CNC technology can help you produce parts with tight tolerances and precision. It is a manufacturing process that uses pre-programmed computer software and automates the machining process. Because it is a dynamic process that can adjust the cutting speed, material removal rate, and automate complex machinery, it can shape various materials.
In this guide, you’ll understand what CNC machining is, the CNC process, types of CNC machining, and industry applications.
What is CNC (Computer Numerical Control) Machining?
CNC machining is a manufacturing process that uses Computer Numerical Control (CNC) to direct cutting tools to remove material from a workpiece. The material removal from a blank or workpiece makes CNC a subtractive machining process.
CNC machining carves a shape from a bulk material and achieves precision tolerances as tight as +/- 0.002 inches. CNC originated in the 1940s with numerical control systems developed by John. T Parson, and today CNC has evolved significantly from a magnetic punch tape that read into coded instructions.
Modern CNC systems make use of advanced electronics, feedback sensors, and editable CNC programming, enabling automation of advanced jobs with minimal manual control. The entire CNC process is managed by a machine control unit that uses a G-code to control toolpaths, spindle speeds, and other machining tools to ensure repeatable part production and consistency for metal parts.
CNC machinery operates in closed-loop or open-loop systems. Closed-loop systems use sensors and feedback systems for real-time adjustment, which produces consistent parts and identical precision in large volume production. The computer-aided manufacturing process has changed the manufacturing industry, offering high-speed production and minimal visible tool marks.
CNC Programming and Software Guide
CNC programming controls the CNC machining process and also produces the technical drawings and turns the 3D part into machine-readable instructions. Using G-code, CNC programs can transfer instructions to control tool movement.
M-code controls the miscellaneous functions like spindle activation and positioning the cutting tool. Both codes are generated from Computer-Aided Design (CAD) models using Computer-Aided Manufacturing (CAM software).
Key Software in CNC Machining
CAD Software: Tools like solidworks or Fusion 360 can produce detailed 2D/3D models, defining part geometry and tolerances.
CAM Software: Mastercam or Siemens NX converts CAD models into G-code with optimized toolpaths, cutting speeds, and feed rates. CAM software also stimulates the CNC process before CNC machining makes the part, which prevents errors and reduces costs.
CAE Software: FEA software tools can analyze stress and physical performance of a part before CNC manufacturing to enhance part design.
How Does CNC Machining Works?
CNC machines work by interpreting the standardized G-code from 2D or 3D CAD programs to run the repetitive commands and cycles of material removal with no human involvement during the process.
It is also possible to load instructions or edit the pre-programmed instructions in the machine itself. A CNC machinist can easily add commands through manual control of the CNC machine.
A CNC machinist prefers a closed-loop system, which can determine any errors in coordinates and correct them. Closed-loop CNC routers usually have a sensing probe that touches a known coordinate on the bed to re-calibrate after a tool change.
Producing CNC Machined Parts: Steps
The CNC machining process can turn a billet, stock, or workpiece into a finished part in minutes through pre-programmed computer software through the following steps.
Design creation: You can use computer-aided design software to create 2D or 3D models in CNC-readable and editable formats like STEP or IGES.
Toolpath Programming: CAM software can generate the G-code according to your part design, defining tool paths and cutting process parameters.
Machine Setup: CNC operators are required to secure the workpiece in the workbed or produce a fixture for custom parts and load the cutting tools into the machine.
Loading Program: The CNC program is loaded into the CNC machine and the MCU
Machining: The CNC machine automatically cuts the workpiece once the program is loaded into the CNC machine. The cutting process can involve milling, turning, and other methods.
Inspection: Precision tools like CMM can check the final dimensions of the parts produced, and an internal feedback system can allow the probe to check the dimensions at the end of every machining sequence.
Finishing: After the CNC parts are removed from the workbed, they can be further processed for extremely small tolerances using CNC grinders and surface finishing operations like electroplating and powder coating can enhance aesthetics further.
Types of CNC Machines
CNC equipment composes of a number of CNC machines, each tailored for a specific task in the manufacturing process. There are many types of CNC machines, and below are the most important types of CNC.
CNC Mills
CNC mills are machines with cutting tools mounted vertically above the workpiece. They use multi-point cutting tools to shape workpieces. Most CNC mills are 3-axis CNC machines, but modern complex machinery makes use of 5-axis cutting.
3-axis CNC mills moves along the X (horizontal). Y(vertical), and Z(depth) axes. This makes CNC mill machining tools suitable for slots, holes, and flat surfaces. Advanced 4 and 5-axis CNC mills incorporate rotational axes (A and B), enabling the machining of intricate parts, for example, turbine blades.
CNC mills use machining tools like end mills, face mills, and drills for operations like shoulder milling. CNC milling is very efficient for high-speed cutting, as the tool first produces rough cuts to quickly remove material and uses a smaller depth of cut to achieve tight tolerances for metal parts.
