Multi-Process Collaborative Turning for Cycle Time Reduction and Precision Improvement
With the continuous advancement of socioeconomic development, demands for manufacturing efficiency are constantly increasing.
In the machining field, turning processes—a crucial component—must not only optimize part processing time but also ensure manufacturing precision.
Therefore, improving production cycle times and dimensional consistency in turning operations is essential.
Traditional CNC turning often requires frequent tool changes and multiple tool setting operations.
This not only wastes setup time and causes redundant movements but also leads to cumulative errors during repeated tool setting on the lathe.
Based on current production conditions, this paper proposes a combined machining process path grounded in multi-process coordination principles.
By reconfiguring tool arrangement logic and sequence, this method integrates external cylindrical, internal bore, and end-face machining.
It enables multi-process coordination on existing CNC lathes without requiring specialized fixtures or equipment modifications, offering a practical approach to enhancing production efficiency and machining precision.
Process Capability Bottleneck Analysis
Characteristics of Traditional CNC Turning Processes
As shown in Figure 1, taking the CK5235×25/32 CNC double-column vertical lathe as an example, its turning process typically employs sequential tool changes to complete the full machining task for a single part.
For shaft or sleeve-type components, this generally involves multiple steps including external cylindrical machining, end face machining, and internal bore machining.
Due to spatial constraints and clamping limitations on most lathe tool holders, only two turning tools can typically be mounted simultaneously.
This inability to cover all process requirements simultaneously frequently leads to the following issues during machining, as summarized in Table 1.
| Existing Problem | Cause |
|---|---|
| High tool change frequency | Usually requires 2–3 tool changes, resulting in a significant increase in auxiliary time |
| Complex tool setting operations | Each tool change requires re-calibration of the tool position, increasing operator workload |
| Accumulated dimensional errors | Multiple tool changes and re-clamping may introduce cumulative errors, affecting part dimensional consistency |
| Uncontrollable machining cycle | Large fluctuations in auxiliary time make it difficult to standardize the batch production rhythm |
Table 1: Problems encountered during the processing
Analysis of Cycle Time Efficiency Bottlenecks
Taking the machining of a set of similar parts as an example, the processing time comprises effective cutting time and setup time.
Effective cutting time may account for only about 85% of the total time, while tool changes and tool setting during setup consume approximately 10% of the auxiliary time.
Therefore, improving production cycle time requires integrating processes to achieve collaborative optimization.
Multi-Process Collaborative Machining
To further enhance cycle efficiency, this paper categorizes and summarizes commonly used tools and machining processes based on a multi-process collaborative machining strategy, thereby optimizing tool positioning and shortening cutting paths.
As shown in Figure 2, this approach achieves single-setup tooling for both internal/external cylindrical machining and end-face machining.
This not only reduces errors introduced by multiple tool setting operations but also significantly saves setup time.
Collaborative Process Concept and Implementation Approach
Fundamental Concept of Multi-Process Collaboration
In CNC turning, various machined surfaces often require sequential completion using multiple tools.
Each tool change involves auxiliary actions and interruptions to the machine’s operational cycle.
The multi-process collaborative machining strategy achieves rational allocation of tooling resources and optimized process paths by integrating multiple machined surfaces into a single continuous machining flow for simultaneous completion, thereby optimizing the overall cycle time.
To meet these requirements, this paper employs collaborative process design to integrate three primary process categories for key production components into a unified execution system: rough and finish turning of external cylindrical surfaces, finish machining of end faces, and rough and finish turning of internal cylindrical surfaces.
These processes feature clearly defined sequences and smooth transitions between machining zones, providing a solid foundation for integration.
By standardizing clamping references and coordinate systems, repetitive tool setting operations are eliminated, enabling cycle time reduction.
Multi-Process Collaborative Trial
To evaluate the effectiveness of multi-process collaborative machining in actual production, a process trial was conducted using 10 sleeve components with an outer diameter of φ2000mm, inner diameter of φ1800mm, length of 50mm, and material 13MnNiMoR.
The machining parameters are listed in Table 2.
The machining outcomes of traditional tool layouts versus modular tool layouts were compared across roughing/finishing of outer diameters, finishing of end faces, and finishing of inner diameters.
