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Aluminum cutting is essential for the high-precision, high-efficiency production of a wide range of products, including automobiles and electronic devices. While leveraging its light weight and excellent thermal conductivity, there are growing demands for cost reduction and shorter delivery times. This article provides a systematic explanation from optimal tool selection to machining condition adjustments and troubleshooting, offering practical knowledge. Targeting manufacturing executives and procurement managers, we will introduce the optimal solutions proposed by Daiwa Aluminum Vietnam, incorporating specific numerical data and case studies. Please first grasp the overall flow and key points of the article in this chapter.
Cutting Tool Selection
In aluminum cutting, the choice of tool material directly impacts machining quality and cost. For high-speed machining and long life in particular, carbide (WC) end mills and face mills are standard. Carbide has a good balance of hardness and toughness and can withstand high cutting speeds (Vc = 300–500 m/min), making it suitable for mass production.
On the other hand, HSS (High-Speed Steel) drills have a low initial cost and are suitable for prototypes and small-lot machining. Since the wear resistance of the HSS cutting edge is lower than that of carbide, Vc is typically kept around 80–150 m/min, and the basic operation involves extending tool life through frequent regrinding.
Furthermore, PCD (Polycrystalline Diamond) and CBN (Cubic Boron Nitride) tools exhibit extremely high wear resistance and chip evacuation properties for highly machinable aluminum alloys. PCD is particularly effective for long-length machining and high-hardness alloys (such as A7075), with tool life in some cases reaching 5 to 10 times that of carbide.
Tool Shape and Geometry
To enhance cutting accuracy, optimizing the tip angle and relief angle is essential. Generally, a tip angle of 90°–120° is recommended for end mills, and 45°–60° for face mills, which suppresses chip impact and improves chip evacuation. A relief angle of 3°–5° can minimize contact friction between the tool and the workpiece, preventing built-up edge (BUE) on the machined surface.
The chip cross-sectional shape and chip breaker are also important. Chip breakers designed specifically for aluminum break chips into smaller pieces while evacuating them smoothly, thus suppressing heat accumulation during continuous cutting. V-type and U-type breakers are mainstream, and selecting one according to the viscosity of the alloy improves machining stability.
Coatings and Surface Treatments
Coatings are effective for improving the wear resistance of tools. TiN (Titanium Nitride) generally has low friction properties and is effective in reducing aluminum adhesion. While it allows for a 20–30% increase in cutting speed, its heat resistance is inferior to TiAlN, making it suitable for machining at Vc below 350 m/min.
TiAlN (Titanium Aluminum Nitride) has higher heat resistance than TiN and can withstand high-speed machining at Vc of 500 m/min or more, as well as cutting of hard alloys (A7075). The hard layer forms an oxide film due to frictional heat, further suppressing adhesion to the workpiece surface, thus demonstrating excellent performance in terms of both tool life and cutting surface quality.
By combining these materials, shapes, and coatings, the productivity and quality of aluminum cutting can be maximized. The next section will detail how to optimize specific cutting conditions.
Optimization of Cutting Conditions
Aluminum alloys allow for cutting speeds approximately twice that of iron, enabling productivity improvements through high-speed machining.
Cutting Speed (Vc) and Rotational Speed (rpm)
The following table shows typical guidelines for Vc and rpm assuming a tool diameter of 10 mm.
Alloy | Vc (m/min) | rpm (Vc×1000÷πD) |
---|---|---|
A5052 | 300–350 | 9,550–11,140 |
A6061 | 350–400 | 11,140–12,730 |
A7075 | 400–450 | 12,730–14,320 |
By starting machining within this range and making fine adjustments while observing chip shape and runout, the balance between tool life and finish quality can be optimized.
Feed Rate (Fz) and Depth of Cut (ap, ae)
- Feed Rate Fz: 0.04–0.10 mm/tooth (adjust according to tool diameter and number of teeth)
- Axial Depth of Cut ap: 0.5–2 mm (varies for roughing/finishing)
- Radial Depth of Cut ae: 5–30% of tool diameter (stable with shallow cuts, be mindful of chip evacuation with deep cuts)
These parameters are tuned according to the machining ratio (ae/tool diameter) and finishing requirements to control the chip load.
Cutting Fluid and Lubrication Methods
- Water-Soluble Cutting Oil: Suppresses built-up edge (BUE) with excellent cooling and chip-floating properties.
- Mist Lubrication: Extends tool life with Minimum Quantity Lubrication (MQL) and achieves clean machining.
- Air Blow: Promotes chip evacuation and is effective in preventing welding.
Combining cutting oil and air blow is effective, depending on the machining shape and cleanliness requirements.
Machinability Index and Machinability Improvement Technologies
- Machinability Index: An index for evaluating machinability, where a higher number indicates lower cutting resistance. For aluminum, it often ranges from 140–240.
- Improvement Measures: Optimize chip breakers and tool relief angles, reduce adhesion with tool coatings (like TiAlN), and combine fine cuts with high-speed rotation to enhance chip breakability.
By combining these cutting conditions, the productivity and quality of aluminum machining can be maximized. The next chapter will detail specific troubleshooting procedures.
Troubleshooting
This section outlines procedures to prevent frequently occurring troubles in the machining field and to respond quickly when they do occur.
