GO-NoGo Gauges. Concept and design of Go-NoGo Gauge

DESIGN

R.K Verma

8/8/2023

Introduction

Precision and accuracy are paramount in various industries, from manufacturing to engineering, where even the smallest deviations can lead to significant consequences. One of the tools that play a crucial role in ensuring such accuracy is the Go-NoGo gauge. This ingenious device helps determine whether a part meets the required specifications or needs further attention. In this blog, we will learn about the Go-NoGo gauge concept, explore its applications, and provide examples to facilitate a better understanding. Topic Covered are :

  • What is Go-NOGO Gauges

  • Calculation to design GO-NOGO gauges

  • Applications of GO-NOGO Gauges

  • Benefits of GO-NOGO Gauges

  • Conclusion

What is a Go-NoGo Gauge?

A Go-NoGo gauge, also known as a plug gauge or limit gauge, is a mechanical tool used to quickly verify whether a manufactured part conforms to its intended dimensions. The gauge consists of two ends: the "Go" end and the "NoGo" end. If a part fits into the "Go" end but doesn't fit into the "NoGo" end, it is considered acceptable. Conversely, if the part fits into the "NoGo" end, it does not meet the required specifications and is rejected.

Design of GO-NOGO gauges

Let's go through a step-by-step calculation of the "Go" and "NoGo" sizes using a simple example. Imagine we are dealing with a cylindrical pin that needs to fit into a hole. The nominal diameter of the hole is 25 mm, and the acceptable tolerance range is +0.1 mm / -0.05 mm.

1. Given: Nominal Diameter (Target Dimension) = 25 mm Upper Tolerance Limit = +0.1 mm Lower Tolerance Limit = -0.05 mm

Calculation of "Go" Size:

Go Size = Nominal Diameter + Upper Tolerance Limit

Go Size = 25 mm + 0.1 mm Go Size = 25.1 mm

2. Calculation of "NoGo" Size:

NoGo Size = Nominal Diameter - Lower Tolerance Limit

NoGo Size = 25 mm - (-0.05 mm) (Note: Negative becomes positive when subtracted)

NoGo Size = 25 mm + 0.05 mm NoGo Size = 25.05 mm

3. Designing the Gauge: The Go-NoGo gauge for this example would have one end (the "Go" end) calibrated to 25.1 mm and another end (the "NoGo" end) calibrated to 25.05 mm.

Any pin that fits into the "Go" end but not into the "NoGo" end is considered acceptable.

4. Inspection Process: During the inspection process, a pin is checked by attempting to fit it into both ends of the Go-NoGo gauge. If the pin fits into the "Go" end (25.1 mm) but does not fit into the "NoGo" end (25.05 mm), it falls within the acceptable tolerance range and is considered a good part. If the pin fits into the "NoGo" end, it exceeds the lower tolerance limit and is rejected.

Applications of GO-NOGO Gauges 

1. Manufacturing: In manufacturing processes, Go-NoGo gauges are used to inspect components and parts to ensure they meet specified tolerances. This can include dimensions like length, diameter, thread pitch, and more.

2. Assembly Lines: Assembled products often consist of multiple components that need to fit together perfectly. Go-NoGo gauges are employed to verify that these components fit correctly, ensuring the final product's integrity.

3. Automotive Industry: Critical components in automobiles, such as engine parts, brake components, and transmission parts, require precise dimensions for proper functionality and safety. Go-NoGo gauges are used to verify these dimensions during the manufacturing process.

4. Aerospace Industry: Aircraft parts need to meet strict standards to ensure safety and reliability. Go-NoGo gauges are employed to inspect various components, including fasteners, connectors, and seals, to make sure they meet specifications.

5. Medical Device Manufacturing: Medical devices like syringes, catheters, and implants must adhere to precise dimensions to ensure patient safety. Go-NoGo gauges are used to inspect these components and ensure they meet quality standards.

