The Impact of Surface Finishes on CNC Machined Parts: A Comparative Study

Introduction: CNC Machining and Surface Finishes

In the field of manufacturing, Computer Numerical Control (CNC) machining is a powerful tool used to create highly precise parts. It employs computerized controls and machine tools to remove layers from a material according to programmed instructions. One major aspect of CNC machined parts that can affect their utility, longevity, and overall performance is the type of surface finish applied. The impact of surface finishes on CNC machined parts cannot be overlooked as they play significant roles, notably in reducing friction, increasing resistance to wear or corrosion, enhancing conductivity, and improving appearance. For instance, a rough finish might offer additional grip strength where needed.

Overview of Surface Finishes

In the context of manufacturing and mechanical industries, surface finishes refer to the process applied to a component after machining with CNC machines. Designed as per requirements needed for a part to perform its intended function, they augment several aspects such as aesthetics, adhesion, solderability, resistance to corrosion, hardness, or wear resistance.

  • Powder Coating: This type shields against corrosion, enhances aesthetic appeal and assures consistency of appearance. Used in furniture, automobile industry, etc.
  • Anodizing: Mainly done on aluminum parts; increases wear resistance and helps in reducing friction when coupled with traditional lubricants. Common in automotive, aerospace, military sectors.
  • Chromate Plating: Imparts better protection against corrosion compared to paint alone; used often in automobiles and appliances.
  • Nickel Plating: Frequently employed on steel parts; providing an attractive shiny finish whilst enhancing resistance to rust, heat, and wear.
  • Metal Brushing: Bestows an aesthetically pleasing effect through creation of parallel lines; usually serves decorative purposes than functional ones.

The appropriate selection of surface finishes depends greatly on the designated application of the manufactured components ensuring functionality is not compromised. For instance, the high-grade precision required in aerospace or medical applications would necessitate specific suitable types of coatings over others.

Comparison between Different Types of Surface Finishes

When analyzing different types of surface finishes for CNC machined parts, it’s essential to consider their impact on appearance, functionality, and cost. Some common types of surface finishes include:

  • As machined finish
  • Anodizing
  • Black oxide coating
  • Electroplating
  • Passivation
  • Bead blasting
  • Powder coating
  • Brushing
  • Polishing
  • Painting

For professional CNC machining services, consider online CNC service.

Analysis: Impact of Surface Finishing on Dimensional Accuracy

The process of surface finishing in CNC machined parts plays a crucial role in maintaining dimensional accuracy. When we talk about precision levels, the effect of certain finishes can be momentous. For example, techniques such as sandblasting and bead blasting cause minor aberrations to the part’s surface, which may alter its final dimensions by few micrometers. Similarly, anodizing or powder coating, although renowned for their protective features, usually add a thin layer onto the surface leading to somewhat different final dimensions.

  • Anodizing typically adds up to 100 micrometers on each surface while powder coating adds between 60-250 micrometers per surface depending on the material consistency.
  • On the other hand, a smooth finish like polishing aids in achieving high precision due to minimal surface disruption, making it ideal for components requiring utmost accuracy.

In conclusion, careful consideration must be given while choosing a surface finish technique bearing in mind both aesthetic preferences and crucially, the impact on the component’s dimensional accuracy.

Understanding Resistance – Corrosion and Wear

The application of surface finishes on CNC Machined parts can significantly enhance their resistance against corrosion and wear, thereby extending their lifespan. When a part is exposed to certain environmental conditions such as humidity, heat or chemical substances, it may suffer from corrosive damage over time. Similarly, constant friction due to moving parts could result in abrasion-related deterioration. However, the use of tailored coatings not only protects the underlying material from such damaging factors but also improves its durability.

  • An illustrative example involves parts made from stainless steel, a material known for its resilience against rusting. While bare stainless steel already has some degree of natural corrosion resistance, applying an electroplated nickel finish can elevate this resistance further. Post-treatment, these elements were tested under accelerated aging conditions that simulate years of real world usage in a shorter period of time. The results demonstrated lesser signs of corrosion and greater physical stability in the coated parts compared to non-treated ones, affirming the effectiveness of using surface finishes to bolster part longevity.

Financial Implications of Different Finishes

Choosing the right surface finish for CNC machined parts at the design stage significantly influences cost-effectiveness and manufacturing efficiency. A well-considered selection can minimise post-processing steps, by limiting the need for additional polishing or treatments, leading to a reduction in production costs. For instance:

  • In the manufacture of moulds used in food-grade applications, opting for a high-gloss polished finish not only meets the required hygiene standards but also increases lifespan thus reducing long-term replacement expense.
  • For components designed for aerospace industry, selecting anodizing surface finish contributes to resistance against corrosion while enhancing paint adhesion which means savings in terms of maintenance expenses and prolong product’s service life.

This highlights the vital significance of considering the type of finish during the design phase as it directly impacts overall product value not just from aesthetic aspect but more importantly on cost-efficiency perspective.

Considerations for Choosing the Right Surface Finish

Deciding on the appropriate surface finish for CNC machined parts necessitates thorough consideration of numerous factors relating to machine components. Firstly, Dimensional Tolerance is fundamental in evaluating which finishing option suits best as different finishes can influence part size. Secondly, Material Properties play a crucial role since some processes are incompatible with certain materials because they can degrade their qualities or cause damage. The Function and Application of the component need to be considered too; high-wear areas may require tougher surface treatments whereas surfaces that must slide against each other typically need smoother finishes.

An example showing the outcome if an unsuitable or incompatible finish gets applied illuminates this issue further. If one uses plating process on a part meant for high thermal applications without considering its conductivity, it might lead to inefficient heat transfer hence causing overheating or failure of the machine component. This highlights the importance of careful selection of surface finishes based on various aspects including design specifications, functionality and material properties.

Learn more:
Want.Net Technical Team

Want.Net Technical Team

The Want.Net Technical Team has diverse members with extensive education and training in CNC machining. They prioritize precision, efficiency, and innovation to provide high-quality manufacturing solutions globally.

Push Your Order into Production Today!

Table of Contents


You’re one step from the  factory-direct price of part manufacturing services.