5 Things You Need To Know About Anodizing Aluminum

What Is Anodizing?

Anodizing is a process,which is used to increase the thickness of the natural oxide layer on the surface of metal parts. Anodizing does not need to use heavy metals nor does it produce toxic waste, so it is an environmentally friendly process, also it meets the environmental and safety directives of the RoHS.

Some purposes of anodizing are to obtain good wear resistance, corrosion resistance, surface lubricity, adhesion, and aesthetics.

Aluminum is ideally suited to anodizing, although magnesium and titanium can be anodized too. But steel or stainless steel cannot be anodized.

Anodized aluminum parts are commonly found in aircraft and architectural components, as well as home appliances, sporting goods, motor vehicle components, food preparation equipment, furniture, and electronics, etc.

Normal Anodizing Process of Aluminium.

The first step is to pre-treat the aluminum part through degreasing and pickling and providing a visibly smooth, clean surface.

The second step is that the aluminum part acts as the anode, then it is submerged in an electrolytic solution bath along with a cathode. When a current is passed through the electrolytic solution, hydrogen is released from the cathode(the negative electrode), and oxygen at the surface of the aluminum anode(the positive electrode), creating a build-up of aluminum oxide. This results in an anodized aluminum layer growing on the surface of the part. The layer thickness can be more than 100 times as thick as an oxide layer, which would naturally exist on an aluminum part that is only exposed to oxygen.

The third step is color dyeing(if needed). The most common anodizing processes, for example, sulfuric acid on aluminum, produce a porous surface. After immersing the anodized aluminum in an inorganic metal salt bath. An electric current is applied to this bath as the metal salts oxidize in the aluminum’s pores. Depending on the chemical conditions of the bath and the length of time immersed, the aluminum color will vary. The most common colors are yellow, green, blue, black, orange, purple and red. Dyed anodizing is usually sealed to reduce or eliminate dye bleed out.

The last step is sealing. Acidic anodizing solutions produce pores in the anodized coating. These pores can absorb dyes and retain lubricants but are also an avenue for corrosion. When lubrication properties are not critical, they are usually sealed after dyeing to increase corrosion resistance and dye retention. Sealing the anodized aluminum parts can be done in three ways: a cold method, a hot method, or a combination of the two.

Types of Anodizing.

The most common types of anodizing found in MIL-A-8625 are listed below:

Type I-Chromic Acid Anodize, it results in the thinnest anodic coat of the principal three types. It is good for tight tolerance parts or serves as a paint/prime base. It can be dyed in black, and not practical for other colors.

Type II Sulfuric Acid Anodize, it is the most common method for anodizing, and less expensive than other types of anodize concerning to chemicals used, heating, power consumption, and length of time to obtain the required thickness. Normally, the film thickness range from 1.8 μm to 25 μm, the overall thickness of the coating formed is 67 percent penetration in the substrate and 33 percent growth over the original dimension of the part. It is particularly suited for applications where hardness and resistance to abrasion are required. Also it is easy to be dyed with a variety of colors.

Type III Sulfuric Acid Anodize, known as Type III, hard coat, hard anodizing, or engineered anodizing, the coatings are thicker than 25 μm. Hardcoat is specified for aluminum components subject to extreme wear applications where superior abrasion resistance is needed, or corrosive environments where a thicker, harder, more durable coating is necessary. It is suited for applications of valves, sliding parts, gears, swivel joints, and so on. It can be black dyed, but less decorative for other colors. 

Benefits of Anodizing Aluminum.

Anodized aluminum parts are commonly found in a wide range of applications, such as home appliances, sporting goods, electronics, architectural and aircraft components.

The benefits of anodizing include:
Durability. Anodizing is a reacted finish that is integrated with the underlying aluminum. Most anodized products have an extremely long life span, result in offering significant economic advantages through maintenance and operating savings.

Aesthetics and Color Stability. Anodizing offers a large number of color alternatives and eliminates color variations. It allows the aluminum to maintain its metallic appearance. Also, exterior anodic coatings provide good stability to ultraviolet rays.

Ease of Maintenance. During the process of fabrication, handling, installation, surface dirt on the anodized parts may be generated. Normally, rinsing or mild soap and water cleaning will restore an anodized surface to its original appearance. Mild abrasive cleaners can be used for more difficult deposits.

Cost-Effective.  The anodizing part is with a much harder surface than painting and powder coating, but less expensive.

Health and Safety. Anodizing is one of the more environmentally friendly metal finishing processes. Since the anodizing process is a reinforcement of a naturally occurring oxide process, it is non-hazardous and produces no harmful or dangerous by-products. The most common anodizing effluents, aluminum hydroxide, and aluminum sulfate, are recycled.

Some Products Using Anodized Aluminum:

• Building exteriors, such as storefronts, curtain walls and roofing systems.
• Appliances such as refrigerators, dryers, coffee brewers, ranges, televisions, microwave equipment.
• Vents, awnings, dust covers, light fixtures, storm doors, window frames, mailboxes, bathroom accessories, patio covers, and wall switch plates for buildings.
• Display cases, pans, coolers, and grills for the food industry.
• Tables, beds, files and storage chests for homes and offices.
• Golf carts, boats, and camping/fishing equipment for the leisure industry.
• Hundreds of components for motor vehicles of all kinds such as trim parts, wheel covers, control panels, and name plates.
• Exterior panels for aerospace vehicles, clocks and electronic products, fire extinguishers, photo equipment, solar panels, telephones, picture frames, and bathroom accessories.
• Interior decoration and trim.

Is Anodizing Right For You?

