Jigs and Fixtures are two critical instruments used widely for precise manufacturing and quality inspection of parts. Often we are confused between the two. Let’s learn about the differences between jigs and Fixtures in this article.
At the end of the article there will be a link to download the jigs and Fixtures PDF for your future reference.
Why Jigs and Fixtures are used?
Both jigs and fixtures are used to hold, locate, and support a workpiece. But why do we really need jigs and fixtures? The manufacturing industry is rapidly growing and the demand for getting parts quickly and precisely is haunting manufactures.
Maintaining the same quality of all production parts are getting very difficult. That’s where jig and fixtures came into rescue. Whenever there is a need for repeatability and interchangeability of parts in the mass production system, Jigs and fixtures are the most economical way to ensure precise and quality parts.
The quality of jigs and fixtures defines the quality of parts and processes. Jigs and fixtures also ensure that all parts are manufactured considering the same amount of tolerance and the part can be easily fitted even in the worst-case scenario.
Definition Of Jig
Jigs are devices or instruments used for holding, locating, guiding, and supporting a workpiece in any certain operation. In addition to that, jigs are also used to guide the tool movement. So jigs are doing a dual job there.
In other words, jigs guide both the tool and the workpiece in any specified manufacturing operation. The main purpose of the jig is to maintain repeatability, interchangeability, and the overall quality of a part. An example of jig would be drill jig, which guides to make holes at the desired location.
- Jigs are used for uni-directional machine process like drilling, boring, etc.
- Jigs have relatively less weight and quite complex design
- Jigs are not attached to machine beds unless it is a large operation
Types of Jig
Although every company make their own jigs based on the specified manufacturing operation but below are the common types of jigs widely used.
- Plate Jig
- Box jig
- Closed jig
- Sandwich jig
- Angle plate Jig
- Channel jig
- Pump jig
- Leaf jig
- Ring jig
Definition Of Fixture
Fixtures are an instrument that is used for holding, locating, and guiding a workpiece in a certain manufacturing process. The fixture does not guide tool movement. Fixtures are used to hold and locate the workpiece in the proper position for the operation.
- Fixtures are used for multidimensional machines like milling, grinding, etc.
- Fixtures are usually simple in design.
- Fixtures are attached to machine beds.
- Gauge blocks are used for effective handling.
Types of fixtures
Here are the types of fixtures widely used
- Plate fixture
- Angle plate fixture
- Indexing fixture
- Profile fixture
- Vise jaw fixture
- Multi-station fixture
Difference between Jigs and Fixture
The basic difference between jigs and Fixtures is that jig guides the tool but a fixture does not. However, both jigs and fixtures guide, support, and locate the workpiece.
The jig has components like a bush that comes in contact with the tool but in the case of fixture, there is no contact with the tool.
Both jigs and fixtures use 3-2-1 rule to properly constrain a workpiece. 3-2-1 rule is basically locking all degrees of freedom so that the workpiece can not move in any direction.
|Guides the tool||Does not guide the tool|
|Comes in contact with the tool||No contact with the tool|
|Jigs are lightweight||Fixtures are heavyweight|
|Design is complex||Design is simple|
|Gauge blocks are not required||Gauge block may be required|
|Clamping to the table is not required||Due to heavyweight, clamping with a table is required|
|Jigs are costly||Fixtures are cheap|
Design Consideration Of Jigs And Fixtures
Following key aspect we should consider before designing any jigs and fixture
- A proper study of the workpiece
- A detailed study of the tool
- How the clamping arrangement should be done
- Loading and unloading of the workpiece
- Tolerance and precision allowed in the workpiece
- Machine bed size
- Machine capacity
- Power source requirement
- Clearance between different components
Advantages Of Jigs And Fixtures
- Jigs can set the tool position at the correct location. So you will get precise parts every time
- Jigs eliminate the repeated marking, measuring, and setting up workpiece for any operation
- There is very little variability in dimension when jigs are used, So less rejection rate.
- Less variability in part dimension ensures faster cycle time
- Operational parameters like the speed of the tool, the feed can be controlled easily.
- Reduce operator’s fatigues as they don’t need to inspect each and every part.
- Semi-skilled workers can be deployed more.
- No need to check each individual part for quality. Check on the basis of a batch is enough.
Disadvantages Of Jigs And Fixtures
- Each specific operation need separate fixtures
- The initial set up cost is high
- High precision machines are required to build jigs and fixtures
Material For Jigs And Fixtures
Following are the materials widely used in jigs and fixtures
- Stainless steel
- Grey cast iron
- Hardened steel
- Allow steel
I hope your confusion is now clear. You now got a clear idea about the differences between jigs and fixtures. If you still have any questions, do write to me in the comment section and I will be happy to help.