How a Control Panel Builder Cut Enclosure Weight by 35% with SINGI Plastic Shell Metal Parts

A mid-sized manufacturer of low-volt-level distribution cabinets was struggling with heavy, corrosion-prone enclosures. Switching to SINGI plastic shell metal parts reduced unit weight by 35%, cut assembly time by 40%, and lowered total costs by 22%.

Customer Background

The customer is a 300-person OEM based in Guangdong Province that produces low-volt-level distribution cabinets, motor control panels, and custom electrical assemblies. The facility turns out roughly 5,000 units per year, serving both domestic industrial clients and export markets in Southeast Asia and South America.

Production margins were tightening. Export orders required compliance with international standards, while domestic customers demanded faster delivery and lower prices. The company needed to find a way to reduce material costs, streamline assembly, and improve product reliability without compromising safety or performance.

Challenges with Traditional Metal Fabrication

, every enclosure was fabricated from sheet steel. Workers cut, bent, welded, and painted each box manually. This created multiple bottlenecks on the shop floor.

• Heavy weight: A typical wall-mounted cabinet weighed 65 kg, which increased freight charges for export orders and made installation difficult in the field.
• Corrosion issues: Coastal customers reported rust on painted steel shells within two years. The company had to offer costly re-coating or replace units under warranty.
• Long assembly cycles: Welding and painting took two full days per unit. Machined cutouts for breakers and indicators required additional labor and showed misalignment.
• Inconsistent quality: Manual handling led to dents, scratches, and variation in dimensions, which caused rework and delays.

These problems eroded profitability. Scrap and rework accounted for 9% of production costs, and average delivery time stretched to four weeks, causing some clients to switch to competitors.

Why Choose SINGI Plastic Shell Metal Parts

The OEM assessed several alternatives before choosing SINGI. Aluminum extrusion was lighter but too expensive and still required secondary machining. Purely plastic enclosures lacked the mechanical strength and grounding capability needed for switchgear assemblies.

SINGI plastic shell metal parts offered a combined solution. The plastic shell provides electrical insulation, corrosion resistance, and tight dimensional tolerances, while embedded metal inserts and frames preserve structural integrity and enable reliable earthing. The decision came down to four factors:

• Integrated design: Mounting bosses, guide rails, and cutouts were molded into the shell, eliminating separate machining steps.
• Material performance: The proprietary flame-retardant composite withstands 850°C glow-wire tests and meets UL 94 V-0 rating.
• Weight reduction: The design allowed a 35% reduction in total enclosure weight, which would lower freight costs and simplify handling.
• Compliance: The parts were tested according to IEC 61439-1 and IEC 60947-1, so the final assemblies would meet export requirements.

Implementation Process

Implementation took three months from design freeze to mass production. The project moved through these key steps:

1. Design verification: SINGI engineers reviewed the customer's drawings and performed finite element analysis to verify rigidity and heat dissipation for the intended amperage ratings.
2. Mold development: Injection molds were manufactured with multi-cavity layouts, reducing cycle time to under 60 seconds per shell and insert combination.
3. Prototype testing: A pilot batch of 50 enclosures was assembled and tested for dielectric strength, impact resistance, and continuity of the earth-bonding system.
4. Production ramp-up: After minor adjustments to the insert clearance, full production began. SINGI delivered parts on a -in-time basis at 2,500 units per month.

A typical difficulty was ensuring reliable earthing continuity between the plastic shell and metal inserts. The initial prototypes failed the 0.1 kA short-circuit test because the insert-to-frame connection used a simple screw that loosened under thermal cycling. The solution was to use heat-staked brass bushing inserts and a dedicated crimp lug connection, which maintained low resistance after 200 temperature cycles.

Application Results and Quantified Improvements

After six months in production, the customer documented the following improvements:

• Enclosure weight reduced by 35% — from 65 kg to 42 kg for the standard wall-mounted model.
• Assembly time per unit cut by 40% — from two days to one shift (8 hours), because cutouts, mounting bosses, and painted surfaces were no longer needed.
• Total cost per enclosure lowered by 22% — savings came from fewer raw materials, less machining labor, and lower rework rates.
• In-field failure rate dropped by 60% — corrosion-related complaints disappeared over the first year of service.
• Average delivery time shortened from 28 days to 16 days — the shorter assembly cycle allowed the company to accept more orders.

The switch also improved safety. The plastic shell offers double insulation in live parts, reducing the risk of electric shock during maintenance. The company reported that the cabinets passed all type tests for IEC 61439-1 and IEC 60947-1, including short-circuit withstand and temperature-rise requirements.

Customer Voice

"What impressed us most was the engineering support from SINGI," said the production manager at the OEM. "They didn't supply parts; they helped us optimize the design for manufacturability. We've cut our freight costs, and our customers have noticed the quality improvement. The payback period on the mold investment was only eleven months."

Lessons and Recommendations

This case offers several takeaways for other manufacturers considering plastic shell metal parts:

• Start with a complete design review. Involve the supplier early in the product development phase. The most significant cost savings came from eliminating secondary machining, not from the material itself.
• Validate thermal and mechanical behavior under real loading conditions. The heat-staked bushing solution worked only after testing with the actual short-circuit current. Simulation alone was not enough.
• Plan for grounding continuity from the start. Plastic enclosures require careful design of earthing paths. Verify the continuity of all exposed conductive parts against the relevant standard — in this case IEC 61439-1.
• Consider total logistics costs. The weight savings reduced air freight charges, which shifted the project from a materials cost exercise to a logistics optimisation opportunity.

If the OEM were to redo this project, they would invest more time in testing connector leads and cable glands under vibration, as these were the remaining sources of service calls. They also noted that working with a single supplier for both plastic and metal components simplified quality control and communications.

Industry Standards Referenced

This project relied on the following standards to ensure safety and performance:

· IEC 60947-1:2020 — Low-volt-level switchgear and controlgear - Part 1: General rules
· IEC 61439-1:2020 — Low-volt-level switchgear and controlgear assemblies - Part 1: General rules
· GB/T 14048.1-2019 — Low-volt-level switchgear and controlgear - Part 1: General rules (Chinese national adoption)