A cut aluminum alloy billet is firmly fixed on the workbench of the CNC machining center, with fine lines left on the surface from rolling. As the spindle motor emits a low hum, the high-speed rotating milling cutter slowly approaches, and aluminum chips fall in the precise bite of the metal and the cutter, and a journey of precision shaping led by digital instructions begins.
The process of aluminum CNC machining is a complete chain from raw materials to finished products. It is necessary to combine the characteristics of aluminum alloy, part design requirements and equipment capabilities to complete material preparation, processing implementation, quality control and other links in stages. The following is a detailed process:
- Our CNC experts will clarify the core requirements such as part size, tolerance (such as ±0.01mm), surface roughness (such as Ra 1.6μm), material model (such as 6061, 7075) based on the 3D model (such as STL, STEP format) or 2D engineering drawing provided by the customer, evaluate the processing feasibility, determine whether the aluminum parts to be processed have deep holes (aspect ratio>5), thin walls (thickness<1mm), complex surfaces and other difficulties, and develop targeted solutions.
- Choose suitable CNC aluminum alloy billets, and select models according to the strength and corrosion resistance requirements of the parts (such as 6061 aluminum is suitable for general parts, 7075 aluminum is suitable for high-strength parts). The aluminum billets include aluminum plates, aluminum bars, aluminum blocks, etc., and the size needs to reserve processing allowance.
- We also need to remove oil and scale on the surface of aluminum billets, anneal aluminum alloys with too high hardness (such as 7075) (heat to 340℃ and then cool slowly), reduce the hardness to 80-100 HB, and improve cutting performance. Or straighten the billet (especially long strip parts) to avoid deformation after processing due to material stress.
- Start roughing. Prioritize removing a lot of excess material, choose a large diameter tool (such as a 10-20mm end mill), set a high feed rate (1000-3000mm/min) and a medium depth of cut (1-5mm).
- Finishing. For precise dimensions and surfaces, use small diameter tools (such as 3-6mm ball-end tools), high speed (15000-30000rpm), and low feed rate (300-800mm/min) to ensure accuracy.
- Simulate tool paths, check for collisions (interference between tool and fixture, workpiece), optimize paths to reduce idle travel time. Choose machine tools: 3-axis machines are suitable for flat/simple three-dimensional parts, 4/5-axis machines are suitable for complex curved surfaces and multi-angle processing.
- Choose the right tool. Carbide tools (such as WC-Co alloy): suitable for high-speed cutting of aluminum alloys, good wear resistance; Coated tools (such as AlTiN coating): reduce tool sticking and extend tool life; Special tools: such as aluminum alloy special taps (spiral groove design, conducive to chip removal), ball-end tools (curved surface processing).
- Select tooling (such as vises, vacuum cups, custom fixtures) according to the shape of the part to ensure secure clamping and avoid over-positioning (especially for thin-walled parts, elastic supports are required to disperse stress).
- Fix the pre-treated CNC aluminum billet on the machine tool workbench to ensure that the clamping surface is flat to avoid processing errors caused by skewed clamping. Calibrate the tool length and diameter through the tool setting instrument, input the tool parameters into the CNC system, and ensure that the tool coordinates are consistent with the program coordinates (error ≤ 0.005mm).
- Remove most of the excess according to the program and quickly form the general outline of the part; Semi-finishing: remove the tool marks left by rough machining, reserve 0.1-0.3mm finishing allowance, and correct the shape of the part; Finishing: cut according to the final size and accuracy requirements to ensure tolerance (such as ±0.01mm) and surface finish (Ra 0.8-1.6μm).
- Remove sharp edges and flying chips after processing (manual file, sandpaper polishing or automatic deburring machine) to avoid scratching subsequent processes or operators; Clean parts: Use ultrasonic cleaning (to remove cutting fluid residue and aluminum chips) to ensure that the surface is free of oil and dirt.
- Select the surface treatment process according to your needs: Anodizing: Forming an oxide film (thickness 5-20μm), improving wear resistance and corrosion resistance, and can be colored (such as black, silver); Sandblasting: Impacting the surface with diamond abrasive to form a matte texture and cover up minor knife marks; Electroplating: Nickel/chromium plating to enhance conductivity or decorativeness; Passivation: Improve corrosion resistance (especially for easily corrosive models such as 2024).
- Final quality inspection. Dimension inspection: Use a three-dimensional coordinate measuring machine (accuracy ±0.001mm) to detect key dimensions and form and position tolerances (such as parallelism and verticality); Surface inspection: Visually check for scratches and dents, and use a roughness meter to measure the Ra value; Performance sampling: such as strength testing of load-bearing parts (tensile and bending tests).
- Classify and pack qualified parts, use anti-static bags (electronic parts) or foam cushioning (precision parts) to avoid bumps during transportation; if you need to attach a quality inspection report (dimensional inspection data, material certification, etc.), please indicate in advance.
The core of aluminum CNC machining processing is "precise control" and "adapting material characteristics": from preliminary analysis to final delivery, each link needs to optimize parameters based on the characteristics of aluminum alloy's easy cutting and deformation, and at the same time, through programming and equipment linkage, it can achieve high efficiency and provide you with aluminum CNC services. For complex parts, the process may be more subdivided (such as multiple clamping and multi-process connection), but the overall logic always revolves around the balance between "efficiency" and "precision".
When the last cutting process is completed, the spindle stops quietly, and the aluminum parts polished through milling, drilling, boring and other processes have taken shape. After removing the fixture, there are still traces of coolant on the surface of the parts, and the precise lines and holes carved by the CNC program are waiting for subsequent surface treatment to give them a tougher texture and a more refined appearance, and finally integrate into various mechanical structures with a perfect posture.