Filed Under: Plastic Injection Molding, Injection Molding

Plastic is injected hot and is cooled by cooling channels that allow conduction to cool the part. Working fluid is typically water, although oil can be used in high temp applications.

More than 85,000 commercial options for plastic materials are listed in materials databases, and, within those, 45 polymer families can be broadly classified into two categories: thermosets and thermoplastics. At Protolabs, we primarily focus on the latter category, offering hundreds of stocked engineering-grade thermoplastic resins through our rapid injection molding service. In addition to our stocked supply of resins, we have the capabilities to support many more customer-supplied resins as well.

Benefits: Commonly called acetal, it is characterized by high toughness, stiffness, hardness and strength. Acetal has good lubricity and resistance to hydrocarbons and organic solvents. It also has good elasticity and is slippery, so it works well for bearing surfaces and gears.

An injection mold is a tool comprised of a series of parts that allows molten plastic to be formed and cooled in such a way as to create a discrete part shape.

Considerations: PEEK is a high-performance material, and, as a result, is very expensive. Ultem (outlined below) is a slightly less-costly option, and PPSU is worth considering if price is a concern.

Applications: integral hinges or living hinges, fans, snap-over lids (e.g., shampoo bottle tops), medical pipette tubing.

Liquified plastic is pushed through the nozzle of the barrel of the molding machine. The nozzle seats against a surface on the mold called the sprue bushing and locating ring, which help center the nozzle to the mold.

Applications: thin-walled features, combs, spools, gears and bearings, screws, structural parts (with glass), pump parts, under-hood components, cameras.

Benefits: PMMA, aka acrylic, has good optical properties, high gloss and is scratch resistant. Acrylic also has low shrink and has less sink in geometries with thin and think sections.

Benefits: There are many types of PAs, or nylons (4, 6/6, 6, 6/10, 6/12, 12, etc.), each with its own advantages. Generally, nylon parts provide high strength and high-temperature strength, especially when reinforced, and are chemically resistant, except to strong acids and bases. Some, like nylon 6/6, offer great hardness and stiffness, and are abrasion resistant. Nylon 6 is extremely hard and tough at low temperatures, but nylon 6/12 has the better impact strength.

Benefits: PBT provides good electrical properties for power components and works well for automotive applications. It has moderate to high strength depending on glass fill; unfilled grades are tough and flexible. PBT also has good resistance to fuels, oils, fats and many solvents, and doesn’t absorb flavors.

East West is a global manufacturing services company focused on the realization of products, from design through distribution. As specialists in onshore, nearshore and offshore manufacturing, we offer a seamless path to scale and an exceptional speed-to-market strategy while driving down costs and adhering to the highest quality standards. We are one integrated family, working together to support our customers throughout the entire product lifecycle. Our vision is to make the world a better place – cleaner, safer, healthier and smarter.

Benefits: ABS is a tough, impact-resistant plastic that is widely used across many different industries. It has low shrink and high dimensional stability, and it has good resistance to acids and bases. ABS is a good choice for handheld consumer devices. It’s also relatively inexpensive.

Applications: cosmetic parts, handheld devices, housings, and moldings for electrical tools, remote controls, computers, telephone components.

Cavities are areas of the mold where the part is formed into desired shape. Molds must be balanced, so there are typically only a certain number of cavitations allowed (1,2,4,8, etc...)

To order material samples, contact your sales rep or email us at [email protected]. We also offer a detailed white paper that provides a technical look of the thermoplastic materials selection process. And of course, our material comparison guide is an good resource when narrowing down plastic, metal, and elastomer materials.

Navigating supply chain issues is a constant challenge, especially in times of material shortages. To help, we created a detailed guide to resin substitutes for commonly molded thermoplastics.

Applications: gears, pumps and pump impellers, conveyor links, soap dispensers, fan and blower blades, automotive switches, electrical switch components, buttons and knobs.

If you're up for an even deeper dive in the world of plastic injection molding, check out this video from a previous blog post. In it, one of our capable engineers explains the ins and outs of injection molding. The video is about 12 minutes long, and packed with great information.

Considerations: Acrylic can be brittle and thus more susceptible to stress cracking. PC is a good alternative, if needed. Draft is always required in acrylic parts due to its brittleness, often times twice the draft of other materials. Acrylic also has poor chemical resistance.

Applications: Slide bearings, gears and cams; coffee makers and toasters; hair dryer nozzles; vacuum cleaners; handles and knobs for electrical cookers.

Our helpful design aid demonstrates part features that are too thin or too thick, bad bosses, right and wrong ribs, and other considerations to be mindful of while designing parts for injection molding.

No one would blame you for looking for a glossary of terms right about now. Fear not. Below, we break down the components of an injection mold in simple, easy-to-understand language. It even includes labeled cutaway drawings. I promise, if you didn't understand how an injection mold worked before, you will after reading this.

Benefits: ABS/PC combines the strength and heat resistance of polycarbonate with the flexibility of ABS. ABS/PC also provides improved processing during injection molding, increased toughness and dimensional stability, higher heat resistance than ABS, and improved low temperature impact resistance than PC.

