1.0 Introduction

Computer Numerical Control (CNC) machining is one of the most extensively utilized prototyping processes in the manufacturing sector. Prototyping machining with CNC, is nothing more than the use of computers to generate practical and operational prototypes. This method has entirely replaced traditional approaches of prototyping. CNC prototype machining is a procedure in which a machine tool is controlled by a computer, this will be based on numerical data entered into the machine. CAD/CAM software is commonly used and allows machine users to develop the appropriate designs and allows the computer to control the tool’s motions.

Engineers employed routes, shaping machines, vertical millers, and center lathes to create prototypes during the 1980s and 1990s. One of the most significant advantages of utilizing CNC machines in prototype manufacturing is the automation of prototype machining and the elimination of most manual operators.

Traditional prototyping machining necessitated the hiring of human skilled labor, which became expensive in the long run. In prototype manufacturing a single operator is necessary to conduct the entire prototyping process on the CNC prototyping machines. As a result, when it comes to creating functioning prototypes, most manufacturers prefer CNC prototyping as it is a great alternative for precision, efficiency, and speed.  

Some of the sectors that require CNC prototype machining include aviation, metalworking, military, electronics, weaponry, construction, automotive, dentistry, and agriculture.

1.1 Applications that need extreme part precision 

From commercial and private airplanes to interplanetary spacecraft, precision is critical in the aerospace business. Aerospace CNC prototype machining services serve a variety of applications.

The engine.

It is the most important component in an airplane for external functioning, and it must handle and burn fuel without any leaks or component failures. CNC prototyping aids in the production of the engine’s most sophisticated elements, which are vital to its efficiency.

Cockpit components.

CNC prototyping is crucial in the design of interior components for the cockpit. The navigational system, which delivers real-time guidance to the pilots, is made up of some of the tiniest interconnected pieces. CNC prototyping aids in the production of these tiny aerospace parts, which may require periodic fine-tuning and tweaking. CNC prototyped parts are extremely precise and long-lasting, almost eliminating the possibility of failure.

Spacecraft Parts.

CNC prototyping is used to create high-performance spaceship components such as robotic arms, electrochemical systems, tubing, and encasements. Every component used in spacecraft must be light, sturdy, and resistant to the extremes of temperature and radiation found in space.

Exterior Components.

Wing flaps, lights, sensors, and outside panels are all seen on the outside of an aircraft. These components are made of high strength, lightweight materials that are easily manufactured using CNC prototyping technology to resist the severe conditions of air and space flight. CNC prototyping also ensures that external panels and surfaces come together flawlessly for maximum aerodynamic performance.

Runners.

Reciprocal engine induction systems direct air into the engine block via runners and pipework. Precision runners for these systems are designed and manufactured to extremely tight tolerances using CNC prototyping machining.

Housings.

Electronics and delicate equipment are housed in casings to protect them from radiation, temperature fluctuations, and magnetic modulation.CNC prototyping aids producers in the development of streamlined casings that shield sensitive components from undesired interference.

Braking Systems and Parts.

Braking systems for aerospace hardware depend significantly on precision CNC manufactured components, such as brake pedals, cylinders, calipers, pistons, brake shoes, lines, and hoses, these assist in regulation of velocity of the aircraft and spacecraft when on the ground.

Gearbox Components.

CNC prototyping machining benefits gearbox components such as gears, rods, shafts and housings. Transmission, steering, and other important aircraft and spaceship systems operate smoothly and efficiently.

2.0 The Procedures for CNC Prototyping

The phases in CNC prototyping process are as follows:

· Generation of 3D Files:

3D data, such as CAD designs, are used in CNC manufacturing. As a result, the chosen designs are transformed to a 3D file. The 3D files determine the final product’s size, features, and aesthetic standards.

· Identification of Production Sequence:

The machining technique for each feature is determined once the 3D file has been prepared. A seamless CNC machining cycle is used to build the prototype. CNC-machined prototype production may comprise a variety of manufacturing methods, including CNC routing, CNC turning, CNC cutting, CNC milling and CNC drilling.

