What is CNC Machining and How CNC Machining Works?

What is CNC machining?—CNC machining definition

The CNC machining refers to a process method that uses digital devices and information to control parts and cutters’ displacement to process parts on a CNC machine. It is an effective way to solve variable rapid prototyping components, small-batch parts, complex shape parts, and high CNC precision machining components and achieve high-efficiency parts.

CNC machining is a high-efficiency automatic machine tool composed of mechanical equipment and a numerical control system for processing complex shape workpieces.

The CNC machining center is a high mechatronics product. After the workpiece is clamped, the CNC machining system can control the CNC machine tool to select the device automatically, automatically set the tool, automatically change the spindle speed, feed, etc., different procedures.

The rapid prototyping CNC machining can continuously complete drilling, boring. Various processes such as milling, reaming, and tapping greatly reduce the additional process time, such as the workpiece clamping time, measurement, and machine tool adjustment.

The processing shape is more complicated, the precision requirements are high, and the frequently replaced parts have sound economic effects.

CNC machining history

CNC machining technology originated from the needs of the aviation industry. In the late 1940s, an American helicopter company proposed it.
The initial idea of ​​CNC machine tools, the Massachusetts Institute of Technology developed a three-axis CNC milling machine in 1952.

This kind of CNC milling machine has been used for processing aircraft parts in the mid-1950s. In the 1960s, CNC machining prototypes and programming work became increasingly mature and perfect.

CNC machining prototype services have been used in various industrial sectors, but the aerospace industry has always been the most extensive CNC machine tool.

Some large aviation factories are equipped with hundreds of CNC machine tools, of which cutting machines are the main ones.

CNC machining parts include integral wall panels, beams, skins, bulkheads, propellers, aero-engine casings, shafts, discs, blades, and unique cavity surfaces of liquid rocket engine combustion chambers. The initial stage of developing CNC precision machining is based on continuous trajectory CNC machine tools, continuous trajectory control.

What is CNC machining used for?

1, CNC machining can be used to make workpieces that are put into production periodically.

The market demand for some products is cyclical and seasonal. If a particular production line is used, the gain is not worth the loss. The processing efficiency with standard equipment is too low, and the quality is unstable, and the quantity is difficult to guarantee.

The program and related product information can be retained with the CNC machining center after the first piece (batch) are cut.

The next time the product is reproduced, production can be started with little preparation time. CNC machining center working hours include preparation for working hours and processing working hours.

The CNC machining center evenly distributes the long single-piece practice using hours to each workpiece, reducing the average actual working hours for each production and significantly shortening the production cycle.

2, CNC machining can be used for producing high-precision workpieces.

Some workpieces have little demand but are vital components, requiring high precision and a short construction period. Traditional technology requires multiple machine tools to coordinate work, which has a long cycle and low efficiency.

In a long process flow, it is easy to produce waste due to human influence. Cause heavy economic losses. The CNC machining center is used for processing, and the production is wholly controlled automatically by the program.

It avoids lengthy working procedures, reduces CNC machining metal parts investment and human interference, and has the characteristics of high production efficiency and stable quality.

3, CNC machining can be used to produce workpieces in batches.

The flexibility of CNC machining production is reflected in the rapid response to special requirements and can quickly achieve mass production to improve market competitiveness. The CNC machining center is suitable for small and medium batch production, minimal batch production when using the CNC machining center.

Try to make the batch larger than the economic bunch to achieve an excellent economic effect.

With the continuous development of CNC machining technology, financial packs are getting smaller and smaller. For some complex workpieces, 5-10 pieces can be produced, and even single-piece production can also consider using CNC machining.

4, CNC machining can be used to produce complex shapes workpieces

The application of four-axis linkage and five-axis linkage CNC machining machine and the maturity and development of CAD/CAM technology has dramatically increased the complexity of processing workpieces.

DNC’s use makes the same program’s processing content sufficient to meet various processing needs, making the automatic processing of complex workpieces easy.

What are the types of CNC machining?

CNC machining is a manufacturing process suitable for various industries, including automotive, aerospace, construction, and agriculture. It can produce multiple products, such as car frames, surgical equipment, aircraft engines, and manual and garden tools.

The process includes several different computer-controlled machining operations, including mechanical, chemical, electrical, and thermal machining processes, which remove the necessary materials from the workpiece to produce custom-designed parts or products.

The most common mechanical CNC machining operations for CNC machining include CNC Drilling, CNC Milling, CNC Turning.

CNC Drilling

CNC Drilling is a machining process that uses multi-point drills to create cylindrical holes on the workpiece. In CNC drilling, the CNC machine usually feeds the rotating drill bit perpendicular to the workpiece surface plane, producing vertically aligned holes whose diameter is equal to the drill bit’s diameter for the drilling operation.

