CNC Machined Parts: An All-Inclusive Guide

Introduction

In this post, we’ll help you get a handle on the fundamentals of CNC machined parts. So if you are ready to go “all in” in the CNC machined parts, you’ll find this blog helpful. Once we are done with the fundamentals, we’ll discover more about CNC machined parts. Like:

• Best Design Practices for Custom CNC Machined Parts
• Design Process of CNC machined parts
• Advantages of CNC Machined Parts
• Limitation of CNC Machined Parts

And more! Let’s dive right in now.

What are CNC Machined Parts?

CNC refers to Computer Numerical Control. CNC machined parts are the components made with subtractive manufacturing technology by removing material from a solid block using an array of cutting tools to create a final design. People also call them CNC machining parts, custom parts, custom-made CNC parts, machined parts, CNC machined components, bespoke parts, etc. These parts achieve high accuracy, complexity, precision and are cost-effective. (You’ll find more about their benefits later!)

The market for CNC machined parts is growing exponentially. According to a research study published by Facts & Factors, the CNC machining market is expected to hit USD 119.3 Billion by 2026.

Four Production Phases of Machined Parts

When you dig deeper, you realize CNC machined parts are more than just automatically made components. Every CNC machined part undergoes four production phases. They are part design, design conversion, CNC machine preparation, and executing programmed operations.

Part Design: The initial phase of producing the CNC machined part starts with Computer-Aided Design (CAD) software. Engineers carefully plan the final product’s design concerning different parameters, like operating conditions, optimal performance, and acceptable tolerance.

Design Conversion: When the initial phase of the design is over, the CAD model is converted into a functional CNC program and converted into a functional CNC program using Computer-Aided Manufacturing (CAM) software. The software pulls out all the geometrical details of the design from the CAD model and converts it into the G-code or M-code (CNC compatible programming languages).

CNC Machine Preparation:  As the designs are ready, now comes the part of preparing the CNC machine to get into action. The CNC machine operator has to make sure that the correct cutting or drilling tools are properly installed. The operator sets up the workpiece in the stationary clamp or directly attaches it to the stationary clamp.

Executing Programmed Operations: The final phase of the CNC machining is to control the movement of machine tooling and carry out the designed mechanical process.

Best Design Practices for Custom CNC Machined Parts

Below we’ll discuss the best design practices for creating custom CNC machined parts. Let’s dig deep!

General tolerances of custom machined parts

General tolerances signify the level of precision needed for a part that needs to be manufactured. Normally, the company that needs CNC machined parts for their project provides manufacturers with a drawing or specification sheet to follow the model. And they indicate a tolerance standard or a table of general tolerances in the note list or in the information area. These indications might be identical to EVERY company.

However, If the company doesn’t provide any specs, the CNC machine shops would follow their default set of general tolerance. For example, ISO2768-mK is a regularly used general tolerance standard.

Part tolerances of machined parts

Part Tolerance is known to be an acceptable range of dimensions. It’s a special dimension range that could be accepted by the user. They are specially decided and normally tighter than the general tolerances. As we know, the designer of the parts determines the tolerance range based on the form, fit, and function of a part.

NOTE THAT: Tighter tolerances might result in additional cost due to additional fixturing, increased scrap, and special measurement tools. If you want to minimize the cost of your CNC machined parts project, apply the tight geometric tolerances on the critical parts only.

Size Limitations

Part size is determined by the machine’s capabilities and depth of cut required by the feature in part. Thus, depending on the part’s feature and the size determine a part’s height. Shaping capabilities of the CNC machined parts depend on their space, build, and length or the diameter of the part.

Material Selection

If there is one thing that plays a major role in determining the two important factors of the CNC machined parts. These are the overall functionality and cost of the CNC machined parts. The designer of the CNC machined parts must define the important characteristics. Such as:

• Hardness
• Rigidity
• Chemical Resistance
• Heat Treatability
• Thermal Stability

Just to name a few. There is a rule to follow when choosing the “Material Blank” (the blank from which the finished part is made). The blank size has to be a minimum of 0.125 inches larger than the actual part size.

