At InstaVoxel, we pride ourselves on providing top-tier CNC machining services combined with a wide array of surface finishing options. Our goal is to deliver high-quality parts that meet your specific needs, whether for industrial applications, consumer products, or specialized components. Below, we introduce our CNC machining processes along with detailed insights into the various surface finishing methods we offer.
What is CNC Machining?
CNC (Computer Numerical Control) machining is a manufacturing process in which pre-programmed computer software dictates the movement of factory tools and machinery. This process can be used to control a range of complex machinery, from grinders and lathes to mills and routers. With CNC machining, we can achieve precision, repeatability, and efficiency, making it ideal for producing complex parts in both small and large quantities.
Surface Finishing Methods
Surface finishing is a crucial step in the manufacturing process that improves the appearance, performance, and durability of CNC machined parts. At InstaVoxel, we offer a variety of surface finishing methods to meet diverse requirements:
Anodizing is an electrochemical process that enhances the natural oxide layer on the surface of metals, particularly aluminum, to create a durable, corrosion-resistant, and aesthetically pleasing finish. During the anodizing process, the metal is immersed in an electrolytic solution, typically sulfuric acid, and an electric current is applied. This causes oxygen ions from the electrolyte to combine with the metal atoms at the surface, forming a thicker, more stable oxide layer than what naturally occurs.
This oxide layer is porous, allowing it to be dyed in a variety of colors before being sealed to enhance its wear and corrosion resistance. The benefits of anodizing include increased surface hardness, improved resistance to abrasion and corrosion, and better adhesion for paints and adhesives. Anodized aluminum is commonly used in a wide range of applications, including architectural components, consumer electronics, kitchenware, and automotive parts, due to its enhanced durability and decorative potential.
| Pros | Cons | Applications |
| Corrosion resistance
Enhanced aesthetic appeal Increased surface hardness |
Limited color choices Thickness control issues
Not suitable for all metals |
Aerospace components
Automotive parts Consumer electronics |
Hardcoat anodize, also known as hard anodizing or Type III anodizing, is a surface treatment process applied to aluminum and its alloys to enhance durability, corrosion resistance, and wear resistance. During the hardcoat anodizing process, the aluminum surface is immersed in an electrolyte solution and subjected to an electric current, resulting in the formation of a thick, dense oxide layer on the surface of the metal.
Unlike conventional anodizing processes, hardcoat anodizing produces a significantly thicker oxide layer, typically ranging from 25 to 150 microns (0.001 to 0.006 inches). This thicker layer provides increased hardness and wear resistance, making the treated aluminum suitable for applications where abrasion, friction, and exposure to harsh environments are common. Hardcoat anodize finds applications in a wide range of industries, including aerospace, automotive, defense, electronics, and marine. Common applications include aircraft components, automotive pistons, hydraulic cylinders, firearm parts, and architectural hardware.
| Pros | Cons | Applications |
| Extreme durability
Excellent wear resistance High corrosion resistance |
Can be more expensive
Limited to certain alloys Potential for dimensional changes |
Military equipment
Heavy-duty machinery parts |
Bead blasting is a surface finishing process that involves propelling small glass beads a high velocity onto a surface to clean, smooth, or finish it. This method uses compressed air to accelerate the glass beads, which then impact the surface and remove contaminants, paint, rust, or other residues. Bead blasting is commonly used to achieve a uniform, matte, or satin finish and is gentle enough to avoid damaging the underlying material, making it suitable for delicate surfaces like aluminum, stainless steel, etc. Moreover, it can help improve surface adhesion for coating and provide an aesthetically pleasing texture.
| Pros | Cons | Applications |
| Uniform finish
Removes surface impurities Non-abrasive to substrates |
Surface can be roughened
Not suitable for all materials |
Preparing surfaces for coating
Decorative finishes Medical devices |
Black oxide in CNC post-processing is a conversion coating applied to ferrous materials such as steel and iron to enhance their surface properties after machining. This chemical process involves immersing the metal parts in an alkaline aqueous solution containing compounds like sodium hydroxide, nitrates, and nitrites, typically at elevated temperatures. The reaction converts the surface of the metal into magnetite(Fe3O4), resulting in a black oxide layer.
