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CNC Prototype Machining: Everything You Need to Know

The essential thing in production is converting an idea into a tangible product. This is where prototypes come in. These are like real versions of an idea that help engineers and designers test and make their creations better. It is interesting to note that there are various methods you can use to make prototypes, and CNC prototype machining is special. 

Understanding CNC Prototype Machining

CNC Prototype Machining

As the name suggests, a CNC (computer numerical control) is used to produce a prototype. The process aims to create a physical and functional model that looks, behaves, or does both like the final product. Manufacturers use this technique to rectify flaws before producing them on a larger scale. Apart from helping to remove errors, it also brings the overall cost down.   

Types of Prototypes

Visual Prototype

Manufactured using foam, clay, or plastic, this is a non-functional prototype but gives you a visual idea of what the product will look like. Designers use such models to assess the outlook of the product. 

Proof-of-Concept Prototype

An incomplete prototype that functions but isn’t exactly like the final product. Basically, this model helps establish the idea and assess if it will perform well in real conditions. Foam, cardboard, and 3D-printed parts are used to make them. 

Presentation Prototype

Meticulously created prototype designed for marketing purposes or to demonstrate to potential investors. Metal, glass, high-grade plastic, or other high-quality materials are used to make this detailed prototype. 

Working prototype

A functional product that works exactly like the final product. To make them, premium quality materials such as glass, metal, or high-grade plastic are used.

CNC Prototype Production

Step 1: Design Ideation and 3D File Generation

  • Product designers and engineers brainstorm and sketch different design concepts. They focus on functionality, aesthetics, and manufacturability.
  • The design is translated into a detailed 3D model using CAD software. This model defines all dimensions, features, and tolerances of the final prototype.

Step 2: Production Sequence and CNC Programming

  • Engineers determine the optimal order of machining operations. They consider tool changes, material removal efficiency, and minimizing machine travel.
  • Based on the sequence, specialized software generates G-code instructions. These tell the CNC machine how to move its tools, adjust settings, and ultimately create the prototype.

Step 3: Production (Machining)

  • The chosen material (plastic, metal, wood, etc.) is secured on the machine bed.
  • Different cutting tools like drills, mills, and end mills are selected and automatically exchanged throughout the process based on the program.
  • The CNC machine meticulously follows the G-code instructions, removing material bit by bit to form the desired features and geometries of the prototype.

CNC Prototyping Operations

Milling

CNC milling machine

Milling is a subtractive prototype manufacturing process where a rotating cylindrical tool with multiple cutting teeth removes material from a solid block and creates the desired shape. The process can be used to create complex geometries, contours, slots, and intricate features with materials like metals, plastics, and wood. 

Machines used: 3-axis, 4-axis, and 5-axis milling machines are commonly used.

Applications: Prototypes with intricate details, functional components, and precise dimensions, like gearboxes, housing units, and electronic components.

Turning

Also known as lathe machining, turning rotates a cylindrical workpiece against a stationary cutting tool. The tool removes material as the workpiece spins, shaping it into the desired form. It can create shafts, bushings, and gears. It can also be used for the repetitive machining of identical parts.

Machines usedLathe tools such as Turret lathes with tool holders for automatic tool changes and Swiss-type lathes for machining long, slender parts.

Applications: Prototypes for pistons, bearings, and fasteners.

lathe, CNC Prototype Machining

Multi-Axis Machining

5-axis CNC Machine

Multi-axis machining uses machines with more than three axes of movement. This enables the cutting tool to approach the workpiece from various angles and tackle complex geometries. The process is perfect for complex parts with intricate features and undercuts. 

Machines: 4-axis and 5-axis machines, with some advanced machines reaching up to 9 axes.

Applications: Prototypes for molds, medical implants, and intricate mechanical components.

Uses of CNC Prototype Machining in different industries

Marine Industry

The industry requires large-scale manufacturing of water transportation with high-quality craftsmanship. That’s why automation with CNC machining is needed to fulfill the demands. From the hull to interior trimmings, these devices are capable of doing everything. For example, NC mills, electrical discharge machining, and other such techniques help design and develop boat parts for construction. 

Automotive Industry

Before a new car model goes into production, multiple prototypes are created and tested. CNC machining is used to create these prototypes, allowing engineers to test the design, functionality, and performance of the car. From large engine parts to small gears, CNC machining can do it all. An example of this is a combustion engine that uses multiple CNC machining processes. This may include the conversion of large metal blocks into engine body panels or the creation of pistons and cylinders. 

Aerospace

It is believed that the requirements of the aerospace industry have led to the spur in the growth and development of the CNC industry. Nevertheless, the former requires equipment that is made with a focus on safety and high quality, something CNC can fulfill. So, you’ll come across several components used in aerospace that are developed using CNC, such as antennae, landing gear, manifolds, bushing, and more.

Electronics 

Small-scale construction is often in demand in the electronics industry, and these must be consistent. CNC machining handles both internal and external parts in the consumer electronic industry well. Metal alloy casing of smartphones is the prime example. CNC milling machines and CNC routers are used extensively to construct these. Other electronic components that benefit include PCBs, jigs, housings, and heat sinks. 

Military and Defense Industry

Their needs are similar to those of the aerospace industry and can be of great use in the military R&D department. The latter is known to be utilized for manufacturing aircraft, warfare vehicles, and many more applications. The reason they use it is due to the CNC machine’s ability to work seamlessly with the toughest of materials. 