A 5-axis CNC mill offers machining of complex impellers with compound curves, minimizing tool access issues and reducing cycle times while still producing precision tolerances of +/- 0.002″.
CNC Lathes
CNC lathes are also called turning machines or turning centers and work by rotating the workpiece at high speed and feeding a single-point fixed cutting tool into the workpiece. This removes material and produces cylindrical and symmetrical parts.
CNC lathes typically operate on just two axes (X for radial movement and Z for longitudinal movement). Advanced CNC lathes may include more axes for drilling capabilities. CNC lathes are ideal for manufacturing cylindrical components like shafts, bushings, and automotive crankshafts, where parts can make use of rotational symmetry.
Unlike manual lathes, CNC lathes produce consistent results across high-volume production, achieving precision tolerances of +/- 0.005 mm.
CNC Plasma Cutters
CNC plasma cutters use a plasma torch that generates an electrical arc, which creates a high-speed jet of ionized gas that melts and removes molten metal from conductive materials. CNC plasma cutters are ideal for materials like stainless steel, aluminum, and brass.
Generally, CNC plasma cutters work on 2 axes (X and Y) and are ideal for cutting sheet metal or metal plates. These cutters provide high-speed cutting for 2 – 10 mm thick steel sheets, but produce rough edges compared to CNC laser cutters, adding extra finishing steps and costs.
Plasma cutters can only cut conductive materials like conductive sheet metal, which limits their use to industrial frameworks and sheet metal applications.
CNC Routers
CNC routers are specialized for cutting softer materials like wood, composite parts, plastics, or foam. CNC routers are common in the furniture industry, signage, and rapid prototyping. CNC routers are similar to CNC mills and operate on 3 axis with some rare CNC routers operating on 4 and 5 axis.
CNC routers use high speed spindles and machining tools like router bits and are commonly used to cut and shape intricate designs on wood.
Electric Discharge Machines (EDMs)
Electric discharge machines are of two types: Wire EDM and Sinker EDM. Electric discharge machines use electrical sparks to erode hard metal materials to create cuts and designs with extremely high precision.
Wire EDM uses a thin wire as an electrode to cut complex shapes in tough materials like tool steel and titanium. Wire EDM is often used in mold making because of the high precision it offers, and in the aerospace industry. EDMs are slower than CNC machines but offer a much higher precision and tolerance (up to 0.005 mm)
Sinker EDM uses a tool that erodes material from the surface of the material but unlike wire EDM, which has a wire cutting a shape, sinker EDM has a die pre-cut of the desired shape, and the electrode is simply lowered into the material where it slowly erodes conductive material to produce the final shape.
Manual VS CNC Machine
Manual machining relies on highly skilled CNC machinists who use manual control via levers, handwheels to produce cuts and control the feed. In manual machines, there isa smaller RPM range which the machinist controls.
| Manual lathes / mills | CNC Machining | |
| Precision | Tolerances up to ±0.01 in (±0.254 mm) | Tight tolerances as low as ±0.002 in |
| Speed | Slower due to manual adjustments | High-speed, automated tool changes |
| Part Complexity | Limited to simpler shapes | Handles complex machinery and 3D geometries |
| Repeatability | Inconsistent due to human variability | Highly repeatable for mass production |
| Setup | Quick for simple tasks | Longer due to CNC programming and setup |
Manual lathes and mills are useful for one-off / single parts, but CNC machining offers superior precision, repeatability, and efficiency for advanced jobs.
What Materials Can be Machined Using CNC?
CNC services offer machining of various materials depending onthe project and mechanical properties and machinability. Common materials that are easy to machine include.
Metal materials
Aluminum 6061, 7075 and other alloys: Aluminum is lightweight, corrosion-resistant and ideal for aerospace parts and automotive CNC machined parts. It has better machinability than steel and tougher alloys.
Steel (Stainless steel and alloy steel): Durable and has chemical resistance. It is one of the most common materials for producing injection molding molds, parts, prototypes, and machining tools.
Titanium: It has high strength, high corrosion resistance, and small weight, but it is harder to machine than most materials.
Brass: Brass can be easily machined and is used for properties like corrosion resistance and electrical conductivity.
Plastics
ABS: ABS is a cost-effective plastic that is tough and UV-resistant. It is easily machined and can substitute for tough parts that require electrical insulation, rapid prototyping, and for car parts.
Derlin: Derlin is used to produce gears and bearings because of its lower friction
PEEK: PEEK is a plastic with high chemical resistance for medical and aerospace applications. It is highly machinable, and softer tools can be used.
Nylon: Nylon parts are wear-resistant, long-lasting, and perfect for insulator use in non-conductive environments.
The type of material you require will affect the type of CNC metal cutting tools and also the cutting process.
