Client Background
It is a glass candle holders importer with its office located in Seattle, Washington that was in need of a good manufacturing partner to produce the unique line of their high end retail clients in North America with premium candle vessels. They have chosen Mosteb among the five manufacturers in Asia because of the following reasons:
- Technical Capability: Our internal electroplating department would be able to perform their multifaceted metallic gradient finish specification, a skill that only 2 out of 5 factories had.
- Design Flexibility: 3D modeling and fast prototyping: We had 5 business days to complete the design, which allowed us to have quicker iteration cycles.
- Quality Control: Our batch-wise spectrophotometer color testing ensured uniformity of 10,000 plus unit orders- imperative to brand name.
The client needed a hexagonal shaped glass candle holder (280ml) and which has rose gold ombré coating (fading towards the rim) and a weighted zinc alloy bottom insert to ensure luxury.
Challenges
- Consistent transition of ombré electroplating.
The rose gold gradient specification required a transition area of smooth color within a location of 45mm of height. A pilot project showed that there were three technical hurdles:
- Lack of symmetry in Current Distribution: Current was concentrated at angles in the hexagonal geometry resulting in more dark metallic deposits on corners rather than on flat surfaces.
- Coating Adhesion Problems: During thermal shock test that was conducted to involve candle application, the transition zone (where coating thickness varied 0.8 to 0.3mu) exhibited 15 per cent coating delamination.
- Constant Color Variance: Rose gold color changed between batches (ΔE values greater than acceptable 2.0 value) without tight control on the batch of the bath.
- Striking a balance between Aesthetics and Structural Integrity of Weighted Base.
The design of the client required a hidden insert made of zinc alloy (50g) pressed-fitted into a cavity of recessed base. This raised conflicting requirements:
- Glass Thickness Paradox: It was necessary to use 3mm bottom glass to eliminate stress fractures in the process of installing the insert, but this thickness was too much to make the vessel look aesthetically pleasing, as it was considered bottom-heavy.
- Adhesive Compatibility: The standard UV-cure adhesives started yellowing at candle operating temperatures (60-80 C ) and developed visible discoloration using transparent glass.
- Insert Positioning Accuracy: a difference of -0.5mm in the insert depth variability made the vessel to wobble on flat surfaces- cannot be tolerated in luxury positioning.
Result
These issues were solved by the team of our engineers, who worked as a team:
To achieve Electroplating Fidelity:
- Custom-shaped auxiliary cathodes that are designed to redistribute current flow and which are placed 8mm away on each of the hexagonal sides to eliminate corner-to-flat coating variability, which was cut down by half to less than 4%.
- Devised a 2 step plating regimen: complete base coating followed by controlled gradient spray application using masking fixtures which enhanced cohesion by 92%.
- Introduced real-time monitoring of spectrophotometric values during the production process, automatically indicating batches where ΔE exceeded 1.5 to make chemistry corrections.
For Weighted Base Integration:
- Designed a stepped recess geometry -3mm of thick outer ring to ensure strength, 1.8mm center of viewing to make it light to visual eyes, and checked by finite element analysis.
- Replaced high-temp silicone adhesive (maximum 200 o C) with refractive index equal (n=1.52) to keep as invisible as possible.
- Designing of precision jigs with insert depth tolerance of -0.15mm, which were checked with the laser displacement sensors.
We were on weekly video calls with the product development team of the client and provided cross-section samples and videos of thermal cycle testing to make sure everything is on track at every stage of optimization.
How We Delivered
Pre-Production Engineering (Weeks 1-3)
- Performed a simulation of the flow of mold to perfect hexagonal shape, avoiding weak points at the corner transitions.
- Constructed prototypes on the full-scale basis by plating both manually and automatically to determine the best process parameters.
- Conducted accelerated aging tests (500 hours UV exposure and thermal cycling) in order to test the coating durability.
Client Feedback Integration: The client offered to decrease the ombré starting point by 8mm after looking at the initial prototypes, which made the metallic coverage more significant. Within 6 days, we modified spray masking templates and provided amended samples.
Production of Samples (Weeks 4-6)
- Manufactured 50-unit pre-production order based on completed specifications.
- Third-party drop testing (1.2m drop onto concrete) with 98% survival rate, which is higher than the client demand of 95.
- Candle fill test on client-side did not show yellowing adhesives at 80 hours of burn.
Refinishing: Customer asked for a a bit warmer rose gold color (changing the PVD 18K color standard to 14K). We repalated plating bath copper and re-submitted color matched samples within 4 days of order.
Optimization and mass production (Weeks 7-14)
- Full production scale 12,000 units in 3 production runs.
- Adopted statistical process control, whereby, 5 per cent of each batch (600 units) was checked in terms of coating consistency, dimension, and stability of inserted.
- Optimized packaging: custom foam-insert cartons were made that cut down the industry-standard breakage of 3 per cent to 0.4 per cent.
Communication Protocol:
- Bimodal production status report involving photographic documentation.
- Real-time quality alert system- the client was notified immediately when any batch inspection found problems.
- Packed container walkthroughs through video walkthrough of clients prior to shipping.
On-Time Delivery: Product delivered in 8 weeks (that is 2 weeks before the retail deadline of the client), and there was no rejection batch on delivery inspection.
Final Outcome
- Success of product Launch: Our client said that the candle holder line was selling 230 percent of its sales in the first quarter as projected.
- Repeat Business: Client placed bigger order 25,000 units to be shipped during holiday season with two new color options (champagne gold and gunmetal).
- Quality Recognition: No customer complaints on coating or base susceptibility within 6 months after launch.
