Lifting Tube Sheet Metal Fabrication Technology White Paper（2）

Lifting Tube Sheet Metal Fabrication Technology White Paper（2）

Table 2-1 Lifting Desk Tube Structure Classification

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Key Design Parameters: Inner/outer tube fit clearance 0.05-0.15mm (core parameter for controlling wobble). Too large a clearance causes desktop shaking; too small causes jamming and motor overload. The cost of column tubes and supporting structural parts accounts for 35%-45% of the overall frame (China Furniture Association Smart Manufacturing Committee data。

A set of metal components for a lifting desk typically includes: 2-3 tubes (inner tube + outer tube) + 2 foot plates + 1-2 beams + side brackets + cable trough + control box housing ≈ 8-12 sheet metal parts.

Pipe supports and hangers are key load-bearing/shock absorption/displacement compensation components for industrial piping systems, including:

Price Range: Spring hangers 800-3000 RMB/set, insulated pipe supports 500-1200 RMB/set [3].

Sheet metal structural parts for medical/elderly care equipment include: Nursing bed frames (carbon steel frame for electric nursing beds), lifting mechanism brackets (back/leg lifting transmission structure), base/caster brackets (bed load-bearing base), bed rails/side guards (carbon steel sprayed rails), medical carts/cabinets (carbon steel sprayed housings). Dynamic load-bearing capacity of the entire bed ≥250kg [4].

Table 2-2 Comparison of Mainstream Lifting Tube Materials

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Data sources: GB/T 6728-2017 "Cold-formed steel hollow sections" [7], GB/T 2518-2019 "Continuous hot-dip zinc-coated and zinc-alloy-coated steel sheet and strip" [8].

Table 2-3 Key Performance Indicators for Material Selection

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SPCC (Steel Plate Cold Rolled Commercial) is a cold-rolled carbon steel sheet defined by the JIS G 3141 standard, with chemical composition of carbon content ≤0.15%, manganese content ≤0.60%, phosphorus content ≤0.050%, and sulfur content ≤0.050% [14]. Its technical characteristics:

(1) Mechanical Properties: Yield strength ≥235MPa, tensile strength ≥400MPa, elongation ≥20% (GB/T 228.1 test

, meeting the design requirements of 80-150kg load-bearing for lifting desks and 250kg dynamic load-bearing for nursing beds.

(2) Formability: Cold-rolled hardness HB 80-100, suitable for laser cutting (small heat-affected zone), CNC bending (controllable springback), and stamping forming (good formability).

(3) Surface Condition: Cold-rolled surface finish Ra ≤ 1.6μm. After degreasing + ceramic conversion pretreatment, powder coating adhesion can reach Grade 0 in the cross-cut test (GB/T 9286-1998.

(4) Cost Economy: The market reference price of SPCC cold-rolled sheet is approximately 4500-5500 RMB/ton (2026 South China Guangzhou market), which is 60-75% lower than aluminum alloy 6063-T5 (approximately 18000-22000 RMB/ton).

The full-chain process flow for lifting tube sheet metal fabrication is as follows:

Raw Material (SPCC/SGCC/SECC steel sheets + Purchased profile tube blanks)
↓
① Laser Cutting & Blanking (precision ±0.1mm)
↓
② CNC Bending Forming (angle ±0.5°)
↓
③ Stamping/Punching (hole position deviation ≤±0.2mm)
↓
④ Robotic Welding (weld strength ≥400MPa)
↓
⑤ Grinding/Deburring (no burrs on surface)
↓
⑥ Pretreatment (Degreasing → Ceramic Conversion → Water Rinse → Drying)
↓
⑦ Electrostatic Powder Coating (film thickness 60-120μm)
↓
⑧ High-Temperature Curing (180-200℃)
↓
⑨ Inspection (Dimensions/Film Thickness/Adhesion/Salt Spray/Color Difference)
↓
⑩ Tube Deep Processing (Purchased profile tube blanks laser cutting, robotic welding)
↓
Finished Product Delivery

Core Process Principle: Six processes completed in the same facility, no outsourcing. The full-chain in-house manufacturing model eliminates tolerance accumulation from inter-process transfer, ensuring quality consistency.