6. Electronics Assembly: In the electronics industry, components like connectors, pins, and sockets must fit together accurately to establish proper electronic connections. Go-NoGo gauges are employed to verify these connections during assembly.

7. Precision Machining: Machined parts often require precise measurements to function correctly. Go-NoGo gauges are used to ensure that machined components meet the required tolerances.

8. Tooling Verification: Tools used in various industries, such as molds, dies, and cutting tools, need to be manufactured with precision to ensure proper performance. Go-NoGo gauges are used to verify the accuracy of these tools.

9. Plastic Injection Molding: During plastic injection molding processes, Go-NoGo gauges are used to ensure that the molded parts meet the specified dimensions and fit together correctly.

10. Bearing Manufacturing: Bearings, critical components in machinery and equipment, require precise dimensions for smooth operation. Go-NoGo gauges are used to verify the inner and outer diameters of bearings.

11. Gauging Stations: Dedicated gauging stations in production facilities use Go-NoGo gauges to inspect parts at specific points along the assembly line, ensuring that dimensions are within tolerances.

12. Thread Verification: Threaded components like screws, nuts, and bolts must have accurate thread pitches and diameters for proper engagement. Go-NoGo gauges are used to verify these characteristics.

Benefits of GO-NOGO Gauges

1. Speed and Efficiency: Go-NoGo gauges allow for rapid and straightforward inspection. A trained operator can quickly determine whether a part meets specifications without the need for complex measurements or specialized equipment. This speeds up the quality control process, reducing production downtime and increasing overall efficiency.

2. Simplicity and User-Friendly: These gauges are designed to be intuitive and easy to use, requiring minimal training. The "Go" and "NoGo" designations provide clear indications of acceptability, reducing the chances of operator error and misinterpretation.

3. Reduced Human Error: Since Go-NoGo gauges provide a clear binary result (pass/fail), the chances of subjective errors or variations due to different operators are minimized. This consistency in inspection results enhances the overall reliability of quality control.

4. Cost-Effectiveness: Implementing Go-NoGo gauges can be cost-effective compared to using more advanced measurement equipment. The gauges themselves are relatively simple devices, and the training required for operators is typically less intensive than for using complex measurement tools.

5. Enhanced Quality Control: Go-NoGo gauges contribute significantly to maintaining consistent product quality. By quickly identifying non-conforming parts, they prevent defective products from entering the market, reducing the risk of recalls and customer complaints.

6. Real-Time Inspection: As production progresses, parts can be inspected in real time using Go-NoGo gauges. This allows for prompt adjustments to the manufacturing process if deviations are detected, ensuring that the production remains within specified tolerances.

7. Support for Mass Production: Go-NoGo gauges are well-suited for mass production scenarios where numerous parts need to be inspected rapidly. They enable a high throughput of parts to be checked without compromising accuracy.

8. Visual and Tactile Inspection: These gauges often involve visual and tactile inspection, which can be advantageous for identifying surface defects or irregularities that might not be detected using measurement instruments alone.

9. Standardization: The use of Go-NoGo gauges promotes standardization across different stages of production and different facilities. This uniform approach ensures that quality standards are met consistently, regardless of location.

10. Compliance with Industry Standards: Many industries have specific standards and regulations that must be adhered to. Go-NoGo gauges help ensure compliance with these standards by providing a simple and effective means of verifying part dimensions.

11. Feedback Loop: The use of Go-NoGo gauges can provide valuable feedback to the manufacturing process. If a higher frequency of "NoGo" results is observed, it can trigger investigations into potential issues in the production line.

12. Integration with Automation: In automated production environments, Go-NoGo gauges can be integrated into robotic systems for even faster and more consistent inspections.

Conclusion

In summary, the "Go" size represents the maximum allowable dimension, while the "NoGo" size represents the minimum allowable dimension. The Go-NoGo gauge is designed based on these sizes, and parts are inspected by attempting to fit them into the appropriate ends of the gauge. If the part fits into the "Go" end and not the "NoGo" end, it meets the acceptable criteria.