If you have any more questions about anodizing, please feel free to contact us, we can offer advice to you not only on anodizing but also on many different kinds of finishing, which might be used on the cnc machining parts or prototypes of your projects. Also we will help you to find the solution that meets your target price and delivery date.

Types of CNC machines

Some types of CNC machines

There are so many types of CNC machines are present in the industries to manufacture the products. Generally, there are six types of CNC machines, they are used for different purposes :

1. CNC milling machines: In fact, they might be the most popular type of CNC machines used today. Milling machines utilize rotary cutters to shape workpieces as requested. They can be programmed to provide the required depth, angle and cutting direction.

2.CNC Lathes: A lathe is utilized to develop highly precise conical and spherical shaped parts. This particular machine uses turning centers wherein the cutting tool shaves off the excess material while the material is rotating on a spindle.

3.CNC Routers: A CNC router is like a CNC process. It accompanies the capacity to utilize PC numerical control to course instrument ways that empower the machine to work. CNC router diminish waste and increment efficiency, creating different things in a considerably shorter measure of time than utilizing different machines.

4.CNC Plasma Cutters: Plasma cutters uses a plasma beam to cut the materials into 2D shapes.

5.CNC Grinders: This type of machine utilizes a rotary wheel that abrades the material into the desired shape by repeatedly grinding it.

6.CNC Electric Discharge Machines: Electric discharge machining, or EDM for short, includes making a particular shape inside a specific material by utilizing electrical releases or starts. The material is expelled from a particular workpiece by a progression of repeating electrical releases between two anodes. These anodes are isolated by a dielectric liquid, which regularly gets an electric voltage.

What is CNC Machining

CNC machining is a type of manufacturing process to produce the machined parts, products, items by using CNC machines. CNC Stands for Computer Numerical Control or Computerized Numerical Control. 

While a CNC machine is an electro-mechanical device, it comprises of the computer acted as the control unit, which directs the machine tools to perform various machining operations as per the program of instructions fed by the operator. CNC machine works like the Robot, which has to be fed with the program and it follows all your instructions.

The basic CNC machining process for producing machined part can be broken down into 3 steps.

1. Design the CAD model of the part. 

2. Transfer the CAD model file into a CNC program (G-code) and set up the machine. 

3. The CNC system executes all machining operations to remove material and create the machined part.

A short video of precision machining process on our machine shop.

If you want to know more about CNC machining, please check our website.

8 Tips to Optimize Design for CNC Machining Parts

CNC machining process is widely used to produce custom machined parts with strong strength and tight tolerance. It is the fast and cost-effective way to manufacture prototypes and production parts. An optimized designed CNC machined part will help to accelerate production time while saving cost.

To fully optimize your design for CNC machining parts, you should look at below design tips:

1. Round the Internal Corners

The CNC machining tools – such as an end mill or milling cutter – will leave rounded inside corners. The corner radius can be reduced by using a smaller diameter machining tool, but it requires both a smaller tool to machine away material and more passes – often at a lower speed to reduce the risk of deflection or tool breakage – Resulting in more machining time.

So we would suggest to add an inside corner radius of at least 1/3 of the depth of the cavity and use the same radius in all internal edges, This helps eliminate tool changes, which adds complexity and can increase run time significantly.

2. Avoid Deep Cavities

The end mill cutting tools have limited cutting length, they typically work best when cutting cavities with a depth of up to 2-3 times their diameter. To minimize cost, we suggest limiting the depth of the cavity to the 4X diameter of the tool to ensure good results. Anything greater than that will increase the cost, as special tooling or multi-axis CNC systems are required.

If larger cavity depth is required, consider designing parts with a variable cavity depth.

3. Increase the Thickness of Thin Walls

CNC parts with thin walls have a tendency to chatter, which slows down machining speeds. They can also cause distortion, which makes it difficult to machine them accurately. The result can be an additional machine time and cost.

In order to keep machining costs low, thin walls should have a minimum width of 0.8mm for metal parts, and 1.5 mm for plastic parts.

4. Optimize the Depth of Tapped Holes

Regarding the Tapped holes, by increasing the length of thread in a hole does little to hold the bolt tighter. It’s really just the first two or three turns that do all the work. Going deeper just increases the risk of tap breakage and adds time to the tapping operation.

So we don’t suggest to thread a hold to more than 3 times of the hole’s diameter, normally, the thread length would be from 1.5X to 3X of the hole’s diameter.

5. Limit Use of Tight Tolerances

Typically, only a few surfaces of a part are critical to its function. The more features with tight tolerances, the more expensive a part to be manufactured. Because it increases the machining time and cost.

So we would suggest to only assign tight tolerances on some critical features and surfaces, other less significant features should be controlled by standard tolerances of ± 0.125 mm, which is sufficient for those features.

6. Reduce Small Features

Small features such as micro-holes (less than 2.5mm in diameter) will increase the machining difficulty and machining time, thus should be avoided unless absolutely necessary.

7.Split Up Complex Parts

Machining multiple simple parts are less costly than machining one complex part. especially for parts with deep pockets, which would require hours of machining time to remove material, plus additional material costs. And most shops will charge a premium for more complicated parts. This is because if a mistake occurs it is costlier to redo a complex part than it is to redo a simple one.

So we would suggest to split up the complex parts to some simple parts and assemble them together if possible.

8. Design Holes with Standard Size

Holes can be CNC machined fast and to a great accuracy using standard drill bits.  it won’t need end mills or reamers to finish the hole size to a non-standard dimension. This will helps reduce machine time and lower the cost. Also, limit the depth of all holes to 4 times their diameter. 

Contact us if you aren't familiar with standard drill bits sizes.