Scratch Resistance and Stain Resistance Treatment of Home Appliance Shell Injection Mold
2026-05-08 13:32:10
Injection Mold
As high-grade appearance injection molded parts, home appliance shells directly determine product grade and user experience in terms of surface texture, wear resistance and antifouling performance. Common problems such as scratches, fingerprint residue, dust accumulation and easy wiping marks in daily production are mostly caused by unreasonable mold material selection, surface treatment, molding process and maintenance methods. To stabilize the appearance quality of home appliance shells and improve their scratch resistance and stain resistance, it is necessary to sort out the complete set of mold processing technology and control key points.
1. Mold Steel Selection and Basic Polishing ProcessMold steel is the fundamental condition to determine the wear resistance and tensile scratch resistance of the shell. The appearance cavity must select mold steel with good polishing performance, corrosion resistance and stable hardness. High-gloss white home appliances and transparent appearance parts prefer S136 or 420 stainless steel, with uniform organizational structure, mirror effect after polishing, and no rust or material sticking and scratching during long-term production. For mass production or modified plastic products filled with glass fiber, H13 and SKD61 hot work mold steel can be selected. After vacuum quenching and tempering, the steel hardness is maintained in a reasonable range, which can resist long-term melt erosion and wear, and avoid peeling and pit defects of ordinary soft steel.
Cavity polishing quality directly determines the fineness of plastic parts. The standard polishing process includes CNC finish milling, ultrasonic fine polishing, gradual sandpaper grinding and fine treatment with diamond abrasive paste. The cavity surface roughness is strictly controlled to avoid tool marks, sand holes and orange peel lines. The smoother and denser the mold surface, the higher the surface density of molded home appliance shells, the smaller the friction resistance, the less likely to produce fine scratches, and the reduction of dust adsorption to form a natural stain-resistant foundation.
2. Cavity Surface Strengthening Treatment of MoldAfter basic polishing, the cavity surface needs strengthening treatment to further improve hardness, wear resistance and demolding smoothness, which is the key process for scratch and stain resistance of home appliance shells. PVD super-hard coating is mostly used for high-end home appliance molds. Common coating materials include CrN, TiN and DLC, with uniform coating thickness and ultra-high hardness. It can reduce the friction coefficient of the mold surface, prevent cavity wear caused by melt erosion in the production process, and effectively eliminate plastic part pulling scratches and surface carbon deposition problems. The dense coating structure is not easy to adsorb oil and dust, and the molded plastic parts have self-cleaning properties, suitable for high-demand appearance products such as refrigerators and kitchen small household appliances.
Ion nitriding is an economical surface strengthening process, which forms a hardened layer on the cavity surface through medium-temperature ion penetration, improving mold wear resistance and optimizing demolding effect. This process has moderate cost and strong stability, mostly used for matte ordinary home appliance shells to meet the basic scratch-resistant production needs, but insufficient in anti-fingerprint and hydrophobic properties, not suitable for high-gloss pure white home appliances and products with heavy oil pollution.
Texture etching is a common appearance treatment method for home appliance shells. Fine and uniform leather grain and matte grain are selected for production. Moderate texture can cover welding lines and minor defects generated in the production of plastic parts, weaken the visual effect of scratches, and fingerprints and dust will not be significantly exposed, which can keep the shell clean with simple daily wiping. The texture processing should control the depth properly. The fine texture takes into account beauty and stain resistance, and the excessively deep texture is easy to accumulate dirt and difficult to clean.
3. Special Optimization Design for Stain Resistance and Fingerprint ResistanceTo further improve the practical performance of home appliance shells, special optimization for anti-fingerprint and dust absorption reduction is required. The mold cavity surface can be coated with fluorosilicon low surface energy coating to form a stable hydrophobic and oil-repellent protective film. The molded shell surface is not easy to retain water stains, oil stains and fingerprint marks, and can be restored to clean with simple wiping, suitable for high-frequency use home appliances such as washing machines, air conditioners and kitchen electrical appliances.
In the production stage, adopt anti-static optimization scheme, complete mold grounding treatment, add compliant anti-static additives into raw materials, reduce the electrostatic adsorption capacity of plastic part surface, reduce the accumulation of dust in the air, avoid black dust accumulation after long-term use, and maintain the long-term cleanliness of the shell.
The appearance structure design conforms to practical principles, reducing deep grooves and sharp edges and corners on the surface of plastic parts, adopting rounded transition as a whole to avoid dead corners of cleaning. Reasonably plan the position of the gate and parting surface, avoiding the visible appearance area, reducing artificial scratches caused by later grinding and modification, and ensuring the overall appearance integrity of the shell.
4. Control of Injection Molding Raw Materials and Molding ProcessRaw material quality and molding process determine the basic molding quality of plastic parts. Before production, complete drying operation according to material standards, strictly control drying temperature and duration, control raw material moisture within the standard range, avoid silver streaks and internal micro-cracks caused by moisture molding, and prevent the decline of scratch resistance caused by loose surface of plastic parts.
Reasonably debug process parameters during injection molding, abandon high-speed and high-pressure molding methods, adopt medium speed and medium pressure with precise holding pressure, reduce the erosion and wear of melt on the cavity, and protect the surface structure of the mold. Adjust mold temperature according to appearance type, appropriately increase mold temperature for high-gloss shell to improve surface compactness and gloss, maintain medium and low temperature setting for matte texture shell to ensure uniform and regular texture, reduce internal stress of plastic parts, and prevent scratch and cracking in later use.
Reasonably set up exhaust grooves and control the groove depth, timely discharge the gas inside the mold cavity, avoid burning and carbonization of materials at high temperature, attach to the surface of plastic parts to form stubborn stains, and affect the appearance cleanliness.
5. Standard of Mold Mass Production MaintenanceMold maintenance is an important link to maintain scratch and stain resistance. After each batch of production, clean the cavity and parting surface in time, use soft cloth with neutral special cleaning agent to remove material residue, oil stains and slight carbon deposition, and strictly prohibit hard tools and steel wire balls from wiping the cavity to prevent artificial scratches on the mold and replicating defects to the plastic parts.
Regularly disassemble and inspect the cavity wear state after reaching a fixed number of molding times, finely repair minor scratches on the surface with diamond abrasive paste. Use black-free high-temperature grease for moving parts such as thimbles and sliders, strictly control the coating amount, and prevent grease leakage from polluting the appearance surface of home appliances.
Before long-term shutdown and storage of the mold, clean the residual water in the cooling water channel, spray special anti-rust agent on the cavity, and do a good job of sealing and dustproof treatment to protect the polishing surface and strengthened coating from damage, ensure that the mold can still produce high-quality appearance plastic parts when put into production next time, and stabilize the scratch resistance and stain resistance of home appliance shells.
6. SummaryThe scratch and stain resistance design of home appliance shell injection molds runs through the whole process of steel selection, surface strengthening, structural optimization, process debugging and daily maintenance. Only by strictly controlling each technical link can we eliminate inherent defects such as scratches, fingerprints and dust accumulation, improve the appearance grade and service life of home appliance products, and meet the high standard appearance and use needs of the market.
