CNC machining: Everything you need to know

Jack Lie CNC machining expert

Specialize in CNC Milling, CNC Turning, 3D Printing, Urethane Casting, and Sheet Metal Fabrication Services.

CNC machining is commonplace in the current manufacturing industry. If you have come to read this, it is likely that you already know what CNC machining is, but you may want to learn more about this manufacturing process. So, keep reading as we give you more details.

Is CNC machining hard

This may be a very subjective question, so you could get many different answers depending on who you are asking. However, there are some aspects to consider before getting into a conclusion on whether the answer should be a yes or a no. Let’s go through them.

First, it is important to define the level of CNC machining that you need, since different levels take different time and effort to achieve. When asked is CNC machining hard, some experts say this:

  • Basic level takes about a week if you have math and basic machining knowledge.
  • Intermediate level takes about a year.
  • Advanced level takes several years to master.

Another important aspect is the type of programming that you will use. There are two common approaches to CNC machining. These are:

  • Manual programming – More control but more time needed. It also requires G-Code knowledge.
  • Computer Aided Manufacturing (CAM) – the most common nowadays thanks to the most recent technological developments. It is very powerful since a computer program using a model offers you a very quick way to describe the paths for the tools and other parameters required for the most complex parts.

Finally, the type of machine will be definitive to conclude how hard CNC machining can be. It is not the same programming a simple mill work in 3 axes than one 5-axis work in a multifunctional machine.

Is CNC machining a good career

Again, many different answers can be given to the question is CNC machining a good career. Obviously, a successful CNC machinist will immediately give yes as an answer. But, what should you consider to determine if CNC machining is a good career for you?

To make an informed decision on whether CNC machining is a good career for you or not, you should consider the following:

  • You don’t really need a university or college degree to get started.
  • It offers long-term employability and a broad employment market.
  • It is a challenging yet rewarding work.
  • It is interesting work if you are into hands-on experiences with machines and manufacturing.
  • You will be turning innovative ideas into reality.
  • You will be producing parts for almost anything, from helicopters and ships to robotic applications and more.
  • The pay isn’t bad at all.

Also, consider the fact that technology keeps moving forward, and this means the demand for quick and high-quality production such as the one provided by CNC machining will continue to grow. So, we could say there’s a bright future ahead for the CNC machining career.

Is CNC machining dangerous

Every single industrial activity involves some kind of hazard. And CNC machining is not the exception.

The most common hazards associated to working in a CNC machine shop are:

  • Exposure to dust and smoke deriving from machining operations.
  • Exposure to moving parts.
  • Exposure to sharp objects such as sharp edges of the part before it is finished or the tools themselves.
  • Slipping and falling hazards which are related to the working environment like in any industrial activity.
  • Electrical shocks.
  • Fire hazard.

There might be other hazards that we are not mentioning here, but you shouldn’t be scared away by them. These hazards can be dealt with according to norms and health and safety standards which allow to reduce the risks and make CNC machining a safe operation.

In other words, the answer to is CNC machining dangerous is that it will depend on the shop and your commitment to safety.

Is CNC machining profitable

As we said before, the pay for CNC machinists isn’t bad at all. The average hour rate in the United States during the year 2020 was around $19.00, and it could reach up to $22.00 which means an annual salary in the range of $41,000 to $46,000.

Now, to speak about CNC profitability, we should also see the business side of it. Some people claim that successful CNC machining shops can expect a 10% to 15% of net profit.

Of course, remember that profitability depends on many other aspects, but we could be safe by saying that CNC machining can definitely be a very profitable sector.

Is CNC machining expensive

One more time, there are different perspectives to answer the question is CNC machining expensive.

From the client point of view, the more complex the requirements and the more custom the part required is, the more expensive it will be. Simple CNC turning operations usually cost around $35 per hour, while complex operations requiring multi-axis and multi-functional CNC machining can have an hourly cost in the range of $75 to $120.

Now, from the business side, while the initial cost of a CNC machine might be high, it is important that most CNC machines provide 5,000 hours in operation. This time is used to calculate the costs together with other aspects such as:

  • Tool wear and replacement costs.
  • Labor costs.
  • Material costs.

So, if the calculation is done properly, the return on investment (ROI) can be worthy, and it could be considered that CNC machining is not expensive.

Can I learn CNC machining online

Online learning has been around us for a while, and with the pandemic striking in 2020, it has become more of a trend to have online training programs available and people looking forward to take them.

While we mentioned that CNC machining is a hands-on activity, there are several high-quality CNC machining online programs that will teach you everything you need to know to select the type of machining required, set up the tools and of course to learn how to set the G-Code program and CAM programs to achieve your CNC machining goals.

Then, the answer to the question can I learn CNC machining online must be a resounding yes, you can.

What is CNC machining and what is it used for?

Many people think CNC machining is a specialized process for metal manufacturing. However, CNC machining is more than that, as it can make manufacturing more efficient for many different industries. Keep reading as we give you the details.

