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What Is CNC Precision Machining?
Precision machining involves crafting a finished product from raw material by eliminating excess material according to a CAD or CAM blueprint. This process finds application in various manufacturing processes and across different materials.
Prior to manufacturing any product, it’s essential to utilize CAD or CAM programs to create a detailed blueprint. These programs generate intricate 3D outlines that guide the precise machining process in faithfully replicating the intended product.
Products ranging from toys and medical devices to automobiles and space shuttles, all with component parts, necessitate precision machining. The process encompasses actions such as cutting, milling, turning, and electrical discharge machining to achieve the desired end product.
While the oversight of a skilled precision machinist is imperative, much of the work is automated. The CAD software generates the design, which is subsequently translated into manufacturing instructions by the CAM software for the machine. A final post-processor software encodes these instructions into a format understandable by the machine. Machinists then load these instructions into the CNC equipment to initiate the manufacturing process.
The Precision Machining Process
Precision machining companies typically follow a standardized sequence of steps for diverse part types.
Material Selection
The process begins with CNC machining material selection. High-precision CNC machining proves effective across a range of metals and plastics. Here are the common ones:
Metals
- Aluminum
- Steel
- Stainless Steel
- Bronze
- Brass
- Copper
- Titanium
- Carbon Steel
- Tool Steel
- Exotic Alloys
Plastics and Other Materials
- Acrylonitrile Butadiene Styrene (ABS)
- Polycarbonate (PC)
- Polyamide (PA)
- Polymethyl Methacrylate (PMMA)
- Polyoxymethylene (POM)
- Glass
- Graphite
Graphical Model Design
A graphical model is necessary to create a part. This is achieved through Computer-Aided Design (CAD) software. CAD software allows designers to create accurate 2D and 3D models of parts for manufacturing.
Initial designs often begin as hand-drawn sketches to grasp the fundamental concepts of the part. Subsequently, the CAD designer utilizes these sketches as a reference to develop a precise graphical model with the correct dimensions.
Various free and paid software programs are available for Computer-Aided Design. Alternatively, manufacturers have the option to outsource the design process, especially for complex design development.
Converting File Formats
Computer-Aided Design translates the part into a digital graphical representation, making it easily comprehensible for designers, operators, and manufacturers. However, CNC machines cannot directly interpret this digital format.
These machines comprehend coordinates to move the cutting tool or adjust the workpiece. Consequently, the part design must be in a suitable format that provides essential manufacturing instructions. To achieve this, Computer-Aided Manufacturing (CAM) software comes into play. CAM software transforms the CAD model into a CAM format that CNC machines can interpret.
Two types of codes are utilized in CAM software. G codes control cutting tool coordinates. M codes manage auxiliary machine functions, such as activating or deactivating the coolant flow.
Machine Setup
After preparing the designs in CAM format, the next step involves setting up the machine. This typically includes calibrating the machine tools and securing the workpiece onto the machine. The choice of machine tools depends on the material of the workpiece and the final part’s design. Various precision machining tools cater to different purposes. During this phase, it is crucial to securely tighten all clamps and verify that machine parameters meet the required standards.
Machining Process and Completion
The actual processing step involves executing the programmed instructions to shape the raw material to meet precise specifications. Various CNC processes like milling, turning, drilling, and surface finishing are employed.
After the precision CNC machine completes manufacturing the part, it can be taken out. The part might undergo additional processes like grinding or polishing based on specific needs. Manufacturers also employ finishing techniques like anodizing, bead blasting, electroplating, and powder coating. In many instances, a product produced through precision machining is finalized without requiring any further secondary processing.
Various Precision Machining Tools
Various processes demand distinct equipment for their execution. Depending on the scenario, these tools may be integrated into a single precision CNC machine, simplifying the machinist’s role in initiating and concluding the process. Alternatively, certain situations necessitate the placement of tools on different machines. This makes the precision machinist transfer the workpiece or raw material between them. Some examples of tools used in precision machining include:
CNC Milling Tools
Milling is the process of using rotary cutters to eliminate excess material from a workpiece. Different types of mills help complete this precision machining process. They include end mills, chamfer mills, and helical mills. Precision CNC-enabled mills come in variations like hand milling machines, plain milling machines, and universal milling machines. They come with either horizontal or vertical orientation.
These machines are known for reshaping stationary raw materials using a rotating cutting tool. As a result, they produce face-milled features like flat surfaces and shallow cavities, as well as peripheral-milled features like deeper cavities such as threads and slots. Precision CNC milling machines are primarily used to create square- and rectangular-shaped components with various features.
