CNC machining or “Computer Numerical Control” is a process used for automated manufacturing. In this process, pre-programmed computer software controls the movement of the factory’s machinery and tools. CNC machining can control a broad spectrum of complex machinery, including grinders, lathes, mills, and routers.
CNC Machining Process: An Overview
As you know by now - CNC machining uses computerized controls to manipulate and operate cutting tools and machines to shape up your stock material into custom designs and parts. Although CNC machining offers various operations and capabilities, the fundamental process remains mostly the same for all.
Basic CNC machining involves the following stages.
CAD Model Design
The CNC machining process starts with creating a 3D solid part or 2D vector. You can have an in-house CAD design team or hire a CAD/CAM design service from a professional company.
CAD software allows manufacturers and designers to produce a model of their part with necessary technical specifications, i.e., geometrics, dimensions, etc. Once you have your CAD design, the design can convert it into a CNC-compatible file format, i.e., IGES or STEP.
For conversion of the file into a CNC compatible format, a designer runs the CAD design file through a Computer-Aided Manufacturing Software (CAM). This software extracts the design’s geometry and generates a digital programming code that can be used to control the CNC machine for the production of the desired designed part.
CNC Machines use several programming languages such as M-code and G-code, latter being the most well-known CNC programming language.
The CNC machine operator first prepares it for operation. This includes affixing a blank material piece on the machinery spindles in the machine or similar work-holding devices. Then he attaches the required tools such as end mills, drill bits to the machine’s component.
Once the CNC machine is ready for operation, the operator runs the CNC program. A computer runs the program and controls the tools and CNC machines according to the metrics and specifications in the program.
You can perform CNC processes in-house or invest in hiring a company to obtain and maintain your processes by using their own CNC equipment. You can also out-source dedicated CNC machining services.
Five CNC Machining Operations
Here are five types of CNC machining
CNC Drilling employs multiple point drill-bits in order to create cylindrical holes in a workpiece. In this process, a CNC machine typically feeds the rotating drill-bit perpendicularly on a plane workpiece surface, creating vertically aligned holes. The diameter of these holes is equal to the drill bits’ diameter.
However, you can use specialized work holding devices and machine configurations to perform angular drilling operations. Operations capabilities of CNC drilling include countersinking, counter-boring, tapping, and reaming.
CNC milling is a process involving the rotation of multiple-point cutting tools to remove any material from a workpiece. In the CNC milling process, a CNC machine feeds a blank workpiece or material to the cutting tools. The machine feeds the workpiece in the same direction as the rotation of the cutting tool.
One of the CNC milling operation capabilities is face milling that involves cutting shallow, flat-bottomed, and flat surfaces into a blank workpiece. The other capability is cutting deep cavities such as threads and slots into the blank workpiece.
Milling operations further include
- Chamfer milling
- Drilling, tapping, boring, etc
- End Milling
- Face Milling
The Grinding CNC machine removes material using a rotating grinding wheel. The aim is to give a metal part a finish with high precision. The achievable results for surface quality are quite high. Hence, it is better to use CNC grinding for the finishing process rather than as an initial process of creating a part from raw material.
It is somewhat similar to the CNC machining process as CNC routing also uses a rotating piece as a cutting head. The main difference between the two is the material used for cutting. Routing is perfect for cutting softer and non-metallic materials.
The reason is the lesser output power of a routing machine. However, CNC routers are quicker; therefore, they can produce parts in quick succession.
CNC turning involves a single-point cutting tool to design or remove material from a workpiece while it is rotating. In this process, a CNC machine typically a turning machine or a lathe operates a cutting tool along the surface of the workpiece in linear motion. The workpiece continues to rotate during the cutting process.
The cutting tool removes material around the work piece’s circumference until it accomplishes the desired diameter. CNC turning is effective for the production of cylindrical parts with internal and external features such as tapers, slots, and threads.
CNC turning has operation capabilities such as facing, boring, thread cutting, and grooving.
What are the Different Types of CNC Machines?
Numerical control machines first appeared in the 1940s. Since then, these machines have evolved from analog to digital computing leading to the rise of the phenomenon we call CNC machining. Some of the most common CNC machines are hole-punching ultrasonic welding and laser cutting. However, the main CNC machines used presently are:
Lathes machines use indexable tools to cut pieces in a circular direction. CNC machining in lathes allows the tools to carry out the cutting task with precision. CNC lathes are capable of producing intricate designs that will otherwise be impossible to achieve via manual machines.
You use a unique proprietary code or G-code to direct CNC lathes. However, typical CNC lathes involve two axes, i.e., X and Z.
Electric Discharge Machines
Electric-discharge machining or EDM is also known as “die sinking and spark” machining. This process molds pieces into desired shapes via electrical sparks. In EDM, current discharge occurs between two electrodes and removes sections of the given piece.