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)

CNC machining advantages and disadvantages

In general, CNC machining advantages overcome the disadvantages. However, here we share the most relevant of both groups.

CNC machining advantages:

  • Production can run 24/7.
  • Production is always consistent with high precision and repeatability.
  • Fewer and less skilled operators can do the job of many when compared to manual machining.
  • Possibility of upgrades by improving and updating the software used.
  • Complex geometries that could not be achieved with manual machining can be manufactured with high accuracy.
  • Tighter tolerances are possible, guaranteeing increased uniformity.

CNC machining disadvantages:

  • Higher initial investment than manual machining.
  • Manual skills loss.
  • Possibility of an increase in unemployment since fewer operators are needed.

CNC machining Delrin

Delrin is a high strength thermoplastic technically called Polyoxymethylene or just POM. It can also be found by the names of acetal, polyacetal, or polyformaldehyde. However, DuPont is the company with the great marketing job to make their brand Delrin the most popular one.

This material boasts properties that make it a favorite for different industries, including automotive, consumer electronics and household manufacturers. The most relevant properties are:

  • High strength and stiffness.
  • Great dimensional stability.
  • Superior hardness and toughness.
  • Excellent machinability.
  • High humidity and chemical resistance.
  • Great resistance to stress and fatigue.

Looking at these properties, especially the machinability which allows results with very tight tolerances, it is clear that CNC machining Delrin is a great idea for many applications.

However, here are some things to consider while CNC machining Delrin:

  • Consider the material properties since the design phase. Trying to keep wall thickness uniform is recommended together with the use of fillets and ribs if necessary.
  • Be careful with large parts since they may be prone to warping.
  • Delrin does not react well to temperatures above 121°C (250°F).
  • Air-based coolants are recommended over liquid ones. They help to remove chips more quickly.
  • Keep everything clean as Delrin is very susceptible to contamination. This is especially important for manufacturing healthcare products.
  • Use the sharpest tools, usually carbide is recommended as the best option.

CNC machining vs 3D printing

When comparing CNC machining vs. 3D printing, there are some differences to highlight. While both CNC machining and 3D printing are considered the leading manufacturing solutions for the current market, those differences must be carefully analyzed before selecting one over the other for your specific application.

Here are the main differences:

  • CNC machining is a subtractive process, meaning that it begins with a block of material that will be cut into the desired geometry. On the other hand, 3D printing is an additive process, as it begins with some kind of raw material in the form of filaments or powder which is added in layers to achieve the desired part.
  • CNC machining can be used with almost any type of material including different metals and alloys, wood, and thermoplastics like Delrin. However, 3D printing is more focused on working with different types of plastics although recent developments have made it possible to 3D print with other materials but at very high prices.
  • Another important difference is the part size that can be manufactured. Although 3D printing technologies are escalating in this aspect, it is CNC machining which still wins the battle for the biggest sizes.
  • When it comes to surface finish, CNC machining is the go-to option. With 3D printing you will usually obtain parts that require post processing, while CNC machining can achieve the smoothest surfaces possible.
  • Tolerances are an important aspect as we mentioned above, so while 3D printers can usually work with tight tolerances in ranges similar to the standard CNC machining processes, the most demanding requirements will require post machining.
  • When it comes to money, the initial investment of 3D printing is usually well below compared to CNC machining. This is good for a low production volume or prototyping only. However, if the production volume is increased CNC machining is a more cost-effective option.

CNC machining vs injection molding

As it happens with any other comparison, especially when it comes to manufacturing processes, comparing CNC machining vs injection molding requires considering the advantages and disadvantages each process offers. This will help assess the differences to decide which one corresponds better to the requirements of the application in hand.

Here are some of the most relevant considerations when comparing CNC machining vs injection molding:

  • Lead time and costs are higher when it comes to injection molding, as it requires the creation of a mold and its verification to guarantee dimensional tolerances. In contrast, CNC machining only requires the CAD/CAM file to be processed in order to have the code and set up the machine.
  • Following the previous point, while CNC machining works well when quick turnarounds are needed, injection molding is much more cost-effective for large volume production once it is set up, as it allows to produce thousands of parts in one single run.
  • Similar to 3D printing, injection molding is a manufacturing process dedicated to plastics (thermoplastics and thermoset resins) only. However, if other materials need to be processed, CNC machining is a better option.
  • As we started speaking about tolerances, this is another aspect to consider when comparing CNC machining vs injection molding. Injection molds usually achieve standard tolerances in the range of ±0.005″ (0.13mm), while CNC machining can achieve tighter tolerances when required to precision levels such as 0.001”.
  • When it comes to surface finish, injection molding presents a limitation. Part of the process requires the ejection of the part from the mold, which is achieved by means of ejector pins that can leave imperfections affecting the aesthetics. If the smoothest of surfaces is required, you are better off with CNC machining.

CNC machining vs manual machining

There has always been the debate to decide the winner when facing CNC machining vs manual machining. However, as we have mentioned before, it all comes down to the specific situation.

