Inspection & Checking Fixtures & Gauges

Inspection Fixtures

• Purpose: Inspection fixtures are devices used to hold or support a part or assembly in a fixed position during the inspection process. They are designed to ensure that parts are inspected in a repeatable, consistent manner.
• Design: These fixtures are often custom-built for a specific product or part. They may be made from materials like aluminum, steel, or composite materials, depending on the requirements.
• Functionality: They ensure that the part is positioned correctly during measurement, preventing human error or variability in the inspection process. They may incorporate sensors, cameras, or mechanical elements to support inspection.
• Types:
  • Go/No-Go Fixtures: Used to determine if a part fits within specified limits.
  • Checking Fixtures: Used for verifying complex geometries or multiple features on a part, such as holes, angles, and lengths.

Checking Fixtures

• Purpose: These fixtures are more advanced than basic inspection fixtures, often designed to check a range of parameters or features simultaneously.
• Design: Checking fixtures might incorporate adjustable elements, clamps, or probes to measure the features of the part as it is held in the fixture.
• Use: These fixtures are used to verify critical dimensions or to confirm that the part conforms to the design specifications. They are typically used in the final stages of the production process.

Gauges

• Purpose: Gauges are tools used to measure the size, shape, or other dimensions of a part to ensure it fits within specified tolerances.
• Types of Gauges:
  • Linear Gauges: Used for measuring lengths, widths, and heights. These include micrometers, calipers, and height gauges.
  • Angular Gauges: Used for measuring angles, such as protractors or specialized angular gauges.
  • Thread Gauges: These check the pitch, diameter, or shape of threads, such as pitch gauges, plug gauges, and ring gauges.
  • Depth Gauges: Used to measure the depth of holes, slots, or recesses.
  • Go/No-Go Gauges: These are simple gauges used to determine whether a part is within specified tolerances, often by checking if it fits into a ‘Go’ side or fails a ‘No-Go’ side.
• Functionality: Gauges are precise, and they ensure that each part produced meets the required specifications for functionality and fit.

Importance of Inspection Fixtures and Gauges

• Accuracy: These tools help ensure that parts are manufactured to precise tolerances, ensuring they function properly in assembly or final use.
• Consistency: They enable repeatable, consistent measurements, reducing human error in the inspection process.
• Cost Reduction: By identifying defective parts early in the production process, inspection fixtures and gauges help reduce waste, rework, and warranty costs.
• Compliance: These tools ensure that products comply with regulatory standards and customer requirements.

Automation in Inspection

• Coordinate Measuring Machines (CMM): These are often used in conjunction with inspection fixtures to measure parts automatically. CMMs use a probe (touch or laser) to measure the exact dimensions and compare them against CAD data.
• Vision Systems: Modern checking fixtures may integrate optical or laser vision systems to detect defects or verify features without physical contact with the part.

Examples of Common Inspection Fixtures and Gauges

• V-Blocks: Used to inspect cylindrical parts, ensuring roundness or the correct diameter.
• Surface Plates: Flat, smooth surfaces used as a reference for precision measurements.
• Check Fixtures for Complex Geometries: Fixtures designed for parts with complex shapes, often used in aerospace or automotive industries.