What are the surface treatments for robot CNC machining parts? What is its function?

The surface treatment of robot CNC machining parts commonly includes five categories: anodizing, electroless nickel plating, passivation, PVD coating, and laser cladding. As the core process of surface treatment for robot parts, their role goes far beyond rust prevention and aesthetics - wear resistance, assembly accuracy, electromagnetic compatibility, and service life are all directly linked to the choice of surface treatment.

This article will help you break down the core characteristics, applicable scenarios, and precautions of each process one by one, and help you choose the most suitable surface treatment solution for robot parts.

1、 Anodizing: The Preferred Process for Aluminum Alloy Robot Parts

In robot parts processing, aluminum alloy (6 series/7 series) is used the most, and anodizing is the most common surface treatment method. It generates an aluminum oxide film layer on the surface through electrochemistry, which has both corrosion resistance and decorative effects.

Process characteristics:

1、Ordinary anodized film thickness is 5-15 μ m, while hard anodized film can reach 50-100 μ m

2、Film hardness: Ordinary oxidation has lower hardness, and the hard anode can reach 300-500HV. The wear resistance is 10-20 times higher than that of untreated aluminum alloy

3、Good corrosion resistance, can be made in various colors such as black, natural color, gold, etc

Issues to be noted:

Anodizing will increase the size, and if compensation is not reserved for precision fitting holes, they may not fit in after processing. In addition, ordinary anodes are insulated. If the parts require conductivity or electromagnetic shielding, chemical conductive oxidation (film thickness<1 μ m) must be selected.

Applicable scenarios: Robot structural components, joint shells, connecting rods and other aluminum alloy parts.

2、 Chemical nickel plating: a uniform coating scheme for complex structural parts

In the surface treatment of robot parts, chemical nickel plating is a commonly used wear-resistant and rust proof treatment method for carbon steel, copper parts, or stainless steel parts that require high hardness.

Process advantage: Excellent coating uniformity.

Traditional electroplating has the problem of "power line distribution", with thick coating at corners and inability to coat the inner walls of deep holes. Chemical nickel plating is deposited through a chemical reduction reaction, and as long as the solution can come into contact, the film thickness is basically the same. This is crucial for complex robot joint components.

Key points of the process:

The surface hardness can reach HV1000 or above after heat treatment, with a film thickness of usually 10-20 μ m, and the wear resistance is about 1.2-1.5 times that of ordinary electroplated chromium plating

1、The pin shafts, micro gears, and high-frequency reciprocating joint parts of humanoid robots can be chemically plated with nickel to provide good wear resistance and rust prevention protection

2、Before plating, it is necessary to confirm the surface roughness of the substrate, as excessive roughness can affect the adhesion of the coating

3、If there are blind holes or deep cavities in the parts, it is necessary to confirm that the medicine can flow fully, and if necessary, design process holes

Applicable scenarios: transmission shafts, gears, complex shaped joint parts, steel/copper parts that require wear and rust resistance.

3、 Stainless steel passivation: zero dimensional increment rust prevention treatment

For precision robot parts made of stainless steel (303, 304, 316, etc.), passivation is the preferred rust prevention treatment method if extremely high dimensional accuracy is required. The precision machining of these robots requires particularly strict surface treatment - passivation does not increase any size, but can provide reliable rust protection.

Process feature: No increase in size.

The principle of passivation is to remove surface free iron through acid washing and enhance the chromium oxide film of the material itself. It is not a coating, so it will not change the geometric dimensions of the part - which is very important for precision parts with strict tolerance requirements.

limitations:

Passivation cannot conceal the knife marks or scratches left by the previous CNC machining, and has certain requirements for the surface quality of the machining. If the appearance requirements are high, it is necessary to cooperate with the polishing process.

Key points of the process:

1、Micro pin shafts, sensor mounting bases, and other ultra precision matching parts for fingertip joints are recommended to be passivated

2、If you need to balance appearance and rust prevention, a combination of passivation and polishing process can be used

3、After passivation, it must be thoroughly cleaned to avoid secondary corrosion caused by acid residue

Applicable scenarios: stainless steel precision pin shafts, sensor seats, medical robot parts.

4、 PVD coating: the preferred solution for high-end precision parts

PVD coating (physical vapor deposition) is a commonly used high-end surface strengthening method in precision machining of robot parts. It deposits a high hardness thin film on the surface of the part through vacuum coating, such as titanium nitride (TiN), diamond-like carbon (DLC), etc.

1、Process features: Ultra thin and super hard, almost without affecting the size.