CNC Uses By Industry
Aerospace
CNC technology produces lightweight aluminum and titanium parts for the aerospace industry. Components like turbine blades and structural brackets can be produced using multi-axis machining. CNC mills can achieve tight tolerances and materials like titanium and inconel ensure reliability in extreme conditions.
Automotive
CNC machining makes engine blocks, transmissions, and all types of gear and chassis components. CNC lathes are commonly used to produce shafts and symmetrical parts like custom nuts, bolts, and components with consistency.
Medical and Dental
CNC manufacturing can also cut biocompatible implants and surgical tools from PEEK and titanium, offering diversity in material choice by adjusting the cutting parameters.
Electronics
For PCB enclosures, heat sinks, and other electronics, CNC mills can create intricate designs and custom parts, optimizing performance in compact devices.
Marine
Marine applications require corrosion-resistant material machining, such as stainless steel 316 and aluminum. CNC lathes can produce high-performance propeller shafts from corrosion-resistant alloys and CNC laser cutters can shape sheet metal for structural parts.
CNC Machining Cost
| Description | Range | |
| Material | Better alloys increase material costs | Aluminum: $2 -5/Kg Titanium: starts at $20/Kg |
| Machine Type | 5-axis machining has the highest costs, and EDMs are more expensive because of their precision and setup costs | 5-axis:
$50 -150/hr 3-axis: $30 - 90 / hr |
| Part Complexity | Complex parts require more CNC programming and machining time. | Simple: $10–$50/part; Complex: $100–$500/part |
| Post-Processing | Finishing like powder coating adds costs. | $5–$50 per part |
| Volume | High volumes reduce per-unit costs. | 1 part: $100–$500; 1,000 parts: $10–$50/part |
Cost Saving Strategies
Material: Most applications can use aluminum parts unless high structural strength is required.
Optimize design: Simple geometries are easier to machine. Adding unnecessary design complexities can decrease tool access and increase machining costs.
Batch production: Increase your production volume to reduce CNC costs
Benefits and Limitations
CNC machining offers unmatched precision and rapid part manufacturing. It is also easy to scale production when CNC machining because the process simply has to be repeated a given number of times.
Benefits of CNC Machining
Precision
CNC machining allows clients to get quality controlled parts and manufacturers have the freedom to use various methods to make tight tolerances. The automation removes any human error.
Cost Effective
CNC machines are now available in many bed frame sizes. Buying a CNC machine has a large initial cost, but it offers high volume production, precision, and overtime the cost effectiveness increases.
Various Materials
You don’t need different CNC machines to cut metals and plastics. You can simply change the cutting tool and work with different materials.
Limitations of CNC machining
Large Initial Investment
CNC machines have a high setup cost. As the number of axis increases, the cost of the CNC machine increases significantly. Plus, manufacturers have to hire CNC machinists to calibrate and maintain the CNC machines.
Most CNC come with a basic set of tool and specialized cutting requires you to invest in more tools.
Part Complexity
While CNC machines can produce many shapes, there are some shapes which are difficult to achieve using CNC. Components with internal features are not ideal for CNC machines and usually discharge machining is used for such parts.
Size Range
You CNC machine parts in an enclosure, because the coolant can be recycled and the chips don’t fly out everywhere. But this enclosure also limits the size of your part. For large parts especially large internal and external gears, casting and forging processes are employed.
Large parts need re-orientation, new setups, sectioned machining which adds time and cost to the part.
Tool Wear
The largest running expense of a CNC machine is the tool wear. While this depends on the material, feed rate, depth of cut, and speed, almost all tools wear out eventually and need replacement.
An amateur CNC operator can lead to quick tool burns and skilled operators add cost to manufacturing.
Conclusion
CNC technology is extremely important for the manufacturing industry and for users looking for custom machining solutions. Computer numerical control allows you to simply design your part and produce its relevant G-code files, which can be machined easily using the type of CNC you require.
A final tip: It is not important to machine using 5-axis, you can optimize your design to be machined using a 3-axis CNC mill, which reduces time and offers cost-effective digital manufacturing.
FAQ
Q: What Does CNC Stand For?
A: CNC means Computer Numerical Control. CNC is a technology that uses pre-programmed instructions to automate machining tools and produce precise parts.
Q: What is the job of a CNC machinist?
A: A CNC machinist programs, sets up and operates CNC machines, ensuring precise tool cutting and loading the parts correctly. It also involves checking technical drawings and measuring for quality control.
Q: CNC Machinist Definition
A: A CNC machinist is a skilled professional who programs and operates computer numerical control machines
Q: How is CNC Machining Pricing?
A: The pricing of CNC depends on the type of machine and the machining process complexity. It also depends on material costs and volume. The typical cost of CNC ranges from $10 to $50 per part for simple parts.
Q: How Much Do CNC Machinists Make?
A: CNC machinists can make up to $63000 annually in the US. The median salary for CNC machinists is $50,600