Manufacturing process

Injection Molding

Injection molding produces plastic parts in high, repeatable volumes by injecting molten polymer into a precision mold — with the mold itself as the main up-front investment.

Process overview

Injection molding produces repeatable plastic components by injecting molten material into a controlled mold cavity. The process supports complex geometries, integrated features and a wide range of thermoplastic materials for low-to-high production volumes. Manufacturing requirements can include resin and grade, tooling, surface texture, dimensional tolerances, color and inspection criteria.

Plastic granulate is melted in a heated barrel and injected under pressure into a closed steel or aluminium mold; the part cools, the mold opens and ejector pins push it out. Cycle times commonly range from a few seconds to around a minute, so the piece price is low once the mold exists. The mold, however, is an engineering project in its own right: its design, steel, number of cavities and hot- or cold-runner system determine part quality, cycle time and tool life.

Part design needs to suit the process. Uniform wall thickness reduces sink marks and warpage, draft angles allow ejection, and gate position affects weld lines and appearance. Shrinkage differs by resin and by flow direction, so tight tolerances are usually agreed with the moulder after mold-flow analysis or first samples.

Many moulders also offer overmolding, insert molding, in-mold labelling and assembly. Low-volume or bridge production may use aluminium or prototype tools, while long-running programs commonly use hardened steel molds.

Typical capabilities & what manufacturers can produce

What manufacturers can produce

  • Technical housings, covers and enclosures
  • Clips, fasteners, connectors and snap-fit parts
  • Gears, bushings and functional mechanical parts
  • Overmolded parts combining rigid and soft materials
  • Insert-molded parts with metal threads or contacts
  • Mold design and manufacture for customer-owned tools

Capabilities under this process

Suitable materials

Materials commonly used with this process — an editorial reference, not a statement about facilities in the Metraxio network. Suitability always depends on the part and its application.

  • ABS

    Housings and consumer parts with good surface quality.

  • Nylon / PA

    Glass-filled grades for structural and under-hood parts.

  • POM / Acetal

    Gears, clips and low-friction parts.

  • Polycarbonate

    Transparent and impact-resistant parts.

  • Polypropylene (PP)

    Economical parts, living hinges and containers.

  • TPE

    Soft-touch grips and overmolded seals.

  • PPS

    High-temperature, chemically resistant electrical parts.

  • PMMA / Acrylic

    Transparent covers and light guides.

  • PEEK

    Demanding high-temperature applications; needs specialist processing.

Relevant industries

Industries whose Metraxio industry guides list Injection Molding as a common process, with the typical use in each.

What buyers should specify

The details that make Injection Molding quotes comparable and let facilities be assessed on the right criteria.

Resin and grade
Polymer family and specific grade or accepted equivalents (for example PA66 GF30 or PC/ABS), including flame rating or food-contact needs.
Tooling status
Whether a mold exists and where, whether it must be transferred, or whether it must be designed and built — and who will own it.
Annual volume and batch size
Drives the number of cavities, the mold steel and how far cycle time is optimised.
Tolerances
Critical dimensions and fits; a plastics tolerance standard such as ISO 20457 for the rest, where used.
Surface and colour
Texture (for example VDI 3400 or SPI finish), colour (RAL or masterbatch reference) and cosmetic faces.
Compliance
REACH, RoHS, UL 94 flammability, food-contact or medical requirements, as applicable.
Secondary operations
Inserts, ultrasonic welding, pad printing, assembly and packaging.

On Metraxio these details become a structured manufacturing requirement. Processes, capabilities, materials, certifications and part size are checked against facility profiles; tolerances, finishes and inspection details travel with your drawings and are reviewed during quoting rather than used as automatic filters.

Frequently asked questions

How much does an injection mold cost?

It varies widely with part size, complexity, number of cavities, steel and runner system — from a modest prototype tool to a large multi-cavity production mold. Quotes are easiest to compare when tooling is separated from piece price.

Who owns the mold?

Usually the buyer pays for and owns the mold, while the moulder stores and maintains it. Ownership, maintenance and transfer terms are best written into the order.

Can I start with low volumes?

Yes. Aluminium or simplified prototype molds can produce initial quantities at lower tooling cost, although tool life and achievable finishes may be limited.

Can an existing mold be moved to a new moulder?

Often, if the mold fits the new moulder’s machines. Mold drawings, the original machine size and sample parts help the new supplier assess it.

Injection Molding by country

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