2、Film thickness: usually 1-5 μ m, with minimal impact on the size of precision fittings

3、Hardness: DLC can reach HV2000 or above, TiN is about HV2300

4、Friction coefficient: extremely low, with self-lubricating effect

Key points of the process:

1、PVD coating requires extremely high surface smoothness of the substrate, and the surface quality of the previous CNC machining directly affects the coating effect

2、High equipment costs and expensive processing fees, usually only used in critical areas such as high-frequency motion joints and precision bearings

3、Batch hours, it is recommended to share the cost with other parts in the furnace

4、Applicable scenarios: high-end components such as precision bearings, high-speed gears, and dexterous hand joints for humanoid robots.

5、 Laser cladding: strengthening process for heavy-duty high wear parts

Laser cladding is a strengthening process in robot CNC machining of parts to cope with extreme wear scenarios. It uses high-energy laser beams to fuse a layer of high hardness alloy on the surface of the part, forming metallurgical bonding with the substrate.

Process features: extremely strong wear resistance+repairable old parts.

Coating hardness: Cobalt based or nickel based alloys can reach 55-62HRC

Bonding strength: metallurgical bonding, will not peel off like electroplating

Repackable worn parts, extending service life by 3-8 times

Key points of the process:

Large equipment investment, high processing costs, and complex processes

Usually only used in critical parts with heavy loads and high wear (such as heavy-duty joints and large gears in industrial robots)

If it is a new part design, a fusion allowance can be reserved in areas prone to wear and tear

When repairing old parts, it is necessary to first evaluate whether the substrate still has sufficient strength

Applicable scenarios: Heavy duty robot joints, large gears, high wear transmission parts.

6、 How to choose based on a clear chart

7、 Practical case: How Huiwen helps customers choose processes

At Shenzhen Huiwen Intelligent Manufacturing, CNC machining and surface treatment are delivered in an integrated manner. During the drawing review stage, engineers will confirm with customers whether this hole is an interference fit or a clearance fit? Should the compensation amount for surface treatment be included? What level of wear resistance is required for moving parts?

Taking an aluminum alloy joint shell as an example:

Main structure: ordinary anodized (corrosion-resistant+aesthetically pleasing)

Bearing hole: Reserve anode compensation amount to ensure accurate size after processing

Grounding position: Use chemical conductive oxidation to ensure electromagnetic compatibility

This integrated thinking of "processing+post-processing" can avoid many overturning situations where "processing is not a problem but cannot be installed after processing".

Huiwen Intelligent Manufacturing has a factory area of 20000 square meters, equipped with 370+processing equipment and multiple five axis machining centers, covering the entire delivery process from CNC machining to surface treatment. It has the ability to provide full chain services for design, manufacturing, and assembly, and can meet the full stage of OEM services for humanoid robots, mechanical dogs, flexible robotic arms, bionic robots, medical robots, and other parts from single piece sampling to medium to large-scale production.

In terms of robots, Huiwen Intelligent Manufacturing relies on its own full industry chain service capabilities and innovatively adopts a combination of "new materials+new molds+precision machining" technology to meet the trend of mass production demand in the robot track. In addition, we can provide comprehensive OEM services for mechanical dogs, flexible robotic arms, bionic robots, medical robots, and more.

At present, Huiwen Zhizao has passed ISO9001 and IATF16949 quality management system certification. It is a national high-tech enterprise and a specialized and innovative enterprise. It has served many listed companies and industry-leading companies, such as Lenovo, Xinsong, Xiaomi Ecological Chain, Beijing Institute of Technology and other customers, with reliable and guaranteed quality.

Frequently Asked Questions

Q: What is the most commonly used surface treatment for robot CNC machining parts?

A: Aluminum alloy parts are most commonly anodized, steel parts are commonly chemically nickel plated, and stainless steel parts are commonly passivated. The specific choice depends on the functionality, fitting accuracy, and usage environment of the parts.

Q: Will surface treatment affect the accuracy of parts?

A: I will. Anodizing and electroless nickel plating both increase the film thickness (ranging from 5-50 μ m), and if compensation is not reserved, precision fittings may not be able to be installed. The passivation and PVD film thickness are extremely thin, which has little impact on the accuracy of precision machining of robot parts.

Q: Can the processing and surface treatment be done together by one factory?

A: Suggest integrating delivery as much as possible. Separating processing and surface treatment can easily lead to responsibility shifting and tolerance alignment issues. The full process service of robot CNC machining parts and surface treatment provided by Huiwen Zhizao takes into account post-processing compensation from the drawing review stage to avoid assembly problems.

If you need a robot CNC machining part solution or quotation, please feel free to provide drawing consultation.