Medical Industry

To ensure the making of parts that carry micro-level precision, CNC machines are used in the medical industry. From metals to plastics, a variety of materials can be used, something the medical industry can make use of. For instance, the CNC machining process can be used for biopsy tubes, implant holders, prosthetics, surgical scissors, and more. These demand tough tolerances and should be highly accurate and precise in function. 

Oil and energy industry

Its use is not just restricted to producing prototypes for fragile items; it is also used for products that have high physical strength, such as in the oil and energy sector. The industry needs parts that can help mine products deep within the earth’s core. In the energy sector, it helps reduce adverse environmental impact. 

Advantages of CNC Prototype Machining

For a manufacturer, there are a number of benefits of using CNC prototype machining in the manufacturing process. Let’s check a few of them. 

Extensive range of materials

These machines are compatible with a number of materials, and the best part is that most of them are long-lasting. These may include aluminum, stainless steel, zinc, steel, magnesium, titanium, brass, copper, and bronze. 

Quality and Consistency

Unlike other machines that rely on humans and their skills, CNC machines work as instructed. Not only this, they can repeat the process without making any changes to the prototype. This helps in manufacturing new iterations from the existing prototype. This also means that the same machine can be used for producing the final products. 

Affordable

Given the ability of CNC machines to produce small numbers of prototypes, the manufacturer can check on how the product will look or work. This helps them avoid losing money as they can fix any error that arises in a small batch.  

Saves Time

No need to make molds and other prerequisites saves time with CNC machines. Also, designs can be modified faster as the only modification required is in CAD and CAM software, and the rest is handled by the machine itself. 

Why choose CNC machining instead of 3D printing?

Undoubtedly, CNC machines have an edge over 3D printing for prototype development. Here are a few reasons why:

  • Parts created with CNC machining are more accurate because the machine can maintain closer tolerances.
  • The layer-by-layer construction process in 3D printing makes it difficult to fully replicate the raw potential of high-performance engineering materials. Whereas on the other hand, CNC machining preserves the strength and stability of these materials. 

Preparing CAD Models for CNC Prototype Machining: SomeTips

You can always improve your design for manufacturing, as this will increase your chances of making a successful prototype. Here’s what you can do:  

Implement cavities, edges, holes, and walls carefully.

Machines have restrictions, and CNC machines are no different. Hence, it is suggested that you optimize the different sections of your CAD model with care. 

Depth and diameter of cavities: Most end mills can only cut three to four times their diameter. So, for best results, keep the cavity depth within this limit.

Edges: Take into consideration the diameter of the cutting tool when your design has corners.

CNC Prototype Machining, CAD Models

Holes: Standard drill bits have limitations, so be mindful of the size and depth you need. If your hole requires a precise diameter, consider reamers and boring tools.  

Wall thickness: Thin walls tend to vibrate, and this can cause the cutting tool to compromise the surface finish. So, keep the wall thickness to a minimum of 0.8 mm or higher.

Select CAD Software wisely.

This application of CAD has led to a spur in the development of numerous CAD software. Undoubtedly, some are effective, while others are too complex to understand and operate. Therefore, choose the correct CAD applications for your specific industry. For instance, the software made for mechanical engineering and sheet metal forming may not work for architecture, and vice versa. 

Create Checklist Beforehand

For designs and features you desire in the final prototype, create a checklist. This will save you time and effort later on when the design demands a modification. 

Make simple drawings

While several methods can be utilized to design a prototype, simplifying designs is the best strategy to minimize the machining process. For example, divide the drawing into two parts and assemble them later if the design is complicated.

How do you choose different cutting tools in CNC machining?

When selecting cutting tools for CNC machining, consider the following:

  • Type of material: This is important as tool materials and geometries vary depending on the material.
  • Mechanical properties of the material. When the cutting speed is not optimal, both cutting efficiency and tool longevity are compromised. For instance, a hard material will require a different cutting speed than a soft material. 
  • Cutting Efficiency. To enhance the efficiency of the tool, check its feed rate and depth of cut. Also, see if it can handle the cutting force you will be applying. 
  • Cutting stability. It helps prevent vibration and resonance. To ensure this, assess the tool’s rigidity and stability.
  • Life of the tool: Longer the shelf life, the lower the chances of replacement or repair. Thus, it also helps in saving money. 
  • Cost: Evaluate the cost-performance ratio of the cutting tool. Make sure there is a favorable balance between the price of the tool and its performance. 

Parting Thoughts

CNC Prototype can prove to be an investment you will not regret later. So, if you have any plans to enhance your manufacturing, then don’t give it a second thought. This machine will make your journey from pixels to prototypes easy and worthwhile. And do not forget sight of your goal; that’s the most important consideration! 

FAQs

What is the normal workflow for CNC prototype machining?

The process involves 

  • 3D CA3D CAD model creation
  • CAM programming 
  • Machine setup
  • Machining process 
  • Finishing and inspection

How much does CNC prototype machining cost?

The cost of CNC prototype machining depends on several factors, including:

  • Type of the material
  • Labor cost
  • Part Design 
  • Geometry
  • Precision and tolerances 

How long does it take to create a CNC prototype?

The turnaround time for CNC prototypes can vary from a few days to a few weeks, depending on the complexity of the design and the workload of the machine.

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