One of the most popular processes for casting aluminum is sand casting. The technique is relatively simple but efficient; involving forming aluminum into a mold pattern formed in sand. It is a famous method used to produce about 60% of metals.
Also, aluminum sand casting is known to be one of the oldest techniques, dating back to 2000 years ago. It has proven to be successful in creating single pieces, small and medium ones too. With aluminum sand casting, you can produce even the most complex castings efficiently and fast.
Also, molds made using sand are cheap and sufficiently refractory.To know more about this popular and famous casting method, read through this blog.
Types of Sand Casting Aluminum Processes
There are two main types of sand casting for aluminum, first is green sand casting and another is dry sand casting.
Green Sand Casting
With green sand casting, ‘green sand,’ which is nothing but a mixture of water and sand clay, creates the mold. It is created by placing the green sand around a pattern removed to leave a cavity in which the molten aluminum will flow. This sand-casting method is simple and cost-friendly but cannot be used to create complex shapes.
Dry Sand Casting
In dry sand casting, the mold is created using sand and thermosetting resin that helps harden the sand to make the mold stable. There is greater control over the mold’s properties in this procedure. Also, it is perfect if you want to produce more complex shapes.
Step By Step for Sand Casting Process
Sand casting is a simple but effective method that most aluminum casting manufacturers utilize. The process involves the following steps:
Making the Pattern
Like any other casting procedure, the first step involves making the pattern. Determine the part that you need to cast, then create a pattern that is a replica of this part. You can make your pattern from wood, metal, or plastic.
Ensure that the pattern is slightly larger since the item you’ll perform sand casting on will contract during solidification. Also, it should be accurate regarding the shape and size you want to achieve.
Make the Mold
After you’ve created the pattern, go ahead to make the mold. This step is crucial as it determines the final shape and quality of the casting. To make the mold in sand casting, place the pattern in a mixture of sand and binder.
The binder is a mixture of clay and water that helps hold the sand together and give it shape. After this, you must let the mold dry.
Aluminum is Poured into It
You now have your dried mold, and the next step is placing it in a casting flask where the molten aluminum is poured onto it.
The aluminum should fill the mold and will instantly take the shape of the mold pattern. Just like the aluminum die casting procedure, it is let to cool and solidify.
Shakeout
At this point, the process of removing the solidified casting from the sand mold begins. This is done by breaking the mold, but first, you need to remove the clamps holding the two halves of the mold together.
After the mold opens, the sand around the casting is made loose by rapping the sides of the mold using a hammer. The loose sand is then removed by shaking it. You should then lift the casting out of the mold.
This process is pretty messy, and you might generate a large amount of dust and sand. It is recommended to spray the mold with water to make it damper before breaking it.
Cleaning and Finishing the Casting
The final step for the aluminum sand casting procedure is cleaning and finishing the casting. You do this so that it reaches your desired specifications. At this point, you remove any remaining sand, rough edges, and burrs and correct any imperfections your casting may have.
To clean the casting, you can do sandblasting or use a mechanical method known as tumbling, which involves placing the casting in a drum with an abrasive media to rotate the casting until all sand is removed.
To remove the rough edges, other imperfections, and burrs, you use the polishing, grinding, or sanding process. After this, your casting is ready for use. However, the casting may go through secondary operations on customers’ requests.
Components for Making Sand Casting Aluminum Mold
As mentioned earlier, to perform the process of sand casting, you need to use a mold. Now, the mold is made of four main components, as discussed below:
Base Sand
This type of sand is used to make the mold without any binder. You can opt to use silica sand, olivine sand, chromite sand, chamotte sand, and zircon sand for this process.
Binder
Of course, sand particles tend to be loose on their own. To make them stick together, add a binder as an additive that acts as a glue for the mold. The most commonly used binders include clay and water, resin, oil, and sodium silicate.
Additives
Additives are a crucial component in the manufacturing process, including molding materials. During the sand casting procedure, they modify the base sand so that the final product is high quality, looks great, and performs well. Coal powders, as well as fuel oil serve as additives to the molding material, preventing the liquid metal from adhering to the sand particles.
Parting Compound
This is a mixture of talc, graphite, dry silica, mineral oil, and water-based silicon solution.
The use of this mix is used to get the replicated parts out of the mold pattern with relative ease.
Advantages and Disadvantages of Sand Casting Aluminum
If you are considering to sand cast aluminum, here are some potential benefits you’ll rip from the process:
- The process is relatively inexpensive, unlike other techniques such as aluminum die casting; therefore, it is a great choice for low-volume production runs
- With aluminum sand casting, you can create complex shapes that are dimensionally accurate.
- Sand aluminum casting is a versatile procedure that allows you to produce a wide range of parts sizes and shapes
Some of the disadvantages of sand aluminum casting include:
- Sand casting can have small pockets of air trapped inside that are bound to weaken the casting.
- Most sand aluminum castings end up with a rough surface which is unlike those produced using aluminum die casting
- If you are looking to produce parts that require high precision, then this casting procedure may not be suitable
- Also, the sand casting method is longer since you need to prepare the sand mold and let it dry before casting.
Conclusion
Sand casting is a popular and cost-effective method widely used to cast aluminum. It is flexible and allows for the production of complex shapes. However, it is not ideal if you need high-precision parts, and sometimes the finishing quality is not the best.
If you are looking for a reliable, quick, and high-precision company for your aluminum die-casting needs, look no further than Sunrise Metal. We have over 10 years of die casting and can handle small and medium-volume orders. Request a free quote today!