CNC machining difference between 3 Axis , 4 Axis,and 5 Axis

 CNC machining is a manufacturing process that utilizes computerized controls to operate and manipulate machine and cutting tools to shape stock material—e.g., metal, plastic, wood, foam, composite, etc.—into custom parts and designs.

An axis reference is used to describe a CNC machine that works with multiple axis points. The machine operates in the XYZ plane with at least three axes: X-axis (vertical), Y-axis (horizontal), and Z-axis (depth). The 4th axis is with the A axis (rotation around the X-axis), and the 5th axis includes the B-axis (rotation around the Y-axis).

So what are the differences between 3 axes, 4 axes, and 5 axis CNC machining, the following provides an explanation of it.

3 Axis CNC machining

3-Axis machining is the most simple type of machining, where the workpiece position is fixed, while the cutting tool moves along the X, Y, and Z linear directions to cut away material. This is good for the parts that don’t need a lot of depth and detail. Only one side of the part can be machined for a single fixture setup. 3 axis machining is used to produce mechanical components normally and is suitable for:

• Automatic/interactive operation
• Milling slots
• Drilling holes
• Cutting sharp edges

4 Axis machining

4-axis machining means that a workpiece is processed in an equal manner as a 3-axis system, however, has an extra rotary movement around the X-axis, which is called the A axis. This rotation permits the workpiece to be cut around the A. When holes or cuts need to be made on the sides of a workpiece, this machining method is useful. This additional 4th axis (A axis) allows a workpiece to be mechanically flipped over, so the machine can cut away material from both sides. 4-axis machining is multifunctional and can be used for:

• Intermittent cutting
• Continuous cutting
• Engraving curved surfaces

5 Axis CNC machining​

5-axis machining means that a workpiece can be processed from five sides at one time. In addition to movements along the X, Y, and Z-axis, the machine utilize 2 out of the 3 possible rotation axis(A, B, C), the A, B, and C axis perform a 180° rotation around the X, Y, and Z-axis Normally, the A-axis and B axis will be used as rotational axis on the 5-axis CNC machining. 5-axis machining is one of the multiaxis machining.

There are two types of 5-axis CNC machines normally, 3+2 machines, and fully continuous 5-axis machines.

In 3+2 axis machining, the two rotational axes perform independently to each other, which means that the workpiece can be rotated to any compound angle with respect to the cutting tool. However,  it is impossible to rotate both axes at the same time. 3+2 machining can manufacture especially complicated 3D geometries.

Fully continuous 5-axis machining allows simultaneous rotation of two rotary axes, at the same time as machining and the cutting tool moving linearly in XYZ coordinates. The continuous 5-axis machining can produce very complex 3D geometry, not only planar compound angled features but also complicated curved 3D surfaces, giving us the capability to produce parts normally reserved for molding processes.

This type of machining is used in the automobile, aerospace, and boating industries. 5 axis machining is beneficial when components are very complex and with high precision. This includes:

• Accuracy Features
• Increased productivity
• Higher quality finishes
• Cutting intricate details
• Machining complex geometry

5-Axis CNC machining aluminum part

At CYmanufacturing, we can offer both 3-axis, 4-axis, and 5-axis CNC machining services, If you need assistance manufacturing your machined parts. Please don’t hesitate to contact us.

Surface Finishes for CNC Machining Parts

  There are a number of surface finishing techniques to give CNC machined parts the desired professional finish. It can change the appearance, surface roughness, hardness, and chemical resistance of the machining parts. Below is a quick summary of the most common surface finishes for precision machined components from CNC machining shops.

1. As-Machined

   An As Machined CNC machining part surface finish does not require any post-processing, but the tool marks will be shown on their surface, thus it is not perfectly smooth. The standard surface roughness of an as-machined part is 3.2 um. However, additional smoothing and polishing can reduce the machined texture to surface roughness of 0.4 um. This finish is very cost-effective and most suitable for prototypes and jigs and fixtures.

2. Bead Blasting

   Bead blasting is the operation of shooting the blast media against a surface to affect the surface finish by using compressed air typically. It results in adding a uniform matte or satin surface finish on a CNC machined part.

This process relies on using small beads to remove incremental amounts of material from the CNC machined part’s surface. As the resulting surface roughness is not guaranteed, so critical surfaces or features (like holes) need to be masked to avoid any dimensional change.

Bead blasting is a post-process to get a smooth finish, but will affect the dimensional accuracy of the parts slightly, Therefore, it is used mainly for visual purposes or aesthetic applications without tight tolerance requirements.

3. Anodizing

   Anodizing is a process that is used to increase the thickness of the natural oxide layer on the surface of metal parts, it 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.

In the anodizing process, an electrochemical reaction consumes the material on all exposed surfaces of the part and converts it into hard metal oxide, typically for aluminum or titanium. And the anodic coating grows in both directions equally and it is electrically non-conductive, so a mask needs to be applied to the surfaces with critical dimensions (like threaded holes) or the surfaces that must remain electrically conductive to prevent them from anodizing.

The main advantages of anodizing CNC machined parts are with high aesthetically pleasing surface and more durable. For more information about aluminum anodizing, please click here.

4. Powder Coating

   This is a process where powdered paint is sprayed onto a part which is then baked in an oven. It adds a thin layer of strong, wear and corrosion- resistant protective polymer on the surface of the machined part. Powder coating is compatible with all machining metal materials, some manufacturers also combine the powder coating process with bead blasting to create parts with a smooth finish and excellent corrosion resistance.

This finish is ideal for end-use products, due to some of the advantages listed below:

• Strong, wear and corrosion resistant
• Higher impact resistance
• Compatible with all metal materials
• Multiple colors available

But the powder coating will change the dimension of the part, so it doesn’t fit for tight tolerance part, also it is difficult to apply to the internal surfaces.

5. Passivation

   The passivation process is a method of improving the corrosion resistance of stainless steel machined parts by removing ferrous contaminants like free iron from their surface, restoring them to their original corrosion specifications.

Passivation is a post-processing best practice for newly-machined stainless steel parts and components. Benefits include:

• Chemical film barrier against rust
• Extended life of the product
• Removal of contamination from the product surface
• Reduced need for maintenance.

To passivate stainless steel machining parts, they must be submerged in a chemical solution of citric acid or nitric acid for a certain period of time and at a certain temperature. Passivation is a chemical treatment and not an electrolytic process, it does not depend on electrochemical reactions, unlike electropolishing or anodizing. And passivation is not a method to remove oxide scale from machined parts after heat-treating or welding. Also, passivating stainless steel does not change the color or surface appearance of the metal. This process is not necessary for items that will be painted or powder-coated.

You can passivate stainless steel to improve its corrosion resistance, but not all grades are suited for this process, and some parts may require additional cleaning operations beforehand.

General Rule of Thumb for Surface Finish on CNC Machining Parts:

• An as-machined finish is best for the machining parts with tight tolerances, where aesthetics is not the major concern.
• Bead blasting is best for machined parts with matter uniform finishes, when maintaining dimensional tolerances is not the key issue.
• Anodizing Type II is good for the titanium and aluminum parts which need aesthetically pleasing.
• Anodizing Type III is better for engineering applications, where very high wear resistance and surface hardness are required.
• Powder coating is good for the machined components which need high-impact strength or it can not be anodized.
• The passivation process is mostly for improving the corrosion resistance of stainless steel CNC machined parts.

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.