Complexity 

When a CNC machined part has more complexities or limitations, the designer has to deal with contoured geometry and cut multiple faces. The more complex the part, the costlier would be the expense of machining the final product. But… You can minimize the cost and reduce the time by reducing the need for tool changes. 

5-axis CNC machining

5-axis CNC machining (also five-axis machining) is a machining practice that can help the part move around multiple axes in five ways. Simultaneously! The 5-axis machining allows for very complex parts to be manufactured more efficiently. Because:

• It minimizes setups
• Attains faster-cutting speed
• Achieves better surface finishes
• Generates more efficient tool paths

Design of CNC Machined Parts

Design process in CNC machining

It all starts with the conception of CNC machined parts. Then, a 2D vector or a solid part CAD design serves the purpose. Besides the design requirements, engineers also must keep in mind the limitations and capabilities of the CNC machined parts. These complexities and limitations will help the machinist in the actual cutting operation.

But first, the engineer must convert the CAD model’s origin file into a CNC-compatible format. The open-source formats (STEP/IGES) or more restricted formats like (IPT/SAT). Another best practice can be to send a technical drawing along with the digital CAD instructions. This drawing will be super helpful to the machinist while cross-checking salient features, tolerances, and geometrics of the final product.

Next, choose the right tool for the job. Moreover, the machinist also needs to set a datum point to reference the machine. Do you know the reason?  To determine a ZERO Point for the program.

When everything is all set, the machinist needs to command the software that the part is ready to turn into a fully fleshed CNC machined part. Your CNC machined part is just a press away! Here is a video source that will help you understand the process in a better way.

Design rules in CNC machining

Below are some design rules that must be followed to get the best results.

Corners: The designer must avoid sharp internal corners while milling. Cutting tools have a cylindrical shape. Each corner must have a radius of at least 1/3^rd of the cavity depth.

Walls: Tall and thin walls in a design are a no-no! The unexpected vibration might result in bending of the part. This bending can end in added cost and delay in the period of the manufacturing.

Cavity Depth: CNC machined parts that have a greater depth (than four times the diameter of the cutting tool) take more time and money to manufacture.

Text: Avoiding text is the best practice to save time and money. Still, if it’s mandatory to add the text, the next best policy is to refrain from embossed or raised text.

Design Restrictions

Here are some of the design restrictions that are the result of the mechanics of the cutting process. Have a look at them below:

Tool Geometry: CNC machining cutting tools have cylindrical shapes, either flat or spherical ends. The exact shape might restrict or hinder the manufacturing of the CNC machined part.

Tool Access: If the cutting tool cannot reach the surface of the workpiece. This limits the maximum depth of the undercut.

Tool Stiffness: If during machining, the cutting tool deflects or vibrates. The consequence can be looser tolerances or tool breakage.

Workpiece Stiffness: The temperature that the workpiece develops during the machining process can also deform the workpiece. The deformed workpiece can limit the maximum wall thickness of the CNC machined part.

What Are The Advantages of CNC Machined Parts?

There are multiple benefits of utilizing CNC machined parts. A few of them are outlined below fyi:

1. High Accuracy with Tight Tolerances

Using CAD models while manufacturing the CNC machined parts results in their high accuracy with relatively tighter tolerances. Top Level Intl. is a professional CNC machining supplier in China. With CNC machining services, the parts we manufacture have tighter tolerances down to ± 0.050 mm. We can even maintain tolerances up to ± 0.025 mm.

2. Superior Quality

Wherever high-quality performance is required, CNC machined parts become the RIGHT choice because of their superior quality and top-notch physical properties.

3. Quick Turnaround Times

Today, it takes 5 days only to deliver the CNC machined parts. Thanks to the advancement of modern technologies like CNC systems and CAM software. They have accelerated their turnaround time!

4. Material Properties

Almost EVERY material can be CNC machined. So, you’ll find CNC machined parts made of different materials. Engineers choose the different materials for manufacturing CNC machined parts based on the material’s properties and the qualities needed in their application.

5. Small-to-Medium Production

CNC machined parts also come in handy for small-to-medium productions. For example, when ordering 10 identical parts, the unit price reduces up to 70% compared to one-off parts.

