In-Depth Comparative Analysis of Two Production Processes for the Same Stainless Steel Vacuum Flask (Drawn Tube Section)

There’s a story in every cup, and warmth in every life. Hello everyone, "Dong Dong's Cup Talk" is here. At a recent exhibition, many visitors asked the same question: What’s the difference between the same model of water cup produced using the drawn tube process versus the deep drawing process? http://www.umbottle.com/ProductsDetail-VB-10523.htmlWhy does the drawn tube process result in higher production costs? Today, we’ll break down the differences between these two production methods for the same stainless steel vacuum flask. Since there’s a lot to cover, we’ll split this into multiple articles.

To give you a concrete understanding, we’ll use a common cylindrical stainless steel vacuum flask (350ml capacity, 70mm diameter, 180mm height) as a case study. We’ll independently analyze the laser-welded drawn tube process and the traditional multi-stage deep drawing process, along with real-world production challenges and solutions. http://www.umbottle.com/ProductsDetail-VB-10523.htmlThe views expressed here are solely those of the author. If you spot any errors, feel free to point them out—via private message or comment—and we’ll learn and discuss together.

Part 1: Full Process Breakdown of Laser-Welded Drawn Tube Manufacturing

Process Flow:

Coil slitting → Laser tube welding → Hydroforming → Bottom trimming → Thread rolling at the mouth → Vacuum sealing welding → Electrolytic polishing → Surface coating

Key Process Challenges & Manual Operation Requirements:

1. Laser Tube Welding Stage

- Material Requirements: Must use 304/316 stainless steel coils with a thickness of 0.3–1.2mm.

- Excessively thick material (>1.5mm) leads to insufficient weld penetration.

- Excessively thin material (<0.3mm) risks burn-through.

- Case Study: In 2019, http://www.umbottle.com/ProductsDetail-VB-10523.htmla batch of business flasks made with 1.6mm-thick sheets had weld seam strength only 70% of the base material due to insufficient laser power, resulting in a leak rate exceeding standards (>5×10⁻⁸ Pa•m³/s) after vacuum sealing. The scrap rate reached 33%. The solution was switching to pulsed laser welding and increasing argon shielding gas flow to 25L/min.

2. Hydroforming Control

- Operation Key Points: Workers must adjust water pressure based on product height (increase by 50bar per 10mm). For this 180mm flask, http://www.umbottle.com/ProductsDetail-VB-10523.html650bar pressure must be maintained for 8 seconds.

- Common Issue: In 2021, a batch of cups developed waist dents after hydroforming. Investigation revealed that the operator failed to replace a worn polyurethane expansion mold sleeve (remaining lifespan: 30,000 cycles), causing uneven pressure distribution.

3. Vacuum Sealing Welding Quality

- Manual Inspection: Before temperature monitoring equipment was adopted, many factories used helium mass spectrometers every 2 hours to check vacuum levels. Operators had to master "sound-based leak detection"—a high-quality vacuum flask produces a ringing sound at 4200–4500Hz. http://www.umbottle.com/ProductsDetail-VB-10523.htmlNow, with temperature testing machines, thermal standards are used to verify vacuum integrity.

Material & Labor Time Correlation:

- Using 0.8mm sheet: Single-unit cycle time = 135 seconds

- Switching to 0.5mm sheet: Due to reduced laser power (from 2000W to 1600W), cycle time extends to 140 seconds

- Material thickness tolerance must be kept within ±0.03mm; otherwise, http://www.umbottle.com/ProductsDetail-VB-10523.htmlwelding misalignment occurs.