The U-Shaped Heat Pipe Vacuum Machine is dedicated to the degassing, sealing, and welding of U-type (U-shaped) copper heat pipes — a geometry that cannot be processed on straight-pipe degassing machines due to its curved form. U-type heat pipes are degassed through a bottom heating mechanism: heat is applied at the lowest point of the U-bend, creating a pressure difference by working fluid expansion that drives non-condensable gas upward and out through the open degassing end at the top of each arm. The machine then automatically performs shearing, sealing, and welding of the degassing end. Six workstations with automatic feed, independently adjustable temperature, product length, and all processing parameters per station. This per-station parameter independence is critical for production lines running multiple U-pipe product variants simultaneously.
Key Specifications
| Specification | Value |
| Product Type | U-shaped (U-type) copper heat pipes |
| Degassing Method | Bottom heating → pressure differential → NCG upward drive |
| Process Integration | Degassing + shearing + sealing + welding |
| Workstations | 6 stations |
| Feeding | Automatic |
| Parameter adjustability | Temperature, product length, and all parameters independently set per station |
| Applicable geometry | U-shaped heat pipes — cannot be processed on straight-pipe machines |
What Is a U-Shaped Heat Pipe Vacuum Machine?
A U-shaped heat pipe vacuum machine is a multi-station automated system designed specifically for the degassing, working fluid injection, and end-sealing of pre-bent U-shaped copper heat pipes. Unlike straight-pipe vacuum equipment, U-shaped configurations require specialized tooling fixtures that accommodate the bent geometry while maintaining airtight clamping at the open end during the vacuum cycle. The machine integrates rough pumping, high-vacuum pumping, fluid metering, and pinch-sealing into a single sequential process, eliminating the cross-contamination and air re-entry risks common in multi-machine handoff workflows.
Vacuum System and Achievable Vacuum Levels
The vacuum system combines a rotary vane pump for rough pumping (down to ~10⁻¹ Pa) with a molecular pump for high-vacuum pumping, achieving an ultimate vacuum of 5×10⁻³ Pa or better at each process station. Vacuum chambers are constructed from 304/316L stainless steel with metal-sealed flanges to prevent virtual leaks. Real-time vacuum monitoring is handled by Pirani gauges in the rough range and cold cathode gauges in the high-vacuum range, with set-point interlocks that prevent the cycle from advancing until the target vacuum is confirmed.
Working Fluid Injection Accuracy
Working fluid injection is performed by a high-precision micro-syringe pump with volumetric accuracy of ±1% or ±0.01 g, depending on the pipe specification. Injection volume is programmable per recipe and stored against the pipe model number, eliminating manual measurement errors. For copper-water heat pipes used in CPU and server cooling, typical fill ratios sit between 15–30% of internal void volume, and the dosing system supports the full range without hardware change. Deionized water supply lines are kept under positive pressure with in-line filtration (≤0.22 µm) to prevent particulate contamination of the wick structure.
Multi-Station Layout, Cycle Time, and Throughput
Standard configurations include 4-station, 6-station, 8-station, and 12-station rotary indexing tables, with the station count selected based on target throughput and the rate-limiting step (usually high-vacuum pumping). A typical 8-station machine processes one U-shaped heat pipe every 8–15 seconds per index cycle, yielding 240–450 pieces per hour depending on pipe length, diameter, and required vacuum level. Each station performs one discrete operation — load, rough pump, high-vacuum pump, fluid injection, secondary degassing, sealing, cooling, unload — so total dwell time per pipe is the cycle time multiplied by the number of process stations, not the total station count.
Pinch-Sealing Mechanism and Seal Integrity
End sealing is performed by a servo-driven pinch-and-cut mechanism that compresses the copper tube end under controlled force (typically 2–5 kN, recipe-dependent), forming a cold-welded seal before the cut blade severs the excess tail. Seal force, hold time, and blade position are all servo-controlled and logged per pipe. The pinched seal is immediately followed by an optional TIG or laser spot weld at the pinch tip for long-term hermeticity, particularly required for heat pipes destined for high-reliability applications. Helium leak rate after sealing is typically ≤1×10⁻⁹ Pa·m³/s when paired with downstream leak testing.
Compatible Pipe Specifications and Recipe Management
The machine handles copper heat pipes with outer diameters from Φ3 mm to Φ8 mm as standard, with custom tooling available for Φ2 mm or Φ10 mm. Pipe lengths after bending are typically 80–300 mm, with U-bend radii from 5 mm upward. Wick structures supported include sintered powder, grooved, mesh, and composite — vacuum and injection parameters are adjusted by recipe rather than hardware change. Recipes are managed through a Mitsubishi, Siemens, or Omron PLC paired with a 10" or 15" HMI touchscreen, with multi-level user authority and full per-pipe data logging exportable via Ethernet or USB for SPC and traceability.
U-Shaped Heat Pipe Degassing Challenges — Why U-Pipes Need a Dedicated Machine
U-shaped heat pipes present a degassing challenge that straight-pipe machines cannot solve: the U-bend at the bottom of the pipe creates a gravity trap for working fluid during degassing. In a straight pipe, NCG and vapour can exit freely through the degassing end in the direction of gas flow. In a U-pipe, any NCG in the lower section of the U-bend cannot travel 'uphill' against gravity through the working fluid in the bend — it would remain trapped unless the degassing process creates sufficient pressure differential to lift it. The bottom heating approach in Cooling-Thermal's U-pipe machine solves this directly: by heating at the lowest point (the U-bend apex), the working fluid expands upward in both arms simultaneously, carrying NCG with it toward both degassing ends. The pressure differential created by this thermal expansion is sufficient to drive NCG up through the working fluid column regardless of pipe length or bend radius.
Production Line Position — Where This Machine Fits in the Heat Pipe & Thermal Solution Manufacturing Sequence
The heat pipe degassing station sits at Step 5 in the complete 11-step heat pipe production sequence — after working fluid injection and before welding/sealing at Step 6. It is the quality gate that determines the internal vacuum quality and working fluid charge accuracy of every heat pipe that proceeds to welding, hot pressing, bending, and performance testing. A heat pipe that leaves the degassing station with incorrect NCG level or working fluid volume cannot be corrected at any downstream step.