However, it is also possible to perform bevel drilling operations using a dedicated machine configuration and workpiece fixture. The drilling process’s operational capabilities include count holes, counter holes, reaming, and tapping CNC milling.

CNC milling

CNC milling is a machining process that uses rotating multipoint cutting tools to remove material from the workpiece. In the CNC milling service, the CNC machine tool usually feeds the workpiece to the cutting tool in the same direction as the cutting tool rotation. In contrast, in manual milling, the machine tool provides the workpiece opposite the cutting tool rotation.

The operational capabilities of the milling process include face milling (cutting a shallow, flat surface and flat-bottomed cavity into the workpiece) and peripheral milling (cutting a resonant cavity (such as grooves and threads) into the workpiece).

CNC turning

CNC turning is a machining process that uses a single-point cutting tool to remove material from a rotating workpiece. In CNC turning, the CNC machine tool-usually a lathe or lathe-feeds the cutting tool in a linear motion along the rotating workpiece’s surface.

Removing material along the circumference until the required diameter is reached produces the CNC turning components with an outer and outer cylinder inside Features, such as slots, Taper, and thread. The operating capabilities of the turning process include bland, end face, grooving, and thread cutting.

How does CNC machining work

CNC machining process

Although the CNC machining process provides various functions and operations, the process’s basic principles are the same in all aspects. The necessary CNC machining process includes the following stages:

• Design CAD model
• Convert CAD files into CNC programs
• Prepare CNC machine.
• Execute processing operations.

CAD model design

The CNC machining process starts in-house or is created by a CAD/CAM design service company to create a 2D vector or 3D solid part CAD design.

Computer-aided design (CAD) software enables designers and CNC machining suppliers to produce models or renderings of their parts and products and the necessary technical specifications, such as dimensions and geometric shapes, to create parts or products.

The design of CNC machining parts is restricted by the functions of the CNC machines and tools. For example, most CNC machine tools are cylindrical, so the part geometry produced by the CNC machining process is limited because the tool will form curved corners.

The processed materials’ characteristics, tool design, and machine processing capabilities limit the design possibilities, such as the minimum part thickness, maximum part size, and the inclusion and complexity of internal cavities and features.

After the CAD design is completed, the designer exports it to a CNC compatible file format, such as STEP or IGES.

Convert CAD files into CNC programs

The formatted CAD design file is run through a program. Usually, computer-aided manufacturing (CAM) software uses part geometry and generates digital programming code that will control CNC machine tools and manipulate tools to produce custom-designed parts.

CNC machine tools use several programming languages, including G code and M code. The most famous general-purpose or geometric code (called G code) in CNC programming language controls when, where, and how the machine tool moves, for example, when it is turned on or off and how fast it moves to the machine tool.

The specific location on the workpiece, what path to take, etc. Miscellaneous function codes (called M codes) control the machine’s auxiliary functions, such as automatic removal and replacement of machine covers at the beginning and end of production.

After generating the CNC program, the operator loads it onto the CNC machine tool.

Prepare CNC machine tools–Machine setup.

Before operators can run CNC programs, they must prepare the CNC machine for operation. These preparations include fixing the workpiece directly on the machine, on the mechanical spindle, on machine vision or similar workpiece fixing devices, and connecting the required tools (such as drills and end mills) to the appropriate CNC machining components.

After the machine is fully installed, the operator can run the CNC program.

Mechanical Execute Processing Execution

The CNC program is used as the CNC machine’s instructions; it submits machine commands indicating the tool’s actions and movements to the device’s integrated computer, which operates and manipulates the machine tool.

The startup program will prompt the CNC machine to start the CNC machining process. The program will guide the machine through the entire process while performing the necessary machine operations to produce custom-designed parts or products.

If the rapid prototyping company invests in purchasing and maintaining its CNC equipment, it can execute the CNC machining process in-house or outsource it to a specialized CNC machining service provider.

CNC machining process flow chart

CNC machining materials

CNC Metal Materials and Plastics Materials

What are the CNC machining advantages and disadvantages?

CNC machining rapid prototyping has realized the automation of small and medium batch processing and improved working conditions. Also, it has a series of advantages, such as high productivity, stable processing accuracy, and low product cost.

To further exert these advantages, CNC prototype machining has been developed toward “process concentration,” that is, a CNC machine (i.e., a machining center) that can complete multi-process processing after clamping CNC machining parts at a time.

Rapid prototyping CNC machining select aircraft parts with complex profiles as the processing objects from the very beginning, which is the key to solving ordinary processing methods’ difficulty. The most significant CNC machining feature is punched tape (or tape) to control the machine tool for automatic processing.

Airplanes, rockets, and engine CNC precision machining parts have different characteristics: airplanes and rockets have zero features, large component sizes, complex shapes, engine zero, small component sizes, and high precision.