· CNC Programing:

The CNC program directs the CNC machine through the sequence of manufacturing processes and tool operating instructions. The computed values are placed into G-codes or M-codes to generate a CNC program. G-codes and M-codes instruct the CNC machine which tool to use, how long the tool should travel, how fast it should feed, and how deep it should cut. All instructions are included in the CNC software, allowing for CNC rapid prototyping automation based on production needs. Feed rates, cutting depths, number of runs, and tool travel distance are all calculated throughout the programming process.

· Prototyping;

The CNC program is then loaded into the CNC machine’s numeric control panel.

The seamless CNC machining process begins after the workpiece is positioned on the tool and the machine is turned on. The prototype of the intended product is created from various CNC machining procedures performed on the workpiece. A dummy or a fully working look-alike-work-alike prototype can be used.

3.0 The types of CNC prototyping

3.1 CNC Milling Prototyping

Milling prototype is the most adaptable CNC prototyping method. Depending on the prototype’s complexity, a 5-axis CNC machine is sometimes required. The additional axes of movement enable for considerably more precise cutting and sophisticated part fabrication, nevertheless they come at a higher cost. CNC milling involves cutting the final prototype from a bigger block of material sheets with a computer-controlled tool head. CNC mills are the most prevalent form of CNC prototype machine, with high accuracy (tolerances of roughly 0.001″) and the ability to work with a wide range of shapes and materials.

3.2 CNC Turning Prototyping

Turning machines, often known as lathes, produce circular components by keeping a block in place while rapidly turning it, meanwhile a tool cuts portions from the original stock using CNC computer code. Due to their restricted all-round CNC prototype applications, lathes are suited for prototyping objects with circular mid-sections.

3.3 CNC Router Prototyping

CNC routers function similarly to CNC mills, they are simply less expensive versions created using a gantry design to optimize work area for the machine’s size but with less complexity consequently. Routers are better for wood, plastic, and mild metals like aluminum, and are better suited to individuals and small enterprises who aren’t focused on intricate metal cutting. They frequently employ three axes, which provides good complexity for the price, but they lack precision when compared to CNC mills. Creating CNC files based on the tool and machine still requires a large learning curve.

3.4 CNC Laser Cutter Prototyping

Small firms can use more powerful laser cutters to cut metals like aluminum, plastics and acrylics, textiles, and manufacture wood CNC prototypes. Smaller studios wishing to build a range of prototypes without blowing the cash may appreciate their adaptability. The laser’s heat, however, can leave “scorch” markings on the prototype, and intricacy is frequently limited because most CNC laser cutters only operate on two axes.

4.0 Materials used in the aviation sector for CNC prototyping

Several materials are used in airplane production, including those mentioned below.

i. Lightweight Metals

The CNC machining materials used by aerospace firms are determined by two essential features, qualities of strength and weight. Metals such as steel, while robust, are not suited for most sections due to their extreme weight, which results in less fuel-efficient (and consequently more costly) planes. Therefore, the industry considers strong and lightweight metals such as titanium and aluminum alloys

Both metal materials, which are employed in CNC machining, are simple to deal with. Titanium, for example, is around 30% stronger and 50% lighter than steel and it is very resistant to high heat and corrosion. This makes it is perfect for aircraft functional components and exterior elements.

Aluminum, on the other hand, is lighter than titanium but only approximately half the strength. This highly machinable metal is less expensive compared to titanium and is also suitable for a wide variety of aviation components.

ii. High-Performance Plastics

Even though metal components have greater applications in an aircraft’s functional architecture many interior components are made of polymer-based materials. Compared to metals, these materials are much lighter. Interior wall panels, ventilation ducts, airplane doors, wire conduits, bearings, and other items are made with their assistance. They are made of aerospace-grade polymers that are light, robust, and fire-resistant.

