Overview
ISO 230-2:2014/Amd 1:2016 is an important international standard that specifies the test code for machine tools, focusing on Part 2: the determination of accuracy and repeatability of positioning of numerically controlled (NC) axes. This amendment enhances the methodology for assessing machine tool performance, ensuring precision in automated machining processes. The standard is maintained by ISO/TC 39 subcommittee SC 2, specializing in metal cutting machine tool testing conditions.
The document provides a practical framework for evaluating the positional accuracy of linear and rotary axes in CNC machines, essential for quality assurance and optimal machine operation. It includes provisions to measure positioning errors and introduces a test for the least increment step, a critical parameter defining the smallest movement a machine tool can accurately execute.
Key Topics
- Accuracy Determination: Defines procedures to measure how closely the machine tool's actual position matches the commanded position on numerically controlled axes.
- Repeatability Assessment: Describes methods to evaluate the consistency of axis positioning over multiple cycles, crucial for maintaining machining precision.
- Least Increment Step Test: Introduced in Amendment 1, this test identifies the smallest increment the machine tool can reliably position, factoring in mechanical and control system resolution limits.
- Measurement Techniques: Utilizes instruments such as laser interferometers, non-contact displacement sensors (eddy current or capacitive types), and high-resolution LVDTs to measure small movements with minimal hysteresis.
- Test Conditions and Procedure: Includes step-wise movement commands with dwell times, repeated in positive and negative directions to ensure reproducibility and accurate determination of the least increment step.
- Error Sources Considered: Accounts for factors influencing positioning accuracy, including ballscrew pitch, reversal error, thermal distortion, geometric errors (straightness, squareness, parallelism), and axis coordination.
Applications
- Machine Tool Manufacturers: Use ISO 230-2:2014/Amd 1:2016 to validate and certify CNC machine tools, demonstrating compliance with global quality and precision standards.
- Quality Control and Maintenance Teams: Apply the standard to monitor machine wear and degradation over time by regularly testing axis accuracy and repeatability, ensuring consistent machining outcomes.
- Process Engineers: Optimize machining parameters by understanding machine positioning capabilities and limitations, enabling improved compensation strategies for errors and enhanced product quality.
- Metrology Laboratories: Implement standardized testing to verify the resolution and accuracy of machine tools, providing traceable measurements for industry customers.
- Research and Development: Employ the standard's methods when developing new CNC technologies or upgrading machine control algorithms to maintain high positioning performance.
Related Standards
ISO 230-2:2014/Amd 1:2016 is part of the broader ISO 230 series covering test codes for machine tools, including:
- ISO 230-1: Geometric accuracy of machines operating under no-load or quasi-static conditions.
- ISO 230-3: Determination of thermal effects on machine tools.
- ISO 230-4: Testing of machine tool feed drives.
- ISO 230-5: Testing of circular tests for numerical control systems.
- ISO/IEC Directives, Part 1 and Part 2: Guidelines for the preparation and maintenance of ISO standards, outlining editorial and procedural rules relevant to this amendment.
Leveraging these interconnected standards ensures comprehensive assessment and maintenance of CNC machine tool performance, facilitating interoperability and adherence to international quality benchmarks.
This standard is a vital resource for industry professionals seeking to maintain and improve machining accuracy through rigorous, standardized testing methods. It supports enhanced manufacturing precision, reduced errors, and improved repeatability, helping businesses achieve higher product quality and operational efficiency in CNC machining environments.
Open preview (PDF)Test code for machine tools — Part 2: Determination of accuracy and repeatability of positioning of numerically controlled axes — Amendment 1
