Hardcore Guide: How to Eliminate Sink Marks on Injection-Molded Plastic Parts for Golf Club Brushes

During manufacturing of golf club brushes, surface depressions known as sink marks on plastic handles and connectors are common defects that ruin appearance and compromise assembly precision. Sink marks form when melt feeding volume fails to compensate for material shrinkage, generally caused by uneven wall thickness, insufficient packing pressure or unbalanced cooling systems.

To resolve this issue systematically, we analyze standardized troubleshooting workflows, coordinated optimization of molds & materials, and precision manufacturing strengths of professional source factories across three dimensions.

Sink mark elimination cannot rely on random parameter adjustments. We follow the standardized principle: simple adjustments first, complex measures later; optimize molding process before modifying molds.

Process optimization is the primary solution to sink marks. Priority should be given to optimizing packing settings with multi-stage packing technology:

Apply high pressure (90% of filling pressure) for the initial 2–3 seconds for rapid shrinkage compensation, then reduce pressure to 60% and hold until gate solidification.

Moderately raise mold temperature (10–20℃) and melt temperature (5–10℃) to lower melt viscosity, delay skin layer solidification and reserve sufficient time for internal feeding.

In addition, adopt slow injection speed (≤50 mm/s) over thick-wall zones to build a favorable temperature gradient for shrinkage compensation.

If parameter adjustment fails, mold design must be reviewed:

Place gates as close as possible to thick-wall sections and enlarge gate cross-section to extend the feeding channel. Optimize cooling circuit layout with conformal cooling channels or beryllium copper inserts. Keep mold temperature difference between thick and thin wall areas within 5℃ to avoid aggravated shrinkage deviation caused by uneven cooling.

For golf club brushes requiring premium surface quality, low-shrink modified plastics (glass-filled or nano-filled compounds) are preferred. Alternatively, implement volcano-style material reduction at rib roots during mold design to equalize wall thickness fundamentally and release shrinkage stress.

Plastic components for golf club brushes require precise assembly with metal brush heads or magnetic accessories. Tiny sink marks and deformation will lead to assembly failure.

Dongguan Enyong Plastic & Hardware Products Co., Ltd. stands out as an experienced source manufacturer with 28 years of industry experience. Our in-house mold workshop and fully automated production lines support sophisticated injection molding processes.

Backed by decades of technical accumulation, Enyong masters rheological characteristics of various engineering plastics and shrinkage compensation calculation. We leverage advanced Moldflow simulation and precision mold machining to avoid sink mark risks at the design stage.

We provide full-spectrum OEM & ODM customization: anti-slip texture on brush handles, blemish-free high-gloss injection molding, and precise branding logo embedding. One-stop services from R&D to mass production guarantee consistent dimensional stability and premium surface finish on all plastic components.

Golf accessory buyers enforce strict quality standards, demanding both high production yield and agile supply chain response.

Dongguan Enyong operates a highly elastic flexible production system. Hot-selling standard models are stocked in bulk for immediate shipment, and small-batch rapid reorders are available to capture market trends.

Our combination of rigorous precision craftsmanship and fast lead times enables brand partners to maintain efficient capital turnover with low inventory pressure. Supported by a 98% repeat customer rate from reliable product performance, every market opportunity in the golf gear sector translates into sustainable profits.

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