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GB/T 40178-2021Ophthalmic optics - Formers (English PDF)

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Issued by

SAMR; SAC

Level / Type

National · Recommended

Issue date

May 21, 2021

Implementation date

December 1, 2021

Scope

GB/T 40178-2021 (Ophthalmic optics - Formers) is available as an English-translated PDF.

GB/T 40178-2021 — This document specifies the characteristics of the formers which are used by the edge-cutting instrument when the lens is edge-cut. This document applies to the formers which are used by the edge-cutting instrument when the lens is edge-cut. This document does not apply to separate formers which are required for additional processing of lenses, such as grinding.

Document preview — GB/T 40178-2021

National Standard of the People's Republic of China

Issued by: SAMR; SAC

Foreword3
1 Scope4
2 Normative references4
3 Terms and definitions4
4 Former types4
5 Size requirements of former fixing hole5
6 Marking5

1 Scope

This document specifies the characteristics of the formers which are used by the edge-cutting instrument when the lens is edge-cut.

This document applies to the formers which are used by the edge-cutting instrument when the lens is edge-cut.

This document does not apply to separate formers which are required for additional processing of lenses, such as grinding.

2 Normative references

The contents of the following documents constitute the indispensable clauses of this document through normative references in the text. For dated references, only the version corresponding to that date is applicable to this document; for undated references, the latest version (including all amendments) is applicable to this document.

GB/T 26397, Ophthalmic optics - Terminology (GB/T 26397-2011, ISO 13666:1998, MOD)

3 Terms and definitions

Terms and definitions determined by GB/T 26397 are applicable to this document.

4 Former types

4.1 General principles

According to the lens size former (see 4.2) or lens ring size former (see 4.3), distinguish the lens former.

Materials and thicknesses that are dimensionally stable shall be selected.

4.2 Lens size former

The lens size former is a former that has the same size and shape as the to-be-made spectacle lens.

They can be configured into each size in a specific frame style [see Figure 1a)], and can also be configured as a special size for the specified size range (including larger and smaller sizes) [see Figure 1b)].

4.3 Lens ring size former

The lens ring size former is a former that has the same shape as the to-be-made spectacle lens, but it is a standard chamfer smaller than the size of the finished lens. They shall be able to be firmly installed in the lens ring by hand without changing their size or shape; there shall be no visible gap between the lens ring and the former.

5 Size requirements of former fixing hole

The size requirements shall use the sizes and tolerances that are given in

Figure 2.

For the fixing holes of two formers of the same nominal size and shape, the size difference between any corresponding points on the circumference shall not exceed 0.2 mm.

Note: Figure 1 shows the standard size of former fixing holes that are based on global use.

The former that is shown in Figure 1a) is considered the most suitable former for future development.

6 Marking

The former shall be marked with at least the following information:

a) Identification of the manufacturer or supplier;

b) Former identification;

c) The nose side of the former that is indicated by the letter "N", combined with the enclosing-square method symbol.

The former type that meets the requirements in 4.2 shall also be indicated the lens size of the horizontal enclosing-square method (unit: mm).

The former type that meets the requirements in 4.3 shall also be indicated the lens size of the horizontal enclosing-square method that is intended to be made (unit: mm), and shall also have the words of "lens ring size".

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This preview omits tables, figures, formulas and parts of the technical clauses. The complete document — all pages — is available in the English PDF.

Referenced standards

Normative references

GB/T 26397 · GB/T 26397-2011 · ISO 13666

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