In CNC machining, black oxide is often used for components in automotive, aerospace, firearms, tooling, and industrial machinery industries. It not only enhances the appearance and corrosion resistance of the parts but also helps maintain the precision and functionality of critical components. To further enhance corrosion resistance and achieve a smoother surface finish, the black oxide coating is often followed by a post-treatment of oil or wax.
| Pros | Cons | Applications |
| Cost-effective
Reduces light reflection |
Limited to ferrous metals
Minimal corrosion resistance Can wear off over time |
Tooling and fasteners
Automotive parts Firearms and military gear |
Chem-Film (Alodine)
Chem-film, also known as chromate conversion coating, is a chemical treatment used to protect aluminum and aluminum alloys from corrosion and to enhance the adhesion of subsequent coatings such as paints and primers. This process involves applying a solution containing chromates or dichromates to the aluminum surface, where it reacts with the metal to form a thin, protective, and corrosion-resistant film. The chromate conversion coating significantly improves the durability of aluminum parts by preventing corrosion, while also providing an excellent base for paints and primers, ensuring they adhere more effectively and last longer. Additionally, the coating maintains the electrical conductivity of the aluminum, making it suitable for electrical and electronic applications. Its minimal thickness means it does not alter the dimensions or mechanical properties of the treated parts, preserving their original specifications. Furthermore, any damage to the coating can be easily repaired with touch-up solutions, restoring its protective properties without the need for complete re-coating.
Chem-film is widely used in aerospace, automotive, electronics, and military industries, where both corrosion resistance and paint adhesion are critical.
| Pros | Cons | Applications |
| Good corrosion resistance
Enhances paint adhesion Electrically conductive |
Contains hexavalent chromium
Environmental concerns |
Aerospace and defense
Electronics Marine applications |
Electropolishing is an electrochemical process used to smooth, polish, and enhance the surface finish of metal parts, typically stainless steel, aluminum, and other alloys. In this process, the metal part is submerged in an electrolyte solution, usually composed of a mixture of acids, and connected to the positive terminal of a direct current power supply, making it the anode. A cathode is also immersed in the solution. When the current is applied, metal ions are dissolved from the surface of the part, preferentially removing high points and microscopic roughness, resulting in a smoother and more reflective surface.
Electropolishing is widely used in various industries, including medical device manufacturing, food processing, aerospace, automotive, and semiconductor fabrication, to achieve superior surface quality and performance in metal components.
| Pros | Cons | Applications |
| Removes surface defects
Improves corrosion resistance |
Can alter dimensions
Limited to certain metals More expensive than other methods |
Medical devices
Food processing Semiconductor |
Heat treatment is a controlled process used to alter the physical and sometimes chemical properties of a material, typically metals and alloys. The process involves heating the material to a specific temperature, holding it at that temperature for a predetermined period, and then cooling it at a controlled rate. The primary purposes of heat treatment are to increase the material’s hardness, strength, and toughness, relieve internal stresses, improve machinability, and enhance wear resistance. Common heat treatment processes include annealing, quenching, tempering, and case hardening, each tailored to achieve specific material properties and performance characteristics.
Heat treatment is widely applied across various industries to enhance the performance and durability of metal components. In the automotive industry, it is used to improve the strength and wear resistance of engine parts, gears, and suspension components. In aerospace, heat treatment ensures the structural integrity and reliability of critical components such as turbine blades, landing gear, and airframe structures. The tool and die industry relies on heat treatment to produce cutting tools and molds that can withstand high stresses and temperatures. Additionally, heat-treated components are essential in the construction, energy, and manufacturing sectors, where they contribute to the longevity and efficiency of machinery, pipelines, and structural elements.
| Pros | Cons | Applications |
| Increases hardness
Enhances wear resistance Improves strength |
Can cause distortion
Energy-intensive process Requires precise control |
Automotive parts
Tools and dies Aerospace components |
Electroless nickel plating, also referred to as autocatalytic nickel plating, is a chemical process used to deposit a layer of nickel-phosphorus or nickel-boron alloy onto various substrates without the need for an external electrical current. Unlike traditional electroplating methods, electroless nickel plating relies on a series of chemical reactions to facilitate the deposition of nickel onto the surface of the substrate. This process starts with meticulously cleaning and pre-treating the substrate to ensure optimal adhesion and uniformity of the plated layer. The substrate is then immersed in a specialized plating solution containing nickel ions, a reducing agent, and other additives. Through controlled chemical reactions, the nickel ions are catalytically reduced and deposited onto the substrate, forming a highly uniform and precisely controlled layer of electroless nickel coating.
