What is the difference between CNC Turning and Centerless Grinding

Table of Contents

I. Introduction

Have you been debating whether to utilize CNC Turning or Centerless Grinding? They are both key methods in fashioning raw materials into precision components. But before we proceed, understanding both techniques are crucial as they have their merits and limitations. While CNC Turning creates cylindrical parts by rotating the material and the cutting machine discards the excesses to form the desired component, the centerless grinding method doesn’t require a spindle to do that. The workpiece is ground into form by being put between two wheels. Let us assist you grasp these two ways by providing all the information you want in this article. So, strap up and let’s go.

II. What exactly is CNC turning?

The CNC turning machine is an equipment comprising of a computerized numerical control (CNC) module that operates through computer programming. The CNC turning machine is a cutting-edge equipment that accurately shapes materials. An artisan turns a piece of wood on a lathe with elegance and flair, methodically molding it into a beautiful, consistent shape. 

However, if you replace the artisan with a computer-controlled machine that shapes your material into components, you will have an efficient, precise, and consistent means of creating tools. In essence, it is rotating a piece of material on a spindle as the cutting tools travel along it, eliminating undesired materials as it acquires shape. The cutting tool’s computer software determines the depth, movement, and speed of the material while cutting. 

Additionally, there are several types of CNC turning machines. This comprises both the horizontal and vertical lathes. The location of the material on each lathe is what distinguishes them. Vertical lathes are usually employed for more elaborate and larger items, despite the fact that horizontal lathes are the most commonly used for cutting cylindrical components.

Because CNC machining is a computer-controlled production method, its major benefit is its ability to work round the clock with minimal supervision. Another is the precision it offers for complex parts. It always ensures consistent results and increased productivity. Nonetheless, the cost of the machine is a major concern as it’s pretty expensive. Both acquisition and maintenance are not pocket friendly. Installation and setup also require skilled programming and expertise. 

Over and above that, it is widely applicable in several industries. Some of which are the medical, automotive, and aerospace industries. It is used for gears, shafts, and other intricate components like chamfers. The CNC turning machine’s high precision has allowed manufacturers to efficiently produce complex tools.

III. What exactly is centerless grinding?

The elimination of superfluous material from cylindrical workpieces is accomplished by centerless grinding. However, unlike other grinding procedures, centerless grinding does not require a spindle or chuck to hold the workpiece in place. As a result, centerless grinding makes use of a work rest blade and is supported by a regulating and grinding wheel. The job of the abrasive grinding wheel is to remove material from the workpiece. This revolutionary technique accounts for high precision and efficiency in grinding operations. Like the CNC turning machine, the centerless grinding machine has two distinct types. 

The through-feed and the in-feed centerless grinding machines. For the in-feed machine, the workpiece can either be fed into the in-feed grinding machine manually or automatically. It is super-efficient for grinding workpieces with irregular shapes. Moreover, only a certain amount of material can be removed at a time when using the in-feed grinding machine. However, with the through-feed centerless grinding machine, the workpiece is constantly, automatically fed through the grinder with an exit on the other side of the grinding machine. This type is well-suited for long, regular workpieces with symmetrical diameters.

Consequently, the centerless grinding machine provides faster grinding cycles, increasing productivity due to its fully automated operational system. In addition, it offers excellent precision and symmetry in the finished component. And because no spindle is needed, it eliminates setup time that may be time-consuming and has no risk of part deformity. Its limitations also include its inability to be used for grinding complex materials with intricate characteristics. Furthermore, it requires a careful setup of its grinding and regulating wheels responsible for consistent outputs, and it can be time-consuming. 

It is extensively used in the aerospace, industrial, medical, and automotive industries for grinding cylindrical rods, shafts, and tubes. Centerless grinding is also used for precision-ground bars, pins, and other brittle and heat-sensitive materials.

CNC Turning and Centerless Grinding

IV. The distinctions between CNC turning and centerless grinding.

For shaping and finishing materials into components, two processes are usually utilized. CNC turning and centerless grinding are two of them. These two methods efficiently produce precise and consistent results but are distinct in many aspects. Let’s explore and understand the differences in these processes. 

  • Materials: Firstly, CNC turning, and centerless grinding have dissimilar choices in the materials they work with. CNC turning works better with softer materials like aluminum, plastic, and brass. Centerless grinding, on the other hand, works better with steel and other harder materials. 
  • Tolerance and accuracy: Secondly, CNC turning offers higher precision in its dimensions when considering tolerance and accuracy. At the same time, centerless grinding in its capacity provides superb straightness and roundness in the components, especially in parts that require tight tolerance. 
  • Surface finish: Thirdly, surface finishing is another significant difference to consider. CNC turning surface finishing is completed when the material goes from a rough surface to a smooth surface. In contrast, Centerless grinding provides a surface finish that is extra smooth with a mirror-like look. Centerless grinding is a preferable solution for CNC turning in this regard. 
  • Speed and efficiency: Fourthly, we need to consider speed and efficiency. They both offer a certain level of speed, but the CNC turning has the capacity to produce higher volumes of parts in less time. Compared to centerless grinding, which requires more time to set up.
  • Cost and complexity: Though it can be more expensive when compared to other innovative methods like plastic injection methods that require mold manufacturing, its speed and efficiency makes CNC turning very cost-effective. Its ability to produce more parts in a shorter time, with less human intervention and error, helps to save costs. On the flip side, centerless grinding takes more time to set up and cannot produce the large quantity a CNC turning machine will produce in the same time frame. With complexity, CNC turning also takes the frontrunner as it only involves cutting and shaping, but centerless grinding involves more meticulous grinding and finishing.

