Automotive parts, medical implants, defense equipment parts, and many other applications require tight tolerances to perform their functions, often as low as ±0.001 inches. Standard machining methods cannot achieve this level of accuracy. This is where CNC precision machining comes in. Different precision machines and tools perform machining operations to manufacture precision parts and products for various industries.
To take full advantage of this manufacturing precision, you need to understand its nuances. Therefore, let’s discuss the process, equipment, materials, advantages and applications of precision CNC machining.
What is CNC precision Machining?
Let’s start with what is CNC machining first. This is a computer-controlled process that automatically removes material based on uploaded designs and digital instructions. The automation of tool movement provides tighter tolerances than traditional machining methods. At the same time, precision machining usually involves tolerances of ±0.1 to 0.2 mm. Therefore, dedicated machining tools, optimization parameters and expert handling are the main strategies to achieve this precision.
The main importance of CNC precision manufacturing lies in producing the same parts for the automotive, medical, defense and other industries. Manufacturers use multiple devices, such as milling machines, EDM units, and lathes, to produce precision machined parts.
In addition, CAD and CAM also play a vital role in this process. CAM converts 3D models of parts into machining instructions for CNC machines. The machine then instructs the movement of all cutting tools in a predetermined path until the desired shape is formed.
A step-by-step guide to CNC precision machining processes
Design and CAD modeling
After determining the final requirements, the engineer or designer creates a detailed 3D engineering design that includes dimensions, tolerances, features, proportions, and other information. Often, computer software such as AutoCAD or Solidworks helps with CAD modeling of the intended part or product. In addition, design for manufacturability (DMF) is an important consideration at this stage. Models must be compatible with precision CNC machining technology.
CAM and CNC programming
Next, the CAM system software generates tool movement instructions based on the CAD model, called G&M code. This process is also known as CNC programming; These codes can be read by CNC precision machines. CAM can also simulate the optimal tool path for material removal, which helps minimize rounding errors and improve accuracy.
The setting of CNC machine tools
Precise CNC machine setup involves two main tasks: tool setup and workpiece clamping. First, the operator installs the tool in the chuck or tool holder and the workpiece on the machine bed or chuck. However, machine tools can also have an automatic tool change (ATC) mechanism.
At this stage, choosing the right tool (end mill, face mill, drill, etc.) and stably fixing the workpiece and tool are crucial to the final accuracy. Improper machining tools or misalignment between the tool and the workpiece can lead to serious quality defects in precision machined parts.
Machined part
The machine is connected to the control system to process the operation instructions. This is the actual machining stage, where the CNC operator manually sets the spindle speed, depth, feed rate and other parameters. Next, the machine executes the instructions and the tool moves to process the workpiece. At the same time, test fine-tuning parameters can help produce parts according to accuracy requirements.
Post-processing and finishing
This is the last and most important step in CNC precision machining. Machined parts may contain knife marks, burrs, or notches, affecting dimensional accuracy and aesthetics. Post-treatment methods such as grinding and deburring can be used to precisely obtain the desired dimensions by removing trace amounts of material from the surface. Subsequently, finishing strategies such as sandblasting, electroplating or polishing can improve surface quality and aesthetics. At the same time, some low-friction applications, such as hydraulic rods or rotating parts, require finishing in order to perform their functions and performance.
Types of precision CNC machine tools
Milling machines, lathes, EDM machines, drill presses and many other machines have brought precision to manufacturing. Each machine has a number of specific functions, suitable for specific machining tasks. For example, CNC lathes are ideal for symmetrical items, while milling machines are best for flat surfaces. Therefore, which CNC machine is right for you depends on the 3D design and the desired features.
CNC milling machine
CNC milling machines involve rotary cutting tools that can move along a multi-axis and rotational motion and feed the workpiece linearly. The spindle can be rotated at high speeds (up to 2400 rpm) without compromising accuracy and quality, as low as +/-0.0025mm. CNC precision milling can manufacture complex parts from flat and flat workpieces. In addition, the spindle can be positioned horizontally or vertically. At the same time, some advanced milling machines can also have spindle positioning function.
CNC lathes and lathes
Lathes and lathes are also part of CNC precision manufacturing. A CNC lathe or turning center rotates the workpiece, and the tool moves linearly (along and through the workpiece) to remove and shape the material. Therefore, they are used in the manufacture of axisymmetric items, such as cylindrical products.
