china school desk and chair set factory - Bulk Supply and Specification Guide

How Consistency Is Held Across Batches

Steel tube wall thickness is the single variable that drives both freight cost and service life. The factory runs 1.2 mm, 1.5 mm, and 1.8 mm ERW tubing on the same bending cell; the die set does not change, only the feed stock. Every coil receives a mill certificate, and the incoming QC station verifies wall thickness at four points per 6 m length with a calibrated ultrasonic gauge. Tolerance held to ±0.05 mm.

Powder-coat adhesion follows a fixed pretreatment sequence: alkaline degrease, iron phosphate conversion, DI rinse, and a 180-second cure at 195 °C. Salt-spray exposure is logged at 500 hours for standard grey and 720 hours for the optional antimicrobial white. Colour drift across a 5,000-unit run stays within ΔE 1.2 when measured on a spectrophotometer at 45°/0° geometry.

What Gets Checked Before Shipment

Final inspection follows a three-tier sampling plan. Level 1: 100% visual for coating defects, edge-band flushness, and bolt torque (marked with paint dab at 18 N·m). Level 2: AQL 2.5 on dimensional criticals — seat height ±3 mm, desktop flatness ≤2 mm over 600 mm, frame squareness ≤1 mm diagonal difference. Level 3: Destructive pull on one unit per 500 — peel test on edge band, cross-hatch adhesion on coating, and static load 120 kg centre-point for 10 minutes on the desktop.

Packaging drop test simulates LCL handling: 76 cm corner drop onto concrete, five orientations. Carton burst strength rated 275 psi (ECT 44). Inner poly bag 50 µm LDPE with desiccant sachet at 2 g per 0.1 m³. Palletised 20 sets per 1.1 × 1.1 m Euro pallet, stretch-wrapped 70 µm, strapped with two 12 mm PET bands.

Capacity, Tooling and Scheduling

Tooling amortisation decides the economic floor. A dedicated bending die for a custom leg profile costs $4,800 and pays back at 2,000 sets when the per-unit saving on secondary machining hits $2.40. Standard profiles share existing dies — no NRE, but the buyer accepts the 30 mm tube OD and 65° bend radius as fixed. Powder-coat colour changeover on the line takes 45 minutes and 3 kg of purge powder; minimum batch per colour is 300 sets to keep changeover cost below 1.5% of run value.

Current throughput: two welding cells at 180 frames/hour each, one powder line at 220 frames/hour, two assembly lines at 140 sets/hour. Bottleneck is assembly. A 10,000-set order with two colours and three sizes ships in 18 working days from material release. Blanket orders with monthly call-offs lock capacity and reduce lead time to 10 days per release because material is pre-staged and die changes are pre-scheduled.

Stock Availability and Reorder Planning

Standard grey frame (RAL 7035) with beech melamine tops in sizes 2-6 (EN 1729) holds 1,200 sets in finished-goods buffer. Replenishment trigger at 300 sets per SKU pulls a 2,000-set production kanban. Lead time from kanban to dock is 9 days. Private-label SKUs are not stocked; they run to order with a 30% deposit and balance against copy B/L.

Seasonal demand peaks August-October and January-February. Buyers placing blanket orders in April for August delivery lock 2024 steel pricing and avoid the 6-8% Q3 surcharge. Inventory carrying cost on the factory side is $0.12/set/week; this is baked into the unit price for call-off orders but itemised for spot buys.

Setup, Use and Replacement Parts

Assembly requires a 13 mm socket or ring spanner and a 5 mm hex key. Four M8×40 bolts per leg bracket, two M6×35 bolts for the seat pan, four M6×25 wood screws for the desktop. Torque sequence: frame bolts first to 18 N·m, then seat pan to 10 N·m, desktop screws to 3.5 N·m. No adhesive, no loose washers. A 300-set container unloads and assembles in 4.5 hours with two installers.

Replacement parts stocked for 7 years from last production date: leg brackets (SKU LB-30/38), seat pan pressings (SP-400/500), PVC edge band 22×0.6 mm (EB-BCH/GREY), M8 flange nuts (FN-M8-ZP). Touch-up paint pens matched to RAL 7035 and antimicrobial white available at $4.20/unit MOQ 50. Powder-coat repair on site is not warranted — field touch-up fails salt-spray at 120 hours.