CNC Fixture: Types, Applications, and Design Tips

What Are CNC Fixtures?

CNC fixtures are work-holding tools for stability and positioning. They are often used in securing, supporting, or fixing a workpiece appropriately on the CNC machine. A CNC fixture is an essential tool that facilitates conformity and interchangeability when machining workpieces.

CNC workholding fixtures ensure a seamless manufacturing operation by reducing the amount of human input. Workholding fixtures are not the same as jigs, even though most people often compare them. A machining fixture secures, supports, and stabilizes the machined part but does not guide cutters. The jigs guide the tool cutter’s movement. In addition, the CNC workholding fixtures move relative to the workpieces’ movement while the jigs remain stationary.

Applications of CNC Fixture

CNC fixture applies to a broad range of manufacturing operations involving CNC machining. Its functions are incorporated with the type of CNC processes used in manufacturing. It is used in CNC turning, CNC milling, CNC grinding, and CNC slotting. Besides, the design of CNC fixtures determines its application:

• Positioning: CNC workholding fixtures ensure the workpiece maintains the appropriate position relative to machine tools during machining. Also, it ensures the machined parts meet specific design specifications.
• Clamping: Once you have positioned the workpiece, the CNC workholding fixture grips it tightly by applying force on it during any manufacturing operation.

CNC workholding fixtures utilize these two attributes in their functions. For instance, positioning and clamping contribute significantly to machining processes in the automotive industry. These workholding tools are responsible for holding and guiding the vehicles during the welding and assembly process.

Types of CNC Fixture

Even though the concept and performance of CNC fixtures seem straightforward, it can be quite challenging to classify CNC workholding fixtures. However, workholding fixtures can be classified based on different criteria such as machining operation, uses, and power source:

Classification Based on CNC Machining Operations

Regarding CNC operations, workholding fixtures used in CNC machines can be grouped into five types based on their tool installation and structure. They include:

Milling Fixtures

CNC milling is a cutting method that uses a computer to program the cutting tool to cut the workpiece into a preferred shape and size. In this manufacturing process, rotary table fixtures, vise fixtures, fixture plates, T-slot, and indexing fixtures are common types of CNC milling fixtures.

Turning Fixtures

CNC turning is a machining technique in which the cutter cuts excess material from the workpiece while turning/rotating on a single axis. Common examples of turning fixtures include faceplate, collet, chuck, and mandrel fixtures.

Grinding Fixtures

The CNC grinding process removes part of a workpiece using a grinder. It is a commonly used CNC machining process aside from milling. Fixtures applicable to CNC grinding processes include centerless, magnetic chuck, and sine bar fixtures.

Drilling Fixtures

Drilling operations is a famous CNC machining process for creating features like holes in a workpiece. Drill jigs, angle drilling, radial drill, and multi-spindle drill fixtures are typical CNC drilling fixtures.

Boring Fixtures

CNC boring is a machining process that involves enlarging holes already drilled with the CNC drilling process. Typical CNC boring fixtures are boring bars and boring head fixtures.

Classification Based on Their Uses

Among the standard types of CNC fixtures, most of these tools are used according to their different purposes in manufacturing. Here are typical CNC fixtures based on their uses:

CNC Vise Fixtures 

CNC vises are versatile and widely used for different machining setups due to their ease of use. A CNC vise fixture provides higher levels of precision than the traditional mechanical vise commonly used in woodworking and manual machining. These CNC vises deliver impressive clamping power via a pneumatic/hydraulic screw mechanism.

The internal mechanism of these fixtures possesses two inclined surfaces pushed against each other, increasing rigidity and tackling jaw lift. Besides, these fixtures feature flat and perpendicular precision ground edges on their exterior periphery. It allows accurate positioning of the CNC vise on the worktable.

Angle Fixtures

These are another popular CNC workholding fixtures that primarily hold the workpiece tightly at specific angles. It commonly applies to CNC machining processes involving chamfering, drilling, and beveling at angles.

Angle CNC fixtures are rigid and reliable. The angle plate features a hole grid that allows convenient mounting and placement of parts. More so, machinists handling parts beyond the capability of their CNC machine benefit optimal utility from using angle fixtures.

Modular Fixtures

Modular fixtures are innovative workholding fixtures since they are simple to reconstruct and reconfigure to match the demand of any workpiece. A modular fixture comprises interchangeable components, making it well-suited for handling several workpieces. Clamps, supports, tooling plates, and locators of different sizes are typical reconfigurable components of modular fixtures.

Modular fixtures provide remarkable positioning precision, cost-effectiveness, and considerable flexibility, allowing a more efficient manufacturing process. Moreover, you can disassemble this machining fixture after completing the process.

