Fabrication fixtures are the unsung heroes of the manufacturing process. They’re so important that they’re key to ensuring welding precision and efficiency. Merriam-Webster defines fixturing as “the process or means by which an object is supported and secured during a manufacturing process.” Welders consider them a must-have for holding and positioning workpieces during various fabrication processes.
Whether in a manual or automated/robotic operation, a fixture accurately positions and orients a part, rigidly clamps the workplace in position and provides support, increasing the stiffness of a part’s compliant regions. However, unlike a jig, a fixture does not guide the cutting tool. So, what are the different types of fixtures?
A fabrication fixture can be as simple as a vise jaw or chuck or as complex as a multi-axis CNC machining fixture—a cutting tool controlled by Computer Numerical Control (CNC) with the ability to move in at least four directions. According to the Society of Manufacturing Engineers (SME), fixtures generally fall into five categories:
- Plate fixtures – constructed from a plate with a variety of locators, supports, and clamps;
- Angle-plate fixtures – a modification of plate fixtures that is set perpendicular to the mounting surface
- Vise-jaw fixtures – modified inserts for vises designed to accommodate a particular workpiece
- Indexing fixtures – used to reference workpieces that need machining details set at prescribed spacings
- Multi-part or multi-station fixtures – Normally used for either machining multiple parts in a single setup or machining individual parts in sequence, performing different operations at each station.
Fixtures may also be classified according to the process or machine tool to be used in the machining process, such as:
- Lathe fixtures
- Milling machine fixtures
- Drilling machine fixtures
- Boring machine fixtures
- Grinding machine fixtures
- Gear machine fixtures
WHEN FIXTURES SHOULD BE USED
Simply put, when efficiency and accuracy are paramount, a fixture is essential to ensure correct results in:
- Mass production – fabrication fixtures ensure uniformity when producing large quantities of identical parts.
- Complex geometries – components with intricate shapes or tight tolerances require specialized fixtures to hold them securely during machining, welding, or assembly process
HOW FIXTURES ARE BUILT
Each fixture is custom-built to fit a particular shape or part using CAD (Computer-Aided Design) software. Once the design is finalized, the fixture components are fabricated using various techniques, such as CNC machining, welding, and additive manufacturing (e.g., 3D printing).
The four main stages of the design and manufacturing process include:
- Setup planning – identifies which features must be machined in each setup and determines locating datum for each setup.
- Fixture planning – determines precise locating and rigid clamping of workpieces according to part design and process requirements.
- Unit design – the conceptual and detailed definition of the locating and clamping units of a fixture composed of the base plate
- Verification – ensures that developed fixture designs satisfy the fixturing requirements.
The design must also meet other design requirements, including fixture cost, weight, and assembly time.
HOW TO MAINTAIN FIXTURES
Routine maintenance of fabrication fixtures is critical for preserving their accuracy and extending their lifespan. Best practices include:
- Clean after each use – keep the fixture clean from dust, debris, and coolant residues
- Inspect and repair regularly – look for signs of wear, damage, or misalignment, and address any issues immediately
- Lubricate and protect according to manufacturer recommendations – prevent friction, ensure smooth operation
- Calibrate periodically – ensures the fixture maintains accuracy and repeatability over time
The bottom line is that fabrication fixtures streamline the setup process to reduce production downtime and increase overall efficiency. They also guarantee that each part meets stringent quality standards—a must for industries such as aerospace, automotive, and medical device manufacturing.