How to Improve the Roughness of the Machined Parts?

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Surface finishing plays a critical role in deciding the performance of manufactured parts using CNC. A smooth surface finish improves the aesthetic appearance of the final product. This is especially important in industries such as automotive, aerospace, and medical, where the appearance of the parts plays a significant role in the end user’s perception of the product’s quality. Not only this, but a smooth surface finish improves the performance of the machined parts as well. In many cases, a smooth surface can reduce friction between moving parts, which can increase efficiency and reduce wear and tear on the parts. This will eventually reduce the operating cost in many industries.

KAIAO is a leading player providing high-precision CNC machining and surface finishing services. Our fast turnaround and reliance on high-quality materials make us the best CNC machining parts supplier.

This article will introduce how to measure and improve a workpiece’s surface roughness. Keep on reading to figure these questions out!


How to Measure the Surface Roughness of a Machined Part

To put it simply, surface roughness refers to the amount of irregularity in a surface compared to a perfectly flat surface. The most commonly used method to measure surface roughness is calculating average surface roughness, or Ra, which is typically expressed in microinches. This value is determined by calculating the mean deviation in height between different points on the surface and the flat reference line. However, it’s important to note that this measurement only considers 2D aspects of the surface and does not consider other factors such as waviness, defects, or errors. While these additional aspects can be measured through 3D evaluations, it’s not typically done when calculating surface roughness.

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Get a Smoother Surface of CNC Machined Parts

Getting a smoother CNC machined part is a challenging thing. You have to consider a whole range of steps. You can get smooth surfaces in two sections:

  1. During CNC Machining
  • Increase the SFM

Increasing the Surface Feet per minute speed (SFM) allows the material to remain in contact with the tooltip for a relatively shorter period. This will also reduce edge buildup on tooltips, being one of the primary reasons for low-quality surface finishing.

  • Reduce Your Feed Rate

Reducing the feed rate increases the insert’s stay in the machine and reduces the flank wear, which results in better surface finishing.

  • Increase the Top Rake Angle

Increasing the top rake angle can improve the surface finishing of CNC machining parts in several ways. The top rake angle refers to the angle between the top surface of the cutting tool and the workpiece surface. Increasing this angle makes the cutting edge more inclined, allowing it to slice through the material more smoothly and reducing the cutting forces and heat generation. Positive rake angles are usually associated with better surface finishing.

  • Use a chip breaker & clean the chip

Having a chip breaker will help you to break up chips into smaller pieces, making them easier to evacuate from the cutting zone. This can prevent chip clogging, thus reducing the risk of built-up edge and improving the surface finish. Similarly, chip breakers are also helpful for reducing cutting forces and heat generation during the process, which leads to better surface finishing.

  • Use a large nose radius

The nose radius impacts both the shape and direction of the chips. So, when you use a larger nose radius, you end up improving the surface finish. A larger nose radius also helps in reducing machine vibration.

  • Use a wiper with an insert

A good wiper insert will help you in wiping the surface of the machined parts in a better way, which will make the surface of your machined parts smooth.

  • Check Your Tool Holding and Workholding

A well-conditioned tool holder is always a good choice for better surface finishing. Old and torn-out tool holders result in machine vibration that is detrimental to surface finishing.


  1. Surface finishing

Grinding and polishing are yet other choices for better surface finishing. Polishing the surface is helpful in reducing any roughness on the surface, which results in a smooth surface.

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KAIAO CNC Machining & Surface Finishing Services

When you want to get the perfect machined parts, none of the above steps can be overlooked. Some manufacturers reduce the roughness of the parts while trying to increase the smoothness. Both smoothness and roughness have their own charm in the machined parts, which brings us to the need to achieve optimal smoothness and roughness at the same time. This is where KAIAO jumps in. KAIAO is a professional machine parts supplier that will save you all the time of going through these steps one by one. Choosing KAIAO has other benefits as well, including,

  • Fast delivery of premium quality CNC parts
  • Highly personalized CNC machining service
  • Reliance on modern-day technology to bring you the best results
  • Different material options for CNC machining
  • Detailed inspection report.


Wrapping Up

KAIAO has been dominating the rapid prototyping service for more than 27 years and the CNC service for 20 years. We have introduced new trends in rapid prototyping and precision machining parts, which has helped us in becoming a reliable brand. We have worked with numerous top-notch industries globally that have helped us in gaining tremendous experience along the way.