The Role of Surface Finish in CNC Machining

In modern manufacturing industry, CNC machining technology has become one of the core processes for producing complex parts by virtue of its high precision and flexibility. And in the process of CNC machining, surface finish is one of the important indicators of part quality. It not only affects the appearance of parts, but also has a profound impact on the performance, service life and reliability of parts. In this paper, we will discuss the role of surface finish in CNC machining, analyse its impact on the performance of parts, and provide practical strategies to optimize surface finish to help you stand out in Google search.

I. Definition and meaning of surface finish

Surface finish refers to the degree of smoothness of the surface of the workpiece, usually quantified by the surface roughness (Ra value). The smoother the surface, the smaller the Ra value; conversely, the rougher the surface, the larger the Ra value. Surface finish not only determines the aesthetics of a part, but also directly affects its functionality. For example:

Wear resistance: the higher the surface finish, the better the wear resistance of the part. A rough surface increases friction and accelerates wear.

Corrosion resistance: smooth surfaces are less likely to accumulate corrosive substances, thereby increasing the corrosion resistance of the part.

Stability of fit: For mechanical parts, surface finish directly affects the stability of the fit. For example, the rougher the surface in the gap fit, the gap will gradually increase, affecting the accuracy.

II.The impact of surface finish on the performance of CNC machined parts

1. The impact on the fatigue strength of parts

The rougher the surface of the part, the deeper the trough, the more obvious the stress concentration, the lower the fatigue strength. Under the action of alternating loads, the parts are more likely to fatigue damage.

Optimisation strategy:

Use high-precision tools and stable machining parameters (such as appropriate cutting speed and feed) to reduce surface defects.

Select the appropriate cutting fluid to reduce the cutting temperature and reduce thermal deformation.

2. Impact on the wear resistance of parts

The higher the surface finish, the better the wear resistance of the part. A rough surface increases friction and leads to rapid wear of the part.

Optimisation strategy:

Use finishing processes (such as grinding or polishing) to reduce surface roughness.

Use cutting fluids with lubrication to reduce friction between the tool and the workpiece.

3. Impact on the corrosion resistance of the part

Rough surfaces tend to accumulate corrosive substances, accelerating the corrosion process of parts. Smooth surfaces can effectively retard corrosion.

Optimisation strategy:

Select materials with excellent corrosion resistance.

Surface treatment (such as plating or coating) after processing to further improve corrosion resistance.

4. Impact on the stability of the fit of parts

Surface finish has a direct impact on the stability of the fit properties (clearance fit, interference fit) of the part. For example, rough surfaces can reduce the joint strength of an interference fit.

Optimisation strategy:

Strictly control the processing parameters to ensure that the surface roughness meets the design requirements.

Use high-precision testing equipment (such as coordinate measuring machine), real-time monitoring of surface finish.

III. Key factors affecting the surface finish of CNC machining

1. Tool selection and wear

The material, geometric parameters and wear state of the tool directly affect the surface finish. For example, the use of dull cutting tools can lead to an increase in surface scratches.

Solution:

Regularly check tool wear and replace them in time.

Select a tool material suitable for the material to be machined (e.g. carbide or diamond coated tools).

2. Role of cutting fluid

Cutting fluid plays an important role in lowering the cutting temperature, reducing friction and cleaning chips, thus improving surface finish.

Solution:

Choose the right type of cutting fluid for the material being machined (e.g. water-based, oil-based or synthetic).

Ensure that the cutting fluid flow and pressure are moderate, avoiding too much or too little.

3. Machining parameter settings

Parameters such as cutting speed, feed and depth of cut have a direct impact on surface finish. For example, too high a cutting speed can lead to higher cutting temperatures, which affects surface quality.

Solution:

Optimise the cutting parameters by experimenting to find the best combination.

Use CNC programming software to simulate the machining process and predict the surface finish.

4. Workpiece material properties

Material properties such as hardness, strength and thermal conductivity can affect the surface finish after machining. For example, high hardness materials are more difficult to achieve a high finish.

Solution:

Select a suitable machining process (e.g. high-speed milling or low-temperature cutting) according to the material characteristics.

For difficult-to-machine materials, preheating or cooling measures can be used to improve surface quality.

IV. How to optimise surface finish in CNC machining

Process optimisation:

Use multiple machining processes (roughing, semi-finishing, finishing) to gradually improve the surface finish.

Use hobbing machine and other high-precision equipment to ensure that the surface finish of the gear meets the design requirements.

Equipment upgrading:

Introduce high-precision CNC machine tools (e.g. 5-axis machining centre) to improve processing stability and surface quality.

Equipped with advanced testing equipment (such as roughness measuring instrument), real-time monitoring of surface finish.

Personnel training:

Improve the skill level of operators to ensure that the processing parameters are set reasonably.

Regularly organise technical exchanges to share experience in surface finish optimisation.

V. JLCCNC: Expert Service Provider of Surface Finish for CNC Machining

JLCCNC focuses on providing high-precision, high finish CNC machining services, and is committed to meeting the needs of various industries for complex parts:

Technical Strength:

Equipped with advanced 5-axis machining centre and CMM to ensure surface finish Ra≤0.4μm.

Professional team optimises machining parameters to reduce tool wear and cutting temperature and improve surface quality.

Service Advantage:

Provide full-process service from design to delivery to meet the needs of small batch customisation and mass production.

Rapid response, provide quotation within 24 hours and deliver the first sample within 72 hours.

Industry Applications:

Automotive, aerospace, medical equipment and other fields to help customers improve product quality and market competitiveness.

Contact JLCCNC today for professional and efficient CNC machining solutions!