Bottle caps/caps are small, but the mold is by no means simple. From the fine tolerances on the threads, the smoothness of the sealing surface, and the uniformity of dozens of cavities — any deviation will lead to water leakage, loosening, or defects. Taeyoung Industrial Company, which has been designing and manufacturing precision cap molds since 1992, has summarized the ‘4 factors that determine quality’ confirmed in the field.
1. Cavity/core processing precision
The shape of the cap is created by engaging the core and cavity. Since errors of several micrometers that occur during the processing stage are directly transferred to the molded product, shape tolerances must be managed through precision CNC machining and electrical discharge machining (EDM). Taeyoung Industrial minimizes errors between design and processing by linking its own CAD/CAM design data to processing equipment.
2. Thread precision
The thread part determines the connection between the cap and the container. Even if the pitch, lead angle, or starting point are slightly off, the feeling of fastening will change, and in severe cases, loosening or water leaks may occur. The threaded part has a lot of undercut structure, so the design completeness of the force release (stripping) or rotational extraction (unscrew) mechanism is directly related to the quality.
3. Cooling circuit design
Cooling time accounts for most of the injection cycle. If the cooling circuit does not cover the entire cavity evenly, shrinkage deviation, warpage, and dimensional defects occur. Uniform cooling has a direct impact on productivity (cycle time) as well as quality.
4. Multi-Cavity Balance
Cap molds are often made with multiple cavities, such as 16, 32, or 48 cavities, for productivity. At this time, the key is 'balance design', which ensures that the resin reaches the same pressure and point in all cavities through the runner and gate.If the balance is lost, the weight and dimensions of each cavity change.
Taeyoung Industrial Co., Ltd. reviews these four together from the design stage and is responsible for mass production. For inquiries regarding cap molds, please leave an online inquiry at or and we will provide you with detailed information.