In application, electroless nickel plating finds widespread use across a multitude of industries and applications where enhanced corrosion resistance, wear resistance, and dimensional stability are paramount. One of its primary applications is in the aerospace industry, where it is utilized to coat critical components such as aircraft landing gear, engine parts, and hydraulic systems to provide protection against corrosion and wear in harsh operating environments. Additionally, electroless nickel plating is extensively employed in the automotive sector for applications including fuel injection systems, transmission components, and piston rings, where it enhances durability and extends service life.
| Pros | Cons | Applications |
| Uniform coating thickness
Excellent corrosion resistance Hardens the surface |
Can be costly
Limited to nickel alloys Requires precise chemical control |
Oil and gas industry
Electronics Aerospace |
Passivation in CNC machining refers to a chemical process used to treat the surface of metal parts, particularly stainless steel, to enhance their corrosion resistance. During CNC machining, the surface of metal parts can be altered, leaving them susceptible to corrosion or rust. Passivation involves immersing the metal parts in a passivating acid solution, typically nitric acid or citric acid, which removes contaminants and forms a protective oxide layer on the surface. This oxide layer helps prevent further corrosion and improves the longevity of the parts. Passivation is often performed after machining processes to ensure the parts meet specific quality and durability standards, particularly in industries where corrosion resistance is critical, such as aerospace, medical, and automotive.
| Pros | Cons | Applications |
| Enhances corrosion resistance
Removes free iron Improves surface cleanliness |
Can be a lengthy process
Limited to stainless steel Requires precise handling |
Medical instruments
Food industry Chemical processing equipment |
Polishing in CNC machining is a finishing process that involves smoothing and refining the surface of a metal part to achieve a high-quality, reflective, or smooth finish. It typically follows machining operations such as milling, turning, or grinding. During polishing, abrasive materials such as sandpaper, abrasive pads, or polishing compounds are used to remove surface imperfections, scratches, and tool marks. The process may involve several stages of progressively finer abrasives to achieve the desired level of smoothness and shine. Polishing not only enhances the appearance of the part but also improves its functionality by reducing friction, preventing corrosion, and facilitating easier cleaning. It’s commonly used in industries where aesthetics and precision are important, such as jewelry, automotive, aerospace, and medical device manufacturing.
| Pros | Cons | Applications |
| Reduces friction
Increases cleanliness |
Labor-intensive
Can be expensive Requires specialized equipment |
Jewelry
Automotive parts Consumer electronics |
Zinc plating, also known as zinc electroplating or galvanizing, is a process used to apply a thin layer of zinc onto the surface of metal objects, typically steel or iron. This protective coating helps prevent corrosion and rusting of the underlying metal substrate. The process involves cleaning the metal object to remove contaminants, preparing the surface through treatments like etching or pickling, and immersing it in a plating bath containing a solution of zinc salts. When a current is passed through the bath, zinc ions are deposited onto the surface of the object, forming a thin layer of zinc. Post-treatment processes such as passivation or chromate conversion coating may be applied to further enhance corrosion resistance and appearance. Zinc plating is widely used in industries like automotive, construction, electronics, and appliances due to its excellent corrosion protection properties, relatively low cost, and ease of application. Additionally, it can serve as a base for additional coatings such as paint or powder coating for added protection and aesthetic appeal.
| Pros | Cons | Applications |
| Cost-effective corrosion resistance
Provides sacrificial protection |
Limited to ferrous metals
Not as durable as other coatings Potential for hydrogen embrittlement |
Fasteners and bolts
Automotive parts |
Silver plating involves coating an object with a thin layer of silver through an electroplating process. This technique is widely used for both aesthetic and practical purposes, such as improving electrical conductivity and providing a shiny, reflective surface. The process involves immersing the item in a solution containing silver ions, with a silver anode acting as the ion source. When an electric current is applied, the silver ions deposit onto the object’s surface, forming a thin silver layer. The thickness of this layer can vary from a few microns to several micrometers, depending on the application requirements. Silver plating offers a glossy finish, excellent electrical conductivity, and moderate corrosion resistance, making it ideal for use in jewelry, electronics, cutlery, and optical components.
