What is CNC machining?

CNC stands for Computer Numerical Control, so CNC machining can be defined as a manufacturing process where a computational code controls the parameters of the process, including:

• Movement of the machine tool head.
• Movement of the part or feed.
• Rotational speed.
• Tool selection, for multi-tool heads.
• Amount of coolant if needed.

In simple words, it means using computational power to control and monitor all the necessary movements of a machine to manufacture parts out of raw material.

How does CNC machining work?

Basically, the CNC program provides commands that the machine can read and understand. These commands tell the motors of the machine when and how to move the corresponding components to achieve the desired results.

The first CNC machines used punch cards with the written code and had limited flexibility for the movement of the tool.

However, current CNC machines can be associated with CAD/CAM software (Computer Aided Design/Computer Aided Manufacturing). This means that the designer can create a 3D model of the part and then translate the parameters of the part into a CNC program by means of the CAM software.

This final program, created by the CAM software, is fed into the machine and the manufacturing process begins. The part is finished when the machine finishes running the program.

Another important aspect of the current and the most sophisticated CNC machines is the flexibility they have, since they can move in a range of 2.5 axes, 3 axes or 5 axes depending on the type of machine.

CNC machining for wood
While many might think that wood working is an art for only the most skilled carvers, the truth is that CNC machining for wood allows for a more efficient work. Even for the most complex designs.

With CNC machining for wood is possible to produce larger parts in a shorter time. It also allows the woodworker to keep the natural beauty and strength of the wood used intact, something difficult to achieve with other type of machines for processing wood.

Other benefits from using CNC machining for wood are:

• Complex shapes that are too difficult for manual work can be achieved easily.
• Higher precision and shorter production times.
• Higher efficiency and reduced material waste.
• Increased profitability.

CNC machining for medical industry
It is well known that the medical industry is a very demanding one with all the standards that must be met. This is the case of CNC machining for medical industry.

Fortunately, as it was mentioned above, the main benefits of CNC machining are high efficiency and high accuracy that leave almost no room for error.

This makes CNC machining for medical industry the best manufacturing option in the sector, being precision machining the chosen alternative to meet the tight tolerance requirements. Other common requirements include:

• Complex geometries that usually require 5-axis machines.
• Very high levels of cleanliness.
• Possibility of machining different special materials.
• Top-level surface finish.

Common applications of CNC machining for medical industry include:

• Implants and prosthetics.
• Surgical instruments.
• Electronic components for medical equipment.
• Micro medical devices which require micromachining.

CNC machining for casting
Casting is a manufacturing process that depends of good molds to obtain desired results. This means that it is necessary to select the best process to produce the molds.

CNC machining for casting in 5-axis machines reduces the chance of error due to having to move the casting between machining operations. This error reduction allows for the casting to meet the tightest of tolerances.

Another good application of CNC machining for casting is that most castings require a post processing to improve surface finish. CNC machining for casting allows to achieve the surface finish desired in a quick and efficient way.

Moreover, CNC machining can deal with the type of materials commonly used for castings such as aluminum, which can be a problem for other manufacturing problems.

CNC machining for aluminum

Being a lightweight metal, aluminum is the preferred material for many applications, being automotive and aerospace the top users. However, its use in some of these applications requires very complex shapes.

Moreover, thin parts may be required, which increases the possibility of deformation due to the low hardness and high thermal expansion of the material.

Here’s where CNC machining for aluminum becomes important. 5-axis CNC machining for aluminum provides benefits such as:

• It is simple to set up, which reduces lead times and improves the efficiency
• It allows to work with complex geometry thanks to the ability of avoiding collision with the tool holder while tilting the wok table or the cutting tool.
• It can use shorter tools that are more rigid, some with high spindle speed rates which is achieved by reducing the load on the cutting tool.
• The parts don’t have to go through different workstations, meaning that the errors are reduced, the accuracy is increased, and the quality is ensured.
• These machines can use other alternatives such as water jet cutting or laser cutting which eliminate the problems of working with very thin aluminum pieces.

CNC machining for aerospace parts

With the number of components needed to assemble an aircraft, and the complexity of such components, it is clear that the aerospace industry requires the highest precision and efficiency possible out of a manufacturing process.

Therefore, CNC machining for aerospace parts has grown in popularity, and it is now the go-to option for aerospace components manufacturing.

CNC machining for aerospace parts needs to deal with complex requirements such as:

• Working with thin walls.
• Limiting material deformation, for example, when working with aluminum and other lightweight materials.
• Working with curved and complex geometries.

On the other side, CNC machining is the best option for aerospace parts production as it provides the following benefits:

• It is a cost-effective process.
• It can provide high-quality results.
• It can work with custom designs.
• It provides high accuracy and precision engineering.
• It reduces and sometimes eliminates human error.
• It can produce complex geometries.

CNC machining for jewelry

In the past, jewels were only made by hand by fine artisans. However, it is not the case anymore, as more and more jewel producers are implementing methods to improve their efficiency and increase their profitability.

There are different ways CNC machining for jewelry help artisans and jewel producers in general. The most common benefits found are:

• Easily create master models for casting the jewels.
• Quickly create casting molds with high accuracy.
• Create fine end-use jewels when using sophisticated CNC machines.
• Quickly and accurately create custom engravings.
• Easily finishing the jewels with marble faceting and jewel polishing processes.

CNC machining tolerances

It is true that CNC machining has taken manufacturing accuracy to very high levels. However, as it happens with other manufacturing process, the dimensions of the end product are never perfect. And here is where CNC machining tolerances play an important role.

We have to remember that tolerances represent the maximum allowed variation for the same dimensions of two parts from the same series. They are usually set in the design phase.

There are different aspects to be considered when setting the tolerances required:

• Mating components.
• Type of materials.
• Manufacturing processes available.
• Tighter tolerances are usually more expensive to achieve.

Tolerances are usually classified according to how tight they are in the following groups:

• Fine tolerances.
• Medium tolerances.
• Coarse tolerances.
• Very coarse tolerances.

In general, the limits for each group are set based on International Standards, including ANSI B4.1, ANSI B4.2, ISO 286, ISO 1829, ISO 2768, EN 20286 and JIS B 0401.

For CNC machining tolerances, the standard limits are in the range of ± 0.005″ or 0.13mm. However, some very sophisticated services claim they can provide CNC machining tolerances as tight as ±0.0025mm.

Here are some standard CNC machining tolerances depending on the CNC process:

• Lathe — ±0.005″ (0.13mm)
• Router — ± 0.005″ (0.13mm)
• 3-Axis Milling — ± 0.005″ (0.13mm)
• 5-Axis Milling — ± 0.005″ (0.13mm)
• Engraving — ± 0.005″ (0.13mm)
• Flatness — ± 0.010″ (0.25mm)