V. Which Processes to Choose?

Selecting a suitable process is determined by certain factors. Some of these factors include the type of material, the size, and the required finishing expected from the output. Therefore, before a process is chosen, you might want to consider its working principles, to guide you in deciding on which approach is most suitable for your component production. However, there are specific scenarios where one process supersedes the other. We’ll also be putting this into consideration. But for starters let’s see how to determine an acceptable process. 

The machinability of a material is a critical property for its suitability in CNC machining, especially when accuracy of the shape and dimension is the goal. Hence, choosing materials like aluminum and brass, which are easily machinable is important to this end. Additionally, CNC turning produces a high-quality finish with precise tolerances. For instance, instead of using plastic molding which often involves a mold design in producing a batch of identical cylindrical parts for an automotive company, utilizing CNC turning can offer a better option.

Now let’s consider the centerless grinding process. This process deals more with materials that are hard to machine, such as tungsten carbide or hardened steel. The process involves grinding material to shape between a grinding wheel and a regulating wheel. It also produces components with tight tolerances and super smooth finishings. Therefore, choosing this process means you’re dealing with the materials mentioned and trying to produce a complex-shaped component. It is also definitive in achieving high precision and surface finishing. Centerless grinding may be your go-to option for component productions requiring extreme precision, such as pin or valve production used in the aerospace industry. 

However, in situations where there is complexity in materials used for production and a similar result is necessary, it is instructive to deploy the centerless grinding process. And, if your manufacturing comprises smaller pieces and softer materials, CNC turning is the ideal option.

CNC Turning and Centerless Grinding

VI. CNC Turning and Centerless Grinding Benefits

Despite their differences, CNC turning, and centerless grinding provide various advantages to a variety of industries, and we will look at some of these advantages. Even sight some practical examples of how advantageous they are to component production. 

The first and one of the most important advantages of CNC turning and centerless grinding is their ability to create highly accurate and consistent components with simple and complex shapes once setup is complete for both processes. 

These two approaches have made their way into a wide variety of applications. Therefore, with the benefits accompanying them, industries have found it valuable to deploy them. A good example is the automotive industry. CNC turning is used to produce engine components with tight tolerance. While the shafts, pins, and axles are produced using the centerless grinding process. Furthermore, due to the demand for accuracy and quality required in the medical field, prosthetics, surgical instruments, and implants are produced under these methods. 

Other advantages of these two systems include decreased labor, greater efficiency, and increased production. CNC turning can be automated, which means a faster operational system, higher quality, and lower margin for human error. 

Centerless grinding, on the other hand, avoids the use of collets and center holes, which increases setup time and productivity. On top of that, both of these processes are environmentally friendly because their waste is quite limited. 

Another advantage is in the aerospace factory where CNC turning is used to produce crucial aircraft engine parts. Production time was reduced by over thirty percent especially with rapid prototyping, while precision and quality were increased by ninety-nine percent. 

Likewise, the centerless grinding process helped a medical equipment manufacturer reduce waste and attain micron-level tolerances. Conclusively, these methods are revolutionary methods that are helping manufacturers of parts achieve higher quality via their versatility, efficiency, and precision in production.

CNC Turning and Centerless Grinding

VII. How to Optimize CNC Turning and Centerless Grinding

Efficiency has always been key in production, especially in manufacturing. But how do you optimize both of these methods in component production? 

Optimizing the CNC turning, and the centerless grinding may require some technical knowledge. Having said that, some production practices can likewise eliminate many problems encountered during production. 

One such is choosing the appropriate cutting tools for the different materials used during production. As it has been established that CNC turning works effectively with simpler and softer materials, any attempt to use a material other than what the machine can handle can damage the machine. The appropriate grinding tool should also be used for centerless grinding. Adopting this practice will ensure your components come out with the desired surface finish and meet the industry quality standards. 

Another noteworthy practice that can help optimize both methods is to regulate the machines’ speed time and feed time to a regular level. Some technicians may feel that increasing the speed and feed time will increase accuracy and limit production time, but the reverse is the case. If by any chance this happens, the machine could be damaged, and production jeopardized. Therefore, both processes require the machine to work at the specified speed and feed time but at the required rate. 

And lastly, a crucial practice that will optimize CNC turning and Centerless grinding is the regular inspection and maintenance of the machines. Assessing tool alignment, material setup, and continual modification of machine settings will assure top performance of CNC turning machines. And for centerless grinding, ensuring the proper setup of the grinding machine is essential. This includes alignment and balancing. Furthermore, regulating wheel speed and feed rate will improve efficiency and ensure quality finish surfaces. Maintenance reduces the risk of machine breakdowns, costly repairs, and production collapse. Remember, precision and quality are paramount to production.

VIII. Conclusion

In summary, CNC turning, and centerless grinding are two distinct methods of component production with crucial differences. While CNC turning uses the spindle to remove materials from the workpiece, centerless grinding does not require one but uses a grinding wheel and a regulating wheel. Choosing what process to use is determined by factors such as the type of material used, production volume, and desired outcome. In all, precision and quality are guaranteed. Ultimately, it is important to consult an expert to guide you in making an informed decision with your desired outcome in mind and to help answer any further questions you may have regarding your manufacturing needs.


Gary Liao

Gary Liao

Gary Liao is the Engineering Manager of TDL Company and has more than 20 years of mold design experience.

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