Compared to other formative technologies, like injection molding or Investment Costing, which have high start-up costs and are only suitable for the production volumes in the 1000’s, CNC machined parts can be manufactured in the volume of 10 and 100’s.

6. One-off Custom Parts

CNC machined parts are made without any special tooling. Therefore, if there is ever a need for one-off custom parts, CNC machined parts tend to be the most cost-effective solution.

7. Consistent Product Quality

CNC machined parts are way more precise than manual machined parts. Also, they can be produced exactly with the same dimensions and precision repeatedly, in the same manner which they were produced before.

8. Increased Efficiency

CNC machined parts are the result of an automotive operation. Hence, the speed and quality of manufacturing CNC machined parts are matchless.

And, as you know, machines don’t need any breaks. As a result, they have lower chances of making mistakes, so the efficiency of the manufacturing process and the final products increases more than the manually manufactured parts.

9. Cost-Effective

CNC machined parts are manufactured in a way that reduces the chances of inaccuracies to almost ZERO. Therefore, there is no unnecessary waste. On the other hand, the CNC machines do NOT require separate operators per machine. Instead, only a single skilled operator is enough to handle multiple CNC machines. So CNC machined parts are more cost-effective than manually manufactured parts.

What Are The Limitations of CNC Machined Parts?

There are so many advantages for us to use machined parts. However, we should be aware that nothing is 100% definitely perfect in a way. When we enjoy all the benefits of custom machined parts mentioned above, please keep in mind the following limitations of CNC machining.

1. Higher Start-up Cost

The start-up costs of CNC machined parts mainly depend on the process planning. Thus the start-up cost of CNC machined products is relatively higher and fixed than some other formative technologies involving automated process planning. Like, 3D printing. 

2. Geometric Complexity

When more complex CNC machined parts are needed, they definitely come with a higher price tag. Because, for attaining the geometric complexity, multi-axis machining will be used. And, if that’s not the requirement, the complex geometry of the CNC machined parts might require excessive labor from the machinist. Realigning or repositioning, for instance.

3. Tool Access and Workholding Restrictions

For manufacturing of the CNC machined parts, there are two conditions. First, the part should be held in place tightly. Second, the tool must have access to the surfaces. If the engineers cannot meet both conditions, this can be a MAJOR restriction in manufacturing CNC machined parts.

However, experienced engineers can find a way to deal with these situations. Therefore, before you make any final decision, a detailed discussion with the CNC machining supplier is worth dedicating some time to. 

Applications of CNC Machined Parts in Different Industries

It’s no secret that every industry today requires precision. Be it the medical industry, aerospace, or robotics. You won’t find a single industry that can compromise the precision of its machined parts.

Not surprisingly, that’s the reason why more industries are using CNC machined parts in their projects. CNC machined parts can serve a variety of industries using different machining techniques and materials. So let’s break down the details about different industries using CNC machined parts.

Automotive: CNC machined parts also play their role in the automotive industry, where manufacturing parts require high performance.

Space: There are various reasons behind choosing CNC machined parts in space appliances. The foremost reason is their EXCELLENT accuracy, of course.

Aerospace: There are three parameters that every machined device must meet in the aviation industry. High speed, fast air currents, and extreme pressure. A small mistake in the precision of the aircraft parts can take a toll on the aircraft parts.

CNC machined parts for aircraft must meet a high precision requirement. In addition, the parts must be as tight as 0.00004 inches. Parts made with CNC machining of the aerospace industry include airfoils, antennae, manifolds, bushings, and radiofrequency suppression materials.

Robotics: Robots work along with humans (NOT instead of them). Hence, a high amount of accuracy and precision is required in their movement and positioning. Robots are used in the manufacturing of other parts, BUT they too are to be made somehow.

Medical: Medical industry deals with the matters of life and death. So, there can be NO compromise on the dimensions and fit of the product. However, a minor error in the measurements can result in a medical misdiagnosis or produce a malfunctioned product.

There is a wide range of medical parts that can be created with CNC machined parts. Such as orthotic devices, electronic enclosures for monitoring devices, MRI machines, research equipment, and medical instruments.

Industrial Manufacturing: The most common industrial application of CNC machining is the manufacturing of tooling for other processes. For example, the mold of Injection Molding is commonly CNC machined from Aluminum and Tool Steel.

