BS6 Exhaust Muffler Outlet Bend Pipe Drilling Fixture

Abstract

This study presents the design and development of a BS6 exhaust muffler outlet bend pipe drilling fixture to improve accuracy, efficiency, and productivity in automotive exhaust systems manufacturing. The fixture ensures precise hole drilling on complex geometries of bent pipes, which are crucial for the adherence to BS6 emission norms. Challenge is to drill a bigger size diameter 23 mm hole into a BS6 Exhaust Muffler Outlet Bend Steel Pipe having sumptuous wall thickness of 2mm and which is having Curvature Shape due to its peculiar placement in a BS6 Exhaust System of a reputed Diesel Locomotive. The research outlines the design process, material selection, and performance testing of the fixture, demonstrating its potential to streamline production and reduce manufacturing errors. Results indicate significant improvements in operational efficiency and hole-placement accuracy, aligning with the industry\'s demand for high-quality emission-control components.

Introduction

Background & Motivation

The automotive industry is undergoing rapid transformation to meet BS6 emission norms, which require cleaner exhaust systems. One critical challenge in this process is precision drilling on bent exhaust pipes, especially near the flange to accommodate components like the Diesel Particulate Filter (DPF). These bent pipes are geometrically complex, making manual or conventional drilling prone to high rejection rates (up to 25–30%), especially when scaled for mass production.

Research Objective

This study focuses on designing a specialized fixture for drilling a 23 mm hole into SUS 439 stainless steel bent exhaust pipes used in BS6-compliant vehicles. The fixture aims to:

• Ensure repeatable precision,

• Enable mass production, and

• Minimize rejection due to misalignment or improper clamping.

Literature Review Highlights

• BS6 Norms: Drive need for advanced exhaust designs with tighter packaging and after-treatment devices.

• Drilling Challenges: Curved surfaces cause hole misalignment and depth inconsistency; require advanced fixturing.

• Pipe Bending Issues: Precision bending is vital to avoid deformation that complicates downstream processes like drilling.

Methodology

Design Requirements

• Pipe: SUS 439, 200 mm length, 44 mm diameter, 2 mm wall thickness.

• Drill: 23 mm diameter, 118° point angle, solid carbide twist drill.

• Machine: HAAS VF-2 CNC vertical mill.

Fixture Design Principles

1. Rest-Locate-Clamp (3-2-1 Principle): Ensures firm holding and positional accuracy.

2. Material Selection:

   • Fixture body: AISI 1045

   • Locators: EN31 (case hardened)

   • Clamps: High-tensile steel bolts (Grade 8.8, M6)

3. Poka-Yoke Integration: Prevents incorrect part loading and enables error detection.

Fixture Components

• Bottom Half: Contoured surface for pipe resting.

• End Face Locator: Uses shims to accurately position the pipe end.

• Top Half: Developed surface for secure clamping over curvature.

Drilling Force Calculations

• Drilling thrust: ~715 N

• Required holding force: ~2860 N (with factor of safety)

• Tangential cutting force: 357.5 N

• Radial force: 214.5 N

• Shear and axial forces on bolts calculated for safe clamping design.

Slope Analysis

To allow easy loading/unloading of curved pipes, parting lines between upper and lower fixture halves are developed using slope analysis (±3° around the hole axis) to match pipe geometry accurately.

Results & Implementation

• Final fixture design achieves precision drilling within ±0.05 mm.

• CNC integration ensures minimal operator dependency and consistency.

• Fixture design supports mass production, reduces rework, and ensures compliance with BS6 emission standards.

Conclusion

The development of a BS6 exhaust muffler outlet bend pipe drilling fixture marks a significant advancement in precision manufacturing for the automotive industry. This fixture successfully addresses the challenges of drilling on complex geometries by integrating robust resting, locating, and clamping mechanisms, adhering to the 3-2-1 principle. The detailed calculations of drilling forces, bolt loads, and fixture strength, combined with slope analysis for parting line development, ensure operational reliability and ease of use. The implementation of this fixture in mass production has demonstrated improved hole-placement accuracy, reduced component rejection rates, and enhanced efficiency. This aligns with the stringent quality and emission standards required in modern automotive systems, supporting the industry\'s transition toward BS6 compliance. Future work could focus on further optimizing the fixture design for higher automation levels and scalability to accommodate evolving manufacturing demands.

References

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Copyright

Copyright © 2025 Laxmikant Mangate, Saee Kshirsagar, Prathamesh Khedkar. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.