically 0.4% to 2.5% by resin), gate sizing, vent depth (0.025 to 0.05 mm by material), break-even volume, tolerance cost multipliers, and overmolding bond compatibility. The formulas come from our own production records, not textbooks.
How accurate are these calculators?
On most projects they land within ±25% of a real Weilin quote. Final pricing depends on geometry, surface finish, packaging, and tooling complexity, which no generic calculator can capture. For an accurate number, send us your CAD file and Frank reviews it within 24 hours.
Can these tools estimate low-volume injection molding cost?
Yes. The Break-Even Calculator is built for low-volume scenarios: it shows the volume where steel tooling starts paying back versus aluminum. Under 50,000 pieces a year, aluminum tooling is often the cheaper route. Under 10,000, rapid tooling or 3D-printed inserts are worth a look.
How do I choose between aluminum and steel mold tooling?
It hinges on annual volume and how long the program will run. Aluminum tooling is faster (3 to 4 weeks) and 30 to 50% cheaper, but tops out around 10,000 to 100,000 cycles. Steel lasts a million cycles and more, which makes it the right choice for established programs. The Break-Even Calculator finds the crossover point for your numbers.
What's the difference between a cost estimate and a real quote?
A calculator estimate uses generic material costs and machine rates. It's a budget number, not a commitment. A real quote factors in your specific geometry, surface finish, packaging, secondary operations, and our actual capacity. Frank reviews every Weilin RFQ personally within 24 hours, which is the part no calculator can do.
Why are these tools free? Do I need to sign up?
No sign-up, no email gate, no sales call. Most molding shops won't show you numbers before getting you on a call. We'd rather you know the math first, then decide whether Weilin is the right fit.