The electric field grows more intense as the space between the electrodes decreases. This enables the current to pass between two electrodes allowing it to cut off the workpiece into the desired shape.
There are two subtypes of EDM.
This process uses dielectric fluid to soak the workpiece and electrodes to achieve the desired formation.
This process uses spark erosion to remove specific portions from an electronically conductive material.
This process can operate on programs consisting of letter and numbers-based prompts to guide tools across various distances. The programming used for mill machines can be your own unique language developed by your manufacturing team. However, you can also use G-code.
Basic CNC mills have a three-axis system, i.e., X, Y, and Z. However, newer iterations are capable of accommodating three additional axes.
Laser Cutting CNC Machines
The name says it all; this type of CNC machine uses lasers for cutting. These machines are suitable for sheet cutting as they provide better surface finishes. Additionally, they are ideal for achieving intricate designs; all you need to do is install the program and let the machine take care of the rest.
These machines are expensive, and it can take some time to have them fixed in case of any damage.
CNC Router Machine
Router machines work similarly to lathe and milling machines. The only difference is that all the carpenter work is carried out manually, such as interior or exterior decorations, door carvings, wood panels, wooden frames, signboards, musical instruments, etc.
You can sketch the design on the surface and then let the machine do the rest. These machines provide an immaculate finish.
5-Axis CNC Machine
As the name suggests, the machine has 5-axis to cut in 5 different directions. A 5-axis CNC machine is ideal for making sculptures.
3-D CNC machines are highly efficient at layer by layer printing on metal materials. These machines are ideal for printing models of building and construction projects.
CAD and CAM software produce the drawing and designs, and the 3-D CNC printer works on creating a physical model as per instructions.
Benefits of CNC Machining
CNC machining comes with many advantages, and some of them are:
It offers autonomous machining, along with a digital template of CNC machining. CNC machining literally eliminates human error and helps achieve the desired results with accuracy within 1/1000th.
Once you have entered the specifications and desired design parameters into a CNC machine, it will consistently afford flexible scalability and execute vast quantities.
When you use CNC machines in tandem with advanced software, they create results that are impossible to replicate via manual machines. These CNC machines are capable of producing any shape, size, or texture you may desire.
Lower Labor Cost
CNC machining does not require a lot of workforce to execute your production tasks. A single skilled operator can efficiently run several autonomous CNC machines. You will need one programmer to load these machines with desired protocols and designs.
It gives you a competitive edge in the market over other manufacturers as you save on the workforce. You can pass this advantage on to the customers by offering competitive prices.
The main advantage of using CNC machining over conventional methods is the consistent design output. A CNC machine will continuously produce a uniform product without error.
Fewer Glitches and Hiccups
Manual machining is susceptible to various elements, such as human aspects and financial headaches when you are short-staffed. With CNC machining, you do not have to worry about if people are off sick, on vacations, or other human errors.
Apart from continuous production and consistent designs, CNC machining offers a safer working environment. The CNC machines’ operators can maintain distance from sharp tools and avoid any direct contact.
Once you load a design into your CNC machining software and produce a perfect prototype, you can save it into the software and retrieve it in the future to create the same object again. It saves you time and effort to input the code every time.
CNC machines generally do not need much maintenance. Mostly you need to change the cutting implements at regular intervals and perform light cleaning.
You can use CNC machining to create virtually any design or component you want. Some of the CNC machines’ models include special accessories and features to simplify and expedite your production. These include automated tool changers and touch screens.
Applications of CNC Machining
Virtually it seems as if CNC machining does not have any limitations when it comes to the applications. You can use them on a wide range of raw materials, including metal, foam, plastic, wood, and other composites.
From 3-D cutting to complex 5-axis milling to producing complex designs with precision and low-volume prototyping, CNC machines can do it all. Therefore, these machines are the top choices used by various industries, such as:
- Food and Beverages
- Industrial machinery and spare parts
- Product designs etc.
In short, CNC machines have proven their metal as a useful and reliable means of producing parts with precision. However, sometimes quality comes at a higher price in comparison to other methods for fabrication.
That is why the best way is to turn to a company that offers CNC machining services. It saves you from the hassle of investment in CNC machining, plus they have all the expertise necessary to produce top-notch results.
Materials for CNC Machining
There is a wide variety of materials that you can use in CNC machining. Some of the common ones are as follows.
Brass is a metal commonly used for fittings and electronic hardware. It is a heavy metal with a low cost and a higher strength point. However, the cost is the biggest factor for its use.
It is another affordable CNC machining material and offers numerous options to suit various tasks. For example, 1018 steel offers low cost with a higher formability factor. However, it is ideal for items such as rivets because it has poor machining characteristics.
Aluminum is one of the most popular materials due to its cost-effective and plentiful aspects. Most high-tech industries use aluminum to build their machines because it is light in weight but offers higher strength.
CNC machines often contain parts made from Beryllium copper. You can generally find them in fiber optic and computer components, or electrical contacts and connector and precision measurement devices.
