A combined rolling and milling process is proposed for the fabrication of heat pipe radiator bases. By performing both the preliminary flattening of the heat pipes and the precision machining of the base on a single CNC machine tool, a high degree of flatness consistency is achieved between the heat pipe contact surface and the base surface. Experimental results demonstrate that this process limits the overall flatness error to within 0.05 mm and achieves a surface roughness (Ra) of 0.8–1.2 μm. Compared to traditional methods, the processing time per unit is reduced, offering high precision, high efficiency, and feasibility for mass production. This method provides reliable technical support for the efficient manufacturing of heat pipe radiators and similar metal components.
The flatness of the heat pipe radiator base directly impacts heat dissipation performance and assembly quality. Traditional multi-step machining processes involve numerous pieces of equipment, lengthy workflows, and frequent clamping and transport, all of which limit production efficiency and precision. To enhance efficiency and accuracy, a combined rolling and milling process is proposed; this integrates preliminary heat pipe flattening and base precision machining into a single CNC machine operation, enabling high-precision mass production. The study also explores the industrial application value of the process design, experimental validation, and optimization strategies.
02
Image
Design of the combined rolling and milling process for heat pipe radiator bases
Image
2.1 Analysis of Process Principles
During the machining of the heat pipe radiator base (see Figure 1), the quality of the heat pipe contact surface and the base's upper surface directly affects heat dissipation and assembly quality. The rolling process utilizes a tool equipped with uniformly arranged balls to flatten the heat pipes, bringing their contact surfaces close to the base's upper surface and ensuring preliminary flatness. Subsequently, a milling process is employed to precision-machine both the rolled heat pipes and the base, ensuring they are perfectly flush and creating a smooth, flat surface. This combined rolling and milling approach integrates multiple traditional steps into a single CNC operation, reducing workpiece transport and re-clamping time while improving machining precision and surface quality; consequently, it significantly boosts production efficiency and lowers manufacturing costs. Figure
Figure 1: Schematic of the heat pipe heat sink base
2.2 Process Scheme Design
In the process scheme design, the rolling tool utilizes multiple balls arranged uniformly in a circle to ensure uniform pressure application and base flatness; the number of balls and their spacing can be optimized based on the heat pipe diameter and groove width. A face milling cutter is selected, capable of 360° rotation; transverse feed is used to complete the milling of the bottom surface, ensuring the heat pipe's pressure-bearing surface is flush with the base surface. The machining sequence is controlled by a CNC machine tool, enabling continuous processing that transitions from rolling to tool changing and then to milling. This scheme eliminates the need for switching between multiple machines and processes, thereby increasing the level of automation. It also ensures high synergy between the initial leveling via rolling and the precision finishing via milling, ultimately enhancing overall process stability [1].
2.3 Machining Equipment and Fixture Design
The machining equipment selected is a CNC machine tool equipped with an automatic tool changer. This allows for both the 360° rotation of the rolling tool and the switching to a milling cutter for bottom surface milling, enabling composite machining on a single machine. The heat sink base is clamped onto the machine table using a dedicated fixture, ensuring no displacement occurs during rolling and milling, which improves machining accuracy. The fixture design accounts for positioning and uniform clamping force after the heat pipe is inserted into the groove, while preventing deformation of the heat pipe. Safety designs for the equipment and fixture also ensure operator safety and workpiece integrity, thereby guaranteeing the stability and repeatability of the composite machining process.
03
Figure
Experimental Study on Composite Rolling and Milling Machining
Figure
3.1 Experimental Materials and Workpieces
The heat pipes used in the experiment are standard copper pipes with an 8 mm diameter, and the base material is aluminum alloy. The groove design complies with dimensional tolerance requirements for the heat pipes, ensuring a tight fit and facilitating the flattening process. The base surface undergoes pre-treatment to improve finish quality, reducing surface scratches and stress concentrations during machining, thereby ensuring the reliability of the experimental data.
The depth and spacing of the base grooves are optimized to ensure uniform force distribution on the rolling balls. Heat pipes are cleaned prior to assembly to prevent oil or impurities from affecting the rolling results. The base is secured to the CNC machine tool table using a fixture, ensuring that the heat pipe and base maintain a stable relative position during the transverse feed process, thereby establishing a reliable experimental foundation for the subsequent combined rolling and milling operations.
3.2 Experimental Procedure
The heat pipe is inserted into the groove of the base and secured with a specialized fixture, ensuring parallelism and uniform force distribution to prevent deformation or displacement during clamping. The fixture is fastened to the CNC machine table to maintain the workpiece's stability during the subsequent rolling and milling processes. The CNC machine then controls the rolling tool to rotate 360°, performing a rolling pass under transverse feed; this brings the compressed surface of the heat pipe close to the upper surface of the base for initial leveling, while the uniform force applied by the rolling ball ensures the overall flatness of the base.
Upon completion of the rolling process, the tool automatically switches to a face milling cutter to perform a 360° rotary milling operation. This step machines the compressed surface of the rolled heat pipe until it is perfectly flush with the upper surface of the base, creating a smooth, flat finish. Key parameters-including rolling pressure, number of rolling balls, feed rate, and milling settings-are meticulously recorded throughout the experiment to provide reliable data for subsequent process optimization, quality control, and mass production [2].
