**Abstract:** This paper discusses the current status and user requirements of heavy-duty horizontal lathes and roll lathes, as well as the process of transforming conventional models into highly integrated, technologically advanced, aesthetically pleasing, and user-friendly CNC heavy-duty lathes. It compares three types: the traditional C61200 model, the new digital pull-type machine, and the CNC retrofit version. The focus is on how modernization can enhance performance while maintaining cost-effectiveness.
**Keywords:** Heavy-duty lathe; Roll lathe; Numerical control; Design; Transformation
**1 Introduction**
The modernization of traditional heavy-duty horizontal lathes and roll lathes through CNC transformation offers a quick and effective solution for factories looking to upgrade their equipment. These machines are essential for high-efficiency cutting in both rough and finish machining processes involving materials such as carbon steel, forged steel, alloy cast iron, high-speed steel, and Gaoming steel. With CNC technology, precise and low-roughness automatic cutting of outer surfaces, inner holes, end faces, tapers, internal and external threads, arcs, and complex curved holes can be achieved. For example, the Tangshan Heavy Machine Tool Plant has successfully modernized several large-scale heavy-duty horizontal lathes, including the C61125A, C61160, and C61200G, for China’s largest metallurgical roll manufacturer, resulting in significant economic benefits.
**2 Comparison of Main Parameters and Performance Between Conventional and New CNC Heavy-Duty Lathes (Roll Lathes)**
As shown in Table 1, the main parameters and drive speed ranges of both the conventional and new CNC versions are largely similar. However, key differences exist in feed range, speed control, and machining efficiency.
- **Feed Range and Speed Control**: The conventional model has a narrow, step-variable feed range that relies on multiple mechanical components to achieve movement. In contrast, the CNC version offers an infinitely variable feed range with AC servo motors for each axis, enabling faster and more accurate movements.
- **Machining Principle**: Traditional lathes require forming templates for complex shapes, leading to inefficiency and lower accuracy. The CNC system allows for precise control using interpolation and program adjustments, making it easier to adapt to changing hole shapes.
These improvements highlight the importance of modernizing the main drive and feed systems to enhance performance and flexibility.
**3 CNC Transformation Design Details**
The transformation process involves several key components:
- **Bed Modification**: The original lead screw and guide rails are removed and replaced with high-precision helical racks. Plastic guide rails and automatic lubrication reduce friction.
- **Main Drive Optimization**: A digital encoder is installed at the spindle end, and the speed control system is upgraded to either a DC or AC variable frequency system.
- **Feed System Redesign**: The tool rest, carriage box, and feed box are replaced with CNC-compatible units. This includes a horizontal slide driven by an AC servo motor, ensuring precise X-axis movement.
- **Slide Box and Tool Holder**: The slide box uses a double pinion anti-backlash structure for long-distance Z-axis movement. Precision gratings provide closed-loop feedback for accurate positioning.
- **Tool Rest and Operation Panel**: Designed for ease of use, the tool rest features a rigid structure and rapid tool change mechanism. An operation panel is mounted for centralized control of all functions.
- **Measurement System**: A Renishaw probe is added for precise part inspection.
- **CNC System Options**: The system can be configured with brands like FAGOR, Siemens, or others, offering functions such as linear/circular interpolation, tool compensation, and simulation.
**4 Comparison of Performance Between New and Retrofitted CNC Heavy-Duty Lathes**
As shown in Table 2, the new CNC lathes and retrofitted models share similar main parameters and performance. However, the retrofitted version may have slightly more complex internal mechanisms, which can affect maintenance. Additionally, the new CNC model provides better protection for the bed's long tool rails, enhancing long-term accuracy and durability.
**5 Conclusion**
In summary, after CNC transformation, the performance of heavy-duty horizontal lathes and roll lathes is comparable to that of new CNC models, except for bed protection. The transformed machines offer a cost-effective alternative, typically priced at about one-third of new models, with a production cycle reduced by half. This makes them an attractive option for manufacturers seeking to modernize without replacing their entire fleet.
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