Robotic Polishing vs Chemical Polishing for Jewelry Finishing (Labor Costs & Surface Uniformity)

PFT, Shenzhen

Abstract
This study evaluates robotic polishing and chemical polishing techniques for jewelry finishing, focusing on labor cost efficiency and surface uniformity. A comparative analysis was conducted using a sample set of 120 silver and gold components. Robotic polishing employed a six-axis articulated arm with variable-speed polishing heads, while chemical polishing applied controlled acid baths under standardized conditions. Surface roughness measurements (Ra) were recorded using a contact profilometer, and labor costs were calculated based on process time and operator involvement. Results indicate that robotic polishing achieves consistent surface uniformity (Ra variation ≤5%) with higher initial equipment costs but lower per-piece labor expenses. Chemical polishing delivers comparable uniformity for simple geometries but exhibits greater variability on complex surfaces and incurs higher safety-related operational costs. Findings support the selection of robotic polishing for high-volume, intricate jewelry production, whereas chemical polishing remains suitable for simpler batch finishing with limited investment.

1. Introduction

Jewelry finishing requires high precision to meet aesthetic and quality standards. Surface smoothness and uniformity directly influence product appeal, while labor costs significantly impact production economics. Robotic polishing and chemical polishing are two widely adopted finishing methods, yet their comparative performance regarding operational efficiency and surface consistency requires quantifiable assessment. This study provides a systematic evaluation to guide process selection in industrial jewelry manufacturing.

2. Research Methods

2.1 Design Approach

A comparative experimental framework was established, focusing on labor input and surface roughness outcomes. The study incorporated repeatability and reproducibility by testing identical jewelry components under controlled conditions.

2.2 Data Sources

Data were collected from a Shenzhen-based jewelry manufacturing facility over a four-week period. Component types included 60 silver pendants and 60 gold rings, representing a range of surface geometries.

2.3 Experimental Tools and Models

• Robotic Polishing: Six-axis robotic arm (KUKA KR6) equipped with variable-speed polishing heads, programmed for automated path control.

• Chemical Polishing: Standardized acid bath setup with temperature control (25 ± 1°C) and timed immersion protocols.

• Measurement Tools: Contact profilometer (Mitutoyo SJ-410) for Ra measurements, labor cost calculated from operator time logs.

All procedures were documented to ensure reproducibility, including robot path scripts, chemical bath compositions, and safety protocols.

3. Results and Analysis

3.1 Surface Roughness Comparison

Table 1. Surface Roughness (Ra) Comparison

Robotic polishing demonstrated lower variability across both simple and complex geometries, ensuring uniform finishing. Chemical polishing showed higher Ra variation, particularly on complex shapes.

3.2 Labor Cost Evaluation

Figure 1. Labor Cost per Piece

Labor cost analysis indicated robotic polishing reduced operator involvement by 60%, whereas chemical polishing required continuous monitoring for safety and quality control.

4. Discussion

4.1 Mechanistic Interpretation

The higher uniformity in robotic polishing is attributed to precise tool-path control and consistent contact force. Chemical polishing uniformity is geometry-dependent, limited by differential acid exposure in recessed areas.

4.2 Limitations

• Robotic setup requires higher initial investment and maintenance.

• Chemical polishing poses environmental and safety management challenges.

4.3 Practical Implications

For high-volume production of intricately designed jewelry, robotic polishing optimizes both surface quality and labor efficiency. Chemical polishing remains applicable for simpler, low-volume batches with cost constraints.

5. Conclusion

Robotic polishing provides superior surface uniformity and lower per-piece labor costs, making it suitable for complex, high-volume jewelry finishing. Chemical polishing is adequate for simple geometries but entails higher labor monitoring and safety overhead. Future research may explore hybrid approaches combining robotic pre-polishing with chemical finishing for optimized efficiency and surface aesthetics.