Development of Fully Automatic Machine Tool for Extrusion Processing of Truncated Cone Pipe Fittings

Literature Overview

This paper by Zeng Yihui, Bai Chunwang, Zeng Xianjun, and Chen Shengli, published in Machine Tool and Hydraulics (2004, Vol. 32, No. 9, pp. 133-135), reports on the development of a fully automatic extrusion machine tool specifically designed for manufacturing truncated cone pipe fittings. The authors from Hunan Normal University's Department of Mechanical Engineering and Jiangnan Machine Factory describe a complete system that integrates preheating, extrusion forming, and automatic loading/unloading with dual-piston core rod and ejector rod mechanisms controlled by a PLC-based automatic control system.

Core Technical Findings

The developed machine tool addresses the specific process requirements of truncated cone pipe fitting manufacturing through several integrated innovations. The system employs a tube-type preheating furnace to bring the workpiece to the appropriate forming temperature, followed by extrusion through a forming die. A distinctive feature is the dual-piston mechanism that independently controls the core rod and ejector rod, enabling precise push-out and core extraction operations. The automatic control system is built around a Programmable Logic Controller (PLC), with loading and unloading manipulators serving as auxiliary devices.

Practical results demonstrate that the machine achieves high automation, high production efficiency, material savings, and excellent product quality, making it worthy of broader promotion and application.

Technical Parameter Analysis

Interpretation of Technical Points

The extrusion process for truncated cone pipe fittings requires careful control of several interrelated parameters. The preheating temperature must be sufficient to achieve the required material plasticity without causing excessive oxidation or grain growth. The tube-type furnace design provides uniform heating around the circumference of the pipe, which is critical for achieving symmetric deformation. The extrusion die geometry must accommodate the taper of the truncated cone while maintaining dimensional accuracy throughout the forming process.

The dual-piston mechanism is a particularly significant design feature. In conventional extrusion operations, the core rod and ejector rod are often mechanically linked, which limits the precision of core extraction. By independently controlling these two functions, the system can optimize the push-out force and timing for different fitting geometries and material conditions. This flexibility is essential for maintaining dimensional accuracy across the range of truncated cone angles and diameters that may be required in production.

Integration with Engineering Practice

The PLC-based automatic control system represents a mature and reliable approach to machine automation. PLCs are widely used in manufacturing environments due to their robustness, ease of programming, and availability of standardized input/output modules. For the extrusion machine, the PLC coordinates the sequence of operations: workpiece loading, preheating, positioning, extrusion, cooling, core extraction, and unloading. This sequential control ensures consistent process parameters for each cycle, which is fundamental to maintaining product quality.

The integration of loading and unloading manipulators further enhances the automation level by eliminating manual material handling. This reduces operator fatigue, improves cycle time consistency, and enables unattended operation during production runs. The material savings aspect is also significant, as the extrusion process inherently uses less material than machining methods, and the automated control minimizes scrap through consistent parameter maintenance.

Key Questions and Reflections

While the paper reports successful practical results, several technical details would be valuable for engineers considering similar developments. The specific preheating temperature range used, the extrusion force requirements, and the cycle time achieved would provide important benchmarks. The dimensional accuracy and surface finish of the produced fittings relative to standards such as ASME B16.9 or ASTM A234 would establish the quality level achieved. Additionally, the wear characteristics of the extrusion die and the maintenance requirements of the dual-piston mechanism are practical concerns for sustained production.

The scalability of this approach to different fitting sizes and materials also warrants consideration. The system described appears to be designed for specific truncated cone geometries, and adapting it to other fitting types or material grades may require significant modifications. The energy consumption of the preheating furnace relative to the production rate is another practical metric that would inform economic evaluation.

Study Insights and Implications

This work demonstrates that purpose-designed automation can significantly improve the manufacturing of specialized pipe fittings. The integration of preheating, forming, and material handling into a single automated system represents a complete manufacturing cell concept that reduces labor intensity while improving consistency. For engineers evaluating manufacturing options for truncated cone fittings, this approach offers a compelling alternative to machining methods, particularly for production volumes that justify the capital investment. The key lesson is that process-specific machine design, combined with modern control technology, can unlock manufacturing capabilities that are difficult to achieve with general-purpose equipment.