CNC Turning and Lathe Machines
Turning is a machining method where the workpiece rotates alongside a single-point cutting tool. The cutting tools move linearly along the turning bar stock, removing material around the circumference to achieve the desired diameter and features.
Common tools for precision CNC turning include lathes, such as turret lathes, engine lathes, and engine-purpose lathes. Other turning equipment includes straight turning, taper turning, external grooves, and threads.
CNC Swiss lathes, a type of CNC lathe, rotate and axially slide workpieces into the machining tool through guide bushings. They provide better support for shaping the part and resulting in components with tighter tolerances.
CNC turning machines create both external and internal features on components, such as bores, reamed and drilled holes, broaches, tapers, threads, tappings, and slots. Components produced on these machines include bolts, screws, poppets, shafts, and more.
CNC Drilling Equipment
Drilling creates cylindrical holes in raw materials or workpieces using rotating multi-point drill bits. The design of these drill bits facilitates the removal of chips from the workpiece, maintaining the cleanliness of the drilled holes.
Various types of drill bits find application in CNC machining processes. Additionally, specific drill presses are designed for particular drilling tasks. Some common examples of drill bits used in high-precision CNC machining include:
- Spotting drills: they assist in creating shallow or pilot holes.
- Drill presses: they are designed for custom drilling tasks
- Screw machine drills: they are used for generating holes without an initial pilot hole
- Chucking reamers: they help to enlarge previously created holes
- Peck drills: they reduce the number of chips produced from workpieces.
Electric Discharge Machining (EDM) Tools
Electrical Discharge Mining uses electrical discharges to achieve precision machining. The setup consists of a tool electrode and a workpiece electrode separated by a dielectric fluid and subjected to electrical voltage. This process is also called spark machining, eroding, burning, die sinking, or wire erosion.
In EDM, controlled electrical sparks are employed to shape materials into desired forms. During the process, the technician positions the component beneath an electrode wire. The programmed machine then emits electrical discharges from the wire, generating intense heat. This heat melts the material, and an electrolytic fluid is used to flush and achieve the desired feature or shape.
Moreover, EDM is capable of creating precise slots, micro holes, angled or tapered features, and various other complex features on workpieces. It proves to be an ideal process for hard metals that are typically challenging to machine.
Precision Grinding Machines
Precision grinders are essential for CNC precision machining that meets smooth surface roughness requirements. These grinders play a crucial role in achieving exceptional accuracy when creating parts. Typically, rough surfaces are initially produced by CNC lathes and CNC mills. Subsequently, the grinders become necessary for the final surface finishing.
Plasma Cutting Machines
Utilizing a high-powered, computer-controlled plasma torch, these tools assist in cutting materials. The plasma torches employed can attain temperatures exceeding 50,000 degrees Fahrenheit, enabling the melting of workpieces and the creation of cuts in the material. Materials used with plasma cutting machines must possess electrical conductivity. Such materials include steel, aluminum, stainless steel, copper, and brass.
Tolerances in CNC Precision Machining
While precision machining tools are highly accurate, they cannot precisely replicate the dimensions of products as outlined in the CAD blueprint. Hence, machinists employ CNC machining tolerances.
Tolerance refers to the acceptable deviation in a part’s dimension according to conventional standards, also known as dimensional accuracy. There is no standard precision CNC tolerance, as the strictness of tolerance varies based on the manufacturing process. The number of decimal places in a tolerance value indicates the measurement’s strictness.
Various tolerance measurement systems exist for successful precision machining. Here are some examples:
- Unilateral Tolerances: In this method of tolerance measurement, deviation is permitted only on one side of the nominal value. For example, if the nominal value of a shaft meant to fit into a bearing is 20mm, a shaft larger than this would not fit. Consequently, machinists only permit the deviation for such a shaft on the smaller side.
- Limit Tolerances: In this scenario, the tolerance value is specified within a range. For instance, if the nominal value for the shaft is 15mm, and the tolerance is set at 15 – 15.5mm, this indicates a limit tolerance.
- Bilateral tolerances: This tolerance type permits deviation on both sides of the nominal value and is commonly expressed as a +/- value. For example, if a machined part measures 25mm with a tolerance of +/- 0.05mm, it implies the value can range between 24.95mm and 25.05mm.
Understanding when to opt for tighter tolerances in part manufacturing is crucial. While the entire part may not necessitate tight tolerances, critical structural components should have a minimal deviation from the nominal value to prevent compromising the part’s integrity.
Tolerances are vital in precision machining processes, contributing to cost reduction and quicker turnaround times. Despite their importance, achieving accurate tolerances demands skill and patience. CNC machines typically adhere to a standard tolerance of 0.005 inches.