So you've designed a product. You've gone through the RFQ process, sharing your CAD drawings with engineers who probably made even more tweaks. The part is going to be made of plastic using the injection molding process. But you've never made a plastic injected part before. There are a lot of new words and phrases being tossed around and you don't really know what they all mean.

Plastic flows through the sprue bushing in a sprue, then to individual runners which take the material to the gates - the entry point of the material to the individual cavities.

Considerations: There can be sensitivities in thick sections of parts that may cause voids, bubbles and sink, and PC parts possess poor chemical resistance. An ABS/PC blend is a good alternative for opaque parts with these issues, and Acrylic (outlined below) is another option for parts with thick geometries.

Applications: These blends are typically used in the automotive, electronic, and telecommunications industries among others applications.

Narrowing down that extensive list of materials can sometimes seem like a formidable task, so we’ve prepared this list that outlines the benefits and applications of some of our most commonly molded materials. By choosing the right material, you can improve the form, fit, and function of your parts.

Considerations: Due to shrink, customers must specifically design for acetal with uniform wall thickness. Painting and coating acetal parts is difficult because of their lubricity. It’s also difficult to achieve a high-cosmetic finish using acetal. If a limited number of prototype parts are needed, it can easily be machined through Protolabs.

Benefits: PP is an inexpensive resin option with higher impact resistance in some grades; propylene homopolymer can be brittle in cold temperatures, with copolymers more resistant to impact. PP is wear-resistant, flexible and can have very high elongation. It’s also resistant to acids and bases.

Proto Labs, Inc. 5540 Pioneer Creek Dr. Maple Plain, MN 55359 United States P: 877-479-3680 F: 763-479-2679 E: [email protected]

Considerations: PPSU is sensitive to thick sections in part geometries, which could result in voids, bubbles or sink. Organic solvents and hydrocarbons can also attack PPSU material. Colorant cannot be added to Protolabs-supplied PPSU resins.

Benefits: PPSU is a high-temperature, dimensionally stable material with high toughness and heat resistance. It also has resistance to radiation sterilization as well as alkalis and weak acids.

Applications: Medical and chemical instrumentation; tableware and catering; HVAC and fluid handling; electrical and lighting.

Tough Black (Loctite Henkel 3843) and Ceramic-Filled (BASF 3280) are two new advanced photopolymer materials now available for 3D printing.

Considerations: ABS-molded parts will show knit lines and can have sink and voids in thick areas. Reduction of sink can possibly be had by switching to an ABS/PC-blended material. ABS also mates well to PC parts.

Protolabs has many additional stocked resin options including PPS, TPE, TPU, LCP, HDPE, LDPE and PSU, and most resin properties can be improved by additives such as glass and carbon fiber.

The ejector pins are mounted in an ejector plate. The motion of the ejector plate forward allows the pins to move forward, pushing the part off the core. The ejector retaining plate holds the pins into the ejector plate.

Get machined parts anodized and chromate plated with our quick-turn finishing option. Eligible materials include aluminum 6061/6082 and 7075.

Considerations: Glass-filled PBT resins are prone to warp, and have poor resistance to acids, bases and hydrocarbons. Thin parts can also be hard to fill with PBT. Nylons should be considered as alternatives.

Benefits: PC is strong and extremely impact resistant with low shrink and good dimensional stability. It’s a transparent plastic that is available in optically clear grades. PC has good heat resistance and accepts high cosmetic finishes well.

Considerations: Thick sections in part geometry can void and show bubbles. Shrink and warp may also occur in PP parts. If the part has living hinges that require higher stiffness, K-Resin is a good alternative.

Mold halves are attached to the molding platens by the clamp plates. Mold clamps use large bolts to hold them in place; other machines hold the mold onto the platen with magnets.

Benefits: PEEK is one of the most recent materials added to the Protolabs menu. It’s a high-temperature, high-performance resin used in medical, aerospace and automotive industries for a variety of reasons including heat resistance and flame retardancy; excellent strength and dimensional stability; and good chemical resistance.

Benefits: PEI, or Ultem, is the second of two high-temperature, high-performance resins recently added to the growing list of materials available through Protolabs. Like PEEK, it’s used in medical, aerospace and automotive industries for its heat resistance and flame retardancy; excellent strength and dimensional stability; and good chemical resistance.

Applications: Medical instrument components, sterilization trays, automotive fuses, interior aircraft parts, hot water fittings, sockets and connectors.

Applications: Lenses, indoor and outdoor lighting, cell phone housings, electrical components, medical devices, bulletproof glass.

Cavity and core mold halves are insured to be in proper alignment during mold close by the use of guide pins (or pillars) and guide bushings (or sleeves).

Our digital factories create prototypes and low-volume parts fast, while our manufacturing network, offers advanced capabilities and volume pricing.

Considerations: Nylon can be more susceptible to warp due to non-linear shrink, so keep that in mind when choosing a specific type of nylon. If your part will be exposed to moisture, you should consider avoiding nylon as it is a hygroscopic material that will absorb moisture, causing dimensional and potentially structural issues.

Considerations: ABS/PC materials oftentimes can minimize thick molding concerns found in ABS or PC materials when molded alone. It is frequently used when increased mechanical properties are required when using ABS or when a lower cost PC is required.