Effect of Feed Force on Productivity and EMG Activity in a Drilling Task

Abstract

The paper aims to examine how feed forces during manual machining processes, namely, drilling, affect productivity and the musculoskeletal condition of the operator. The study investigates the correlation between the levels of feed force, drilling efficiency, material removal rates (MRR), and muscular strain, which is measured based on sEMG. This is to determine an optimum range of feed forces that would maximize productivity and at the same time reduce the degree of physiological stress on workers. A laboratory is a controlled test where 10 male participants (22 to 30 years) were asked to conduct manual drilling with three levels of the feed force, namely low (30 to 40 N), medium (50 to 60 N), and high (70 to 80 N). The productivity was quantified by the drilling time, MRR, and hole count and the muscle activation was tracked by touching four upper limb muscles with sEMG sensors. EMG data were recorded in order to get the percentage of muscle activation (%MVC) and root mean square (RMS). Findings revealed that there was a positive relationship between feed force and the productivity because the drilling time was shorter and MRR was higher with high feed forces. But increased feed forces also led to increased muscle activation especially in the biceps and anterior deltoid. The biomechanical sweet spot was located at the medium feed force range (~55 N) that delivered the best drilling speed and ergonomically safe drilling speed. The research also brings out the issue of productivity and musculoskeletal strain balance in manual machining tasks.

Introduction

This study explores the dual impact of feed force in manual drilling operations — balancing mechanical productivity with human musculoskeletal health. Drilling, a common subtractive manufacturing process, remains heavily reliant on human operators, especially in small and medium enterprises (SMEs). A critical factor in drilling efficiency is feed force — the axial pressure applied to the drill — which, if excessive, enhances productivity but increases the risk of musculoskeletal disorders (MSDs) such as tendonitis and carpal tunnel syndrome.

Key Issues:

1. Muscle Strain and Ergonomics: Manual drilling involves repeated use of upper limb muscles (biceps, triceps, deltoids, forearm flexors), risking fatigue and injury when excessive feed force is applied.

2. Surface Electromyography (sEMG): sEMG is introduced as a tool to monitor muscle activation and fatigue levels, offering real-time insights into physiological strain during drilling tasks.

3. Productivity vs. Human Health: Higher feed forces improve drilling time and material removal rate but lead to ergonomic risks. There’s a clear trade-off between maximizing productivity and safeguarding workers’ health.

4. Occupational Health Concern: MSDs from forceful and repetitive motions are a global concern. This research aligns with occupational safety by addressing this ergonomic paradox.

5. Integration with Industry 4.0: Incorporating sEMG data into real-time, adaptive systems enables human-centered tool design and dynamic task adjustment, aligning with Industry 4.0 principles.

Identified Gaps:

• Lack of empirical models connecting feed force with muscle fatigue.

• No real-time feedback systems currently in use to monitor operator strain.

• Current optimization models focus only on mechanical performance, ignoring human physiological costs.

Research Objectives:

1. Quantify how varying feed forces affect productivity (e.g., drilling time, MRR, hole quality).

2. Use sEMG to assess muscle activity during drilling.

3. Identify an optimal feed force range that balances efficiency with safety.

4. Explore individual differences in muscle responses.

5. Investigate biofeedback systems for ergonomic tool and training development.

Literature Insights:

• sEMG has become a core tool in ergonomic studies, enabling quantitative assessment of muscle activity, posture, fatigue, and biomechanical stress.

• Studies show poorly designed tools or ergonomics (e.g., high vibration, bad grip) increase muscle load and injury risk.

• sEMG helps evaluate posture and movement quality and detect early signs of fatigue, supporting preventive ergonomic strategies.

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Copyright

Copyright © 2025 Mohd Azmeen, Sanjeev Kumar Sarswat. 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.