What key factors influence the unit cost of injection molding parts production?

Quick Answer

Injection molding costs are driven by seven factors: mold complexity ($5,000-$100,000+), part design (wall thickness, ribs, undercuts), material selection (commodity vs engineering resins), production volume (amortization of tooling cost), cycle time (30-90 seconds typical), surface finish (textured vs polished), and secondary operations (assembly, packaging).

1. Tooling Cost

The mold (tool) is the largest upfront expense. A simple single-cavity mold for a small part costs $5,000-$15,000. Multi-cavity family molds for high volume range from $20,000-$60,000. Complex molds with slides, lifters, and hot runner systems can reach $50,000-$150,000 or more. Tooling cost must be amortized across total production volume to calculate per-unit cost.

2. Part Design

Uniform wall thickness (1.5-3mm recommended), adequate draft angles (1-3 degrees), and generous radii reduce cycle time and defect rates. Sharp corners, non-uniform walls, and deep undercuts increase mold complexity and slow production. A Design for Manufacturability review typically identifies 10-20% cost savings through design optimization.

3. Material Selection

Commodity plastics (PP, PE, PS) cost $1-3/kg. Engineering plastics (ABS, Nylon, PC) cost $3-10/kg. High-performance polymers (PEEK, LCP) cost $30-100/kg. Material typically accounts for 10-30% of total part cost.

4. Production Volume

Volume is the biggest lever for reducing per-unit cost. 1,000 units may cost $5-15 each (including tooling amortization). 10,000 units: $1-4 each. 100,000+ units: $0.20-1.00 each. The price break usually occurs between 5,000-25,000 units as tooling costs become fully amortized.

Why Choose SOMI Custom Parts

At SOMI Custom Parts, we provide transparent cost breakdowns showing tooling, material, molding, finishing, and shipping costs separately. Our engineering team offers free DFM analysis to identify design changes that reduce costs without compromising function. We also offer cost-saving recommendations for material alternatives, cavity optimization, and production scheduling. Request a free quotation and DFM review today.

Case Study

A consumer goods company needed injection-molded ABS housings for a new product. Initial quotes ranged from $3.50-$5.00 per unit. SOMI's DFM review recommended reducing wall thickness from 3mm to 2.2mm, adding ribs for strength instead of solid sections, and changing from a 1-cavity to a 2-cavity mold. The revised cost: $1.80 per unit at 25,000 units -- a 48% savings.

Industry Data

According to the Plastics Industry Association, tooling costs account for 30-60% of total injection molding project costs at low volumes, dropping to 5-15% at high volumes. The average cycle time for injection molded parts has decreased by 18% over the past decade due to advances in mold cooling design and material flow simulation (Plastics Technology, 2025).

Related Questions

• What is the difference between injection molding and 3D printing?
• How can I reduce defects in injection molded parts?
• What is a typical MOQ for injection molding?
• How to design parts for injection molding?