The top 25 most frequently asked questions about aluminum casting.
With competitive price and timely delivery, Golden Jash sincerely hope to be your supplier and partner.
The Basics
1. What&#;s a casting?
While the word casting (noun) can be used to describe the finished product, casting (verb) can also be used to the describe the manufacturing method.
Metal casting is the process of pouring molten metal into a custom mold and shaping the metal as it solidifies.
2. Are there different casting processes?
There are four common casting methods: sand casting, die casting, investment casting, and permanent mold casting.
3. What metals are used for casting?
Iron, aluminum, bronze, zinc, steel, and copper are common metals used in casting. At Batesville Products, we cast aluminum (A356) and zinc (ZA5 and ZA12).
4. What aluminum alloys can be cast?
There are a variety of aluminum casting alloys, but we prefer A356. This alloy is preferred because of its castability, strength, weight, and corrosion resistance. A356 is also medical-grade and food-safe.
Aluminum ingot. A356.
Properties of Aluminum
5. Is cast aluminum heavy?
Compared to other metals like zinc or iron, cast aluminum is very lightweight. The weight of the casting depends on the size, wall thickness, hollows, and density of the part.
For example, this large casting used on building corners is about twenty pounds.
6. Is cast aluminum strong?
Cast aluminum is very strong, known for its high strength-to-weight ratio. Since it can withstand weight and stress, it&#;s often used in industrial machinery.
To further increase strength and remove flexibility properties, aluminum castings can be heat treated. T5 and T6 are common heat treatments.
7. Where does aluminum come from?
At Batesville Products, we use primary aluminum. Rio Tinto, a North American based aluminum producer, uses an advanced hydropower damming system to produce aluminum. Did you know that 40% of the cost of making aluminum is electricity? This hydropower system gives a competitive edge in comparison to coal burning smelters.
However, lots of aluminum in use today is recycled, or secondary. Aluminum is fully recyclable and can be recycled indefinitely without losing quality. Did you know 75% of all aluminum ever produced is still in use today?
8. Can cast aluminum be painted?
There are special air-dry or bake-on primers and paints for aluminum castings.
9. Can cast aluminum be powder coated?
Powder coating is one of the most common cast aluminum finishes. Know that castings must be prepped, cleaned, and degassed (or heat treated) before powder coating for the best results.
10. Can cast aluminum be anodized?
Aluminum castings can be anodized or chromated to provide corrosion resistance, oxidation protection, wear resistance, strong insulation, heat transfer properties, and an aesthetic appearance.
11. What can you cast with aluminum?
You can cast almost anything with aluminum! From frying pans to dental chairs, fan blades to electrical housings. Here are some examples.
Where&#;s aluminum used? Aluminum is used to make products in hundreds of industries, including&#;
12. Will cast aluminum rust?
Unlike iron, aluminum will not rust. To protect against other forms of corrosion, aluminum can be anodized or coated.
13. Will cast aluminum bend?
Aluminum is known for its high ductility. Unlike other metals, aluminum will bend before it breaks.
14. Can aluminum be welded?
Cast aluminum can be welded. It&#;s possible to cast different aluminum parts and welded them together to assemble your final product.
However, casting your product into 1 piece rather than welding many pieces together saves a lot of time and money. We recommend working with one of our expert engineers to see how you can turn your project into 1 piece.
Custom permanent mold castings manufactured by Batesville Products
Permanent Mold Casting
15. What&#;s permanent mold casting?
Permanent mold casting is the gravity-fed process of pouring molten metal into a reusable steel mold.
16. How&#;s permanent mold casting different from die casting?
Both processes use a reusable steel mold to form metal castings.
The main difference between die casting and permanent mold casting is the way the metal is fed into the mold. Die castings are quickly pressure injected, while permanent mold castings are gravity-fed by a slow tilt. This slow tilt pour means less internal porosity that could become an issue during machining.
Die casting tooling is more complex, meaning it can be up to five times more expensive than permanent mold tooling. Therefore, die casting process is ideal for high volume production runs (example: 50,000 pieces per year). It&#;s commonly used in the automotive industry. Permanent mold is ideal for moderate volume production runs (example: 5,000 pieces per year).
17. Why permanent mold?
Permanent mold is known for high-quality surface finish, low-porosity, high precision, repeatability, and easy secondary machining.
Permanent mold castings are denser than die or sand castings. Permanent mold is ideal for moderate volume production (500-20,000 pieces per year).
18. How much does permanent mold cost?
9 factors impact the cost of a casting.
The primary cost driver is mold tooling. Permanent mold casting is less expensive than die casting, but more expensive than sand casting.
Sand molds are one-time use, while permanent molds are reusable steel tools. Sand casting&#;s low-cost tooling and high piece price makes it ideal for low-volume production. However, you will often see a return on investment on permanent mold tooling if you are producing over 500 pieces per year.
