Automated Painting Solutions for Cookware Coating

Cookware coating must not only meet the rigid requirement of "food contact safety" (in line with GB 4806.10-2016 standard) but also possess properties such as high-temperature resistance (no cracking after dry burning above 260℃), wear resistance (no substrate exposure after 5000 Taber wear tests), and easy cleaning. Traditional manual painting has problems such as uneven coating, material waste (utilization rate ≤60%), and poor quality stability, which are difficult to meet the needs of large-scale cookware production. As a professional manufacturer of coating line equipment, we have created a full-process automated solution of "pretreatment - intelligent spraying - precise curing - quality inspection" for different cookware forms such as frying pans, woks, and stockpots, balancing safety, efficiency, and cost.

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1. Automated Pretreatment: Laying the Foundation for Food-Grade Coating​

Cookware substrates are mostly aluminum alloy or cold-rolled steel plates, with stamping oil and oxide layers on the surface. Pretreatment needs to achieve "no residue and high cleanliness" to avoid affecting coating adhesion and food safety.

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This link adopts an automated process of "ultrasonic degreasing → high-pressure spraying → passivation → drying":​

1. Ultrasonic Degreasing: A 28kHz high-frequency ultrasonic tank (power 500-800W) is used, combined with a neutral food-grade cleaning agent (pH 7-8), to efficiently strip oil at 50-60℃. The tank is equipped with an automatic slag removal system (slag discharge once per hour) to avoid secondary pollution from impurities;​

2. High-Pressure Spraying: Three stages of countercurrent rinsing are carried out with 0.3-0.5MPa high-pressure water flow (water temperature 40-50℃). The last stage uses deionized water to ensure the cleaning agent residue is ≤50ppm. The spray arm adopts a 360° rotating design (rotating speed 15-20r/min) to cover the inner and outer walls of the pot and the handle connection;​

3. Passivation Treatment: Aluminum alloy cookware uses a zirconium-titanium-based chromium-free passivation solution (film thickness 50-100nm), and cold-rolled steel plates use phosphating treatment (film weight 2-4g/m²). A roll-coating passivation machine is used to achieve uniform coating, avoiding uneven film thickness caused by manual operation;​

4. Drying and Curing: A hot air circulation drying room (temperature 80-100℃, wind speed 1-1.5m/s) is used, with a drying time of 15-20 minutes to ensure the surface moisture content of the workpiece is ≤0.5%. An infrared thermometer (accuracy ±2℃) is equipped at the exit of the drying room, and unqualified workpieces are automatically diverted.​

2. Intelligent Spraying System: Precise Coating Adapting to Cookware Forms​

Cookware comes in various forms (flat-bottomed, curved, with handles), and automated spraying needs to solve three core problems: "no dead corners, uniform film thickness, and material saving".​

a. Flat Cookware (e.g., Frying Pans): Composite Solution of Roll Coating + Spraying​

• Primer Roll Coating: A precision roll coater (rubber roll hardness 60-80 Shore A) is used, with the coating amount controlled at 5-8g/m². A scraper (gap accuracy ±0.01mm) is used to ensure the dry film thickness is 15-20μm, and the line speed is 20-30m/min, suitable for mass production;​
• Topcoat Spraying: Two 4-axis spraying robots (repeat positioning accuracy ±0.1mm) are configured, equipped with high-atomization spray guns (atomization particle size 10-15μm). The edge of the pan is identified through visual positioning, and the spraying path is automatically adjusted. The "pulse spraying" mode (frequency 5-10Hz) is used in the pan mouth area to avoid paint accumulation.​

b. Curved Cookware (e.g., Woks): Collaboration between Robot and Rotating Conveyor​

• Conveyor System: A pneumatic rotating fixture (rotating speed 30-50r/min) is used to drive the wok to rotate 360° to ensure uniform paint application on the curved surface;​
• Spraying Strategy: A 6-axis robot is equipped with a fan-shaped nozzle (angle 60-90°) to spray back and forth along the generatrix direction of the wok. An additional topcoat spraying is added to the center area of the wok bottom (the area with the highest temperature), increasing the film thickness to 25-30μm to enhance high-temperature resistance;​
• Electrostatic Assistance: 60-80kV electrostatic voltage is turned on, increasing the paint utilization rate from 60% in traditional manual operation to over 85% and reducing material waste.​

c. Cookware with Handles: Zoned Spraying + Shielding Protection​

• Handle Protection: An automatic shielding mechanism (silicone material) is used to automatically wrap the handle during spraying to avoid paint contamination;​
• Zoned Spraying: The robot is divided into a "pot body spraying unit" and a "pot ear spraying unit" to adapt to the sizes of different areas. A "small-flow spray gun" (paint output 5-10g/min) is used for small parts such as pot ears to accurately control the coating thickness.​

3. Precise Curing and Quality Inspection: Ensuring Coating Performance and Safety​

a. Curing System: Adapting to Different Coating Characteristics​

• PTFE Coating: A high-temperature curing oven (380-420℃, holding time 5-8 minutes) is used, and nitrogen is introduced into the oven (oxygen content ≤5%) to prevent coating oxidation and yellowing;​
• Ceramic Coating: Low-temperature infrared curing (180-220℃, time 20-25 minutes) is used, with the heating rate controlled at 5℃/min to avoid coating cracking;​
• Energy Consumption Optimization: The curing oven is equipped with a waste heat recovery device, increasing heat utilization rate by 30% and reducing production costs.​

b. Automated Quality Inspection​

• Film Thickness Detection: An online laser thickness gauge (accuracy ±1μm) detects 100% of the coating thickness, and an automatic alarm is triggered when the deviation exceeds ±2μm;​
• Adhesion Test: Sampling is conducted every hour using the cross-cut method (cross-cut spacing 1mm), and the adhesion grade is automatically determined (requiring ≥5B);​
• Food Safety Testing: Samples are regularly sent to the laboratory to test the heavy metal dissolution of the coating (lead, cadmium, etc. ≤0.1mg/kg) to ensure compliance with food-grade standards.​

Application Case: Upgrade Effect of a Cookware Enterprise​

After a medium-sized cookware enterprise introduced this automated solution, key indicators improved significantly: the coating qualification rate increased from 82% to 99.3%, the single-shift production capacity increased from 500 pieces to 1200 pieces, the paint loss rate decreased from 40% to 15%, saving more than 3 million yuan in annual material costs; the products passed FDA and LFGB certifications, exports increased by 40%, and successfully entered the high-end kitchenware market.​

Conclusion​

The core of the automated painting solution for cookware coating is "safety adaptation, form compatibility, and efficiency improvement". Through automated pretreatment to ensure cleanliness, intelligent spraying to adapt to various forms, and precise curing and inspection to ensure performance, enterprises can be helped to achieve large-scale and high-quality production while meeting food-grade safety requirements. As an equipment manufacturer, we can customize solutions according to the enterprise's cookware categories (frying pans, woks, stockpots) and production capacity scale (500-2000 pieces per shift) to help enterprises build core competitiveness.​