Jig Fixtures

Jigs are essential machining tools commonly used to guide the cutting tool’s motion and position it over the workpiece. Jigs are often used in CNC drilling operations. Custom jigs are efficient workholding tools in CNC machining. Typical types of jigs include:

• Plate jig
• Leaf jig
• Angle jig
• Diameter jig
• Template jig

Clamp Fixtures

Even though this machining fixture is available in various types and sizes, they all perform the same function. Camp fixtures hold the workpiece in place using mechanical force from springs or screws. Although clamps do not really qualify as a CNC fixture, they belong within the broad bracket. Typical clamp types are edge, step, toe, and hold-down clamps.

Universal Fixtures

Universal CNC fixtures are compatible with any workpiece that can be adjusted easily. You can adjust and replace each part of the universal fixture to match any workpiece. As its name implies, these fixtures have a broader scope and application.

These fixtures are compatible with any workpiece and can effectively manage and stabilize the workpiece for different surface finishing and other machining processes.

Classification Based on their Power Source

Here, CNC fixtures are categorized according to their power source. Here are the common power sources of CNC fixtures:

• Manual fixture
• Electrical fixture
• Pneumatic fixture
• Magnetic fixture
• Hydraulic fixture
• Vacuum fixture

Helpful Considerations for Custom Fixture Design

It can be quite challenging to design CNC fixtures. However, the difficulty may vary based on the part design and machining capabilities. This section discusses expert considerations for the effective designing of CNC workholding fixtures:

Define the Design Requirements of Your CNC Fixture

It is crucial to clearly define the design requirements of your CNC fixture, as with any engineering project. You must define your goals as regards production accuracy, timing, cost, etc., to clarify the intended design.

Gather Relevant Information from the CNC Shop

The next thing to do is collect relevant information about your resources, including the types of CNC machines available, the materials your CNC fixture will work with, the sequence and number of machining operations, and the workpiece specifications.

Create More Drafts for CNC Fixture Design

CNC workholding fixture is incredibly versatile and offers an extensive range of solutions. You can be innovative with fixture design and develop multiple workholding solutions. However, it would help to gather all ideas and develop a basic draft design for comparison.

Choose the Appropriate CNC Fixture Idea

Having developed different CNC fixture designs, the next step is to examine their pros and cons according to the needs of your project. As such, you will eventually settle on the best fit for your application. However, it is advisable to consider factors such as tooling costs, manufacturing costs, product life, and maintenance.

Optimize and Implement the Preferred CNC Fixture

Lastly, optimizing the chosen fixture design and concluding its production plans is critical. The aim is to ensure cost-effectiveness and improve the accuracy of the machining fixture. Expert advice is to employ standard components, including studs, clamps, plates, etc., since they are economical and offer quality.

It would be best not to focus too much on the surface finishing when machining fixture. However, you can apply sophisticated surface finishes where necessary. In addition, you should avoid extra-tight part tolerances because they add cost without necessarily improving positioning accuracy.

AT-Machining: Your Reliable CNC Machine Shop for Custom Fixtures

Having explored the different types of CNC fixtures, it would help to understand that there are situations when certain parts are difficult and near impossible to hold and secure using standard workholding fixtures. As a result, you may require a custom CNC fixture to effectively machine parts. Like its name, it is a custom-made or bespoke fixture for specific purposes.

AT-Machining delivers the best custom CNC fixture for your CNC machining operations. Our team of qualified engineers and designers leverage our state-of-the-art engineering resources to offer quality CNC fixtures and other CNC machining services at competitive prices. We pay attention to details and possess ISO 9001:2015 certification, which shows we prioritize customers’ wants. Contact us today to discuss your workholding needs and receive an instant quote!

Conclusion

CNC fixtures play a significant role in upholding quality standards in manufacturing different machined parts. These fixtures save time by guiding the workpiece, ensuring efficiency during the production process.

However, using the right fixtures for your CNC machining processes is essential. Additionally, this article has discussed everything you need to know about CNC fixtures to determine a suitable one for your application.

FAQs

How Is A CNC Fixture Different from A Jig?

A CNC fixture differs from a jig in the way it works. The fixture holds, supports, and stabilizes a workpiece in the required position during machining. Conversely, the jig guides the cutting tool’s movement as it removes material. Also, the CNC fixture moves relative to the workpiece’s movement while jigs remain stationary.

What Are the Common Types of Workpiece CNC Fixtures Can Hold?

CNC workholding fixtures are versatile tools that can secure and hold CNC workpieces with cylindrical, round, plates, prismatic, and irregular shapes.

What Are the Common Benefits of Using Workholding Fixtures?

CNC fixtures offer many benefits, such as mitigated operator fatigue, optimized productivity, accuracy, and repeatability in manufacturing processes.