For those experiencing surface defects during injection molding

～Support for improving surface defects and preventing recurrence through mold maintenance services～

Surface defects such as scratches, haziness, and uneven gloss that occur in injection molded products are critical issues affecting appearance quality and product inspection pass/fail criteria. Especially for precision molded products like electronic components and connectors, even small defects may fail to meet quality standards. To maintain stable mass production, it is important not only to check molding conditions but also to inspect the condition of the mold surface and implement appropriate mold maintenance services.

■ What are Surface Defects? Causes and Countermeasures

Surface defects are a general term for appearance defects such as scratches, haziness, uneven gloss, contamination, and transfer failures that appear on molded products. Microscopic damage or foreign matter on the mold surface can be directly transferred to the product. Furthermore, if the temperature distribution within the mold is not uniform, differences in resin flow and cooling conditions can occur, leading to an unstable surface condition.

■ Main Causes

Surface defects are primarily caused by the following factors:

• Mold surface damage: Scratches, wear, or corrosion in the cavity are transferred to the product surface.
• Release agent residue: Excessive application or insufficient cleaning causes haziness or uneven gloss.
• Temperature unevenness: Variations in mold temperature lead to non-uniform resin transferability and cooling conditions.

Even if the appearance of defects is similar, the causes may differ, so it is necessary to isolate and check the mold, material, and molding conditions.

■ Main Countermeasures

If scratches or wear are found on the mold surface, polishing or repair will be performed according to the condition. If resin contamination or release agent is adhering, cleaning will be carried out using methods that do not damage the mold material or surface treatment. Furthermore, it is important to review the amount and application position of the release agent and avoid using more than necessary. For temperature unevenness, not only the mold temperature settings but also the flow rate, blockages, and piping condition of the cooling circuit should be checked.

■ Key Points for Purchasers

When requesting improvement for surface defects, sharing photos of the defects, their location, frequency of occurrence, resin used, type of release agent, and molding conditions will facilitate cause analysis. The mold's shot count, repair history, and cleaning frequency are also important information. By preparing samples of good and defective products, the differences in surface condition can be concretely confirmed.

■ Features of SHINKO PRECISION VIETNAM's Mold Maintenance Services

At SHINKO PRECISION VIETNAM, we specialize in precision injection molds under 100t and propose polishing, cleaning, and repair methods tailored to the condition of surface defects. Beyond merely correcting immediate defects, we also consider maintenance that contributes to extending mold lifespan, based on the occurrence of wear and contamination. Furthermore, if the cause lies in mold design, such as cooling structure or demoldability, we also provide consulting from a design perspective.

If scratches, haziness, or uneven gloss are repeatedly occurring, there may be room for improvement in the mold surface or temperature management. By sharing defective samples and molding conditions, we can propose countermeasures tailored to the cause.