Overview
ISO 3408-3:2006 - "Ball screws - Part 3: Acceptance conditions and acceptance tests" defines the technical acceptance conditions, permissible deviations and specified acceptance tests for ball screws used in machine tools and motion systems. The standard establishes how to evaluate geometrical accuracy, travel deviations and run‑out so vendors and users can agree objectively on conformity at delivery.
Key topics and requirements
- Scope and objective: Specifies acceptance tests and permissible deviations for ball screws; tests to be agreed between manufacturer and user.
- Tolerance grades: Six standard tolerance grades are defined (0, 1, 3, 5, 7, 10) to classify accuracy and functional requirements.
- Geometrical tests: Procedures for measuring travel deviation and travel variation over specified useful travel lengths, including mathematical (least‑squares) and graphical evaluation methods.
- Acceptance tests (E1–E6):
- E1.1 / E1.2 - Mean travel deviation checks for positioning and transport ball screws (specified and nominal travel).
- E2 - Travel variation within useful travel for positioning screws.
- E3 - Travel variation within any 300 mm axial segment (common for transport screws).
- E4 - Travel variation per revolution (2π rad) for thread periodicity.
- E5 / E6 - Radial run‑out and location tolerances (shaft outer diameter, bearing seats) to assess straightness and concentricity.
- Measurement methods and instruments: Basic measuring principle (angular measuring instrument, travel measuring instrument, clamping/drive, measuring slide) and references to ISO 230‑1 for test code and procedures.
- Evaluation and tables: Numerical tolerances, equations for permissible travel variation by grade, and complementary tables in Annex A support practical application.
Practical applications and who uses it
ISO 3408-3:2006 is used by:
- Ball screw manufacturers for defining production acceptance criteria and inspection procedures.
- Machine tool builders and OEMs when specifying linear motion components for positioning or transport applications.
- Quality and metrology laboratories performing incoming inspection and final tests.
- Procurement and contracts to establish objective acceptance rules between supplier and buyer.
- R&D and maintenance teams assessing replacement parts and verifying functional performance.
Typical uses include verification of positioning accuracy, ensuring thread periodicity, and confirming radial run‑out and bearing seat tolerances for reliable machine performance.
Related standards
Keywords: ISO 3408-3:2006, ball screws, acceptance tests, acceptance conditions, travel deviation, run‑out, tolerance grades, machine tools, positioning ball screw, transport ball screw.
