Jigs and Fixtures
What are Jigs and Fixtures?
Jigs and fixtures are manufacturing aids which are employed during the machining process. The two are often confused and sometimes misunderstood by those who are not familiar with the machining process. Sometimes the two terms are also used interchangeably.
However, there are several key differences between jigs and fixtures.
Firstly, before we go any further, it will be important for the sake of this article to understand what exactly jigs and fixtures are, and to identify the central difference between the two.
A jig is a tool that guides the cutting tool during the machining process.
A fixture holds, supports, and locates the workpiece during the machining process. However, unlike a jig, a fixture does not guide the cutting tool.
Jigs and fixtures are indispensable aids to manufacturers. They help to maximise efficiency, minimise production time, improve manufacturing quality, and reduce production costs.
Let’s look at each in more detail….
A jig is secured to a CNC machine tool during the machining process. It dictates the location and motion of the cutting, thus guiding the machine tool. A jig is unique in that when it moves, the tool itself remains stationery.
Jigs are usually made of metal. The most commonly used metals to create jigs tend to be steel or aluminium. Jigs are usually fitted with positioning devices called bushings, or drill bushings. These bushings are an essential component of the jig, as they help to guide the drill as it moves through the workpiece. This is important for speed, accuracy, and quality.
Jigs are commonly used devices in the CNC machining process. They help to improve precision. A jig is often a custom part that has been designed by the manufacturer for this specific purpose.
Types of Jigs Used in the CNC Machining Process
There are many different types of jigs. One of the most common types is a drill jig. A drill jig guides the drill bit to the intended location.
Here are some of the other commonly used types of jigs within the world of CNC machining:
Template jigs: high precision and renowned for speed, these jigs are also versatile and easy to use.
Plate Jigs: similar to template jigs, the key difference being that clamps are used with plate jigs to hold the workpiece in place.
Angle plate jigs: as you would expect from the name, this type of jig is ideal for holding parts at angles during the drilling process.
Leaf jigs: the leaf jig has a leaf that can be swung open or closed for loading or unloading purposes.
Diameter jigs: diameter jigs are used to drill radial holes on cylindrical workpieces. A clamping plate and a clamping bolt are used to provide additional security.
A fixture is an agent of stability, support, and positioning during the CNC machining process. It is there to hold the workpiece in the same place during cutting to achieve consistent and highly repeatable results.
Fixtures are usually attached to the machine and can be used for milling, turning, and grinding.
Like jigs, fixtures are made from metal, commonly aluminium or steel. They can be custom built for a particular application or workpiece, or they can be purchased as generic fixtures.
Fixtures help to reduce operator error by acting as an invaluable aid during machining, and they also help to improve safety by always locating the workpiece in a fixed orientation.
This can result in cost savings as there will be less perishable material through human error. The use of a fixture will also speed up the process whilst simultaneously improving accuracy.
Types of Fixtures Used in the CNC Machining Process
There are many different types of fixtures which are available to the CNC machinist. Choosing the right one will depend on several factors, including the part, the machine, and the machinist.
Here are some of the main types of fixtures for CNC machining:
Angle fixture: highly reliable CNC fixture which is employed to hold the workpiece at specific angles. Angle fixtures are often used for applications such as beveling and drilling.
Indexing fixture: used in the manufacture of parts which have evenly spaced geometric features. These fixtures are very sturdy and can be easily attached to a worktable.
Modular fixture: modular fixtures consist of a wide range of interchangeable components designed to hold a workpiece securely and accurately in place for machining.
CNC vise fixture: versatile and easy to use, the CNC vise fixture uses two inclined planes that act against one another to provide strong clamping power via a hydraulic screw mechanism.
Benefits of Using Jigs and Fixtures
Jigs and fixtures are important components of the manufacturing process. They provide many advantages to the machining process and can help to improve final product quality.
- Increased precision and accuracy
- High repeatability of process, allowing multiple parts to be produced to a consistent level of quality
- Reduced material wastage, which is positive for environmental sustainability
- Increased productivity
- Reduced human error
- Provides added level of safety for the machinist/operator
- Customised jigs/fixtures can be developed, allowing for greater flexibility of process
- Option to automate work
- Reduced production costs
- Heavy and complex parts can be manufactured more easily
- Improved cycle time
Key Differences Between Jigs and Fixtures
There are several important differences between jigs and fixtures.
These differences are captured in below:
- A workholding device which guides the cutting tool for a specific operation
- Small in size and light in weight
- Used in uni-dimensional machining processes
- Complex design
- High cost
- Not always fixed to the machine table
- Used in drilling, tapping and reaming
- Easy to use and requires less operator skill
- A workholding device that holds, supports and located the workpiece but doesn’t guide the tool
- Large in size and bulky to handle
- Used in multi-dimensional machining processes
- Simple design
- Low cost
- Fixed to the machine table
- Used in milling, grinding and shaping
- Complicated to use and require more operator skill