Injection Molding
A manufacturing process where molten plastic is injected under high pressure into a steel or aluminum mold cavity, then cooled to form a solid part. It is the most common process for producing plastic components at scale.
Injection molding is the workhorse manufacturing process for plastic products. It works by heating plastic resin pellets until molten, then injecting the liquid plastic under high pressure (typically 10,000-30,000 PSI) into a precision-machined mold cavity. The plastic cools and solidifies in the shape of the cavity, the mold opens, the part ejects, and the cycle repeats -- typically every 15-60 seconds depending on part size.
The economics of injection molding favor high volumes. The upfront tooling cost (the mold) is significant, but once the mold is built, each part costs very little to produce -- often just pennies for small parts. This makes injection molding extremely cost-effective for production runs of 1,000+ units. Common injection-molded products include phone cases, water bottle caps, food containers, toy parts, electronic housings, and automotive interior components.
Key design considerations for injection molding include: uniform wall thickness (to prevent sink marks and warping), draft angles (slight tapers that allow parts to eject from the mold), gate location (where plastic enters the cavity, which can leave a small mark), and undercuts (features that complicate mold design). Working with a designer experienced in DFM (Design for Manufacturability) can save thousands in tooling costs and prevent production headaches.
Why it matters
Request a DFM (Design for Manufacturability) review from your factory before finalizing tooling. They will identify potential issues like sink marks, weld lines, or ejection problems that are cheap to fix in design but expensive to fix in steel.
Practical Tip
Request a DFM (Design for Manufacturability) review from your factory before finalizing tooling. They will identify potential issues like sink marks, weld lines, or ejection problems that are cheap to fix in design but expensive to fix in steel.
You'll hear this when…
When briefing a factory
“"We need the Injection Molding process clearly documented in your quality control plan."”
When reviewing samples
“"Can you confirm which Injection Molding standard was applied during production of these samples?"”
When placing an order
“"The purchase order includes a clause requiring Injection Molding compliance for all production runs."”
Related Terms
Tooling
The molds, dies, jigs, and fixtures required to manufacture a specific product. Tooling is typically a one-time upfront cost that enables mass production of your custom design.
Bill of Materials
BOMA comprehensive list of all raw materials, components, sub-assemblies, and quantities needed to manufacture a finished product. The BOM is the foundation of cost estimation and production planning.
Minimum Order Quantity
MOQThe smallest number of units a manufacturer will produce in a single order. MOQs exist because factories need minimum volumes to justify setup costs, material purchases, and production line time.
Blow Molding
A manufacturing process for creating hollow plastic parts by inflating a heated plastic tube (parison) inside a mold cavity using air pressure. Used for bottles, containers, and hollow shapes.
Thermoforming
A manufacturing process where a plastic sheet is heated until pliable, then formed over a mold using vacuum, pressure, or both. Used for packaging trays, clamshells, and large thin-walled parts.
This term appears in every Bottlecap report.
See it in action — explore a full sample analysis.
Ready to put this knowledge to work?
Get a complete manufacturing feasibility report for your product idea — with cost breakdowns, supplier recommendations, and optimization tips.
Analyze my idea →