Various design features and materials are utilized in plastic molding depending on the kind of part that is produced. Most tools or molds are produced out of aluminum or steel. In addition, part design may necessitate side actions to mold the cores that are most of the time, vertical to the mold’s normal draw. These actions may be hydraulically or cam actuated.
Plastic Tooling Material Choices
Aluminum and steel are two of the most popular materials that are utilized in building the tools required for plastic molding. Steels provide greater strength for injection pressure application. Aside from that, this is also the most common material that is chosen by plastic manufacturers. Another great thing about steel is that it offers a trouble-free repair as welding steel is considered a better and easier option than welding aluminum.
Aluminum offers several advantages where just a lower pressure of injection is acceptable. As compared to steel, aluminum offers superior heat transfer characteristics. It can also enhance processing conditions and cycle times. Another plus point of aluminum is its cheaper cost due to its machining ease and light weight. However, this plastic tooling is more vulnerable to damage.
Several designs of plastic parts are more complex than what an open and close mold can produce. There are some cases when a feature should be molded into plastic parts that are vertical to the mold’s line of draw. In order to add this type of feature in the tool, a side action is utilized. It is known to protrude from the different sides of the mold. This action moves away when the certain mold is opened to remove a part. However, it returns when it is already closed to let the desired feature be molded into the specific part.
Side Actions that are Cam Actuated
A cam pin is commonly added to ½ of the mold at a definite angle that comes available with a receiving port in the mold’s other half. What is great with side actions that are actuated is that they are inexpensive process for adding a side action in a certain mold.
Side Actions that are Hydraulically Actuated
There are times when the feature comes with design features that call for more strength in order for the side action to be pulled. Cores with long lengths or small draft angles may not have the capability in pulling out a part with ease as the friction with a shrinking plastic region can be very important. Side actions that are hydraulically actuated add more force and strength to pull the side of action out of the mold. They are costlier than cams, but are required by design. This goes to show that the moving parts increase in a plastic tooling because of side actions necessitate tool care and maintenance.
Now that you already know the material choices and the side actions of plastic tooling, you should also know some of the plastic manufacturing processes. In the succeeding paragraphs, you will be able to discover them.
Injection molding is the process of converting raw materials into functional plastics. These products are utilized to manufacture parts or products from both thermosetting plastic and thermoplastic materials. The materials are liquefied, designed and cooled to be released for usage. One of the industries that benefit a lot from injection molding is car industry.
The molding machines and equipment utilize the pressure technology to provide the required end products. The modern plastic tooling and machines make use of the plunging helical screw’s injection barrel because it is proven to be very quick and efficient.
The process of injection encompasses 4 simple steps such as:
Clamping – in this stage, the mold is securely held by the clamping unit that is hydraulically powered. In turn, it pushes the mold and exerts force in keeping it safely closed while being injected. This process will be more effective if the right plastic tooling is used. This is the reason why plastic part manufacturers are required to use only high quality machines and equipment. This will not just speed up the world but will secure the quality of the manufactured plastics as well.
Injection – the injection unit designed for melting transfers the polymeric material in powdered form into the injection molding machine. Once it is already molten, it is rapidly injected into a pressure pack under the right temperature.
Cooling- after the cooling time, the molten material solidifies right away. As the plastic material cools, it little by little adopts the desired part’s shape. Sometimes, the cooling process is affected by reduction and this is just corrected at the stage of injection where the added material is permitted to flow smoothly into the mold.
Ejection – this stage utilizes a specialized mechanism in pushing the piece out of the mold. A force should be exerted since the piece remains to mold. In order to facilitate a fast and easy ejection, a release agent should be sprayed on the mold’s surface.
The tooling and molding design greatly considers the part design. It includes the following: weld part lines, bosses and ribs, corners and radii, wall thickness and draft. This draft defines the level of the taper that is needed in order to allow the molded plastic’s ejection. The ribs are also important to add the part design’s structure strength. The bosses function in locating, mounting and assembling the molded parts. The radii help in avoiding sharp corners and in strengthening the part.
One advantage of plastic injection molding is the capability of keeping up a high level of production, high level of tolerance in the items and lower cost on labor since the bulk work is done on the machine. In addition to that, the scrap cost is also lower due to little waste.
Good thing, the technology is continuously improving nowadays. This results to the plastic tooling’s improvisation and advancements in all aspects. With high-tech plastic tooling, the plastic industry will continue to thrive in order to cater to the needs of other industries.