To prevent deformation in aluminum alloy doors and windows, strict control must be exercised across the entire process—starting with material selection, followed by structural design, manufacturing processes, installation standards, and routine maintenance. The specific solutions are as follows:

　　I. Material Selection: Ensuring Basic Performance

　　You-quality aluminum alloy profiles

　　Material selection criteria: Prioritize the use of high-purity aluminum ingots (such as 6063-T5 or 6061-T6 alloys), which offer high strength (tensile strength ≥ 160 MPa), excellent corrosion resistance, and a stable coefficient of thermal expansion (23 × 10⁻⁶/°C). Avoid using recycled aluminum or low-purity alloys, as impurities can lead to non-uniform stress distribution.

　　Wall-thickness requirements: Select the minimum wall thickness based on the type of door and window (according to national standards: for casement doors and windows, the wall thickness of primary load-bearing members shall be ≥1.4 mm; for sliding doors and windows, ≥1.2 mm; in high-rise buildings or areas with strong winds, it is recommended to increase this to 1.6–2.0 mm). Insufficient wall thickness can easily lead to deformation of the members.

　　Surface Treatment: Anodizing (thickness ≥ 10 μm), electrophoretic coating, or fluorocarbon spraying is employed to enhance corrosion resistance, particularly in coastal environments with high salt spray.

　　Hardware accessory matching

　　Select high-strength stainless steel hardware (such as 304 or 316) or zinc-alloy hardware (such as hinges, pulleys, and locking mechanisms) to ensure that the load-bearing capacity is matched to the aluminum alloy profiles (for example, heavy-duty sliding doors must be equipped with pulley sets rated for a minimum load of 100 kg).

　　The connection points between hardware components and extruded profiles shall be designed with anti-loosening features (e.g., stainless steel screws paired with nylon lock washers) to prevent loosening over long-term use, which could lead to uneven stress distribution.

　　II. Structural Design: Optimizing Mechanical Performance

　　Reinforcement ribs and cavity design

　　Internal “T-shaped” and “grid-shaped” stiffening ribs are added to the profile (integrally formed via extrusion), enhancing the member’s resistance to bending (e.g., longitudinal stiffening ribs are installed beneath the lower track of sliding windows).

　　A multi-chamber structure (such as a three-chamber or four-chamber design) is adopted, with thermal break strips and reinforcing ribs used to separate and isolate stress concentrations, thereby preventing localized deformation in single-chamber profiles caused by temperature fluctuations.

　　Reasonable grid dimensions

　　Control the width and height of single-leaf doors and windows (for hinged doors, the width of a single leaf shall not exceed 900 mm and the height shall not exceed 2400 mm; for sliding windows, the width of a single leaf shall not exceed 1200 mm). For exceptionally large divisions, additional muntins (horizontal or vertical reinforcing bars) shall be provided, or a thermal-break design shall be adopted to distribute the load.

　　The junction between the mullion and the main profile shall be reinforced with adhesive (using corner-joining adhesive or end-face adhesive) to ensure there is no gap at the joint.

　　III. Manufacturing Process: Precision Fabrication and Detailed Control

　　Cutting and Drilling Accuracy

　　Utilize CNC cutting equipment with an accuracy of ±0.2 mm to ensure precise cutting angles for profiles (e.g., 45° miter joints) and hole positions (e.g., hardware mounting holes), thereby preventing assembly stresses caused by dimensional deviations.

　　When drilling holes, avoid damaging the inner wall of the profile (e.g., ensure that the hole spacing from the edge is ≥20 mm) to prevent stress concentration.

　　Corner-joining process optimization

　　Adjustable corner brackets combined with sealant injection: Elastic adjustable corner brackets (with fine angle adjustment capability) are used in conjunction with two-component corner-sealing adhesive (with a cured strength of ≥30 MPa) to fill corner gaps (gap ≤0.1 mm), thereby enhancing the overall integrity of the joint.

　　Corner-joining process (for high-end products): The profile ends are tightly interlocked by mechanical corner-joining using a press with a force of ≥50 tons, followed by injection of end-face sealant to prevent cracking and deformation at the corners.

　　Welding and Splicing (for Special Structures)

　　When welding is employed (e.g., for aluminum alloy sunroom frames), tungsten inert gas (TIG) welding must be used to control the heat input and prevent localized overheating that could lead to coarse grain formation. Following welding, stress-relief annealing should be performed by heating to 200–250°C and then allowing the material to cool slowly.

　　IV. Installation Specifications: Avoid External Forces

　　Foundation Treatment for Installation

　　Door and window openings must be vertically plumb and horizontally level (vertical deviation ≤ 3 mm, horizontal deviation ≤ 2 mm). Any uneven areas shall be repaired with cement mortar or a dedicated leveling material; it is strictly prohibited to forcibly level the opening by tightening screws, as this can cause stress-induced deformation of the profiles.

　　The opening dimensions shall be 20–30 mm larger than the door and window frame dimensions. The gap shall be filled with an elastic filling material (such as expanding foam), ensuring uniform and full coverage that accounts for approximately 70% of the gap volume. The exterior surface shall then be sealed with sealant having a minimum width of 5 mm.

　　Fixing method

　　Door and window frames shall be fixed to the wall using expansion bolts or nail guns (spacing ≤600 mm, distance from corners ≤150 mm). Fixing directly into brick joints or lightweight masonry units is strictly prohibited; concrete embedded parts must be installed in advance.

　　Sliding windows shall be fitted with non-slip tracks at the bottom (with a flatness tolerance of ≤1 mm), and casement windows shall be equipped with stop blocks at the bottom (to prevent deformation caused by impact during opening and closing).

　　Force equilibrium

　　After installation, check the smoothness of door and window operation (no sticking or binding), and adjust the hinge screws or pulley positions to ensure even force distribution (e.g., consistent force on the left and right hinges of a swing door).

　　V. Routine Maintenance: Extending Service Life

　　Avoid external impact

　　Do not strike the surfaces of doors and windows with hard objects (such as stones or hammers), and when opening or closing them, push or pull gently—especially for sliding windows, avoid applying excessive force or pulling abruptly.

　　High-rise residential buildings must be equipped with wind braces/limiters (e.g., wind braces for casement windows and limiters to restrict the maximum opening angle of sliding windows).

　　Regular cleaning and lubrication

　　When cleaning, use a soft cloth dampened with a neutral detergent (strong acids and strong alkalis are prohibited) to avoid corroding the profile surface; lubricate hinges, pulleys, and other hardware components with silicone-based grease (such as WD-40) every six months to reduce friction and wear.

　　Inspect the sealant strips (made of EPDM rubber) for signs of aging and cracking (replace every 2–3 years) to prevent rainwater infiltration, which can cause profile expansion and deformation.

　　Environmental adaptability

　　In coastal areas, regularly inspect the surface coatings of profiles (e.g., to check for flaking of fluorocarbon paint) and reapply protective coatings as necessary. In northern regions during winter, when there is a large temperature difference between indoors and outdoors, avoid keeping doors and windows closed for extended periods; instead, ensure adequate ventilation to reduce thermal expansion and contraction stresses.

　　Summary

　　The root cause of deformation in aluminum alloy doors and windows lies in the coordinated control of “material strength, structural soundness, manufacturing precision, and installation compliance.” By selecting high-quality profiles and hardware, optimizing the design of reinforcing ribs, employing precise corner-joining techniques, adhering to standardized installation procedures, and conducting regular maintenance, the risk of deformation can be significantly reduced. This ensures that the doors and windows maintain their flatness, tight sealing, and smooth operation over the long term, thereby extending their overall service life to more than 20 years.

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