Chip Welding (Built-up Edge)
Cause Analysis: Due to high temperature and pressure during cutting, a portion of the aluminum alloy adheres to the tool’s cutting edge, forming a built-up edge (BUE). As this progresses, the cutting edge becomes rounded, causing scratches and dimensional variations on the machined surface. Countermeasure Flow:
- Reduce cutting speed (Vc) by 10–20% to suppress heat generation.
- Switch to coated tools (e.g., TiAlN) to reduce adhesion.
- Increase the flow rate of water-soluble cutting oil and use air blow concurrently to improve chip evacuation.
- Establish a plan for post-machining cutting edge inspection and regular regrinding/replacement.
Runout and Chattering
Diagnostic Points:
- Machine Factors: Insufficient rigidity of the spindle/guides, looseness of the table.
- Tool Factors: Excessive overhang, unsuitable number of teeth. Prevention Measures:
- Minimize tool protrusion and keep the cutting edge length within 3 times the tool diameter.
- Adjust the peripheral speed to shift away from the modulation range (rotational speed band where regular vibrations occur).
- Install dampers or vibration-absorbing holders to reduce resonance.
Dimensional Change Due to Thermal Expansion
Background: The thermal expansion coefficient of aluminum is large, about 23×10⁻⁶/K. The workpiece expands due to the temperature rise during machining, causing the finished dimensions to exceed the design values. Management Methods:
- Shorten the cutting time and use intermittent cutting to disperse the workpiece temperature rise.
- Stabilize heat input by managing the coolant temperature (20±2°C).
- Incorporate thermal expansion compensation into the machining program for real-time correction.
Decrease in Surface Roughness
Measurement and Tolerance: Ra (arithmetic mean roughness) of 0.8–1.6 μm and Rz (ten-point mean roughness) of 4–8 μm are common. Measure immediately after cutting with a stylus-type roughness tester, and if the values exceed the tolerance, a cause investigation is necessary. Improvement Measures:
- Reduce the finishing depth of cut to 0.1 mm or less to decrease cutting resistance.
- Fine-tune the feed rate (Fz) to 0.02–0.05 mm/tooth per edge.
- Check for wear and chipping on the tool tip and replace it early.
By implementing these troubleshooting procedures, stable cutting and high-quality finishes can be achieved. The next chapter will show the effects of cost reduction and quality improvement through actual machining case studies.
Case Studies
Cost Reduction Effect in A5052 Mass Production Machining
At Daiwa Aluminum Vietnam, in the process of mass-producing 10 mm thick A5052 products, we switched from conventional tools to carbide end mills (WC, TiAlN coating) and optimized the cutting conditions to Vc = 320 m/min, Fz = 0.06 mm/tooth, and ae = 20%. As a result, the tool life was extended from an average of 30 minutes to 50 minutes, an increase of about 67%, and the annual tool cost was reduced by about 15%. In addition, the cutting cycle time was shortened by 20 seconds per part, and the monthly production capacity increased by 5%.
Quality Improvement Case in A6061 Prototype Part Machining
In the machining of prototype parts from A6061 material, we combined mist lubrication with a carbide end mill with a 4° relief angle, machining at Vc = 370 m/min, ap = 1.2 mm, and ae = 10%. As a result, compared to using only water-soluble cutting oil, the surface roughness Ra improved by 44%, from an average of 1.8 μm to 1.0 μm, and the post-machining polishing man-hours were reduced by 50%. The defect rate at the prototype stage also decreased from 1.2% to 0.3%, and the on-time delivery rate reached 100%.
Tool Life Comparison in A7075 Aerospace Part Machining
In the machining of high-hardness A7075 aerospace parts, a comparison was made before and after the introduction of PCD tools (polycrystalline diamond). While the conventional TiAlN carbide tool had an average tool life of 25 minutes, the PCD tool maintained an average of 180 minutes, an improvement of about 7.2 times. As a result, the number of tool changes decreased by 86%, from 120 times to 17 times per month. Furthermore, although the unit price of the tool is about 3 times that of carbide, the lifecycle cost was reduced by about 20% compared to before implementation.
These case studies show that tool selection tailored to material properties and optimization of cutting conditions are effective for achieving both cost reduction and quality improvement. The next chapter will review the entire article, providing a summary and future outlook.
Conclusion
Review of This Article’s Key Points
This article has shown that the selection of diverse tool materials and geometries, including carbide and PCD/CBN, and coatings such as TiN and TiAlN, influences the productivity and quality of aluminum cutting. Furthermore, it has presented specific parameters for cutting speed, feed rate, depth of cut, and lubrication methods optimized for A5052, A6061, and A7075 respectively, and has explained troubleshooting procedures for common issues like built-up edge, chattering, thermal expansion, and decreased surface roughness. Each case study has demonstrated the concrete effects of significant tool life extension, cost reduction, quality improvement, and enhanced on-time delivery rates, confirming the effectiveness of operations based on quantitative data.
Future Outlook and Daiwa Aluminum Vietnam’s Proposal
In the future, the keys will be CAM optimization using AI, automatic correction of machining parameters through real-time monitoring, and strengthening support for recycled aluminum materials. At Daiwa Aluminum Vietnam, we provide total solutions incorporating the technologies mentioned above, and we have a system in place to achieve both cost competitiveness improvement and stable quality maintenance for our customers. We invite you to realize the next generation of manufacturing site reform with our cutting services.