As mentioned above, although aluminum has a low melting point and good ductility, in actual production, problems such as work hardening, die sticking, and temperature sensitivity often lead to stretching failures. This article will provide a systematic aluminum stretching solution, from material selection to process optimization, to help you improve production efficiency and product quality.

Material Selection: Laying the Foundation for Aluminum Stretching

Raw Material Selection: Prioritize high-ductility aluminum alloys, and exercise caution when using heat-strengthened aluminum alloys. For deep-drawn parts, prioritize aluminum-magnesium alloys such as 5052 and 5083, or pure aluminum series such as 1100 and 1050. Alloys such as 6061 and 6063 have limited tensile properties and are suitable for shallow draws or parts with simple shapes. Use 7-series aluminum alloys with caution, as high-strength alloys such as 7075 have poor tensile properties, except for very simple shapes.

Pay attention to material condition: Choose O (annealed) or H111 (lightly worked) conditions, and avoid work-hardened conditions such as H32/H34. 

Focus on sheet quality: Choose high-quality sheet with uniform grains and a well-defined texture, and avoid materials with severe inclusions or segregation.

Lubrication system optimization: Key to preventing sticking in aluminum drawing.

Use specialized aluminum drawing oil: Choose a specialized lubricant with extreme pressure additives and moderate viscosity; avoid conventional engine oil.

Optimize lubrication methods: Use spraying or dipping to ensure uniform lubrication coverage. For deep drawing, a "wet drawing" process can be used.

Stretch film/cladding technology: Consider using PVC stretch film or PE protective film to provide both physical isolation and lubrication.

Mold surface treatment: Use chrome plating or nitriding to improve mold surface hardness and wear resistance, reducing sticking.

Regular mold cleaning: Clean aluminum chips and oil stains from the mold surface between production runs to prevent scratches and increased sticking.

Blank force control: Ensures uniform deformation during aluminum drawing.

Segmented clamp force control: Use a multi-stage clamp force control method, starting slightly higher and then gradually decreasing to reduce the risk of cracking. Use an elastic blank holder: Nitrogen springs or polyurethane elastomers provide more uniform blank holder force distribution.

Appropriate blank holder clearance: Set an appropriate blank holder clearance based on material thickness, generally 1.05-1.1 times the material thickness.

Pay attention to blank holder parallelism: Ensure the blank holder is parallel to the die plane to avoid excessive local pressure.

Use a multi-pass process for deep-drawn parts: For parts with a depth-to-diameter ratio greater than 0.8, use multiple draw passes, with annealing after each pass.

Drawing speed and temperature control: Key to aluminum's tensile stability.

Control the drawing speed: Generally maintain it within the range of 10-30 mm/s. Excessive speeds can lead to local overheating and cracking.

Use variable speed drawing: Use a low speed initially and increase the speed appropriately after forming to balance efficiency and quality.

Consider using a cooling system: Install cooling water channels within the mold to maintain a mold temperature between 50-80°C. Avoiding work hardening accumulation: For multiple stretching passes, intermediate annealing treatments (300-400°C, hold temperature for 1-2 hours) are required.

Pay attention to ambient temperature: Appropriately reduce the stretching speed during high temperatures in summer and increase it in winter.

Optimize mold design: The foundation for successful aluminum stretching.

Optimize the die corner radius: Choose a larger radius (generally 6-10 times the material thickness) to reduce stress concentration.

Appropriately design the punch shape: Use a spherical or parabolic punch tip to promote uniform material flow.

Control the gap between the die and the punch: Generally, it should be 1.1-1.2 times the material thickness. A gap too large will easily wrinkle, while a gap too small will cause cracking.

Add process cuts or holes: For complex shapes, add process cuts in areas prone to wrinkling to improve material flow.

Use drawbead design: Place drawbeads on the blank holder to control the material flow rate and prevent wrinkling.

Other Practical Tips: Details to Improve Aluminum Drawing Success Rates

Material Pretreatment: Clean the sheet before drawing to remove surface oxide films and oil stains.

Use Intermediate Annealing: Anneal after each drawing pass to eliminate work hardening.

Optimize Billet Shape: Use shaped billets instead of round ones to reduce material waste and uneven deformation.

Use Stepped Drawing: For deep cylindrical parts, use stepped dies for gradual shaping.

Quality Inspection: Regularly inspect die wear and repair or replace them promptly.

Conclusion: While aluminum drawing presents numerous challenges, stable and efficient production is possible through scientific material selection, meticulous process control, and optimized die design. This article provides practical advice covering the entire aluminum drawing process, from material preparation to finished product inspection, and we hope it will provide valuable reference for your production practices. Remember, the key to successful aluminum drawing lies in detailed control and continuous improvement. Only by continuously optimizing each step can we truly solve the challenges of aluminum drawing.