For the aircraft sector, aerospace CNC machining produces robust, lightweight, and complicated plastic parts. Materials like PEEK and other high-performance polymers are used to make these pieces. Aircraft prototype machining, like metalworking, provides the high accuracy required for polymer-based aerospace applications.

5.0 The Benefits of CNC Prototyping in the Aerospace Industry

In the aviation industry, there are several prototype procedures followed. CNC machining, on the other hand, is one of the best. This is owing to the numerous benefits it offers. Here are a few benefits you may acquire from employing CNC machining prototypes.

I. The ability to design as much as is required.

Prototypes range from small components to sophisticated assemblies and can be critical in developing trust in novel designs, materials, and production methods. Prototyping at the component or assembly level may often be done before a manufacturing line is formed and can be an inexpensive way for aerospace businesses to test, assess, and trade alternative design concepts. Several prototypes are frequently created before the ultimate strategy is decided.

II. Validate the shape, fit, and function of the item

Aerospace components must fulfill exacting dimensions, material, and processing specifications to perform safely. Prototypes may be used to test components, substructures, and assemblies and assess form, fit, and function (the attributes that identify and characterize a part or assembly) with almost little margin for mistake. Proper prototype may decrease the time between concept and production, as well as the chance of needing to make engineering modifications after production has started, which can be a costly and time-consuming procedure.

III. Obtain unavailable information

Aerospace systems function in a variety of environments, from mild to severe aerothermal loads. Important structures and systems must withstand a diverse range of environments hence testing and evaluating designs at various phases of the design process is critical. Aerospace prototype allows organizations to build and test a variety of components at full scale and in realistic settings, including structural, thermal, and environmental testing.

IV. Less money spent; more knowledge gained

A well-executed prototype program will aid in the timely and cost-effective development of your aeronautical system. Mock-ups and small-scale prototypes can help you get outside funding and narrow down your options early in the development process. Relevant environment testing of full-scale subassemblies later in the development phase can help to mitigate risk. Prototyping requirements will vary depending on the project. As a result, to get the most out of your prototyping budget, it’s critical to assess each circumstance individually.

V. Precision and Tolerance

Following the specification of size and form in your CAD file, you will wish to employ a manufacturing procedure to get the required output. A high precision value machine will be required to get the desired result. The genuine value divergence will be extremely tiny, even if the dimensions do not match those of the model. This means that CNC machining has a higher tolerance level than traditional prototype methods. These precise tolerances are especially important in sections like the landing gear, which Raymer quotes: “Of the many internal components that must be defined in an aircraft layout, the landing gear will usually cause the most trouble.”

VI. Reduce Human Interference

Human participation in the production process is reduced thanks to CNC machining. Operator mistakes are greatly reduced because of this, and production errors are widely reduced.

As a result, if you need to design a model, the CNC machine can work for a long period.

VII. Repeatability

CNC machines are the greatest replacement for producing flawless replicas of components with accuracy and keeping up with the demand of corporations like Boeing, Lockheed-Martin, Vickers, and others.

Unlike manual milling, which is entirely controlled by humans, variances between copies are enormous, whereas CNC milling ensures an exact replica of the object every time. The incorporation of Computer-Aided Design (CAD) into CNC Mills enables for improved performance and the production of flawless replicas every time.

Prior to production, any part can be designed, modified, or recast as needed. The CAD design may be readily modified, enabling multiple programs to be developed before putting the design into the CNC machine, which allows the mill to manufacture a physical replica of the item. This can quickly lead to quick and simple prototyping.

6.0 Conclusion

The aviation industry expects cutting-edge specifications and strict adherence to industry guidelines. The usage of high-grade components is critical due to the delicate nature of aircraft and spacecraft. Aviation CNC machining is much more time-efficient for engineers to make modifications and perform tests, in addition to giving great accuracy and tolerance.

CNC machining offers a full solution, from reaching exact tolerances to cutting cycle durations. Furthermore, given the current level of innovation in the aviation sector, CNC prototype provides all the essential machining phases for a thorough examination of performance, aesthetics, and manufacturability.