Online Consultation Sheet metal processing involves multiple stages such as cutting, bending, welding, and surface treatment, and the details of each stage directly affect the accuracy, quality, and appearance of the finished product. The following are the key details to pay attention to during sheet metal processing:
1、 Raw material selection and inspection
Material type matching
Choose appropriate metal materials (such as cold-rolled plates, hot-rolled plates, stainless steel, aluminum alloys, etc.) based on the product's intended use, paying attention to the material's strength, ductility, corrosion resistance, and other properties.
For structural components with high strength requirements, Q235 steel plate can be selected, and 304 stainless steel is preferred for corrosion-resistant scenarios.
Material thickness accuracy
Strictly inspect the thickness tolerance of the board to avoid bending angle deviation or weak welding caused by uneven thickness.
Surface quality inspection
Remove materials with cracks, scratches, rust or deformation on the surface to ensure that the machining reference surface is flat and clean.
2、 Cutting and processing details
Selection of cutting method
Laser cutting: Suitable for high-precision and complex graphic cutting, attention should be paid to matching the focal position, power, and speed to avoid burrs or erosion on the incision.
Numerical Control Punching Machine: Used for batch processing of round and square holes, it is necessary to check the wear of the mold in advance to prevent burrs or dimensional deviations on the hole edges.
Scissor machine: suitable for straight cutting, requiring adjustment of blade clearance (usually 10%~15% of material thickness) to avoid deformation or tearing of the board.
Dimensional accuracy control
Reserve machining allowance (for parts that need to be bent later, the unfolded size should be calculated according to the bending coefficient during cutting).
Before mass production, make a sample and use a coordinate measuring instrument or caliper to check the first piece size, with an error controlled within ± 0.1mm (high-precision parts need to be more stringent).
Incision treatment
After cutting, burrs and slag can be removed by grinding, sandblasting, or chemical treatment (such as stainless steel pickling) to ensure a smooth cut and avoid scratches in subsequent processes.
3、 Bending processing details
Bending sequence planning
Fold the small edges first and then the large edges, and fold simple shapes first and then complex shapes to avoid interference or rebound affecting accuracy.
Example: Multi angle parts need to be bent in the order of "from inside to outside" to reduce positioning deviation caused by plate movement.
Selection of bending molds
Select the appropriate V-shaped groove based on the thickness of the board (usually with a groove width of 8-10 times the thickness of the board) to avoid excessive compression that may cause the board to become thinner or crack.
Stainless steel and other hard materials require specialized molds (such as hard alloy molds) to reduce mold wear.
Rebound compensation
Aluminum, stainless steel and other materials have a large rebound, and it is necessary to adjust the bending angle through trial bending (usually 3 °~5 ° smaller than the target angle), or design compensation blocks on the mold.
Positioning and clamping
Use blocking blocks, positioning pins, or CNC systems for precise positioning to ensure that the bending line aligns with the centerline of the mold.
Moderate clamping force to avoid surface indentation on the board (rubber pads or nylon fixtures can be used).
4、 Welding processing details
Welding process selection
Argon arc welding: suitable for precision welding of stainless steel, aluminum alloys, etc., requiring control of current (80~150A) and welding speed (3~5mm/s) to avoid burning through or porosity.
Carbon dioxide gas shielded welding: suitable for thick plate welding, gas flow rate should be maintained at 15-25L/min to prevent weld oxidation.
Preparation before welding
Clean up oil stains and rust in the welding area. Stainless steel needs to be wiped with alcohol or acetone, and aluminum alloy needs to have its oxide film scraped off.
The assembly gap of the workpiece should be controlled within 0.5-1.5mm (adjusted according to the plate thickness) to avoid incomplete welding or excessive deformation.
Welding deformation control
Adopting symmetrical welding, segmented skip welding and other processes to reduce thermal deformation, thick plates can be preheated in advance (such as preheating stainless steel to 100-150 ℃).
After welding, perform leveling (such as mechanical leveling or flame leveling) with an error controlled within ± 0.5mm/m.
Weld quality inspection
Visually inspect the surface of the weld seam for uniformity, absence of cracks, and undercutting. Important structural components require X-ray inspection or air tightness testing.
5、 Surface treatment details
Pre treatment process
Degreasing: Use alkaline cleaning agents to remove oil stains, and electrolytic degreasing can be used for stainless steel to ensure that there is no residual oil on the surface.
Rust removal/oxidation film: Carbon steel is sandblasted or pickled, and aluminum alloy is chromized to enhance coating adhesion.
spraying process
Powder spraying: The spraying thickness is controlled at 60-100 μ m, and the curing temperature is 180-200 ℃ (adjusted according to the powder type) to avoid sagging or orange peel phenomenon.
Electroplating: The thickness of the galvanized layer should reach 8-12 μ m, and the thickness of the chrome layer should be 0.2-0.5 μ m to ensure that the corrosion resistance level meets the requirements (such as salt spray test ≥ 48 hours).
Protection and packaging
After processing, avoid touching the surface with bare hands. Wear gloves or wipe with a dust-free cloth.
The parts are separated by bubble wrap and pearl cotton to prevent scratches or collisions during transportation.
6、 Other key details
tolerances and fits
Clearly indicate dimensional tolerances (such as ± 0.2mm, ± 0.5mm), control hole tolerance within ± 0.15mm, and ensure assembly surface flatness is ≤ 0.3mm/m.
Process holes and process tanks
Design release slots near the bend (to avoid stress concentration and cracking), and reserve exhaust holes in the welded parts (to prevent gas residue during welding).
Batch production first article confirmation
Before each batch of production, it is necessary to verify the first piece, check the assembly matching, appearance, and function, and confirm that there are no errors before batch processing.
Safety operation standards
Wear protective goggles during cutting and welding, and cooperate with two people during bending machine operation to avoid hands entering the dangerous area of the mold.
summary
The core of sheet metal processing lies in precision control and process rationality. From material selection to each processing step, a detailed process plan needs to be developed based on product characteristics, and quality is ensured through first article inspection, process inspection, and final product inspection. At the same time, flexibly adjusting parameters based on material characteristics and equipment performance can effectively reduce waste rates and improve production efficiency.
