Case Study: Helping a Japan Glass Lunch Box Supplier Solve Leakage

Minghang as a professional supplier of glass lunch box was approached by a brand in Japan that deals with quality bento boxes at the office and home. The company was seeking a credible supplier of glass lunch boxes that would offer both style and functionality that is not leaky. They designed rectangular high-borosilicate-glass lunch boxes with rounded inner corners, a snap-lock plastic lid, and a removable silicone sealing ring, which is food-grade. The reason why the client selected Minghang was because of the precision mold ability, strict quality control system, and experience of the company in producing airtight glass food containers into the export markets.

Challenge

Leakage During Transport

Finished lunch boxes leaked sauce and soup during delivery, leading to customer complaints and product returns.

Inconsistent Lid Fit

Some batches showed uneven lid tightness, causing unreliable sealing performance.

Cause Analysis

Minghang ’s engineering team conducted sealing tests and dimensional inspections and identified the core problems:

• Minor dimensional deviations in the glass rim prevented uniform compression of the silicone gasket.
• The lid hinge structure lacked sufficient downward pressure to maintain a tight seal.

Solution

Rim Precision Optimization

We refined rim flatness tolerances, improved mold accuracy, and introduced 100% rim inspection for critical dimensions.

Lid & Gasket Redesign

Minghang strengthened the snap-lock mechanism, adjusted hinge angles, and upgraded the silicone gasket profile for better compression and elasticity.

Custom 350ml 900ml 2000ml Glass Storage Food Containers	Custom 450ml 1000ml 1900ml 3300ml Square Glass Storage Food Containers

Result

Leakage complaints dropped by over 85%, sealing consistency improved significantly, and customer satisfaction increased. The Japanese brand successfully relaunched its glass lunch box line, confirming Minghang as a dependable long-term glass lunch box supplier partner.