The Ultimate Guide to CNC Machining Metal
CNC machining metal is a process of parts manufacturing, involving CNC machining, milling, turning, drilling, EDM and wire cutting, as well as grinding, tapping and other processes. Create parts that meet design and engineering drawing specifications by removing excess material from metal and cutting to the desired shape, size and surface finish. With in-house state-of-the-art CNC machining equipment and experienced machinists, the AN-Prototype team is able to provide precision CNC metal machining services that can handle custom metal parts with tight tolerance requirements and complex geometry needs. Our CNC metal capabilities include prototyping and low-volume custom manufacturing, particularly CNC machining of aluminum and other metals such as copper, brass, magnesium, zinc, titanium, steel and stainless steel, as well as stocking expertise in the surface treatment of various metal parts Knowledge.
3-axis, 4-axis, 5-axis CNC milling is the use of cutting tool movement and rotation to remove excess material, suitable for creating any precision parts, and is also an ideal tool for making molds.
CNC turning removes material by contacting the tool with a high-speed rotating workpiece. It is usually used to manufacture round or tubular parts, and can also process parts with various threads, inner holes and other structures.
Sinker EDM and Wire EDM are the processing techniques that AN-Prototype is good at manufacturing precision metal parts. They use electrical energy to cut or remove excess material from a workpiece.
CNC drilling involves a rotating cutting tool machining a round hole in a stationary workpiece. This drilling is done to accommodate the screws and bolts that later hold the object together.
CNC tapping involves threading a tap into the base hole of the part to be drilled to create the necessary threads. It is a very efficient, efficient, economical and simple threading process.
Precision grinding involves the removal of excess material from a part by a rotating tool consisting of abrasive grains to create the precise surface and dimensions required by the part.
CNC Machining Metal
The most suitable process for machining metal is CNC
Precision CNC milling and turning makes it easy to create parts using a wide variety of metal materials. This gives design engineers a variety of options when creating prototypes and products.
How does CNC metal work?
CNC is an efficient automatic machine tool that can manufacture complex shape parts composed of mechanical equipment and numerical control system. The CNC machine tool is equipped with a tool storage device with automatic tool change function. Therefore, the workpiece can be processed in multiple processes after one clamping. The CNC system can control the machine tool to automatically change the tool, select the spindle speed, feed rate, etc. according to different metal processing operations, so that drilling, boring, milling, reaming, tapping and other processes can be completed continuously. CNC metal processing greatly reduces the auxiliary clamping time such as workpiece clamping, measurement and machine tool adjustment, and is suitable for machining parts with complex shapes, high precision and high repeatability requirements.
Metal Materials Suitable for CNC Machining
The rigidity of the CNC machine tools purchased by AN-Prototype from the United States and Japan ensures that almost any kind of metal material can be processed. From plain aluminum to different grades of steel and stainless steel, including super hard nickel steel alloys. CNC machining is also suitable for magnesium alloys and titanium alloys with the worst machinability parameters.
Let's take a look at the properties of common metals.
Aluminum 6061 is the most common material for CNC machining. The alloying elements of aluminum 6061 are magnesium, silicon and iron. Similar to other aluminum alloys, it has a good strength-to-weight ratio and is naturally resistant to corrosion. Aluminum 6061 has good machinability and CNC machinability, can be welded and anodized, and its wide availability means it is economical.
When heat treated to the T6 state, the yield strength of 6061 is much higher than that of 6061 after annealing, and the corresponding price is slightly higher. One of the disadvantages of 6061 is its relatively poor corrosion resistance when exposed to salt water or other chemicals. Aluminum 6061 is a material commonly used in automotive parts, bicycle frames, housings, etc.
Aluminum 7075 is a higher grade aluminum alloy that contains more zinc as the main alloying element. Aluminum 7075 is one of the strongest aluminum alloys with an excellent strength to weight ratio. Aluminum 7075 is somewhat more difficult to CNC machine than aluminum 6061 because of its strength, which means it tends to spring back to its original shape when cold formed. 7075 can also be anodized.
7075 usually hardens to T6 temper. However, this is a bad option for soldering and should be avoided in most cases. We typically use the 7075 T6 for quick injection molds. It is often used in automotive, aerospace frames, and other stressed parts that require lighter weight.
Similar to brass, copper is very efficient for CNC machining. By implication, it’s one of the most cost-effective ways to CNC machine metal. However, it is raw material prices that are driving copper costs higher. Nonetheless, copper is popular in applications that require good electrical and thermal conductivity. Industries such as automotive, consumer electronics, and healthcare find this CNC metal useful. Other properties include good corrosion resistance.AN-Prototype offers two copper alloys for CNC machining.
Brass, an alloy of copper and zinc, is a relatively soft metal that can usually be CNC machined without lubrication. Brass is also very machinable at room temperature, so it is often used in applications that don’t require a lot of strength. The type of brass largely depends on the percentage of zinc. As this percentage increases, there is a corresponding decrease in corrosion resistance. The brass is highly polished to look much like gold. That’s why it’s often found in ornamental applications. Brass is conductive but non-magnetic, and can be easily recycled.