Gold plating is a process where a thin layer of gold is electroplated onto the surface of another metal object. This process is typically used for decorative purposes or to provide enhanced conductivity in electronic components. Gold plating can be achieved through electroplating, wherein the object to be plated is immersed in a solution containing gold ions, while a gold anode is used as the source of the ions. When an electric current is applied, the gold ions are attracted to the surface of the object, forming a thin layer of gold. Gold plating can vary in thickness, ranging from microns to a few micrometers, depending on the desired application. It provides a luxurious appearance, corrosion resistance, and improved electrical conductivity, making it suitable for a wide range of applications including jewelry, electronics, automotive trim, and decorative objects.
| Pros | Cons | Applications |
| Excellent conductivity
High corrosion resistance Aesthetic appeal |
Expensive
Thin and can wear off Limited mechanical protection |
Electronics
Jewelry Connectors and contacts |
Powder coating is a dry finishing process used to apply a durable and protective layer of color to metal surfaces. Unlike conventional liquid paint, powder coating involves applying a free-flowing dry powder made of resin, pigment, and additives onto the metal surface. The powder is applied using an electrostatic spray gun or a fluidized bed method, where it adheres to the metal due to electrostatic attraction. After application, the coated metal object is cured in an oven, melting and fusing the powder particles into a continuous film. This curing process results in a uniform, smooth finish that is resistant to chipping, scratching, fading, and corrosion. Powder coating offers several advantages over liquid paint, including durability, environmental friendliness (lack of VOCs), and uniform coverage. It finds widespread use in industries such as automotive, appliances, furniture, architecture, and outdoor equipment.
| Pros | Cons | Applications |
| Durable and long-lasting
Environmentally friendly
|
Thick coatings can obscure details
Limited to non-heat sensitive parts Difficult to achieve thin coats |
Automotive parts
Household appliances Outdoor furniture |
Brushing is a surface treatment process used to create texture, remove surface imperfections, or achieve a specific aesthetic appearance on metal surfaces. During brushing, abrasive materials are applied to the surface of the metal using rotating brushes or abrasive pads. These abrasive materials can vary in coarseness depending on the desired finish. The brushing process typically involves moving the abrasive material across the metal surface in a consistent pattern, such as linear or circular motions, to create uniform texture or remove machining marks. The pressure and speed of the brushing operation can be adjusted to achieve different levels of surface roughness or smoothness. Brushing is commonly used in the finishing of stainless steel and other metals to achieve a satin or brushed finish, which is characterized by a soft, muted sheen with visible linear or circular grain patterns. This finish is popular in architectural applications, furniture manufacturing, and consumer products where a visually appealing, durable, and easy-to-maintain surface is desired.
| Pros | Cons | Applications |
| Aesthetic, satin finish
Removes surface imperfections Non-reflective surface |
Can create directional lines
May require additional finishing (Not protective on its own) |
Kitchen appliances
Decorative items Electronics cases |
Choosing the right surface finishing process depends on your specific project requirements. For enhanced corrosion resistance, anodizing or electroless nickel plating might be ideal. If aesthetic appeal is paramount, consider gold plating or polishing. For durability and environmental friendliness, powder coating is a great choice. At InstaVoxel, we are dedicated to helping you select the best finishing process to ensure your parts meet all necessary standards and perform excellently in their intended applications. Trust us with all your CNC machining and surface finishing needs for outstanding quality and service.
We hope this comprehensive guide helps you understand the surface finishing options available at InstaVoxel. Should you have any questions or need further assistance, please don’t hesitate to contact us. We’re here to support you every step of the way.
