What is Permanent Mold?
Permanent mold; It is a technique that enables the casting of complex parts of aluminum, iron and steel. With the permanent mold method, these parts enable the production of high surface quality products. Permanent casting into a metal mold is a mass production method. A permanent mold design is used to produce the same piece over and over again. Its a molding method.
Molds in which more than one casting can be made and can be used repeatedly are called permanent molds.
If steel is to be produced in a permanent mold, between 3000 and 10,000 products can be produced. If aluminum is to be produced in a permanent mold, up to 100,000 pieces can be produced. Permanent molds are produced using heat-resistant materials such as chamotte, clay and ceramics. Durable molds are also used for permanent molds. It is used for mass production.
The permanent casting method is generally used if the size tolerance ranges of complex shaped products are also narrow. Desired casting parts are obtained by this method. The permanent mold design is also quite broad. Especially in the laser cutting sector, the permanent mold method is frequently used in the molding phase.
Permanent die casting (often referred to as “cold casting”) is a metalworking process that uses permanent and reusable molds to create durable parts. The mold is created using extremely durable materials – tool steel or exotic copper alloys. These materials can withstand many thermal cycles.
The molten materials are then poured into the mold by gravity as opposed to injection. This makes permanent mold casting ideal for projects that require high volume or ultra-high durability. Permanent die casting produces parts with tighter tolerances and superior coatings compared to other traditional casting processes such as sand casting.
How is a permanent mold made?
The permanent mold casting process can be divided into four main components. Each of these components may differ depending on the metal casting job you are working on.
Step 1: Creating Mold
The first step of a permanent mold is to create the mold. It’s a process that requires a focus on detail and incredible craftsmanship.
The mold itself consists of two or more sections and cores placed to form many complex molds. It is important to note that no sand is used during this process and that the entire mold is a permanent, solid part.
The surface of the mold is coated with a heat resistant material to withstand the heating and cooling cycles. The coating also affects the heat conduction and lubrication of the mold, so a unique coating is used depending on the needs and complexity of the project.
Step 2: Pouring the Molten Metal into the Mold
After the mold is assembled, the high quality molten metal is slowly poured into the mold via a ladle at the top of the mold. The molten metal will then be transferred to another mold for solidification.
Step 3: Cooling the Metal
This process is simple. The metal is allowed to cool in the mold for a certain period of time. This timing varies depending on the material used.
These are some of the common materials used in permanent mold casting.
- pure copper
- Aluminum alloys
- magnesium alloys
- copper alloys
- Tin alloys
- Zinc alloys
- Lead alloys
Step 4. Opening the Dump
After the metal has cooled, the casting is opened and the part is removed. At this point, depending on the cycle stage, the mold will be set up again and used in a later process.
Excess material attached to the part is also trimmed and used for remelting.
Benefits of Permanent Mold
The permanent die casting method has many benefits.
- Good for high volume productions:
The primary cost associated with permanent mold casting is the casting itself. When applied to high production cycles, cold casting provides better cost per part than other casting methods. The cost savings of permanent mold casting have been the subject of research for years. And permanent mold casting has proven in numerous case studies to be the most cost-effective, high-volume casting method.
- Uniform features:
The homogeneous properties of permanent die casting ensure that all parts are incredibly homogeneous.
- Incredibly high surface quality:
Permanent mold casting provides a superior surface finish compared to other casting methods (eg sand casting).
- Smaller casting holes:
Permanent mold cold casting can create smaller casting holes than other methods, which helps maintain tight tolerances.
- Minimized part variation:
Because you don’t create new molds for each cycle, permanent mold castings offer variations as low as +/- 0.010.
- Thinner edges:
Permanent mold cold casting allows for thinner edges than other casting methods.
Superior mechanical properties:
Mechanical properties (e.g. strength, yield, ductility, etc.) are higher in permanent mold casting due to the nature of the process.
This Gravity casting method consumes much less energy and produces less waste than other casting methods such as sand casting.
Products Produced by Permanent Mold
Cast products produced with permanent mold are quite wide. E.g;
- compressor body
- hydraulic brake cylinder
- connecting rods
- Aluminum typewriter
- Kitchen utensils
Permanent Mold Design
You can see the permanent mold design and examples below.