Injection molding is a manufacturing process used for mass production of plastic parts and components. A press injects molten plastic resins into carefully engineered mold cavities under high pressure to yield large volumes of consistent pieces. The process is highly versatile as molds and materials can be adapted to meet specifications for unique applications across many industries.
D&M Plastics boasts over five decades as an industry leader in injection molding. Our ISO 9001 and ISO 13485 certified facility houses 30 presses, a cleanroom, and a tool room. We perform injection molding using a variety of high-performance plastics to create parts horizontally and vertically with tolerances as close as ±0.001″. In addition to standard injection molding services, we offer overmolding, insert molding, two-shot molding, and mold labeling, which positions us as a single-source injection molding provider for partners across many industries, including aerospace, electronics, and medical.
Best Practices and Considerations
The injection molding process is a cost-effective and highly customizable approach for mass producing plastic components. The design process requires close collaboration between designers, molders, and other stakeholders, each of which should follow best practices and make important considerations to deliver the best value.
Material Options and Consequences
Stakeholders must consider specific tolerance requirements, strength, electrical resistances, flexibility, durability, thermal properties, flammability, and weight when selecting the appropriate plastic for a job. Though they may be easy or inexpensive to source, some plastic varieties may be challenging to mold, so molders and designers must agree on material selection.
Injection molded parts have an average tolerance of ± 0.250 mm (0.010″), and while tighter tolerances are possible, they come at an additional cost. To minimize impacts on finances or production time, designers and molders can add extra clearance to account for tolerance variations and create plans for post-machining, fixturing, adjusting gate locations, and more.
The appearance of sink marks depends on various factors such as gate location, nominal wall thickness, and material. To address the issue of sink marks, it is important to ensure wall thicknesses at the base of a rib or boss do not exceed 60% of the perpendicular or nominal wall, core out solid sections to reduce thickness, or add additional design features like ribbing.
Steel Safe Areas
To address tight tolerance requirements, some designers and molders add steel safe areas to complex sections of a design before mold production to provide clearance for easy machining after initial test shots. These design features can prevent further delays and tooling expenses later in the process.
Proper gate location ensures the flow of molten plastic through the mold. Factors, such as where the heaviest cross-sections of a component exist and the necessary flow path needed to maintain design aesthetic and function, are essential in determining the most suitable gate locations for an application.
A minimum shutoff angle of 3° to 5° and optimally 7° is often required by a molder to leave adequate space between the core and cavity of components that include snap-fits, holes, or handles.
Draft Angle Orientation
Tapering the sides of the vertical walls in a mold allows for quicker, easier ejection of components and reduces the risk of surface blemishes. Feature height, surface finish, parting lines, and part geometry are necessary considerations when determining the correct angle to minimize these effects. Optimal part design would involve allowing 2° minimum draft throughout the part except for areas where draft is detrimental to fit and function.
Texturing and Draft
Texture can play a role in both the aesthetic and function of a part, but larger relief angles are required for these surfaces. Draft angles should be increased by 1° to 3° depending on the extent of the surface texture.
Scheduling of Critical Startup Phases
Close collaboration between designer, molder, and other business stakeholders is necessary to ensure that project timelines are coordinated effectively and that milestones are met. From ordering materials to establishing quality standards, these partnerships help drive product development and manufacturing.
Secondary Operations and Fixtures
Upfront discussions about the possibility for further machining or finishing can align goals and investment expectations ahead of production, while minimizing production problems and delays.
Injection Molding by D&M Plastics
By working closely together from the start, stakeholders involved in the injection molding process can avoid costly production delays associated with materials or component design. D&M Plastics has been an industry leader for decades, and our highly skilled team has extensive injection molding experience and can guide you through the entire injection molding process from design to production. To learn more about our capabilities, contact us or request a quote today.