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Advantages and Limitations
of CNC Machining

Advantages and Limitations of CNC Machining


The advantages of Computer Numerical Control (CNC) machining make it the preferred manufacturing method for several industries, such as medical equipment, automobile and aerospace. By using this manufacturing method, you can have made-to-order parts that have a high level of precision.

Due to the accuracy of this process, delicate parts that must adhere to strict designs are among the best types of projects for CNC machines. However, with all these advantages, CNC machining has some limitations. When choosing part creation methods, learn as much as you can about CNC machining. When you understand how the process works, you can make an informed decision that balances your budgetary needs with the requirements of your project’s precision. Is CNC machining the option for you? Or do you need an alternative for your project?

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Advantages of Using CNC Machinery

As with any manufacturing method that has lasted for decades, CNC machining offers numerous advantages over other part creation methods. By using computer control, this technique allows you to get consistently precise and accurate results with various materials. Additionally, you do not need to create large orders – CNC machines can make a single prototype to give you a tangible example of your proposed project. These machines can also skip the prototype process and create an initial design in the machine to save time and material.

1. Constant Use With Minimal Maintenance

Manual machining can only occur as long as skilled workers are present. When the workers take a break, progress stops. However, CNC machines can operate 24 hours a day. Depending on the design of the project, the operator can program the computer and set the machine to create the required part. The machine then automates the part manufacturing, allowing the programmer to move to set up another machine. By freeing up operators, CNC machines require fewer workers and increase the production of a machine shop.

CNC machines also allow for rapid changes of production. If the operator needs to produce small orders of a variety of parts, all they need to do after completing one design is to change the program to set the next form. With this increased flexibility compared to other manufacturing methods, CNC machine shops can fulfill a variety of orders from large batches of the same parts to individual prototypes.

While CNC machines currently can operate 24 hours a day with minimal maintenance, the future promises even greater efficiency. With the Internet of Things (IoT) technology on the horizon, CNC machines can have sensors that track the amount of wear on parts. These sensors can then send a signal to the operator whenever the machine needs maintenance instead of waiting for the device to break down. IoT could also integrate CNC machines with other robots to automate removal and packing of completed products from the machines.

The current level of automation of CNC machining shows it to be a technology of the future when even more manufacturing methods embrace automation. Today’s CNC machining will only improve with future technological improvements and integration of IoT. With so many possibilities for improving efficiency, creating relationships with CNC machine shops today lets you take advantage of the current and future benefits of this manufacturing method.

2. Precision

The precision of a machine refers to how fine a tolerance it can produce. Not all CNC machines are capable of high precision. Discuss the precision capabilities of any CNC machine shop you work with. If you require tight tolerances for your projects, high precision machining could save lives. Typically, aerospace and defense industries frequently rely on high-precision, machined parts. Creating these parts to their specifications could save lives due to their potential installation in aircraft, automobiles or defense equipment.

3. Accuracy

How close the produced part matches the plans reflects the accuracy of the project. With human machinists, mistakes can create minor differences in the accuracy that could cause major problems. Applications that require parts to meet strict design guidelines may fail with even small deviations from the correct design. Automating production with CNC machining reduces accuracy problems, but the operator still has some control over the process.

The accuracy of CNC machining projects depends heavily on the operator. Because the user regulates the accuracy so much, finding a machine shop that puts extra effort into projects is critical to getting the results you want.

To improve accuracy, the user controls the tool calibration and operating environment when operating a CNC machine. Operators must also recognize when tools dull too much to create required results and if the machine requires service to restore accuracy.

The added accuracy of CNC machining makes repeatability possible. If you have a large order of multiple replicas of a part, with CNC machining, you can have those parts produced with improved accuracy compared to handmade components.

4. Versatility

With alternatives to CNC machining, such as 3D printing, you will encounter limitations in the types of materials you can choose from for your parts. However, CNC machining can occur with a variety of materials.

Talk to your machine shop about the materials they use. Not all places have the same breadth of choices for parts. At American Micro Industries, we can use the following materials with CNC machining:

  • Plastics
  • Phenolic materials
  • Rigid foam
  • Carving foam

When choosing a material for your applications, you’ll need to consider several factors, including heat tolerance, stress resistance, hardness, fastening and design tolerance.

5. Simulated Models or Prototypes

The old method of creating prototypes was to have a machinist create the design by hand. At the time, a manufactured prototype was the only way to examine the part in three dimensions. This time-consuming process did not guarantee accuracy in continued production.

Today, you can have a CNC machine create a single prototype if you require one. However, if you only want to view the part in three-dimensions, you can do that in the computer program used to send directions to the CNC machine.

Using a CNC machine gives you the option of creating a prototype. The computer lets you see the model from all sides before its production. If you choose, you can save material and time if you do not require a physical model.