Die casting molds are complex steel molds that take longer to produce and can be up to five times more expensive than permanent mold. Therefore, you see best ROI on high volume production in die casting, and moderate volume production in permanent mold.
Keep in mind, all parts are custom. For a better cost estimate, please request a quote.
19. What&#;s the permanent mold as-cast surface finish?
Permanent mold castings generally have a surface finish of RMS 200-420.
Aluminum casting for food and beverage industry.
Designing for Permanent Mold
20. What&#;s draft? Why do I need draft?
For more information, please visit What is an aluminum profile?.
Draft, also known as taper, is a slight angle applied to walls, moving away from the parting line. Draft is necessary in casting because it helps parts easily eject from the mold.
21. What&#;s the minimum wall thickness for permanent mold casting?
For permanent mold casting, we recommend a minimum wall thickness of 0.180 inches.
Avoid isolated thin or thick sections. These can negatively impact flow and solidification, and cause shrinkage.
22. What are as-cast tolerances for permanent mold casting?
Permanent mold holds tight as-cast tolerances, almost double that of sand casting! For even tighter tolerances, consider adding a quick secondary machining operation.
Linear tolerance for features on the same side of the mold are 0.015 for the first inch. Add 0.002 for each additional inch. For concentricity, flatness, and other tolerances, view this design guide.
Linear tolerances for permanent mold aluminum casting
Secondaries
23. Why CNC machine a casting?
Castings are near-net shape of the final product. Sometimes, a secondary CNC machining operation is required to achieve tighter tolerances than permanent mold is capable of.
CNC machining also completes drilling, tapping, threading, or milling.
Casting then secondary machining is a great way to create a complex part. By first casting your project, you have a great starting point. Machining a near-net shape instead of a block of billet speeds up the CNC machining process. You can produce a complex part more efficiently.
Not sure if your casting needs CNC machining? Take this quiz.
24. What types of finishing options are available?
Permanent mold has a great as-cast surface finish. Aluminum casting finishing options are:
Zinc castings are preferred for mirror buffing or plating.
Not sure which finish to use? Use this flowchart to find your ideal finish.
25. How much extra material should be added for machining?
If you do not include a machine stock allowance in your design, the final part may be out of spec. Account for extra material if CNC machining your casting.
Machine stock allowance for permanent mold aluminum casting
More Questions?
We're ready to answer them. Comment or message us!
This is linked to our original content: https://batesvilleproducts.com/resource/answering-the-25-most-asked-questions-about-aluminum-casting/
You&#;ve likely seen anodized aluminum products in your daily life. Anodizing is an easy way to add corrosion protection and a splash of color to aluminum. You&#;ll find this finish on sports equipment, automotive parts, handheld devices, and a wide range of other products.
If you&#;re wondering whether anodizing is the best way to finish your aluminum products or would like to know more about the process and its benefits, this article is for you.
Here we answer some of the most commonly asked questions about anodizing aluminum to help you decide if this process is the right choice for your products.
1) What is Anodized Aluminum?Exposing metals to certain environments such as air and humidity creates a metal-oxide layer on the exposed surface. In most cases, the oxide layer is passive, which means it no longer reacts with the environment the way the pure metal does. The rust that forms on iron when it&#;s left unprotected is one example of this.
Like iron and other metals, aluminum naturally forms a layer of oxide when in contact with air or moisture. Unlike iron, however, the layer of oxide formed is not flaky or overly porous, and it serves as a shield preventing any further oxidation of the aluminum.
In other words, aluminum creates its own thin barrier against corrosion by slightly corroding itself. This is similar to how human skin tans to protect itself from further damage caused by sun rays or other ultraviolet light.
When you anodize aluminum, it goes through a process that thickens this naturally-occurring protective layer of oxide. Anodizing enhances the properties offered by the oxide layer, and these properties are addressed one-by-one in the following sections.
2) How Does the Anodizing Process Work?Contrary to intuition, the process of anodizing doesn&#;t require technicians to apply a product to the aluminum surface. As explained before, this process takes advantage of a reaction that occurs naturally on aluminum when in contact with certain elements and takes it up a notch.
Once the aluminum has gone through a forming process &#; extrusion, for example &#; the resulting aluminum part is submerged in an electrolytic bath. While immersed in the liquid, a high-amperage, low-voltage electrical current is applied to the bath. The oxidation chemical reaction occurs as the current flows through the aluminum, forming an oxide layer thicker than the naturally occurring one.
3) Does Anodizing Increase Resistance to Wear?Yes, anodizing does improve wear resistance. The oxide layer that forms in the aluminum surface has ceramic properties, one of which is a heightened resistance to wear compared to the aluminum on its own. Anodized aluminum is better than untreated aluminum at resisting nicks and scratches, providing a more durable finish.
