Darter Plastics has served as a leading producer of injection molded plastic products for the United States, China, Mexico, and Singapore since 1985. Our state-of-the-art facility includes 15 presses, and we are capable of molding a wide range of thermoplastic materials in almost any color. We minimize waste and reduce production costs by recycling unused materials.

In addition to our superior plastic molding services, we proudly offer pad printing, hot stamping, and assembly. Our skilled and knowledgeable engineers are available to assist with every step of the design and prototyping process, and our in-house mold production capabilities allow us to complete a wide range of projects from design to finished product.


Injection molding is a plastic shaping process in which melted plastic material, or resin, is injected at high pressures into preshaped metal molds to produce parts or finished products. It is a simpler process than machining or milling and is useful for the production of high quantities of identical parts in a short period of time. Scrap from moldings can easily be reutilized during the process, thus significantly reducing wastage and material costs.


Injection Molding Process

A plastic injection machine is divisible into two units: the injection unit, which consists of the hopper, barrel, screw, and injector; and the clamping unit, which is responsible for opening and closing the mold and ejecting the finished product. A variety of press sizes are available depending on the manufacturing material and product.

Injection molding machines come in a wide range of sizes based on clamping force. To ensure the correct machine is used for the project at hand, engineers and machine operators must consider the mold dimensions and shot size (or volume) of the mold.

Plastic injection molding machines consist of four primary components: a feed hopper, reciprocating screw, heating barrel, and injector nozzle. The injection process is outlined as follows:

A prefabricated hollow metal mold is clamped into the injection molding machine.

Plastic pellets, granules, or powder are fed into the barrel via the hopper.

The plastic material is heated in the barrel via the friction generated by the turning reciprocating screw. Reciprocating screws for injection machines are manufactured with a wider diameter toward the nozzle end to increase heating friction and injection pressure.

The melted material is transported along the barrel from the hopper to the injector nozzle by the threads of the reciprocating screw. In addition to friction from the reciprocating screw, heating bands around the barrel help keep the plastic in a molten state.

The injector nozzle, which is located between the barrel and the mold, is manipulated to adjust the pressure and quantity of plastic injected into the mold cavity. The sprue (or nozzle opening) connects with the mold and fills it with molten plastic at a predetermined pressure and quantity. If there are multiple molds, runners connect the cavities so that the injector will inject only one shot of resin to fill multiple molds.

Once the plastic in the mold has hardened and cooled, the product is removed through the use of ejector pins. Depending on the material, parts created via plastic injection molding often require minimal finishing.

Injection Mold Materials

The injection molding process utilizes metal molds. They are typically composed of aluminum or steel depending on the type of plastic being molded and the intended production method.

Aluminum is widely used for mold production due to its easy formability, lightweight nature and quick cooling capabilities. It allows for faster and more efficient production, and is significantly less expensive to form into molds than steel. Aluminum designs are also easy to adapt, so there is less potential expense in the event that a mold design must be adjusted. However, because aluminum is less durable than steel, it can warp or wear when used for complex or abrasive plastic blends or during extremely high-volume production.

Steel is the better option for molds that will be used during high-volume production, as it excels at retaining its shape with very little accompanying wear. It is less susceptible to scratching from reinforced or rough plastics that would have scored softer aluminum molds. While it is a more expensive material, steel will eventually pay for itself over the course of a large production run

Injectable Plastics

A wide range of plastics are used in the production of injection molded parts and components, including:

  • ABS
  • Acetal
  • Acrylic
  • Copolymer
  • Homopolymer polypropylene
  • Nylon
  • PET
  • Polyetherketone (PEEK)
  • Polycarbonate
  • Polyester
  • Polypropylene
  • Polystyrene
  • Polyurethane
  • Thermoplastic
  • Thermoset

Benefits of Injection Molding

Injection molding is widely used for the production of plastic parts and components, as it offers a wide range of advantages over other plastic fabrication processes. Some of these advantages include:

Detail and Precision

Plastic is injected into molds at high pressures to ensure that all mold cavities are completely filled with material. This ensures highly detailed precision and accuracy. It further allows for the creation of geometrically complex and sophisticated components that would be extremely expensive to create using other manufacturing methods, such as tooling or milling.

Eco-Friendly and Low Waste

Plastic scrap that is generated during the injection process can easily be ground and reprocessed, thereby reducing wastage for a more environmentally friendly and cost-effective process.