Brass can be welded, but is most often joined by a low-temperature process such as brazing. Another property of brass is that it does not spark when struck with other metals, making it useful for parts in potentially explosive atmospheres. Notably, brass has natural antimicrobial and antimicrobial properties, and its medicinal uses are still being researched. Brass is commonly found in plumbing fittings, home improvement hardware, zippers, and musical instruments.
Stainless steel 303
Sulfur is contained in stainless steel 303 alloy. This sulfur helps make 303 the easiest stainless steel to machine, at the tradeoff of reduced corrosion resistance. Stainless steel 303 cannot be heat treated and is not suitable for welding. It does have excellent CNC machining capabilities, but care must be taken with speed/feeds and cutting tool sharpness. 303 is typically used for stainless steel nuts and bolts, fittings, shafts and gears, etc.
Stainless steel 304
Stainless steel 304 is an easy CNC machining material. One of its great advantages is that it can be soldered. It is also more resistant to corrosion in most normal (non-chemical) environments. For machinists, it should be done with very sharp CNC cutting tools and not contaminated by other metals. Stainless steel 304 is widely used in industry, construction and automotive and is an excellent material choice for the manufacture of kitchen fittings, cutlery, tanks and pipes.
Stainless steel 316
Stainless steel 316 is an austenitic stainless steel that contains molybdenum as an alloying element, giving it excellent corrosion resistance. Besides that, it is also highly formable and weldable. 316 is used in construction and marine fittings, industrial pipes and tanks, automotive trim and kitchen utensils. It is suitable for more extreme applications such as marine or chemical industries.
Carbon Steel 1045
Carbon Steel 1045 is a common grade of mild steel, i.e. not stainless steel. It is generally less expensive than stainless steel, but is stronger and tougher. Carbon steel 1045 is easily CNC machined and welded, and can be work hardened and heat treated to various hardnesses. 1045 steel is used more in many industrial applications to make nuts and bolts, gears, shafts, connecting rods and other mechanical parts that require higher toughness and strength than stainless steel. It is also used in construction, but is often given a finish to prevent rust if exposed to the environment.
Magnesium AZ31 contains aluminum and zinc as alloying elements and is one of the lightest metals. For the same strength, magnesium AZ31 is 35% lighter than aluminum, but it is also more expensive. CNC machining of magnesium is very difficult because it is very flammable, so liquid lubricants must be used in CNC machining. Magnesium can be anodized to improve its corrosion resistance. AZ31 magnesium is usually used in aircraft components that require light weight and high strength, and can also be used in camera housings.
Titanium is known for its strength, light weight, toughness, and corrosion resistance. And, it can be soldered, passivated and anodized for added protection and improved appearance. Titanium is a good conductor of heat and a poor conductor of electricity. CNC machining titanium is very difficult and only special tools can be used. Notably, titanium is generally biocompatible and has a very high melting point. Suitable for the most demanding aerospace, military, biomedical and industrial applications, it withstands high temperatures and corrosive acids very well. Titanium is also a common material in 3D printing.
Finishing Services For CNC Machining Parts
CNC machining is the process of removing excess from raw material to create a part of the desired shape. Visible tool marks are left on the surface of the machined part. To help improve the functionality and aesthetics of CNC machined parts, AN-Prototype supports one-stop surface treatment services for CNC machined parts. Including sandblasting, mirror polishing, painting, printing, laser etching, anodizing, electroplating, passivation, nickel plating, chrome plating, powder coating, etc.
Standard "As Machined" parts have a surface roughness of 3.2 µm, which cleanly removes sharp edges and deburrs parts. The surface roughness of smooth machining is Ra 1.6-0.8μm. The surface roughness of ultra-finishing machining is Ra 0.8-0.2μm.
Anodizing has the characteristics of corrosion resistance, wear resistance and insulation, and can maintain the performance of parts for a long time. Anodizing is often used on aluminum alloy parts to achieve an aesthetic effect. All Apple products are anodized.
Powder coating uses the phenomenon of corona discharge to add a thin layer of protective polymer to the surface of the part, ranging in thickness from about 50 μm to 150 μm. Creates a strong, wear-resistant finish for an even more wear-resistant layer.
Electroplating is a finishing process that deposits metal onto a conductive surface using many specific materials such as alloys, cadmium, chromium, composites, gold, nickel, rhodium, silver, tin, zinc and zinc nickel.
Mirror polishing starts with coarse sandpaper and gradually increases to 2000 grit, aiming to give the prototype a glossy finish or mirror look. Examples include transparent automotive light guides, headlights and rear taillights. The surface of the prototype is smooth enough.
Sand blasting is the impact of fine abrasive glass bead particles on the prototype surface under high pressure. The surface of the CNC prototype produces a grainy-like depression that creates a matte or eroded surface, resulting in a matte surface finish. Glass bead sizes from #80 to #220.
Laser etching is a process that alters the surface of a material to create a permanent mark with information or aesthetic value. Metallic materials most commonly used for laser etching include aluminum, stainless steel, and zinc, and other non-metallic materials include glass, polymers, and ceramics.
Passivation is a method to transform the metal surface into a state that is not easily oxidized, and to delay the corrosion rate of the metal. The material commonly used in the passivation process is stainless steel to further enhance its corrosion resistance.