Many industries use aluminum forging for a myriad of purposes. Most often, forging is used to mold aluminum into a particular shape to create a specific part. If you forge aluminum, you have two choices: closed-die or open-die.
Before choosing which forging process to use, it’s often beneficial to consult a few manufacturers for aluminum forging to discuss your options and price points. Most forgers can help you determine which method makes the most sense for what you hope to accomplish. While you may at first believe open-die forging is your best option, many experienced forgers are quick to point out the benefits of closed-die forging.
Defining Closed-die Forging
In open-die forging, manufacturers place the aluminum between multiple dies, which never fully enclose the materials. In contrast, closed-die forging involves pressing aluminum under high pressure to force it into a specific mold. Since the dies entirely hold the material, this process is also called impression forging.
For closed-die forging, manufacturers start by creating the molding dies. The aluminum is then placed on the dies and forged into the desired shape. Unlike open-die forging, this process involves little-to-no machining, and the resulting part is more precise than if you used open-die forging.
Understanding the Alternative
Open-die forging, or free forging, requires considerably more pressure than closed-die forging. You’ll also need a medium frequency induction heating furnace to heat the metal into its desired shape. During the forging, the aluminum is continuously struck with a forging hammer to reshape the aluminum.
To begin open-die forging, manufacturers attach the top die to the ram, and the bottom dies to a hammer. They make sure the materials heat up to the appropriate temperature to ensure they bend correctly. The forger will then strike the aluminum to reshape it.
Accuracy and Efficiency in Closed-die Aluminum Forging
There are a variety of reasons why closed-die aluminum forging may be a superior option than open-die. Manufacturers typically reserve open-die forging for larger, simpler parts, such as spindles or bars. It can also be a complicated process since the manufacturers have to continuously move the material throughout the forging process. In several scenarios, closed-die is the more advantageous process:
- Product Strength– Closed-die forging increases the internal grain structure of the final product. A closed-die product will be stronger and tighter than an open-die product, which is only necessary for smaller, more delicate parts.
- Large Runs– Since closed-die forging requires less manual labor and fewer machines, it’s your best option if you’re producing a large quantity of the same parts. Open-die forging will be more expensive and take a longer time to complete.
- Wide Material Range– Unlike open-die forging, you can closed-die forge using any material. As such, if you need aluminum for one part but metal for another, you won’t have to change up production or create new dies to switch over to closed-die forging if you started with open-die forging.
- Surface Finish– Closed-die forging generally creates a cleaner finish than open-die forging.
- Few Machines Required– Closed-die forging can create finished products that don’t require touching up with a machine after the initial forging process. To meet specific product dimensions in open-die forging, you’ll almost always need machine help, which can lengthen your product development time.
- Better Net Shapes– Many products will be ready or close to ready after closed-die forging. The process allows for more precision, which means its final net shapes are often better than those produced by open-die forging.
While closed-die forging will often be the right choice for your products, a few scenarios may make open-die forging advantageous:
- Limited Runs– Since dies are expensive, having only limited production runs using closed-die forging can be more costly than open-die forging.
- More Material Waste– Typically, closed-die forging produces more material waste than open-die forging.
Best Fit Forging
For many production runs, closed-die forging is preferred over open-die. Parts can be made more precisely and require less touch-up after forging. However, shorter production runs of larger, simpler products may be better suited for open-die forging. Working with an aluminum forging company can help you determine which process will most efficiently produce the parts you need.