Therefore, the CNC machine tools selected by the aircraft and rocket manufacturing departments and the engine manufacturing departments are different.

In aircraft and rocket manufacturing, large-scale CNC milling machines with continuous control are mainly used. In contrast, in engine manufacturing, both continuous-control CNC machine tools and point-controlled CNC machine tools (CNC drilling machines, CNC boring machines, machining centers, etc.) are used.

CNC machining advantages

Process concentration

CNC machining generally has tool holders and tool magazines that can automatically change tools. The tool change process is automatically carried out under program control. Therefore, the operations are relatively concentrated. Process concentration brings substantial economic benefits:

• Reduce the floor space of the machine tool and save the workshop.
• Reduce or no intermediate links (such as intermediate inspection of semi-finished products, temporary storage, handling, etc.), saving time and human resources.
  automation
• No need for manual tool control during CNC machining processing and the degree of automation is high. The benefits are apparent.

 Reduced requirements for operators:

A senior worker of an ordinary machine tool can not be trained in a short time, and a CNC worker who does not need programming has a short training time (for example, a CNC lathe worker needs one week, and he will write simple processing programs).

Also, the parts processed by CNC workers on CNC machine tools have higher precision than those processed by ordinary workers on traditional machine tools, and time is saved.

Reduce the labor intensity: CNC workers are excluded from the processing most of the time during the processing, which is very labor-saving.

Stable product quality: The processing automation of CNC machining eliminates the fatigue, carelessness, estimation, and other human errors of workers on ordinary machine tools and improves the consistency of products.

High processing efficiency: The automatic tool change of the CNC machining prototype makes the processing process compact and improves labor productivity.

High flexibility

Although the traditional general-purpose machine tool is flexible, it is inefficient. In contrast, the particular conventional machine is highly efficient. Still, it has low adaptability to parts, high rigidity, and inadequate flexibility, and it is difficult to adapt to the fierce competition in the market economy.

Products are frequently modified. As long as the program is changed, new parts can be processed on the CNC machining. It can be automated, with good flexibility and high efficiency so that the CNC machine can adapt to market competition.

The CNC prototype machining can accurately process various contours, and some shapes cannot be machined on standard machine tools. CNC machining technology is especially suitable for the following occasions:

• Parts that are not allowed to be scrapped.
• Development of new products.
• Processing of urgently needed parts.

CNC machining cost

What is the cost of CNC machining?
First of all, CNC machining costs will vary significantly because of the different CNC machining parts you are doing. Before placing an order, it is necessary to check the overall budget of your project. You need to consider several aspects that affect the cost of CNC machining.

• CNC machining design cost;
• The quantity of CNC machining parts;
• CNC machining material costs;
• The cost of using different types of CNC machines;
• CNC machining Surface finishes cost
• CNC machining Labor costs

CNC machining Design cost

Several aspects of design will affect production costs.
The complexity of the design will have an impact on this. More intricate designs will require longer programming time. This will increase your order’s price, and CNC machining suppliers will also charge you for the time spent on digital format.

The quantity of CNC machining parts; 

Your order quantity will also affect the cost that the CNC service company charges you.

Small orders will be cheaper than large orders. However, larger orders will reduce the cost of each item.

For example, suppose you want to order ten units of CNC machining components. A rapid prototyping company might set a price of $15 per unit, which means you have to pay a total of $150.

However, suppose you have ordered 50 units of CNC precision machining parts, each may only cost $5, and you will have to pay a total of $250. Yes, although you have to pay an extra $100, relatively speaking, you get more products.

CNC machining materials cost

Depending on your product, no matter you want CNC plastic machining parts or CNC metal machining parts, these CNC machining materials will affect your cost.

In general, plastic will be cheaper than metal because it is not durable and less expensive to produce.
Your material cost is usually 6″ x 6″ x 1″ piece.

The price of each piece of common materials used in CNC plastic machining parts are:

• ABS cost is $15 per block
• POM (Delrin) charges $25 per block
• Nylon 6 sells for $25 each.

The cost of some popular materials used for CNC machining metal parts are:

• The price of 6061 aluminum CNC machining parts is $20 each.
• 7075 Aluminum CNC machining steel costs $70 per piece.
• Stainless steel CNC machining services cost $80 each.

The cost of using different types of CNC machines

You can rent several different types of CNC machines for the project. Which one you choose may affect your work costs.
The CNC service company sets machine rent as an hourly rate. The CNC machining suppliers use the machine’s price and how long it can run in an hour each year to calculate this. It is usually calculated by dividing the cost of the machine by 5000.

There are two main types of CNC machines: a 3-axis CNC machine and a multi-axis machine.

How much does CNC machining cost per hour?

