All of the examples assume that there are surfaces against which pins can push to eject parts from the mold. There are, however, some designs in which there are no such surfaces. Take, for example, a grate, in which all that faces into the B-side mold half are the tops of ribs.

If the rib edges do not provide enough surface area for the pins to push against, the designer would need to add some bosses to act as ejector pads.

Typically, any large size plastic mold can be classified according to weight — this could range from 50 tons to as much as 2,100 tons, depending on machine availability. With this in mind, you have to make sure that you partner with a leading molding firm like us. Here at Richfields Plastics, our mature supply chain and capacity to provide large size molds to various industries make us the go-to large size mold manufacturer. Our flexibility, price competitiveness, and commitment to industrial plastic molding quality remains unparalleled in the industry.

Protolabs' process, however, usually does not support the production of contoured pins unless a customer requests it. It is done on a case-by-case basis. A customer can have Protolabs look to see if a contoured pin is a viable option.

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

In Protolabs' process, the ends of ejector pins are flat and perpendicular to the direction in which the pin moves. To be effective, the pins need a flat "pad" to push against, and the surface of the pad must be perpendicular to the direction of pin movement. If the part surface at that location is textured, the smooth surface of the pad will be apparent. And if the surface of the part is not parallel to the flat end of the ejector pin, the cosmetic impact will be even more obvious.

However, don’t let these figures discourage you — although they may seem costly initially, you also have to take into account the lifecycle of the product. Some manufacturers may promise cheap molds, but the downside is that they may not necessarily be capable of achieving tight tolerances and high-quality parts.

The default configuration is a center-cut pin, which on an angled or curved face means the pin hits the tangent of the surface. The pin would hit with half indenting the part and half raised pad on the part. See the illustration that shows center cut and shortest and longest pins on the surface. Protolabs does have two other options besides just center cut: shortest, which leaves standing pad under pin; or longest, which fully indents the pin into the part. Keep in mind, with a shortest pin, you will be making a thicker section of plastic, which, if too thick, could potentially lead to a risk of sink on the back side of the part. Additionally, a longest pin, which is fully indenting, makes the plastic area thin, so make sure it is not too thin so that you do not end up with a hole in the part because of a short shot or the pin punching through the surface entirely. You can work with Protolabs' applications engineers to discuss pin locations and pin type on critical areas to ensure molding and part design concerns are solved.

Central to any large size plastic injection mold-making process is the equipment. At Richfields Plastics, our factory houses multiple units of CNC, EDM, wire cut EDM, lathe, gun drilling, and drilling machines to fabricate high-quality molds made out of steel.

The above illustration shows three basic types of pin assignments on a non-flat surface. From top to bottom, these include a center cut pin, which is indented on a curved part surface; shortest cut pin, which adds a pad, shown in blue, above the curved part surface; and longest cut pin, which fully indents the pin into the part.

At Richfields, our time-testing large plastic molding solutions have allowed us to cater to different industries. Aside from specializing in small plastic consumer goods, such as safety products, we also work with clients in the fields of automotive, industrial, petrochemical, food & beverage, and many more.

If a pin needs to act on a part surface that is not parallel to the pin-end, there will have to be a pad provided that is in the same plane as the pin-end rather than that of the part surface. Because it is in a different plane than the part surface, the pad may be raised slightly above the part surface at one edge or recessed slightly below the part surface at one edge. Configuring a pad that is slightly recessed into the part surface is the default configuration for pins on contoured surfaces.

In addition, ejector pins are also sometimes used to help vent deep features in a mold to prevent gas trap at the end of fill.

Designing large size molds is not something that every molding company can achieve. A contributing factor to this is the machinery, expertise, and process requirements. For example, crafting molds for large size plastic products needs to undergo proper mold flow analysis to ensure that the resin will reach the mold cavities. Manufacturers may also conduct various testing methods to ensure quality of the mold.

Aside from the automotive sector, we’ve also been able to produce a number of designs for electronic products, industrial storage systems, tools, and sports equipment. Versatile, dependable, and matured — our large size mold manufacturing operations continue to offer value and reliability to all our customers and professional clients.

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

In most cases, ejector pin placement is a relatively minor concern in the early phases of part design. Protolabs will propose pin placement when an order is placed and present a pin and gate layout for customer approval. At that time, Protolabs will address any questions or concerns and make changes, if necessary, to meet customer requirements.