3.3 Measurement Methods
Flatness is measured using a high-precision Coordinate Measuring Machine (CMM) to assess the flatness of the heat pipe's compressed surface and the base's upper surface, ensuring the overall flatness error remains within acceptable limits. Flatness deviation is calculated based on multi-point measurements, with changes recorded after each rolling and milling stage. Surface roughness is inspected using a surface profilometer to verify that the contact surfaces of the base and heat pipe meet design specifications. Additionally, the flushness between the heat pipe's compressed surface and the base's upper surface is measured to analyze the impact of the combined rolling and milling process on workpiece precision, providing a reliable basis for process optimization and parameter adjustment.
3.4 Experimental Results and Analysis
The experimental results demonstrate that the combined rolling and milling process yields significantly better flushness between the heat pipe's compressed surface and the base's upper surface compared to traditional multi-step manufacturing processes. The overall flatness error is controlled within 0.05 mm, and the surface roughness (Ra) reaches 0.8–1.2 μm, meeting the machining requirements for high-precision heat sinks. The rolling process (see Figure 2) effectively pre-levels the heat pipe, ensures uniform force distribution, reduces the volume of material removed during milling, minimizes tool wear, and enhances both machining efficiency and surface flatness. This method ensures machining precision while reducing stress concentration in the heat pipe base and extending the service life of equipment and tools.
Image
Figure 2: Schematic of the rolling process
1-Heat pipe 2-Rolling tool 3-Ball 4-Heat pipe heat sink base
Compared to traditional stamping and polishing processes, the combined rolling and milling process significantly saves equipment usage time and the time required for secondary clamping; experimental data shows a reduction of approximately 30% in processing time per unit. Furthermore, the process offers high stability and repeatability, ensuring consistent machining precision across workpieces during mass production and reducing the scrap rate [3]. This combined machining approach integrates processes, minimizes manual intervention, optimizes production workflows, and raises the level of automation on the production line.
04
Image
Optimization of Combined Rolling and Milling Technology
Image
4.1 Optimization of Process Parameters
The process parameters for combined rolling and milling directly influence the flatness of the heat pipe contact surface and the surface quality of the base. In the rolling process, optimizing rolling pressure and the number of balls ensures uniform force application on the heat pipe, prevents localized protrusions or depressions, and improves rolling efficiency. Ball spacing, arrangement patterns, and rolling speed must also be adjusted based on the heat pipe diameter and base groove dimensions to accommodate different specifications of heat pipe bases. In the milling process, optimizing cutting depth, feed rate, and tool rotation angle reduces material removal, improves bottom surface flatness and quality, minimizes tool wear and machining vibration, and ensures the high precision and stability of the combined process, thereby providing reliable technical support for the mass production of heat pipe heat sink bases. 4.2 Process Integration and Efficiency Analysis
Combining rolling and milling operations on a single CNC machine tool significantly enhances production efficiency. This process integration eliminates time wastage associated with multiple clamping setups and equipment switching found in traditional methods, while also reducing errors caused by part transport or re-clamping. Experimental results indicate that the processing time per unit is reduced by approximately 30% compared to traditional stamping and polishing processes; equipment utilization improves, and both manual intervention and operational complexity are reduced [4].
4.3 Quality Control Methods
Clamping precision plays a critical role in the quality of the combined rolling and milling process. Designing specialized fixtures ensures the heat pipe maintains a stable position during both rolling and milling, effectively preventing flatness deviations caused by heat pipe displacement or deformation. Comprehensive inspection and correction measures must be established-including flatness measurement, surface roughness testing, and verification of the alignment of the heat pipe's contact surface-to allow for timely adjustments to process parameters or re-clamping in response to anomalous data. Quality control should also incorporate real-time machine monitoring systems to provide feedback-based adjustments of force and displacement during machining. This ensures the stability and consistency of the combined process, thereby meeting industrial requirements for high precision and superior surface quality in heat pipe radiator bases.
05
Image
Process Application and Engineering Value
Image
The combined rolling and milling process offers high stability and repeatability, making it suitable for the mass production of heat pipe radiator bases. Performing both operations on a single CNC machine ensures alignment between the heat pipe contact surface and the base's flatness, minimizes human error, and accommodates various base specifications; production needs can be met simply by adjusting the number of rolling balls, rolling pressure, and milling depth. Process integration reduces the need for multiple clamping setups, material transport, and equipment switching, thereby enhancing production line efficiency and operational standardization. This provides a viable solution for mass production while ensuring consistent product quality [5].
Compared to traditional multi-step machining, this combined process significantly boosts production efficiency and economic returns. It reduces processing time per unit by approximately 30%, lowers equipment occupancy and the need for manual intervention, and decreases both the scrap rate and costs associated with subsequent finishing work. By integrating intelligent control with in-process inspection, the method enables automatic adjustment of process parameters and real-time monitoring. It is suitable for the machining of heat pipe radiator bases and other high-precision metal components, offering broad application prospects.
06
Image
Conclusion
Image
The combined rolling and milling process effectively integrates heat pipe flattening and base milling operations, simplifying the traditional manufacturing workflow and significantly enhancing processing efficiency and automation levels. Experimental results demonstrate excellent flushness between the heat pipe contact surface and the base, with flatness errors controlled within 0.05 mm and surface roughness (Ra) ranging from 0.8 to 1.2 μm. Additionally, the per-unit processing time is reduced by approximately 30%, and the process exhibits high stability. This method is suitable for the mass production of heat pipe radiator bases and other high-precision metal components, offering significant economic benefits and potential for widespread adoption.