4) Does Anodizing Increase Corrosion Resistance?Yes, it does. Like the naturally occurring oxide passive film, the thick layer of oxide obtained by the anodizing process also improves corrosion resistance. The passive film is largely chemically inert and does not break down or corrode in the environment.
As a result, the anodized layer protects the underlying aluminum from corrosion. Anodized aluminum has a thicker passive layer than naturally passivated aluminum, meaning it is more resistant to degradation and subsequent corrosion.
5) How Do You Dye Anodized Aluminum Parts?Another benefit of anodizing aluminum is that the metal&#;s surface becomes porous. Micropores make the anodized aluminum perfect for dye application &#; they act as wells where the dye can collect.
Once the dyes are applied, the pores can be sealed, resulting in the color being embedded in the oxide layer. Because the dye is now part of this passive layer, it will not fade or peel away, providing a durable, long-lasting, and elegant finish.
6) Does Anodizing Improve the Adhesion of Primers and Glues?Yes, for the same reason that anodized aluminum is excellent for dyeing. The porous surface of anodized aluminum means the glue or primer has an increased contact surface and better spots to &#;grab on.&#; The pores allow the glue or primer to partially embed into the surface, resulting in an even layer of glue or primer with great adhesion that is less likely to spall off.
7) Does Anodizing Improve Heat Dissipation?Yes, it does. If an item is hotter than its surroundings, it will start to cool off. The greater the surface area of a hot item, the quicker it will dissipate its heat. Anodized aluminum has a higher surface area than unfinished aluminum and, therefore, it is more effective at releasing its heat.
This improved thermal conductivity, or heat dissipation, results from improved convective heat transfer and enhanced emissivity. Convective heat transfer, which is heat transfer between a surface and the surrounding air, is primarily impacted by design and somewhat by anodizing.
Radiative heat transfer, also called emissivity, occurs between two surfaces and is dramatically improved by anodizing. This property makes anodized aluminum perfect for small heat sinks, as described by our article about anodized aluminum heatsinks here.
8) Does Anodizing Affect the Strength of the Aluminum?No, it does not. The aluminum product&#;s strength will not be affected, either positively or negatively, by anodizing it. The process of anodizing affects only a very small layer on the aluminum surface, on the scale of micrometers.
Since the bulk of the aluminum part remains unchanged, the product retains the properties obtained by the forming and treatment applied before anodizing it.
9) Does Anodized Aluminum Have High Electrical Conductivity?No, it does not. Aluminum is highly conductive by itself; however, the oxide layer has physical and chemical properties resembling a ceramic. One of the principal characteristics of ceramics is electrical insulation.
An anodized aluminum piece is still capable of limited electrical conductivity through contact, as the oxide layer is very thin, but the conductivity is significantly lower relative to untreated aluminum. While there are workarounds, you may want to consider a different finishing treatment for your aluminum products if electrical conductivity is an essential aspect of the item&#;s design.
10) What&#;s the Difference Between Type II and Type III Anodizing?The anodizing process requires the proper selection of many variables: bath type, temperature, voltage, amperage, etc. Because of this, certain specifications are necessary to ensure the desired outcome is achieved consistently.
The most common way to specify different types of anodizing is by the military specification for anodic coatings for aluminum and aluminum alloys MIL-A-. In broad terms, this document separates the types of anodizing into Type I, II, and III.
Type I anodizing, the oldest known method, is performed in a bath of chromic acid. Type II and III are done in sulphuric acid.
The difference between Type II and III is the thickness of the resulting oxide layer. Type II anodizing, being the most commonly applied, has a layer with a thickness ranging between 1.8 to 25 micrometers. Type III anodizing, also known as hard anodizing and used where increased wear and corrosion resistance is desired, consists of oxide layers thicker than 25 micrometers.
Should You Anodize Your Aluminum Extrusions?Choosing whether or not to anodize your aluminum extrusions depends on the intended applications for the products. As this article has highlighted, there are both benefits and drawbacks to anodizing.
Suppose your main concerns are corrosion resistance and a very nice, metallic look, or you&#;re looking to improve emissivity or adherence of primers or glue. In that case, anodizing could be ideal for finishing your extruded products.
However, anodizing might not be the best option if electrical conductivity is essential or if further forming processes are to be performed on the piece. These might cause the oxide layer to crack. Anodizing also slightly increases the dimensions of the piece. Therefore it is not recommended if you are working with very tight size tolerances.
If you are looking for alternatives to anodizing, you might consider using powder coating as a way to finish your aluminum items, giving them a bright colored finish. If a matte finish works for your application, and you need more extended durability and protection against UV fading, you might consider PVDF coating your aluminum products.
If you want to learn more, please visit our website Construction V-Slot profiles applications.