What Is Contract Plastic Injection Molding?
Managing the series production processes of ready molds and the quality control steps to pay attention to.
Contract plastic injection molding is a model in which a manufacturing company brings its own mold or mold design data to an injection molding facility for parts to be produced. It is a common way to secure serial production for companies that do not have their own production capacity or whose capacity is insufficient.
What Is Contract Manufacturing and When Is It Preferred?
Contract manufacturing is preferred for companies that have completed design and mold processes for a product but do not own their own injection molding equipment. It is also used by companies wishing to meet order demands without exceeding their existing production capacity.
- Transitioning to serial production without investing in injection machinery
- Meeting additional capacity needs during seasonal demand increases
- Producing parts requiring different tonnage machines through outsourcing
- Obtaining serial production data at low cost before a new product launch
Machine Capacities
In the plastic injection process, machine tonnage is determined based on part size, mold area, and injection pressure requirements. Machine tonnages that can be evaluated:
- 160 tons — suitable for small and medium-sized parts
- 200 tons — can be evaluated for medium-scale parts and multi-cavity molds
- 250 tons — preferred for parts with large surface area or requiring high fill pressure
- 400 tons — suitable for large mold area, high-volume parts, or tight-tolerance structural parts
Available Materials
A wide variety of thermoplastic materials suitable for different engineering requirements can be evaluated on a project basis. The injection parameters, shrinkage rate, and mechanical properties of each material affect pressing conditions. Materials that can be evaluated:
- PP (Polypropylene) — lightweight, flexible, chemically resistant; common in packaging and automotive applications
- PE (Polyethylene) — flexible, low cost; containers, tanks, and various industrial parts
- ABS — good mechanical balance, easy processability; preferred in consumer products and electronic housings
- PA6 / PA66 (Nylon) — high mechanical strength, friction resistance; gears and structural parts
- PC (Polycarbonate) — high impact resistance and transparency; optical and safety applications
- POM (Acetal) — hard, low friction, dimensional stability; precision mechanical parts
- TPE / TPU — flexible and soft-touch applications; seals, cases, grip surfaces
- PMMA (Acrylic) — parts requiring transparency and optical clarity
- PBT — electrical/electronic applications, heat resistance
- Glass fiber reinforced materials — for projects requiring structural stiffness and strength
Mold Transfer Process
In contract manufacturing, a standard preparation process is followed from the delivery of the mold to the facility to the start of production. Technical inspection of the mold, machine mounting, first pressing trial (T1 run), and sample evaluation are the main steps of this process. The previous operating conditions, maintenance status, and revision needs of the mold are reviewed at the start of the project.
Quality Control Steps
Quality assurance in contract manufacturing is a continuous process throughout serial production:
- Visual inspection: evaluation of visible defects such as surface quality, flash, short shot, color consistency
- Dimensional control: comparison of critical dimensions against reference values
- Sample evaluation: taking first press outputs through an approval process
- Project-based measurement support: additional verification with 3D scanning or other measurement methods can be provided within project scope
What You Want to Know.
- Can I bring my own mold and have contract production done?
- Yes. This is the fundamental purpose of the contract plastic injection molding service. The technical information, dimensions, and production requirements of your mold are evaluated at the start of the project. Mold condition, revision needs, and machine compatibility are reviewed within the scope of the technical inspection.
- Which materials can contract production be done in?
- PP, PE, ABS, PA6, PA66, PC, POM, TPE, TPU, PMMA, PBT, and glass fiber reinforced materials can be evaluated on a project basis. Material suitability is clarified at the start of the project based on machine capacity, mold design, and technical requirements.
- What is the minimum order quantity for contract production?
- Minimum order quantity is evaluated on a project basis. Factors such as part size, pressing time, number of mold cavities, and material properties affect the economical production quantity. This subject is clarified in the project discussion.
- Is quality control performed on parts after production?
- Yes. Visual inspection, dimensional control, and sample evaluation are standard parts of the process. For projects requiring additional 3D scanning or special measurement support, planning the scope at the start of the project is recommended.
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