In precision sheet metal aluminum processing, aluminum deformation is a key issue affecting machining accuracy and product quality. Due to the high coefficient of thermal expansion and low hardness of aluminum alloys, they are prone to elastic or plastic deformation under the combined effects of cutting force, cutting heat, and clamping force. To address this challenge, a systematic approach is needed, encompassing process design, cutting parameter optimization, tool selection, improved clamping methods, and machining sequence planning.
Symmetrical machining is one of the core strategies for controlling aluminum deformation. For aluminum alloys with large machining allowances, continuous single-sided cutting concentrates heat on the machined surface, leading to uneven thermal expansion and consequently, flatness deviations. By implementing double-sided symmetrical alternating machining, each side is cut multiple times, dispersing heat and canceling out machining stresses. For example, milling a 90mm thick aluminum plate to 60mm in two passes can control the flatness to within 0.3mm, a significant improvement over the 5mm achieved with single-sided machining.
Layered multi-stage machining is suitable for aluminum alloys with multi-cavity structures. If cavities are machined one by one, the part may twist or warp due to uneven stress. Using a layered synchronous machining technique—that is, simultaneously performing preliminary cutting on all cavities and then progressively deepening to the final dimensions—ensures a uniform distribution of material removal and avoids localized stress concentration. This method is particularly suitable for machining complex structural parts such as aerospace aluminum series processing pedals, effectively reducing the risk of deformation.
Precise control of cutting parameters is crucial for minimizing deformation. Excessive depth of cut leads to exponential increases in cutting force, easily causing elastic deformation of the part; insufficient feed rate can cause heat buildup, resulting in thermal deformation. High-speed milling technology, by reducing the depth of cut while increasing the feed rate and spindle speed, can reduce cutting forces while maintaining machining efficiency. For example, using climb milling to quickly remove the blank allowance and then using conventional milling for finishing reduces work hardening and improves surface quality.
Optimization of tool geometry is essential for suppressing deformation. Increasing the rake angle reduces cutting resistance, but edge strength must be considered. The clearance angle must be matched to the cutting thickness; a small clearance angle is used for roughing to enhance heat dissipation, while a large clearance angle is used for finishing to reduce friction. Increasing the helix angle disperses cutting forces, while decreasing the principal cutting edge angle improves the force distribution on the cutting edge. Furthermore, reducing the number of milling cutter teeth and increasing the chip space can prevent chip clogging and increased cutting heat, thus preventing deformation of thin-walled structures.
Improving the clamping method is fundamental to controlling deformation. Thin-walled aluminum series processing pedals are prone to elastic bending under clamping force. This problem can be effectively alleviated by using a secondary clamping technique: when finishing near the final dimensions, briefly releasing the clamping force allows stress to dissipate on the part, and then re-fixing with slight pressure eliminates deformation caused by clamping. For irregularly shaped aluminum series processing pedals, using vacuum chucks or caulking methods (such as injecting low-melting-point media) can disperse clamping forces and improve process rigidity.
The machining sequence should follow the principle of "roughing before finishing, and major machining before minor machining." In the roughing stage, large cutting depths are used to quickly remove excess material, ensuring a uniform material distribution for subsequent finishing. The finishing stage employs small cutting depths and high rotational speeds to ensure dimensional accuracy and surface quality. For aluminum series processing pedals with cavities, the internal cavity is machined first, followed by the outer contour, to avoid structural weakening due to material removal.
Deformation control in precision sheet metal aluminum series processing pedals must be maintained throughout the entire process. Through comprehensive measures such as symmetrical machining, layered cutting, parameter optimization, tool improvement, innovative clamping, and sequence planning, machining stability can be significantly improved, meeting the stringent requirements of aerospace, automotive manufacturing, and other fields for high-precision aluminum series processing pedals.