During continuous machining of 10 workpieces per layout, key metrics including average machining time per piece, tool change frequency, and tool setting time were recorded. Statistical results are presented in Table 3.
| Process | Cutting Speed (m/min) | Feed Rate (mm/r) | Cutting Depth (mm) |
|---|---|---|---|
| External Turning | 125 | 0.5 | 5 |
| Facing | 94 | 0.6 | 7 |
| Internal Boring | 90 | 0.4 | 6 |
Table 2: Processing Parameters
| Item | Traditional Structure | Three-Tool Combined Structure |
|---|---|---|
| Machining time per part | 2.5h | 2h |
| Tool change count / part | 2 | 0 |
| Tool change time / part | 5min | 5min |
| Tool alignment count / part | 2 | 1 |
| Tool alignment time / part | 20min | 20min |
| Saved machining time | — | ≈5h |
Table 3 Comparison of Cycle Efficiency and Tool Change
Process Advantages and Application Prospects
In batch turning production, enhancing single-piece machining efficiency and stability remains a core objective.
The multi-process collaborative machining solution proposed herein achieves the following key technical advantages without relying on structural innovation, but through process logic reorganization and coordinated tool position control, as shown in Table 4.
| Advantage | Reason |
|---|---|
| Significantly improved cycle efficiency | Eliminates cycle interruptions caused by frequent tool changes in traditional machining |
| Significantly improved dimensional consistency | Avoids errors introduced by repeated clamping, controlling the accumulation of dimensional deviations |
| Easier operator handling | Reduces the tool-change process, improving the level of standardized operation |
| Enhanced compatibility | Achieved by adjusting tool positions without modifying the machine tool itself |
Table 4: Technical Advantages
Conclusion
In summary, this study analyzed the turning process of the CK5235×25/32 CNC double-column vertical lathe and summarized its machining characteristics.
Without altering the lathe structure or designing special fixtures, process path optimization was achieved solely through optimized tool positioning.
This resolved issues in the original turning process, including frequent tool changes, multiple tool setting operations, and poor dimensional consistency.
Furthermore, process trial results demonstrate that the improved setup reduced tool changes from 2 per part to 0, shortened processing cycles by over 10%, and effectively validated that collaborative machining enhances production cycle efficiency.
This approach not only simplifies operator tasks but also boosts production efficiency and machining precision, offering broad application prospects and providing a practical optimization solution for similar equipment.
What is multi-process collaborative machining in CNC turning?
Multi-process collaborative machining in CNC turning is a process optimization strategy that integrates multiple machining operations—such as external cylindrical turning, internal bore machining, and end-face machining—into a single continuous machining path. By reconfiguring tool arrangement logic and sequencing, it reduces tool changes, minimizes auxiliary movements, and improves overall production efficiency without modifying machine structures or fixtures.
Why do traditional CNC turning processes suffer from low cycle efficiency?
Traditional CNC turning processes rely heavily on sequential tool changes and repeated tool setting operations. These auxiliary actions consume up to 10–15% of total machining time, introduce redundant machine movements, and increase cumulative dimensional errors. Limited tool holder capacity further restricts simultaneous machining, creating cycle time bottlenecks and reducing dimensional consistency.
How does multi-process coordination improve machining accuracy and consistency?
Multi-process coordination improves machining accuracy by eliminating repeated tool setting operations and standardizing clamping references and coordinate systems. Since multiple surfaces are machined in one continuous setup, cumulative positioning errors are reduced, leading to better dimensional consistency, improved surface quality, and higher process stability during batch production.
Can multi-process collaborative machining be implemented on existing CNC lathes?
Yes. One of the key advantages of multi-process collaborative machining is that it can be implemented on existing CNC lathes without structural modifications or special fixtures. The method relies solely on optimized process path design and coordinated tool positioning, making it a practical and cost-effective solution for improving productivity on conventional CNC turning equipment.
What impact does collaborative machining have on production cycle time?
Production trials show that collaborative machining can reduce processing cycle time by more than 10%. By eliminating tool changes entirely and shortening cutting paths, the method significantly reduces auxiliary time. In batch machining scenarios, this leads to higher throughput, more stable machining rhythms, and improved overall equipment utilization.
What types of parts benefit most from multi-process collaborative turning?
Multi-process collaborative turning is particularly beneficial for shaft-type and sleeve-type components that require external cylindrical, internal bore, and end-face machining. These parts often involve multiple turning steps and frequent tool changes in traditional processes, making them ideal candidates for integrated machining paths that enhance efficiency and precision.