Prototyping is one of the major steps in product development, as it helps evaluate a design’s appearance and functionality. Undertaking this process using traditional machining methods is expensive and time-consuming. However, CNC prototype machining makes it possible to make prototypes inexpensively and in a relatively short period.

In this article, we will discuss prototype machining and examine the different applications of CNC prototyping machining, considerations, and tips for the process.

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What is Prototype Machining?

Prototype machining is a process used to create prototypes quickly using a CNC machine. The production batch is usually small, aiming to provide a visual and functional representation of the final product. In other words, prototype machining determines how a digital design would turn out physically.

With prototype machining, it becomes easier for manufacturers to spot design defects and eliminate them before the commencement of large-scale production. Eliminating defects at this stage of product development helps make production cost-effective.

Why is CNC Machining Good for Prototyping Processes?

Several reasons make CNC machining the ideal process for prototyping. Firstly, this process offers a high level of accuracy and precision due to its use of computerized controls that supervise the movement of the workpiece and cutting tool. These computerized controls consider every angle on your design, ensuring the prototype generated is its replica.

Another reason why CNC is good for prototyping is its speed. It is quite different from processes like Injection molding, where the manufacturer and product developer would have to wait a few months for tolerances and mold to be ready.

With the CNC system, prototyping starts with creating a 3D CAD model of the final product and converting it into CAM files. The CAM files contain the G Code, which controls the movement of the CNC machine during the prototyping creation process.

Different CNC Prototyping Operations

There are different prototype CNC machining operations available to manufacturers. The specific operation chosen for a design often depends on several factors, including the design specification and materials used.

Below are the common CNC prototyping machining operations.

Milling

This operation involves creating a prototype with the aid of a milling machine. The CNC milling process is subtractive as the machine cuts materials from a workpiece to create a CNC-milled prototype of varying geometries. The milling machine features multipoint cutting tools, with each cutting point making sharp cuts of varying shapes and lengths on the workpiece as it rotates.

The depth and type of cut made on the workpiece and the axes used by the machine depend on the design’s complexity. For higher cut precision, the milling machine also features additional axes that enhance its movement.

Turning

This process involves making prototypes using a turning machine with a lathe tool. This tool is ideal for use in making detailed prototypes as well as final products with cylindrical features. The lathe cutting tool is stationary in this machining operation while the workpiece rotates close to it.

Unlike the milling machine, the turning machine creates cylindrical parts using a single-point cutting tool to remove materials from a bar stock. CNC turning is ideal for creating linear features on the exterior of a prototype, as well as slots, threads, and tapers on its interior edges.

Multi-axis Machining

This is a more versatile rapid prototyping operation ideal for making prototypes with complex specifications, as it takes into more axes than conventional operations. Here, there are 4-axis, 5-axis, and up to 9-axis machines. Also, the higher the number of axes taken into consideration by the machine, the higher its ability to provide high tolerances and difficult machine parts.

Advantages of CNC Machining for Prototypes

As regards whether to choose the CNC process for your prototypes, here are some advantages of making prototypes through CNC machining.

1. High Accuracy and Precision

CNC machining facilitates the production of prototypes with high precision, tolerances, and accuracy. This precision and accuracy are due to the computerized control placed on the movement of the cutting tools.

Since the machining process is accurate and precise, errors or flaws in the manufactured prototype commonly stem from the design itself.

2. Cost Effective

CNC for rapid prototyping occurs in single or small batches so the manufacturer can assess the product visually and functionally. Small batch production is a fail-safe that protects the manufacturer or product developer from financial ruin. If the manufacturer finds a defect during the assessment, the loss would be minimal compared to detecting a defect after full-scale production.

3. Consistency and Repeatability

CNC prototyping has a high degree of repeatability. In other words, using the same process and design used in manufacturing a particular finished product would produce a replica of that product.

Additionally, CNC prototyping machines are consistent and offer exact imitations of the original design regardless of how many copies are produced. This is quite different from other prototyping processes like injection molding, where after several repetitions, the mold depreciates, causing minute changes to the design.

4. Material Versatility

While there is a limit to the number of materials manufacturing and machining processes like 3D printing and injection molding can work with, CNC prototyping offers more versatility. With CNC prototyping, it becomes possible to machine various materials, ranging from plastics and wood to the strongest metal prototype.

Material options that you can use with CNC prototype machining include plastics like PS, LDPE, HDPE, PC, PP, PMMA, POM, PAGF, PCGF, ABS, and Teflon.