Motorsports Equipment: The motorsports industry needs nothing short of the products that aid in high performance. Right? Most motorsports companies employ CNC machined parts to achieve the desired level of quality and durability.

What Are The HS Codes for CNC Machined Parts?

HS Codes or Harmonization Codes are names or numbers that classify the parts of the traded products. They are important to classify products on export and to calculate applicable taxes and duties on import. HS codes for CNC machined parts follow the same rules. These codes are 6, 8, or 10 digits long.

• A product’s first two digits indicate its classification of the chapter (HS-2)
• The next two digits identify the grouping within the chapter (HS-4)
• The next two digits are more specific (HS-6)

Up to the six digits, all countries classify the products similarly.  A few exceptions might exist in the countries that follow the old versions of the HS. Note: The HS code of CNC machined components used in the importing country may be different from that used in the exporting country. Here are some of the HS codes used for CNC machined parts for your information.

CNC Machined Parts Name	HS Codes
Printing Machinery Components	84439990
CNC Machined Components	84819090
Parts of the Other Machinery	84799090
Precision Turned Parts	82051000
Valve Components	84818049
Body/Adapter	84818030
Tool Holder	84661010
Stainless Steel Nipple Machined Parts	730799
Stainless Steel Machined Parts	730721
Machined Mild Steel Parts	730721
Steel Machined Components Motor Vehicle Parts	851290
Machined Stainless Steel Parts	841899

How to Choose a CNC Machined Parts Supplier in China?

If you have reached this far, we are sure you might have gained a better understanding of CNC machined parts. Right? The next best move for you now is to choose a CNC machined parts supplier. However, finding CNC machined parts manufacturers in China might feel like an arduous task.  Therefore, we are sharing some quick tips that will help you find the CNC machined parts supplier.

First off, you should know the three factors that impact your final decision while going with a certain CNC machined parts supplier company.

• Price
• Service
• Manufacturing Time

You can also decide which two of these three factors matter for you the most and then make the final decision accordingly.

Red Flag! If a CNC machined parts manufacturing company claims to provide stellar service with overnight delivery and at lower prices, beware, they might be a scam!

You can check the company’s website under consideration and ask them for more information on the phone to have a better idea of their services. Furthermore, below is the list of some more factors that you can keep an eye on while you do your research:

• The accreditations of the company
• Their specializations
• The potential materials they deal in
• Their account management process
• Their past case studies
• Their other complementary services (Machine Drawing or Finishing Process)

How does “Top Level Intl.” stand out?

Top Level Intl. is a reliable CNC machined parts provider in China with experience of over 15 years in the CNC machining industry. We have our CNC machining factories in Shenzhen and Dongguan city. There we produce nothing short of high-quality custom CNC machined parts with super precision.

Whether you need custom CNC machined parts made with metals or plastic, we are always there to provide you with the best services. Also, we turn your drawings and samples into real CNC machined parts that suit your needs the best. Several different accuracy levels are available in the CNC machines we offer.

From raw materials to the machining services, and till shaping up the final product, we do it all for you. In short, Top Level Intl. provides the one-stop solution for your CNC machined parts project.

How to get your CNC machined parts done with “Top Level Intl.”?

It’s easy to choose Top Level Intl. as your partner on CNC machining projects. To work with us, you just need to follow three simple steps.

Design and Export CAD File: Prepare your designs in the form of a CAD file.

Create Drawings: You can create the drawings of your final product. Send us your design prints with detailed information (including raw material, surface finish, and order quantity)

Get Your Quote: We’ll go through your provided drawings and other requirements and quote you a good price within 24 hours. Our team will start manufacturing your products once your order is confirmed, using the appropriate tools and machines.

Conclusion

This is an all-inclusive guide of CNC machined parts. In this guide, we shared many practical tips and much valuable information about custom parts and the CNC machining processes. We hope you gathered all the information about CNC machined parts that you needed before you start a machined parts project. That’s great to share with you all this and we feel that our hard sharing and dedication are meaningful.

What are the important factors you’ll consider before choosing a CNC machining service company for your project? We would appreciate a comment from your side on this point. Good luck with your project!