ISO 14744-2:2000

Overview

ISO 14744-2:2000 is Part 2 of the ISO series on acceptance inspection of electron beam welding machines. It describes recommended measurement arrangements, instrumentation and procedures to determine the accelerating voltage characteristics used in acceptance testing. The accelerating voltage is defined as the potential difference between the cathode and the anode in the electron-beam gun. The standard emphasizes safe high-voltage practices and consistent measurement on the full range of beam settings.

Key Topics

• Measurement setup and safety

  • Measurements are often performed at the machine manufacturer's facility because special high-voltage equipment and expertise are required. The standard notes the need for trained personnel and attention to high-voltage safety.
  • A workpiece or a Faraday cage should be placed in the welding chamber when the beam is operated during testing.

• Instrumentation

  • A frequency-compensated voltage divider must be connected between the high-voltage generator and the electron gun. Examples in the standard illustrate a 10:1 divider, rated U = 200 kV with R ≈ 200 MΩ, and a measurement resistor (≈ 20 kΩ) feeding an oscilloscope.
  • The divider output reduces high voltage to a safe, monitorable level for an oscilloscope or other measuring instruments. Degree of frequency compensation depends on the high-voltage generator type.

• Measurement procedures

  • Ripple (peak-to-peak): Use an oscilloscope to record the instantaneous divided voltage and determine the peak-to-peak range. Calculate ripple as a percentage of the mean accelerating voltage.
  • Stability: Record the averaged voltage (with ripple removed) continuously over a specified interval to determine short- and long-term stability; express deviations as percentages relative to the initial value.
  • Reproducibility: Cycle the specified accelerating voltage and beam current on and off multiple times and record the mean monitored voltages to calculate reproducibility as a percentage deviation.

Applications

• Acceptance inspection of electron beam welding machines to confirm that the accelerating voltage meets acceptance criteria defined in ISO 14744-1.
• Factory testing during machine commissioning, routine quality checks, and verification after servicing or repairs.
• Supporting process qualification where voltage stability, ripple and repeatability directly impact weld quality.

Related Standards

• ISO 14744-1:2000 - Principles and acceptance conditions (referenced for test settings and limit values).
• ISO 14744-3:2000 - Beam current measurement (linked procedures for chamber and workpiece arrangements).

For evaluation, measured ripple, stability and reproducibility values are compared with the limit values specified in ISO 14744-1. The guidance in ISO 14744-2 helps ensure consistent, safe and repeatable voltage measurements critical to electron beam welding performance.