ArcSentry™ Weld Quality Monitoring System


System Description


ArcSentry is a data collection and analysis system for automatic Gas Metal Arc Welding (GMAW, MIG, or MAG). Voltage, current, wire feed speed (WFS), gas flow, auxiliary encoder data and up to 42 additional sensor channels are collected at rates of up to 20kHz per channel and processed in 50ms time windows. Weld quality problems can be flagged as they are occurring using advanced analysis techniques developed and refined by researchers from the N. A. Tech., the U.S. Department of Commerce National Institute of Standards and Technology, Tower Automotive and A.O. Smith. These methods are among the most advanced for GMAW weld quality analysis published to date and have been developing since N. A. Tech. scientist, Dr. Jerry Jones, produced his first high speed welding monitor system in his laboratory in 1985.

The ArcSentry hardware consists of the sensors, the Sensor Hub, the ArcSentry Computer, and the cables to connect between them. Data signals are first collected via the sensors. Standard ArcSentry sensors are a current sensor, a voltage sense lead, a wire feed sensor, and a gas flow sensor. Up to 46 digital and analog inputs are available. The sensors are attached to the Sensor Hub which turns all of the sensor data into the appropriate analog signals and transmits them via the Sensor Hub-to-PC Cable to the ArcSentry Computer.

The ArcSentry computer is a factory hardened, rack-mount PC running Windows® NT. Up to four Sensor Hubs can be connected per ArcSentry Computer. Inside the ArcSentry Computer, signals are opto-isolated and then converted to digital signals using Analog-to-Digital converters located on the AED102 daughterboard developed by Signalware Corporation. Using a 100 MHz field programmable gate array (FPGA) processor, these signals are decoded at the appropriate frequency, and directed to the DSP (digital signal processor). This daughter board is connected to the Texas Instrument's TMS320C6201 DSP Board, which is plugged into the PCI bus of the ArcSentry Computer.

A program on the DSP accumulates the digitized raw signal data, processes the signals using advanced numerical techniques developed by N. A. Tech. Using a P/NA3 neural network the system can then reproduce the weld shape information and compare that to the weld specification limits such as weld size, leg lengths, actual or effective throat, penetration, etc. TTL status outputs are set at the end of each weld. These status outputs are connected via a communication link and can be routed to a PLC or robot controller. All data and status's are then transferred via the computer PCI bus to the PC computer. The grapical user interface (GUI) displays the resulting status as green, yellow or red, and stores the data to the hard drive where it can be saved for future reference, or accessed remotely via either wire or RF based LAN. The system allows the user to monitor real-time welding, view previously collected data, and system configuration modification.

Once the data from a weld is collected, summary information and weld status are transferred to the Factory Information System (FIS) Server computer using TCP/IP protocol on either a wire or RF based Ethernet LAN. Total encripted data transmitted via the LAN is 200 bytes per weld, which is then archived in a central database and re-broadcas to any clients that are logged into the system. The FIS Client software can be connected from anywhere via LAN, WAN, or the Internet. It provides an engineer with the capabiliy to view summary charts and reports remotely and plant administrative personnel to access logistic information (e.g. plant wide or specific cell wire usage, gas usage, etc.)

The FIS is a complete plant wide information system. It can be set up to produce e-mail, voice mail, pager, cell phone, or other electronic media messages. For example, the system can be set up to send a message to maintenance personnel that includes the line and cell, the problem, the needed parts, and the necessary tools to correct the problem.



ArcSentry Output Specifications


Real-Time Outputs:

  • Quality Parameters - Arc V average, Arc V std. dev., I average, I std. dev. Arc R average, Arc R std. dev., Tip Wear, Average number/duration of short circuits, Average pulse frequency, Ip, Ib, high/low pulse time, Wire slippage indicator
  • Gas Flow Rate (CFH)
  • Water Flow Rate (GPM)
  • Water Temperature (Degrees F)
  • Water Level in Chiller (% e/f)
  • Water quality (pH) System Resistance ((Varc - Vsupply)/Iarc)
  • Weld Power Supply diagnostics Robot Diagnostics (problems, hours until required PM)

Summary Outputs:

  • Gas flow average
  • Gas flow std. dev.
  • Gas Usage (CF)
  • Gas Remaining (CF)
  • Power Usage by welding equipment (KW)
  • Number of welding tips used (per cell, per time)
  • Wire Usage in inches or lbs./Kgs.
  • Wire Feed Speed (IPM or mm/sec)
  • Wire Feed Speed std. dev.
  • Number of welds of type X (per line, cell, time)
  • Number of parts of type X (per line, cell, time)
  • No. of good/bad welds of type X (per line, cell, time)
  • No. of good/bad parts of type X (per line, cell, time)
  • Production cycle time (per line, cell, time)
  • Length of weld produced (per line, cell, time)
  • Total Length of weld produced (per shift, day, etc.)
  • Digital warning via digital line / RS232 / Ethernet
  • Digital shut-down via digital line / RS232 / Ethernet

Maintenance PM Outputs:

  • PM Schedule adjusted by data and calculated information
  • DYNEX System for conducting PM and for other maintenance activities

Reporting Outputs:

  • SPC of process operation quality indicators
  • SPC of resulting weld quality indicators (e.g. penetration, leg lengths, etc.)

Logistics Outputs:

  • Order / re-order optimums for wire - Calculation of the optimum reorder point (R ), which is defined as the number of wire spools in the inventory systems such that when the inventory level drops to or below this number an order is placed for a number of new wire spools equal to (r)
  • Order / re-order optimums for gas
  • Order / re-order optimums for tips
  • Order / re-order optimums for other consumables
  • Automatic order placement with vendors (phone, FAX, e-mail)
  • Order receipt software for vendors




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