In addition, the precision CNC turning method can machine complex details and shapes because the workpiece rotates rather than the cutting tool. The fixed tool can be moved on the workpiece, enabling a precise material removal process.
CNC drilling machine
Machine-controlled drilling involves rotating the bit and fixing the workpiece. As the bit penetrates the surface, it cuts and whittles away the material in the drilled area to form the hole. The size of the drill is the same as the diameter of the desired hole.
Precise CNC drilling technology includes:
● Point drilling: First, drill a shallow hole in a precise position, and then follow the drill to immerse, especially suitable for hard materials.
● Pecking drilling: For deep holes, the bit should be retracted periodically during drilling to remove chips and reduce heat buildup.
Electric Discharge Processing Machine (EDM)
Edm Technology (1)
This is a non-contact machining process that creates an electrical spark (discharge) to corrode the material, thereby creating a cut. Here, the workpiece and tool act as electrodes and generate an electrical discharge due to the immersed piezoelectric fluid. This precision machining process creates minimal mechanical stress and can cut hard metals and alloys such as titanium and tungsten. In addition, EDM machines are known for their ability to create complex shapes and details with high precision and repeatability, such as molds.
CNC plasma cutting machine
Plasma is a beam of ionized gas produced when air or gas is heated to 10°c. In CNC precision machining, CNC plasma cutters use this gas beam to cut heat-conducting materials. The power supply unit provides high pressure to ionize the gas flowing in the plasma torch. The torch then focuses the plasma on the workpiece through the nozzle, melting the material and cutting it. Unlike traditional shear or water jet cutting, it offers excellent machining accuracy. Plasma cutting tolerances can be as low as 000 inches.
CNC precision grinding machine
CNC grinding machines are post-processing equipment for high-precision manufacturing. They consist of a rotating grinding wheel with an abrasive layer of a specific thickness and granularity. The machined parts are fed into grinding wheels to eliminate surface defects and smooth the surface by cutting tiny materials and irregular parts with abrasives. These machines are not only able to handle size, but also provide polished and even mirror-like surfaces. Precision grinding machines can produce smooth surfaces with a roughness (Ra) value of 3.2 to 0.8 μm.
Materials suitable for CNC precision machining
Plastics, metals, composites and some other materials can be machined with CNC machines. However, CNC precision manufacturing mainly involves metals and plastics. The tools and parameters for each CNC material vary according to its characteristics and level of machinability.
In addition, materials suitable for precision CNC parts should be selected according to the desired function and operating environment of the part.
metalwork
The hardness of metals and alloys requires the use of hard precision tools made of diamond-coated carbides. At the same time, considering thermal expansion and an effective cooling system to counteract heat buildup is essential for metal processing.
Metal selection also affects the total cost of a processing project, as material cost is an important cost factor. Therefore, the material performance requirements and costs are balanced. In addition, you can read more about economical metals suitable for CNC machining by clicking here.
Common precision machined metals are as follows;
Aluminum 6061, 7075, 2024
Steel 1018, 4140, 1045, A2, D2,
Stainless steel 304, 316 and 17-4 PH
Titanium Ti-6Al-4V
Copper: C101 and C110
Brass C360 C260
Bronze C932 and C954
Inconel 718
The Monel 400
plastic
One of the main challenges in plastic processing is its sensitivity to heat. As a result, the production rate is slower than that of metal processing. However, CNC machining of plastics can still provide dimensional accuracy and smooth machining results. At the same time, plastic processing tools are standard carbide cutting tools.
The following is a list of commonly used plastics in CNC precision machining projects;
Nylon 6, nylon 6/6, oil-filled nylon
ABS
Polycarbonate (PC)
polythene
Polyformaldehyde (POM) or acetal
PTFF and PTFE filled (glass, carbon, bronze)
Polyether ether ketone (PEEK)
Acrylic (PMMA)
The main applications and industries of CNC precision parts
Custom precision machined parts
Now, let’s discuss the use of precision CNC machining parts or finished products. These applications can be seen in areas where tolerances and surface finish are critical, such as aircraft parts and medical implants. In addition, plastics are also popular in precision prototyping and the production of industrial components in various industries.
Post time: Nov-09-2024