Metals and metal alloys ideal for CNC prototype machining include aluminum, steel, stainless steel, magnesium, titanium, zinc, copper, bronze, and brass.

5. Time-saving Process

Making prototypes using CNC is a time-saving process as it does not require the production of molds and other prerequisites. Also, modifying designs is fast, as the manufacturer needs to modify the CAD and CAM files and produce the prototype again using the CNC machine.

Limitations of Prototyping with CNC Machining

Prototyping with CNC Machining remains one of the best ways to produce prototypes, but there are still limitations to using this process. Below are some of these limitations;

1. Geometrical Restrictions

One major limitation of the CNC prototyping process is its inability to work on interior geometries. This is primarily because the machine works only on the outside.

In other words, it would be difficult to generate prototypes that have internal components using CNC prototype machining. To make prototypes with internal components, it is best to use additive manufacturing processes like 3D printing that work from the inside to the outside as they are better at manufacturing internal geometries.

2. Technical Expertise

Designing a CAD file and generating a CAM file from it requires technical know-how. Additionally, setting up and operating the CNC machine requires some expertise. CNC prototyping requires knowledge of procedures for testing, innovative approaches, experience, and creative vision.

Additionally, not every manufacturer that undertakes CNC machining can make CNC prototypes without training. This is why it is often advisable to outsource CNC prototype machining jobs to experts like WayKen with years of experience in the prototyping industry.

3. Subtractive Manufacturing Process and Waste of Materials

CNC machining removes materials from the workpiece during the prototyping or production process, making it a subtractive manufacturing process. Consequently, increasing the quantity of material used up during the manufacturing process increases the material cost.

Also, since it is highly unlikely that a prototype will be ideal on the first attempt, this adds to the waste of materials and its associated cost. Additionally, since there is little likelihood of selling the small batch of prototypes produced, even if they meet all technical requirements, it still counts as a waste of materials.

4. Costs More Than 3D Printing

The material costs incurred during CNC prototype machining make the process much more expensive than SLS 3D printing. Also, with prototyping, the focus is often on detail rather than cost optimization, which is why prices are sometimes sky-high.

However, the price is often worth it as prototype precision and accuracy are greater, and the range of materials is wider.

Applications of CNC Prototype Machining

CNC Prototype machining is one prototyping process with wide acceptability across every industry. However, some industries use this process more than others; here are some of these industries.

Automotive Industry

The automotive industry requires parts and models with high precision and tight tolerances. These parts often range from the brakes and gears to the suspension components and even the wheels. All these parts require ultra-tight tolerances to ensure vehicles’ safety.

This industry makes these prototypes and fits them in vehicles to ensure they fit and function properly before mass production. Without CNC prototype machining, it would be challenging to develop automotive prototypes that consistently fit the desired specifications.

Medical Industry

This industry needs parts and equipment with microscopic precision and accuracy. The medical industry also enjoys the versatility in material choice offered by CNC prototype machining with requirements for parts made from metal and plastics.

Additionally, with the advancement in medical technology, there are needs for prosthetics, biopsy tubes, surgical scissors, implant holders, etc., parts that require the tightest of tolerances. The CNC machining process provides this industry with high-quality functional prototypes with high precision and accuracy.

Aerospace Industry

This industry uses CNC prototyping technology for two major purposes. First, to develop parts with a high degree of precision and accuracy. Another reason is to test the performance of these parts and other innovations in the aerospace industry for their functionality, guaranteeing these parts would not fail when an aircraft is airborne. Aircraft parts often made using CNC prototype machining include manifolds, bushings, airfoils, etc.

Military Industry

The research and development department (R&D) mostly uses this technology in the military industry. Military R&D uses CNC prototype machining to produce warfare vehicles, aircraft, and other parts. They rely on this process since it facilitates the rapid production of parts regardless of the hardness of the material used.

Considerations and Tips for CNC Prototyping

CNC prototyping is a reliable method used by manufacturers to ensure that parts meet the requirements and precision before mass production. Want to CNC prototype your design? Here are some tips for you.

Reduce Prototype Complexity

While a complex design might sound like a good idea, it usually isn’t. One thing to note about CNC prototype machining is that the higher the complexity, the higher the CNC machining cost. Aside from the cost, it takes a long time to set up the machine for a design that requires several angles and undercuts, consequently increasing the development time.

So, a complex design increases the cost of developing your product and your time to market by increasing development time.

