Project Profile · Semiconductor & Industrial Process Equipment
HTSI Glass Tube Sealer: PLC & HMI Automation for Inert-Gas Tube Sealing
High Tech Services (HTSI) hired Qualtx Technology to design the control system, PLC software, HMI operator interface, and on-site wiring for an automated glass tube sealer at HTSI's Richardson, Texas facility.
Project Overview
The HTSI Glass Tube Sealer is an automated system that replaces the air inside quartz glass tubes with an inert gas atmosphere — nitrogen or argon — through a repeated vacuum-and-backfill sequence, followed by torch sealing. High Tech Services (HTSI) is building the mechanical system at its Richardson, Texas facility and hired Qualtx Technology to design and implement the software, PLC controls, HMI interface, and on-site wiring that runs the machine.
Qualtx Technology handled the complete control system: PLC programming, HMI screen design, wiring diagrams, on-site wiring and terminations, and system commissioning — delivered as a turnkey package alongside a full user manual.
The Requirement
HTSI's specification called for a system that could evacuate roughly 1-liter-volume quartz tubes to 50 torr or less, then backfill with inert gas back to atmospheric pressure, repeating that cycle automatically with no operator intervention between steps. On the final cycle, the system needed to hold a partial vacuum near 250 torr inside the tube while an operator rotated it on a variable-speed, foot-pedal-controlled fixture for torch sealing — with clear LED/status indication at every step and fail-safe behavior if a vacuum gauge or timing fault occurred.
System Architecture
Qualtx Technology built the control system around an industrial PLC communicating with a color touchscreen HMI over Ethernet/Modbus TCP:
| Component | Specification |
|---|---|
| PLC | AutomationDirect P1AM-100 (Arduino/Modbus TCP firmware) |
| HMI | AutomationDirect CM5-T10W, 10-inch color TFT touchscreen, Modbus TCP master |
| Pressure Monitoring | Two transducers — PT1 (foreline/rough pressure, diagnostic) and PT2 (tube pressure, the process control variable) |
| Gas Flow Control | Four solenoid valves (SV1–SV4) — rough vacuum valve, primary argon/nitrogen backfill valve, needle-valve-metered vent for seal-pressure control, and nitrogen atmospheric vent |
| Operator Status | Three-color signal tower (green/ready, yellow/operating, red/alarm), mirrored on the HMI |
| Rotation Control | Variable-speed motor with foot-pedal enable relay (K1), height-adjustable fixture for 1.25″–2″ diameter, 2–4 ft length tubes |
| Power | 208 VAC main, 24 VDC control/solenoid power |
How the Automated Process Works
The operator loads a tube, presses Start, and the PLC runs the entire purge-and-seal sequence automatically:
- Evacuating (Vacuum): The rough valve (SV1) opens and the vacuum pump pulls tube pressure down toward the vacuum setpoint (default 50 torr).
- Vacuum Hold: Pressure is held at setpoint for a short soak (default 10 seconds).
- Backfilling: SV1 closes and an argon/nitrogen backfill valve opens, raising tube pressure back toward atmospheric (default 760 torr).
- Backfill Hold: Pressure is held at setpoint for a soak (default 15 seconds), then the cycle repeats (default 3 cycles total).
- Evacuating to Seal Pressure: On the final cycle, the rough valve and a needle-valve-metered argon vent open simultaneously, balancing vacuum pump flow against a controlled argon bleed to settle at the seal pressure setpoint (default 250 torr).
- Ready to Seal: Once tube pressure reaches the seal setpoint, the rotation foot pedal is enabled and the operator torch-seals the rotating tube.
- Unload: After sealing, the operator presses Unload; the system backfills above the sealed region to atmospheric pressure and signals when the tube is safe to remove.
Each cycle completes in under two minutes, and every setpoint, hold time, and cycle count is adjustable from the HMI without touching the PLC program. If the system fails to reach the vacuum setpoint within a configurable timeout (default 120 seconds), it triggers a latched alarm, closes all valves fail-safe, and prompts the operator for a reset — rather than continuing an out-of-spec cycle.
HMI Operator Interface
All operation runs through a purpose-built touchscreen interface with three screens: a Main Screen for normal operation, a password-protected Manual Control screen for diagnostics, and a Process Parameters screen for setpoint configuration.
Safety & Reliability
- All solenoid valves are normally closed and fail safe (de-energize closed) on any power loss.
- A manual over-pressure vent protects against tube over-pressurization in the event of a gauge failure.
- The rotation belt-drive assembly is fully guarded, and the rotation fixture is positioned away from the torch flame path.
- A vacuum-timeout alarm halts the process automatically rather than allowing an out-of-spec cycle to continue.
- Only nitrogen or argon are approved process gases; the system is designed around non-flammable, non-reactive inert gases only.
Scope of Work
Qualtx Technology delivered a complete, turnkey control system package:
- PLC control logic and process sequencing software
- HMI screen design and operator interface software
- Complete wiring diagrams for the entire control system
- On-site wiring and termination at the HTSI facility in Richardson, Texas
- Software debug and full system commissioning
- System user manual
- Ongoing complimentary software updates and bug fixes for the post-installation support period
About Qualtx Technology
Qualtx Technology has been providing turnkey automated control solutions for the semiconductor and nanotechnology industries since 1997. Over nearly three decades, Qualtx has delivered control systems and retrofits for a wide range of clients, including AMD, the US Navy, NASA's JPL, NIST, MIT, Texas Instruments, Raytheon, Micron Technology, Cornell, Northeastern University, the University of Texas, Lockheed Martin, Microchip, and Leonardo DRS, across process tool types including RIE/RFPECVD, ECR, ion mill, ion implanter, MOCVD, and sputter deposition systems.
Frequently Asked Questions
What does the HTSI Glass Tube Sealer control system do?
It automates purging air from quartz glass tubes and replacing it with inert gas (nitrogen or argon) through repeated vacuum-and-backfill cycles, then holds a partial vacuum in the tube while an operator performs torch sealing. A PLC runs the process sequencing and a touchscreen HMI displays live pressure readings and system status.
What hardware runs the automation?
An AutomationDirect P1AM-100 PLC communicates over Ethernet/Modbus TCP with an AutomationDirect CM5-T10W 10-inch color touchscreen HMI. Two pressure transducers monitor foreline and tube pressure, four solenoid valves control gas flow, and a relay enables a foot-pedal-controlled rotation motor during sealing.
How many vacuum/backfill cycles does the process run?
The default configuration runs 3 cycles between approximately 50 and 760 torr, each completing in under 2 minutes, followed by a final evacuation to a 250 torr seal pressure setpoint. Cycle count and all setpoints are operator-adjustable on the HMI.
Can setpoints be changed without reprogramming the PLC?
Yes. Vacuum, backfill, and seal pressure setpoints, cycle count, hold times, and the vacuum timeout limit are all editable directly on the HMI Process Parameters screen and are stored in non-volatile PLC memory.
What safety features are built in?
Fail-safe normally-closed solenoid valves, a manual over-pressure vent, a guarded belt-drive rotation mechanism positioned away from the torch flame, and a latched vacuum-timeout alarm that stops the process and alerts the operator if a setpoint isn't reached in time.
Who built the control system?
Qualtx Technology, Inc., a Plano, Texas-based automation integrator serving the semiconductor and nanotechnology industries since 1997, was hired by High Tech Services (HTSI) to design the PLC software, HMI interface, and on-site wiring at HTSI's Richardson, Texas facility.