You may not realize how many options there are for injecting molten plastic into an injection mold. There are six primary types of injection molding gates, and all have specific benefits that make them the best choice for your new project. If you haven’t heard of the different types, or don’t know which type would be best for your new project, read on to learn which could be your best option.
Type 1: Tunnel Gate
You may have heard of the tunnel gate as it is also referred to as a pin or post gate. It is a common type of injection molding gate used in many products. The Tunnel Gate is usually positioned at an angle to enable efficient filling of an injection mold. The Tunnel Gate is a good option for certain types of plastic resin including ABS (Acrylonitrile Butadiene Styrene), polypropylene (PP), low-density polyethylene (LDPE), and high-density polyethylene (HDPE).
Type 2: Cashew Gate
The gate type used is important in determining the quality of the injection mold, and the Cashew Gate is typically used for products that can be distorted during the gate removal process. The Cashew Gate is shaped similar to the tree nut you may find at the grocery store. The Cashew Gate is capable of reaching difficult areas of the injection mold that cannot be connected by the standard tunnel gate. This type of gate isn’t restricted or best suited for any type of plastic resin, so the options are open if you choose this type of gate based on your product design needs.
Type 3: Edge Gate
Out of the six types of injection molding gates listed, the Edge Gate is the simplest of the designs. The Edge Gate, as the name suggests, is used on the edge of a part that requires complete filling of a thicker wall. They don’t leave a sink mark or a surface defect behind after molding, which makes them a simple option for good quality in your next project. They don’t require a particular type of resin wither, which makes them a good choice if your design can be simplified for injection molding.
Type 4: Sprue Gate
The sprue gate is next on the list for simplicity and common use in injection molding. It has a circular cross section with a conical shape that allows for a reduction in pressure during injection molding. Their simplistic design makes them a good choice for an economic option, but they may leave behind a mark on the finished part. They also need to be manually removed from the injection molded part. That may mean the extra resource of a human technician to remove the gate from the part. They can be used with any resin, so they should be on your list of option for your next project.
Type 5: Diaphragm Gate
The Diaphragm gate is similar in appearance to the Sprue Gate as they both taper at the bottom of the gate. These types of gates are typically used with molded parts that have concentric shapes. One of the best characteristics of the Diaphragm Gates is its ability to minimize weld lines and part warping after molding. They are specifically used for larger parts that require a substantial quantity of resin to finish the molding process and completely fill out the part. The Diaphragm gate design is useful for most resin types, so it can be a good option based on the part design without restrictions.
Type 6: Thermal Gate
The five previous gates mentioned are common with cold-runner or cold injection molding. The molten plastic will pass through runners to fill the injection mold cavities completely. The Thermal Gate is used in hot-runner molds that don’t utilize the runner to assist in filling the injection mold. This design feature eliminates the need to remove the gate from the finished part after molding. It can reduce the cycle time of the injection molding process while also reducing the overall cost of making the part. No human interaction is required. The Thermal Gate can also be used with most resin types, which makes it a good option for most designs.
The Best Gate Option for Your Next Project
With each of the six listed gate types come benefits and disadvantages. The gate type is dependent on the need for a defect free part, the dimensions required, the quality of the gate, the cross section needed, and the position required to ensure complete filling of the final part. It may be hard to determine which type of injection molding gate would be best for your project, and that’s where SEA-LECT Plastics comes in. When you’re ready to work with our elite team that produces world-class products, call (425) 339-0288 or email us at info@sealectplastics.mystagingwebsite.com. We look forward to offering support and advice on your next project.
Matthias Poischbeg was born and raised in Hamburg, Germany. Matt moved to Everett, Wash., after finishing his bachelor’s degree in business in 1995 to work for Sea-Dog Corporation, a manufacturer, and distributor of marine and rigging hardware established in 1923.
In 1999, Matt took over the reins at Sea-Lect Plastics Corporation, a sister company of Sea-Dog and a manufacturer of plastic injection molded products with an in-house tool & die shop. Matthias Poischbeg is also a contributor to Grit Daily.