Telecommunications and aerospace industries frequently use beryllium copper as heating increases its durability and strength.
These are excellent for electrical conductivity; therefore, a popular choice for CNC machining processes to manufacture electrical contacts. CA145 and TeCu are copper alloys offering low cost that is ideal for custom machining jobs.
There are various forms of plastics used as CNC machining material, these are:
PVC is corrosion and chemical resistant plastic. It also offers excellent resistance against flames and comes at a low cost. PVC produces excellent medical devices, construction profiles, credit card membranes, children’s toys, and water and gas pipes.
This form of plastic offers excellent impact strength, dimensional stability, and impact resistance. You will find ceramic peeks used mostly in test sockets, connectors, and switches.
It is general-purpose nylon that offers decent flame resistance and high-quality machining. Insulators and bearings manufacturers typically use nylon 6/6.
There is a wide variety of surface finishes you can achieve by the CNC machining manufacturing process.
Bead blasting offers uniform satin or matte surface finish to a machined part, and it removes any tool marks formed during the manufacturing process.
This process involves bombarding a part with small glass beads via a pressurized air gun. It removes some material and smoothes the surface. You can mask critical features and surfaces to avoid any changes to the dimension.
Bead blasting is mainly for visual purposes. As it is a manual process, it will need a skilled operator to achieve the desired finish. The size of glass beads and air pressure are the critical parameters in this process.
Anodizing (Type II & Type III)
Anodizing is all about adding a thin ceramic layer on the outer surface of your metal parts. It will help protect them from any wear and corrosion.
The anodic coating has high hardness, and it is electrically non-conductive. Plus, you can dye it to different colors; however, this process is only compatible with Titanium and Aluminum.
Anodizing Type II
It is also known as a decorative or standard anodizing process that produces a coating with up to 25 μm thickness. The primary use of anodizing type II is for parts with aesthetically pleasing and smooth surfaces.
You can create coatings of different thicknesses and densities by varying the electric current, anodizing time and consistency, and temperature of the solution.
Anodizing Type III
This type of anodizing is also known as hard coat anodizing. It can produce coatings with a thickness of up to 125 μm. However, a typical type III anodizing coating has a 50 μm thickness.
It produces a high-density ceramic coating, which is excellent for protection against corrosion and wear.
The powder coating finish uses a protective polymer to add a very thin layer to the part’s surface. However, it is wear-resistant and offers a strong finish ideal for metallic materials. You can combine it with bead blasting for uniform surfaces with adequate corrosion resistance.
It is somewhat similar to spray painting, but here you use dry powder. The process may involve priming the desired parts with an optional chromatic or phosphating coat for enhanced corrosion resistance. The next step is coating the parts via an electrostatic spray gun and curing them at high temperatures in an over.
Polishing is amongst the most widely used varieties in CNC machining surface finishes. It is useful on both machined parts and mold parts. It adds high quality to the final product and also enhances the wear resistance and corrosion abilities of the material surface.
Plating finish is the finest and most exotic surface finishes in CNC machining. It includes nickel, zinc, chrome, Holocron, and tin. In more expensive cases, you can use gold, silver, and platinum as well.
A chrome finish improves corrosion resistance and durability of the part. You can also use bright chrome plating for a mirror finish, whereas dull chrome gives a matt look. It is ideal for base materials, including copper, zinc, and steel alloys.
Nickel plating enhances corrosion and wear and tear resistance while providing an immaculate and attractive appearance to the material. When it comes to complex components, electroless nickel plating is an ideal surface finish as it offers a uniform coating.
Heat Treatment in the CNC machining significantly increases the material’s hardness. You can apply it as a finishing step. It is useful as high hardness helps reduce the machinability of the material.
There are three ways you can use heat treatment.
In this process, you heat the metal to high temperatures and then cool it down slowly to achieve the desired microstructure. Annealing is ideal for all metal alloys and the most used method for CNC machined parts.
This process involves heating parts at a high temperature employed by the CNC machine. It helps eliminate any residual stresses on the parts created during the manufacturing process.
You heat the part at temperatures lower than the temperatures used in the annealing process. You employ this process after quenching of mild steels (A36 and 1045) and other alloy steels (4240 and 4140) in order to reduce the brittleness and enhance their mechanical performance.
This type of surface finish adds value to the product and enhances its sales appeal. It is ideal for components as it does not interfere and alter their dimensions.
Black-oxide surface finish is highly durable and provides prolonged corrosion resistance to the produced component.
Lets Experts Do it for You
If you are a manufacturer who has needs for CNC machining but does not have the right tools, machines, and workforce to handle the process, you can always get help from the experts.
Rally is the leading expert in CNC machining technology and offers various solutions for several industries. They will sit with your team to understand your desired outcome and offer a solution that suits your company’s needs and budget. Contact the Rally team today and send your inquiry.