Use Default Tolerances

Default tolerances are often best practice, arrived after years of working with a particular material. Achieving tighter tolerances may require specialized cutting tools and additional fixtures, which would impact the cost of production. It is often best to let the experienced engineers working on your design decide which tolerance level would be ideal for your product prototype.

Take Tool Geometry into Consideration When Designing

Consider the axial characteristics of the cutting tools or the machined during prototype CNC machining since machining procedures operate in a rotating fashion. The majority of cutting tools have limited cutting lengths and are round. Therefore, the geometry of the tool will have an impact on all cutting operations.

Use an Experience CNC Prototype Manufacturer

More essential, you ought to collaborate with a seasoned CNC prototyping specialist. As they can focus on streamlining processes to create high-quality prototypes. The specialist also considers the geometric constraints of the machining process required to manufacture the desired prototype design. Without an experienced prototype manufacturer, it would be difficult to reap the benefits of developing prototypes using CNC machining.

Comparison Between CNC Machined Prototypes and Injection Molding Prototypes

While both these prototypes provide a visual representation of the final product, they are quite different from each other. Here is a comparison between both types of prototypes.

Part Tolerance

Injection molded prototypes have a part tolerance ranging from ±. 0.1 to 0.7mm. The low tolerance level obtained with injection-molded prototypes is due to the shrinkage after injection.

On the other hand, the CNC machine prototypes have a very high tolerance level of ± 0.01mm, a testament to the precision and accuracy of the machining process.

Prototype Material

Injection-molded prototypes are usually plastics or elastomers. This is due to the production process requiring molten materials into a mold to form the prototypes. Conversely, CNC Machined prototypes could be wood, plastic, or metal, depending on the material chosen by the manufacturer.

Surface Quality

Although the process of Injection molding is precise, prototypes produced might have minor defects like warping, sink marks, flow lines, weld lines, vacuum shots, short shorts, and jetting. These defects negatively impact the appearance of injection-molded prototypes.

On the other hand, CNC machined prototypes have a better surface finish due to the extensive tooling employed during the process.

Comparison Between CNC Prototyping and 3D Printing

While both are prototyping processes, they are quite different from each other both in the method and solution provided. Also, both processes have their strengths, weaknesses, and ideal scenarios. However, for this article, here is a comparison between both processes;

Material Consumption

Compared to CNC prototype machining, the material waste of 3D Printing is quite low. This is because 3D Printing only makes use of the required material during the manufacturing process. On the other hand, CNC machining cuts excess materials from a block to achieve the desired shape.

Prototyping Cost

CNC processes are costlier than 3D printing. The price difference is due to the number of accessories a CNC machine requires to function optimally. These accessories range from fixtures and cutting tools to cutting fluid delivery systems.

Also, the high cost of acquiring the CNC prototyping machine influences the cost of prototypes produced through the machining process, making them considerably more expensive.

Supported Materials

CNC machining supports materials ranging from wood and plastic to metals and alloys. 3D Printing, on the other hand, commonly supports thermoplastics due to their ease of heating and reforming.

Part Tolerance and Toughness

CNC machines have a tolerance of ±0.01 mm, while next-level 3D printing technologies like DMLS (Direct Metal Laser Sintering) have a tolerance level of ±0.1 mm. Also, CNC prototyping machines produce parts that are tougher than those produced by 3D Printing.

WayKen Offers CNC Services for Rapid Prototyping

WayKen’s cutting-edge technology and more than 20 years of CNC prototyping expertise enable us to produce your CAD models optimally. We provide expert one-stop CNC machining services from precision prototyping machining to complete production runs.

We can create high-quality prototypes regardless of the industry that adheres to the desired specification thanks to our rich industry machining experiences. Simply upload your CAD files to receive DfM and a quote.

FAQs

What are the materials for CNC prototypes?

The materials for CNC prototypes are Metals: bronze, zinc, magnesium, titanium, copper, brass, stainless steel, and aluminum.

Acrylic, ABS, PP, nylon, PC, Teflon, HDPE, LDPE, and PVC are examples of plastics material that are great for CNC prototyping.

Are there better options for prototyping than CNC prototype machining?

CNC prototype machining is one of your finest options if you want a highly durable prototype. However, the material for the task, how structurally robust you want the prototype to be, and a few other criteria will play a significant role in your decision to choose what prototyping processes.

What factors affect the cost of CNC prototyping?

Factors that influence the cost of CNC prototyping include design complexity, tolerances, and choice of material. Other factors include the type of CNC machine used and the surface finishing option chosen.