Enhanced Efficiency and Automation

Injection molding enables production of large quantities of parts in a short period of time, thereby promoting greater manufacturing efficiency. Automation significantly reduces the cost of labor while increasing the rate of output as well. Through the use of computer-aided design (CAD) and computer-aided manufacturing (CAM) programs, injection molded parts are more consistent and less prone to error than those created via processes which require a more hands-on approach.

Improved Component Strength and Durability

Injection molding is highly versatile and allows for the use of fillers and enhancers that improve the strength and durability of plastics during the molding process. Unlike machining and tooling, plastic injection allows the addition of filler throughout the production process.

Multi-Material Injection

In addition to mixing different materials together, injection molding allows a manufacturer to combine multiple plastic materials into one product simultaneously. For example, they can create the basic form of a plastic toothbrush and add the rubber-like grip material on the same production line.

Production-Ready With Minimal Finishing

Injection molding allows for a smooth and detailed finish that rarely requires post-production finishing.

Cost Benefits

Injection molding provides multiple cost-saving benefits, including:

  • Material costs. Reduced wastage and precise computerized calibration ensure lower overall material costs.
  • Production costs. Automation and large-scale production allow for economies of scale that facilitate lower costs per unit on high-volume runs.
  • Tooling costs. Inexpensive aluminum tooling reduces costs on smaller runs, while higher costs of steel tooling are gradually mitigated by larger runs.

Injection Molding With Darter Plastics

Our plastic injection molding is ISO-compliant and meets high industry standards. We mold any plastic material with the exception of rigid PVC. All waste is recycled and reprocessed.

Our advanced machinery is equipped to handle thermoplastic and thermoset materials and can provide shot sizes ranging from 1.5 to 56 oz depending on client specifications. Constructed with a precision ±0.005 in tolerance and maximum 400-ton clamping force, our premium plastic molding has successfully served the needs of a wide variety of industries.

From single prototype to high-volume OEM production, Darter Plastics can manage all your plastic injection molding requirements. Please contact us today to inquire about our additional services, which include engineering, mold making, product development, rapid prototyping, and tooling.

Plastic Injection Molding Capabilities

General Capabilities
  • Contract Manufacturing
  • Custom
Industry Focus
  • Contract Manufacturing
  • Aerospace
  • Communication
  • Consumer Goods
  • Electrical
  • Electronic
  • Gardening
  • Maritime
  • Medical
  • Military
  • Optical
  • Sporting Goods
Industry Standards
  • ISO – Compliant
  • Mil-Spec – Compliant
  • UL
  • ABS
  • Acetal
  • Acrylic
  • Copolymer and Homopolymer Polypropylene
  • Nylon
  • PEEK
  • PET
  • Polyaryletheretherketone
  • Polycarbonate
  • Polyester
  • Polypropylene
  • Polystyrene
  • Polyurethane
  • Thermoplastic
  • Thermoset
Product Capabilities
  • Large Components
  • Micro Parts
  • Miniature
  • Multi-Component
  • Small Parts
Mold Process Type
  • Insert Molding
  • Overmolding – Allows a metal insert to be embedded in a part in one operation for improved product structure and increased strength
  • Solid – A process to manufacture solids parts that do not have hollow cavities
Lead Time
  • Emergency Services Available
  • Quoted on Job by Job Basis
  • Rush Services Available
Production Volume
  • Min 1 Unit to 1,000,000+ Units
  • Specialty Production Shop
  • Prototype
  • Low Volume
  • Small Run
  • High Volume
  • Large Run
  • Long Run
  • Large-Scale Production Volume Run
  • Lean Manufacturing
File Formats
  • Alphacam (AMD, ATD)
  • AutoCAD (DWG, DWZ)
  • BMP
  • CATIA (CATDrawing, CATPart)
  • Delcam (DGK, DMT)
  • DXF
  • GIF
  • IGES
  • Autodesk Inventor (IDW, IPT)
  • IronCAD (ICD, ICS)
  • JPG or JPEG
  • Mastercam (MDX, MC8, MC9, SET)
  • PDES
  • PDF
  • Pro-E or Pro/Engineer (DRW, PRT, XPR)
  • SAT
  • Solid Edge (DFT)
  • STEP
  • Surfcam (DSN)
  • TIFF
  • TurboCAD (TCW, TCX)
  • NX formerly known as Unigraphics (PRT)
Shot Size

(maximum weight of plastic that can be displaced or injected by a single injection stroke, expressed as ounces of polystyrene)

  • 1.5 oz to 56 oz

Clamping Force
  • 45-390 tons
  • ±0.005 in

Our customers come to us first and often, because we provide complete solutions and stop at nothing to meet their needs.

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