Smart Meter (Electricity Meter) Product Development: Improving Mass-Production Capability Using a Hybrid Slide Mechanism

1. Introduction

In recent years, the introduction of smart meters has been advancing rapidly alongside the sophistication of electricity infrastructure.

Particularly since the 2014 revision of the Energy Conservation Law, Japan plans to introduce these meters to all households by 2025. The market size is projected to reach approximately ¥30 billion, with total installations expected to hit around 78 million units.

To meet this large-scale demand, establishing a high-quality and stable mass production system is essential. This article explains the technical points of the ‘hybrid slide mechanism’ that achieved improved mass producibility in the product development of the T-BLOCK, a core component of electricity smart meters.

2. Development Background and Initial Challenges

This development commenced in 2011, triggered by inquiries for smart meters from power companies. In the initial stages, productisation via injection molding using thermosetting resin (dry premix) was considered.

The target product, T-BLOCK,

features a large size and thick-walled structure,

complex shapes including insert components,

and requires high insulation performance.

It was a highly challenging product with limited conventional mass production experience.

The primary challenge was confirming the suitability of the molding machine's capacity. While calculations indicated a 200-ton class injection molding machine would suffice, practical verification using an actual machine was necessary to alleviate the customer's concerns.

Therefore, a test mold was fabricated for molding capacity verification, and actual molding trials were conducted.

As a result, it was demonstrated that molding according to the theory was possible, thereby ensuring reliability for mass production.

3. Integration through Design Support and New Challenges

To facilitate mass production, a design proposal was adopted to integrate the previously separate LOWER and UPPER sections of the T-BLOCK. This integration aimed to reduce the number of components and improve assembly efficiency.

This integration yielded benefits such as:

- Reduction in component count

- Reduction in assembly man-hours

- Stabilisation of quality

However, it also gave rise to new challenges.

Furthermore, driven by cost reduction demands, the material was changed from thermosetting resin to thermoplastic resin (polycarbonate).

This material change made the difference in shrinkage rates a significant problem.

4. Molding Troubles Due to Thermoplasticisation

Compared to thermosetting resins, thermoplastic resins exhibit a greater shrinkage rate. This led to a phenomenon where the molded product became firmly stuck to the slide section.

Specifically,

the product failed to separate from the slide

deformation occurred during demolding

resulting in a non-moldable state

and other serious mass production issues arose.

Conventional hydraulic slides alone could not resolve this problem, necessitating the development of a new mould mechanism.

5. Development of the Hybrid Slide Mechanism

The hybrid slide mechanism was devised to address this challenge.

This mechanism incorporates a combined structure of:

Angular pins (mechanical slide)

Hydraulic slide

■ Operating Principle

① Simultaneously with mold opening, an angular pin initiates the advance movement of a section of the slide.

② Subsequently, the entire assembly is extracted by the hydraulic slide.

This ‘two-stage slide operation’ achieves the following effects:

- Mitigation of clamping force due to contraction

- Reduction in demolding resistance

- Optimisation of balance between slides

Furthermore, the adoption of an S-type angular mechanism optimises slide timing, enabling more stable demolding.

6. Results of Mass Production Improvement

The introduction of the hybrid slide mechanism dramatically improved mass production efficiency.

The main results are as follows:

■ Reduction in molding cycle time

Before improvement: Unmoldable → 65 seconds

After improvement: 48 seconds → Achieved a reduction to 17 seconds

■ Quality improvement

Significant reduction in mold release defects

Elimination of product deformation

■ Enhanced production stability

Stabilisation of slide operation

Achievement of trouble-free mass production

This established a mold specification capable of supporting large-scale mass production of smart meter components.

7. Mass Production Deployment and Future Outlook

This technology enabled mass production to commence for multiple products in the 30A, 60A, and 120A series, establishing a production capacity of tens of thousands to hundreds of thousands of units per month.

Going forward, smart meters are anticipated to maintain stable market demand driven by:

Regular replacement demand (approximately 1.9 million units annually)

Infrastructure renewal demand

Therefore, to further enhance competitiveness, the following are crucial:

Optimisation of mold structure

Shortening of molding cycles

Cost reduction

8. Summary

Crucial to this development was not merely molding capability, but a design philosophy that holistically optimises:

Product shape

Material properties

Mold structure

The hybrid slide mechanism is a prime example of solving a production-specific challenge – “mold release issues caused by contraction” – through mechanical design.

The hybrid slide mechanism, in particular, exemplifies how mechanical design can resolve production-specific challenges such as mold release issues caused by shrinkage.

Moving forward, proposing mold technologies that predict potential problems from product geometry and prevent mass production issues before they arise will remain key to competitiveness in manufacturing.