Limitations of CNC Milling Machines

With as many advantages CNC machines have, they come with some limitations. Cost, size restrictions and operator error could impact your project plans. Considering these disadvantages and how they balance with the positive aspects of using CNC machines will give you the information you need to make the most informed decision for manufacturing your made-to-order parts.

1. Cost

One common complaint with CNC machining is the cost. Compared to other methods, CNC machining may cost more, but with that cost, you have the extra benefits of added accuracy and precision. However, the total cost is not always a set value.

There are some ways you can help reduce the cost of your CNC machining project through the attributes you request. Some things you can do to make your CNC machining project more budget-friendly include keeping the project simple, reducing the need for extra-thin walls on parts and increasing tolerances you request.

2. Size Limitations of CNC

One of the benefits of hand production is the ability of a machinist to move around a large part. For some CNC machining projects, the measurements of the part you have machined may have limitations.

The size of the enclosure and the travel distance of the tools both determine the size of part a shop can machine.

Travel distances typically have measurements along the x, y and z axes. However, some machines may operate on four or five axes, adding more dimensions that the machine can work on at one time. To find out about size limitations, ask the machine shop about their equipment capabilities.

Even if the part size fits into the working area, large components have other issues that may make CNC machining difficult to use. The size of the part may impact the accuracy of the tools working on it. Extra weight puts additional stress on the material, increasing the chances of distortion. To complete the manufacturing process, the machine may require special set up or operator training to ensure the tools have the correct starting positions relative to the design and part size.

Depending on what you need created, extra-large or very heavy parts may not work well with CNC machining. Since some facilities have the equipment necessary to manufacture large parts with CNC machines, though, always ask about any size limitations when requesting a quote or information about your order.

3. Operator Error

The operator has a significant level of control over the accuracy of a CNC machining project. While operator error can cause problems with the accuracy of the machined part or the program used to create it, you can do some things to avoid these issues.

First, find a machine shop with well-trained personnel who know how to get the greatest accuracy from the machine.

Secondly, the shop should verify the accuracy of products produced to ensure they match expectations. In fact, the manufacturing company you choose should work with you for the duration of the entire project. If you bring a part request, the company should help you with creating a CAD drawing, choosing materials, getting approval for the design, creating a prototype and manufacturing the entire order. These steps help to avoid possible errors caused by the operator.

Thirdly, look for a company that acknowledges and learns from its mistakes. While CNC machining has a lower chance for human error than manual part creation, mistakes can happen. The company should correct the error and change procedures based on what the experience taught its workers. When you find a company willing to correct mistakes and learn from any errors, you can develop a relationship with a shop that will continue to improve and provide you with better service.

Should You Use CNC Machining?

Do you need CNC machining for your project? The answer depends on what you need and how quickly you need it. Alternatives to CNC machining may take much longer to execute or have higher chances of errors.

Many projects that require the following tasks can often undergo CNC machining:

  • Milling
  • Drilling
  • Turning on a lathe

CNC machining works well in creating parts that require these operations, need high levels of precision and accuracy, and have moderate sizes.

Pros and Cons of CNC Machining

CNC machining offers some drawbacks such as cost, size limitations and the potential for operator error. However, with the many ways you can make decisions before and during the process of getting your project completed, you may mitigate the effects of some of these negative points on your order.

For many in the defense, aerospace, medical, marine, automotive and electrical industries, the precision, repeatability and accuracy of CNC machining is hard to find a match for. Companies in these industries and many others request made-to-order parts through a machine shop because they can get the components they need in a timely fashion.

By programming the computer and setting the device to run, employees at machine shops can work on orders 24 hours a day, reducing creation time. With a consistent program, the machine produces replicas that all match the level of accuracy and precision of the first part, regardless of the size of the order.

Finding balance when placing orders to a third-party company is always important. If you need the advantages of this manufacturing style and can work with the few disadvantages it has, choose CNC machining for your next made-to-order part project.

Just as you carefully choose the type of manufacturing for your parts, put the same care into finding a company to fulfill your order. Worker training and customer service should not be afterthoughts. Find a company that will work with you throughout the process. If they make a mistake, they should correct the error and ensure you feel confident in the integrity of the parts in your order. AMI is one such company that will do these tasks and more for your satisfaction.

Make AMI Your First Choice for CNC Machining

If you choose CNC machining for your project, trust us at AMI to complete the work. We pay exceptionally close attention to all the details of the parts we make. Every step of the process, from the initial plans to material selection to production, happens at the same location. We can even machine on non-metallic materials to produce a wider range of parts.

For more information about our CNC machining services or to request a quote for made-to-order parts, contact us at AMI.