All of these prerequisites are critical in determining the success of the project and preventing any injection molding issues that will lead to failure. If you already have a prototype for the mold, our experts at Richfields Plastics can help you optimize it better, achieve part success, and come up with a final plastic part that meets your satisfaction. Read on to learn more.

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.

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

As the name suggests, large size plastic injection molds are molds that are capable of creating large plastic parts — whether it be customized, or OEM-grade goods (Original Equipment Manufacturer).

Protolabs uses round ejector pins, and their placement depends on a number of factors. Obviously the shape of the part is one (see example in illustration). Factors like draft and texture of sidewalls and depth of walls and ribs can increase the likelihood that areas of the part will cling to the mold. Resin choice can also affect pin placement or size. Some resins are "stickier," requiring more force for release from the mold. Softer resins may also require the use of more or wider pins to spread force and prevent puncturing or marring of the cooled plastic.

Each mold is cut to size, according to your industrial preferences. Using only the finest and highest grade raw alloy/metal materials out there, our molds are designed to last for several decades, with only minimal maintenance required.

The prices for our large size injection molding services rival that of our competitors. Mold tooling for large plastic parts can be expensive, depending on the size, raw materials, repair costs, and other requirements. In fact, even just a single-cavity mold may cost anywhere between $1,000 and $5,000. Family or multi-cavity molds on the other hand, may fetch for more than 70 times the price — at $80,000.

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A post gate produces an extreme example of a raised ejector pad (see post gate illustration). In cases in which an edge gate cannot be used, resin is injected through an extension of an ejector pin channel. When the part has cooled, the ejector pin pushes against the resulting post and, in the process, clips off the runner. The post is typically removed from the finished part in a secondary operation.

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

Pins are located in the B-side mold half, the side in which the part will stay when the mold opens. Once the mold is opened, the pins extend into the mold cavity, push the part out, and then retract, allowing the mold to close and be refilled.

Ejector pins are the "bouncers" of the injection molding world. They apply a force to eject a part from the mold, and in some cases can leave marks. At Protolabs, our goal is to design and position pins to minimize their effect on your parts, and while Protolabs typically determines pin placement, customers get to sign off on pin locations before an order is finalized.

In any large plastic injection molding project, the customer has to look at the molding firm’s capabilities. Do they have the right machinery to produce the molds? Can they provide insights regarding the success of the mold? Will they be able to achieve tight part tolerances? Asking all of these questions is important because you ultimately want to choose a molding company in China that can offer you the right mold designs at a reasonable value/price range.

Another example would be parts made of liquid silicone rubber (LSR). In those cases, ejector pins are not used. Instead, parts are manually pulled out of the molds.

In most cases, ejector pads (or the vestiges left by their removal) are on the non-cosmetic sides of parts. In some cases, however, this may not be possible. Take for example the case of a clip formed using a pass-through core (see clip hook illustration). In this case, because the clip increases the surface area of that side of the part, the "clip-side" part surface will adhere more strongly to its mold half. This will make that mold half the B-side. The clip would normally be on the cosmetic side of the part, but its presence requires that ejector pads also be on that side of the part.

In a traditional steel production tool it may be possible to machine the end of the pin to match the contour of a part surface that is not perpendicular to the direction in which the pin moves, producing a contoured pin.

Richfields Plastics has been the forefront in the mass-production of large size plastic injection molds. For several decades, our molding company in China has been delivering only the best and most reliable solutions for different finished plastic parts.

Our flexibility means that we can create large size mold prototypes for virtually all kinds of product assembly. We have served a number of car manufacturers, for example, in designing high-quality car bumpers that exceed safety standards and regulations in the industry. Using specialty resins, reinforced plastics, and other types of rubbers, we have been able to mass produce different bumper designs that fit well with the rest of the vehicle.

Looking for a molding company in China that can produce large size plastic injection molds? Here at Richfields Plastics, we have all the capabilities to provide you molding solutions ideal for large designs. Whether it’s for an automotive component, construction part, or any plastic mold that’s bigger than your typical molded product, our well-developed business model and team of resin experts can help you out.

At Richfields Plastics, we not only guarantee high-quality steel or hardened steel molds — we also ensure that you’re getting what you pay for. We will be able to provide you with an estimate based on the kind of features that you need for the final part. Do you need basic, advanced, or intermediate rapid prototyping or insert tooling? Simply tell us what you want your mold to look like and we will undertake the necessary prerequisites and pre-design procedures that can transform your initial mold design into reality.