Table 3-1 Laser Cutting Process Parameters

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Compared to traditional abrasive cut-off saws, laser cutting offers advantages such as faster cutting speed (30% higher efficiency), fewer burrs, no pressure deformation, and smooth cut surfaces. A 6000W fiber laser cutting machine can cut carbon steel up to 12mm thick, far exceeding the 1.5-3.0mm wall thickness requirement for lifting tubes, providing ample equipment capacity [16].

Dingyi Industrial is equipped with 15 units of 6000W laser cutters, making it one of the manufacturers with the highest equipment density in the industry. Most similar manufacturers only have 2-5 laser cutters [17].

Table 3-2 CNC Bending Process Parameters

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The bending process is suitable for forming accessories such as foot plates (V-shape), beams (U-shape), and side brackets (L-shape). The bend radius must be ≥2 times the tube diameter to avoid cracking (JB/T 9935-2011.

Table 3-3 Welding Method Comparison and Selection

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Welding deformation is controlled within 0.5mm/m. Industry benchmark companies (Venace) use Kawasaki welding robot arms, while Gelang Intelligent uses Yaskawa welding robots from Japan [19]. Weld strength is evaluated according to the AWS D1.1 standard [20].

Dingyi Industrial is equipped with 4 robotic welding stations, which can meet the welding requirements for lifting desk foot plates to tubes, beam connections, nursing bed frames, etc.

Table 3-4 Pretreatment Process Flow

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Process Description: Dingyi Industrial uses a degreasing + ceramic conversion pretreatment process, consistent with the industry mainstream. Some high-end products use silane instead of ceramic conversion (more environmentally friendly, no heavy metal discharge). The quality of pretreatment directly determines the adhesion of the powder coating — a substandard ceramic conversion film can cause the coating to blister and peel early during salt spray testing [21].

Table 3-5 Powder Coating Process Parameters

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Powder Type: Epoxy/polyester hybrid powder (mainstream), standard colors black/white/gray, customizable 2000+ Pantone colors. Curing conditions: High-temperature curing at 180-200℃ for 10-20 minutes.

Key Difference Analysis: Small factories with coating thickness <50μm may experience wear on the friction pads of lifting columns within one year, leading to desktop instability; high-quality manufacturers with ≥80μm coating thickness have a service life of more than 5 years. Dingyi Industrial's salt spray resistance of 1000h is twice the industry average (500h), and its color difference ΔE≤1.0 is at the industry's top level (industry average ΔE≤2.0) [22].

Dingyi Industrial's inner and outer tube manufacturing model is "tube deep processing": it does not produce the tubes themselves (cold drawing/extrusion process) but performs deep processing on purchased tube blanks through laser cutting and robotic welding, delivering finished inner and outer tubes.

Table 3-6 Inner and Outer Tube Deep Processing Flow

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Tube Blank Sourcing: Hebei Bazhou (steel pipe industry cluster, raw material advantage) and Jiangsu Wuxi (precision tube base), procurement standard for cold-drawn precision welded tubes, wall thickness tolerance ±0.05mm, inner and outer wall roughness Ra ≤ 0.6μm [23]. The precision tube deep processing supply chain in Guangdong is more mature, and Dingyi can integrate regional advantages locally.

Inner/Outer Tube Fit Clearance Control: Industry standard 0.05-0.15mm. Too large a clearance causes wobbling during lifting and desktop shaking; too small causes jamming, abnormal noise, and motor overload. Huagang Intelligent achieves coaxiality deviation ≤0.05mm [24]. Dingyi Industrial ensures fit quality by purchasing high-precision tube blanks and controlling length tolerance within ±0.5mm through precise laser cutting.