Obviously, CNC machining normally requires a higher initial investment than manual machining.  So, the most important thing to do when comparing CNC machining vs manual machining is deciding whether the advantages that CNC machining can offer are worth the extra money.

Here are the advantages of CNC machining vs manual machining:

  • CNC machining offers higher precision and repeatability, so the process can be more consistent for mass production.
  • CNC machining is an automated manufacturing process, which means the productivity and efficiency are increased.
  • CNC machines usually come with guards, and the most sophisticated ones perform the cutting work inside closed doors. This means that CNC machining is usually safer for operators than manual machining.
  • Due to the automated nature of the process, one single skilled operator can monitor several CNC machines running at the same time, which makes the process more cost-effective than manual machining which requires one operator per machine.

It seems clear that the winner of the CNC machining vs manual machining face-off should be the first one. However, there are situations that make manual machining a better or a necessary option.

For example, a CNC machining shop may have manual machines to cover emergency works, such as machining a spare part to repair a machine or tool in the shop. Doing this in the manual machine will prevent the shop from having to stop production of any CNC machine running at that exact moment.

CNC machining vs casting

Once again the comparison of CNC machining vs casting is one that depends on the application where one technology or the other is needed.

This case is very similar to the CNC machining vs injection molding, since casting and molding are very similar manufacturing processes. The main difference here is that casting does not need the material to be poured (injected) at very high pressures, it sometimes only relies on gravity to fill the mold with the material. Therefore, the molds do not require high resistance materials which are usually costly. This means that there is less time and money to spend when creating molds for casting.

With the characteristics of casting in mind, let’s set the differences found when comparing CNC machining vs casting:

  • CNC machining is more cost-effective for lower volumes (around 100 parts per run), while casting is a better option when producing thousands of the same part.
  • CNC machining usually results in higher precision and tighter tolerances. While casting can achieve very precise complex geometries, there is usually post-processing to be done to improve features such as the surface finish and to clean up undesired imperfections such as burrs or flashes. This is why casting parts usually end up in a machining process.
  • CNC machining usually generates more waste than casting. This is an important advantage for casting. However, recent developments in the technology have allowed CNC machining shops to set up very efficient recycling systems, so the investment might be worthy in case the other aspects take you to the CNC machining decision.

It is important to highlight that CNC machining and casting are used in combination for many applications. Usually, large volumes of the same part are cast and then post-processed in a CNC machine to obtain the desired results.

CNC machining vs CNC milling

When speaking about CNC machining vs CNC milling, it may be difficult to notice there are differences because milling is a type of machining process.

However, CNC machining covers the machines known as CNC machining centers whereas CNC milling is just a milling machine developed with the CNC feature. What this means is that CNC machining usually requires and can do more than CNC milling.

Here are some of the most relevant differences found when comparing CNC machining vs CNC milling:

  • CNC machining usually involves machines with tool magazines which allow them to perform more than one operation on the same part. CNC milling uses one single tool that must be manually changed by the operator in case of needing a different operation.
  • CNC milling does not require the so-called t-code, since this part of the program is the one in charge to control the tool magazine in CNC machining. This makes the program of CNC milling simpler.
  • Considering the tools need to be manually changed for different operations, CNC milling usually takes more time to complete a complex part. CNC machining is a process that never stops once the machine has been properly configured.

CNC machine vs laser cutter

Apart from the clear difference in the name, and the fact that a CNC machine uses a special tool to cut through the material while a laser cutter uses laser, obviously, there are other important differences to highlight when comparing a CNC machine vs laser cutter. Here are some:

  • A CNC machine cuts through the material when the cutting tool is in direct physical contact with it, while the laser cutter never enters in direct physical contact since it uses the laser beam to cut the material.
  • A CNC machine cuts by means of friction, while the laser cutter cuts by means of heat.
  • A CNC machine requires a lower initial investment than a laser cutter. Also, the laser cutter requires a higher power consumption, which makes the operation cost lower for a CNC machine vs laser cutter.
  • While a CNC machine is very precise and can work with tight tolerances, the non-friction cutting method of the laser cutter allows for increased control and higher precision, with some laser beams in the range of 0.1mm of radius.
  • Materials is an important difference when comparing a CNC machine vs laser cutter, since laser cutter can have limitations with some materials such as PVC, ABS, polypropylene foam, and others.

CNC mill vs router

Comparing a CNC mill vs router may seem useless at first, since they are basically designed to perform the same operations.

However, there are important differences between a CNC mill and a CNC router. Here we share some of them:

  • A CNC mill usually has more cutting power and can cut through hard metals, while a CNC router is usually used to cut softer materials such as wood and plastics.
  • A CNC mill can provide higher precision than a CNC router, which is why they are preferred for detailed parts.
  • A CNC router usually works at higher speeds than a CNC mill. This is an advantage if your application does not require toughness but rather quicker turnarounds.
  • CNC routers can cover bigger areas since their cutting tables are designed for the standard presentations of the softer materials. This could be an advantage if you want to work on parts covering big areas. However, it could be a disadvantage if you have reduced space to accommodate your machines.