3-axis CNC machines include CNC milling machines (approximately US$40 per hour operating cost) and CNC turning machines (about US$35 per hour operating cost).
The running cost of the multi-axis machine is higher, so the price is also higher.

Their prices range from 75 to 120 dollars per hour. Some prices may be higher than this, so it is necessary to ask about your machine selection when obtaining a quote.

Surface Finish Cost

For each product, you can carry out a specific surface treatment for CNC machining components. However, surface finishes on the product usually increase the corresponding cost.
Some surface treatments, such as high polishing, are to eliminate any traces of the machining process.
E.g.:

• The surface finish can produce a reflective surface.
• Matte surface treatment or sandblasting eliminates reflections.
• Mirror polish on clear plastic to make them look like glass.
• Finish painting and dyeing can change the color of the product.
• Laser engraving can decorate your products.
• Through printing, you can print letters or patterns on the product after it is finished.
• Soft surface treatment involves applying a rubber-like soft layer on the product.

Some surface treatments play an essential role in making your products more durable. These include galvanizing, anodizing, and brushing.

Some companies may let you combine different finishes on their products. For example, you may be able to get a laser-engraved glossy polished surface, although this may cost more.

Labor costs

The most significant labor cost encountered in CNC machining is the upfront cost of design and digitization. It uses computer software, but it also requires the help of design experts.

Especially when your product is complicated, design time and difficulty will increase. However, regardless of the quality of your order, your design labor costs will remain the same. This means that if you place a large number of orders, your labor costs will drop to less per unit.

The additional labor costs include paying machine operators during production. If your production window is short, then this will be lower. The post-processing, finishing, or assembly of parts also requires additional manual work, which will increase labor costs. This is why it may be cheaper for some projects to outsource manufacturing to a country like China.

In this way, you have to weigh your labor costs. Large ordering reduces the unit design cost, but the manufacturing time is longer. Therefore, you will have to pay more for machine operation.

What is a CNC machining surface finish?

CNC machining surface finish can be divided into:

• Oxidation processing,
• Painting processing,
• Electroplating,
• Polishing,
• Wire drawing,
• Sandblasting,
• Oil spraying,
• Silkscreen,
• Pad printing,
• Electroplating,
• UV
• Metal corrosion processing

1. Oxidation processing: When the CNC machining suppliers produce finished CNC machining parts (mainly aluminum CNC machining parts), it uses oxidation processing to harden the CNC machining product’s surface and make it difficult to wear.

2. Spray paint processing: the CNC service company uses spray paint processing when producing large CNC precision machining parts. The spray paint processing prevents the CNC machining components from rust, such as daily necessities, electrical enclosures, handicrafts, etc.

3. Electroplating: Electroplating is also the most common processing technology for CNC machining parts processing. The CNC machining components’ surface is electroplated through modern technology to ensure that it will not be moldy or embroidered under long-term use. Standard electroplating processing includes screws, stamping parts, Cells, car parts, small accessories, etc.,

4. Polishing: use polishing materials for polishing, polishing wax, rubbing copper water, etc., for manual polishing. Polish the sharp corners into a smooth face so that it will not cause harm to the human body during use.

5. Brushing: draw a few traces on the surface of aluminum or steel parts or other products to make the sample feel better. Plastic wire drawing is generally sprayed with a thick paint layer and then processed by this process. The effect is worse than that of metal CNC aluminum machining parts. The texture is worse than metal parts.

6. Sandblasting: There is a lot of residual plastic on the sample from the computer gong, which is very troublesome to handle manually, especially where there are many holes or multiple buckles, which is incredibly time-consuming.

So use a sandblasting machine. The residual plastic is knocked out. Aluminum CNC machining parts or other metal parts are knife lines that can cover the surface. Some customers also require sandblasting and then oxidation to make the body grainy and robust metal texture.

The sand is delicate glass beads, distinguished by models (for example, No. 60 is coarse sand, and No. 200 is fine apple sand)

7. Oil injection: spray the products we have made according to the customer’s requirements. Our site is a dust-free oil injection room, and the best oil is used. (The injection can be sprayed with rubber oil, bright, semi-matte Light, matte, baking varnish, and different colors of paint)

8. Silkscreen: print words or patterns on the plane of the products we have made

9. Pad printing: printing words or patterns on the uneven surface of the product

10. Electroplating: To make the product’s details more eye-catching, a layer of silver-plated product color is applied. Before electroplating, the sample must be very smooth (polished to the degree of polishing) without any impurities. Then, soaked in the potion Medium (water plating and vacuum plating), water plating can conduct electricity.

11, Over UV: Spray a layer of transparent oil on the sample’s surface and bake it with ultraviolet light to make the product brighter. (UV oil has the function of protecting the work, and it can be smooth and matte. According to the needs of customers Processing)