Advantages of CNC Precision Machining
Cost-effective and high-quality machining demands precision and repeatability. CNC precision machining generally excels in various aspects to fulfill performance and quality requirements. Some of the benefits of this process include:
Machining Technology Excellence
Precision CNC machining equipment represents cutting-edge technology aligned with industry 4.0 standards. It minimizes the need for excessive labor and handling heavy machinery. With various CNC machine tools in use, computer programs enable the automation of most operations. They act as “live operators” to manipulate cutting tools and shape diverse raw materials into desired finished products.
Superior Part Quality
The quality of CNC precision machining is unparalleled, eliminating variations seen in conventional machining through computer numerical control. The CNC machine can run for extended hours. Thus, it demands minimal maintenance and relies on advanced software to meet design requirements. Consequently, even intricate parts can be crafted using advanced processes, ensuring the highest quality that surpasses customer expectations.
Efficient Cycle Times and Reduced Labor Costs
CNC precision machining meets increased production demands through enhanced machining automation and programming capabilities, ensuring uninterrupted machine use. High-precision CNC machining is designed for accuracy and consistent results.
In contrast, conventional machining necessitates manual monitoring and adjustments to tooling and running speeds. In the CNC process, programs are run offline. Thus, a single operator can switch CNC machining centers and oversee various productions. This operator manages loading parts and tooling, conducts offline deburring, and ensures quality control.
As a result, the structure requires minimal operators for monitoring, leading to reduced labor costs. Simultaneously, it ensures swift component creation, irrespective of the quantity.
High Performance and Repeatability
Certain applications can accommodate traditional machining outcomes, but tight tolerance requirements necessitate high-precision machining. Additionally, many industries often need numerous identical parts, which is achievable through the repeatability of precision machining. Quality processes are consistently maintained. The CNC machines execute similar cuts and ensure uniform quality across all parts.
Extensive Range of Applications
Precision machining processes work well with various materials, including high-grade metals and plastics. This adaptability enables businesses of various sizes to compete and provide custom designs and parts. Furthermore, consistently achieving tight engineering tolerances fosters customer confidence. Precision CNC machining is beneficial for several industries, including automotive, metalworking, aerospace, marine, agriculture, consumer goods, and more.
CNC Precision Machining Applications
Precision machining is increasingly gaining popularity in manufacturing due to its versatile applications and cost- and time-efficient processes. The technique finds widespread use in various industries, such as the following:
Automotive Industry
Automobile companies continue to introduce innovations in their latest car models. As a result, developing prototypes for CNC machined parts becomes essential before integrating them into the manufacturing line. Precision machining is the method responsible for creating these prototypes to precise specifications. This technology also produces parts for various transportation modes, including shipping vessels, transport trucks, and more.
Medical Industry
The field of medicine is swiftly advancing, necessitating the creation of new equipment and high volumes of existing ones. Precision CNC machining plays a crucial role in medical device manufacturing. Examples include orthotic devices, safe enclosures, implants, MRI machines, research equipment, and more.
Aerospace Industry
Aerospace vehicles demand highly precise components, from transportation planes to space shuttles. A single error could result in severe damage. The precision machining process is accountable for manufacturing various components in this industry. Examples of these components include landing gear ports, bushings, manifolds, airfoils, and more.
Electronics Industry
The consumer electronics industry is currently undergoing significant downsizing. It now requires smaller and more powerful components designed to be compact and lightweight. CNC precision machining can meet these requirements while maintaining tight tolerances, even in high-volume productions. CNC machining capabilities can manufacture components such as semiconductors, heat sinks, circuit boards, and other elements for consumer electronics.
Military and Defense Industry
CNC has become increasingly relevant as different nations develop various designs for new ammunition and defense systems. The precise CNC process is accountable for bringing these designs to life, employing various materials and processes. Examples of devices manufactured for this industry encompass plane parts, transportation components, communication elements, ammunition, and more.
AT-Machining Reliable Precision CNC Machining Services
CNC precision machining stands out as an effective method for manufacturing custom-made parts, offering cost savings, efficiency, and minimal room for errors. AT-Machining aims to bring your CAD blueprints to life with professional CNC machining services. We leverage extensive engineering experience and capabilities with our extensive CNC machines. Our technical support is unparalleled, and we offer post-processing services to improve your products. We adhere to certified ISO 9001:2015 standards, ensuring the delivery of high-quality finished parts using the latest CNC technology. Additionally, all our services come at the most competitive rates. Obtaining a quotation is quick and efficient; all you need is to upload your CAD file to our website. You will receive an online quotation instantly.
