1、BRITISH STANDARD BS 7010:1988 Code of practice for A system of tolerances for the dimensions of plastics mouldings UDC 621.753.1:678.027.7:678.072:(083.71)BS7010:1988 This British Standard, having been prepared under the directionof the Plastics StandardsCommittee, was published under the authority
2、ofthe Board of BSI and comes into effect on 30December1988 BSI 02-1999 First published as BS2026, November1953 First revision as BS7010 December1988 The following BSI references relate to the work on this standard: Committee reference PLM/45 Draft for comment 86/40495 DC ISBN 0 580 16659 7 Committee
3、s responsible for this British Standard The preparation of this British Standard was entrusted by the Plastics Standards Committee (PLM/-) to Technical Committee PLM/45 upon which the following bodies were represented: British Plastics Federation British Telecommunications plc ERA Technology Ltd. El
4、ectrical Installation Equipment Manufacturers Association (BEAMA Ltd.) Electronic Engineering Association Ministry of Defence Plastics and Rubber Institute Society of Motor Manufacturers and Traders Limited Telecommunication Engineering and Manufacturing Association Amendments issued since publicati
5、on Amd. No. Date of issue CommentsBS7010:1988 BSI 02-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Definitions and explanation of terms 1 3 Tolerance selection 2 4 Draft 2 5 Deflection, twist and angular deviation 3 Figure 1 Mould related dimensions 1 Figure
6、2 Non-mould related dimensions 2 Table 1 Shrinkage factors and dimensional tolerance groups for tolerance levelsA, B andC 2 Table 2 Correlation of tolerance groups with moulding materials 3 Table 3 Tolerance values on dimensions 5 Publication(s) referred to Inside back coverBS7010:1998 ii BSI 02-199
7、9 Foreword This code of practice has been prepared under the direction of the Plastics Standards Committee from a draft supplied by the Ministry of Defence and supersedes BS2026:1953 which is withdrawn. It recognizes deviations during manufacture arising from the following. a) Variation in dimension
8、s due to processing. This depends on the uniformity of the moulding material, machine settings, mould temperature and deformation of the mould under pressure. b) The condition of the mould, i.e. manufacturing tolerances on mould dimensions, wear and variations in the position of moveable parts of th
9、e mould. The tolerances recommended in this code of practice are based on the above considerations. They do not include reversible post-moulding dimensional changes due to thermal expansion/contraction or absorption/desorption of liquids and vapours, or permanent post-moulding dimensional changes ca
10、used by post-crystallization of the polymer or the relaxation of moulding stresses. Attention is drawn to the need to observe the tolerances selected for a particular component, as indicated in this code of practice, since to obtain tolerances smaller than those recommended will be likely to increas
11、e its cost significantly or be technically unattainable. Certainly great care is necessary in component design, mould design, material selection and production conditions to achieve finer tolerances than those recommended in this code of practice. A British Standard does not purport to include all t
12、he necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii,
13、pages1 to6, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on theinside front cover.BS 7010:1988 BSI 02-1999 1 1 Scope This code of practice recommends a system of tole
14、rances for the dimensions of plastics mouldings produced from thermoplastic and thermosetting moulding materials by compression moulding, transfer moulding or injection moulding. The tolerances do not apply to extrusions, blown or foamed mouldings, or deep drawn or sintered parts. The recommended sy
15、stem of tolerances relates to the dimensions of mouldings from a single cavity mould after the mouldings have been conditioned for16h at23 2 C and50 5% relative humidity (r.h.). For multicavity moulds the recommended tolerances should be increased by between1% to5% per additional cavity depending on
16、 the material and the mould design. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Definitions and explanation of terms For the purposes of this British Standard the following definitions apply. 2.1 tolerance the difference between the maximum
17、limit of size and the minimum limit of size 2.2 moulding shrinkage the difference between the dimension of the mould (at23 2 C) and the corresponding dimension of the moulding (the latter having been stored for16h at23 2 C and505%r.h.) expressed as a percentage of the mould dimension 2.3 mould relat
18、ed dimensions dimensions of the moulding not determined by the interaction with moveable parts of the mould (seeFigure 1) 2.4 non-mould related dimensions dimensions of the moulding determined by the interaction of moveable elements of the mould, e.g.wall thickness dimensions and bottom thickness di
19、mensions determined by moving slides and cores (seeFigure 2) 2.5 shrinkage factor K the sum of the moulding shrinkage parallel to the direction of melt flow and the absolute difference between the moulding shrinkage parallel and perpendicular to the melt flow as given in the following equation: K =
20、X + |X Y| where 2.6 dimensional tolerance group a tolerance rating based on the material shrinkage factor and the required tolerance level 2.7 tolerance level tolerance levels A, B and C are defined as follows: a) level A for normal processing conditions; b) level B for normal processing conditions
21、with additional mould adjustments; c) level C for carefully controlled production conditions combined with further mould adjustments. NOTEIt is normal practice for the magnitude of the tolerances to increase in the order C through B to A. X is the moulding shrinkage parallel to melt flow; Y is the m
22、oulding shrinkage perpendicular to melt flow. Figure 1 Mould related dimensionsBS7010:1988 2 BSI 02-1999 3 Tolerance selection 3.1 Procedure for tolerance selection The procedure for tolerance selection is as follows. a) The proposed material should be located inTable 2. b) The dimensional tolerance
23、 group for the tolerance level appropriate to the production conditions envisaged or desired should be identified from Table 2. c) Depending on whether the nominal dimension is mould related, the tolerance values stated for the particular dimension and the dimensional tolerance group should be read
24、off from Table 3. CAUTION. In the event of this tolerance being unacceptably large for the functional requirements of the application, consideration should be given to using a more stringent level of production control to reach the specified lower tolerances, i.e. a different dimensional tolerance g
25、roup or alternatively the use of another material should be considered which will allow the specified tolerances to be attained. It is essential that the component designer considers the likely mould design since the achievable tolerance will depend on whether the component dimensions will be formed
26、 entirely in one mould part (mould related) or in more than one mould part (non-mould related). 3.2 Determination of shrinkage factor 3.2.1 General. For a material not listed inTable 2 the shrinkage factorK should be determined experimentally and the appropriate tolerance group selected in accordanc
27、e withTable 1. It is then possible to select a tolerance fromTable 3 as described in item c) of3.1. At least three test specimens should be moulded in accordance with the recommendations of the material supplier, in accordance with the recommendations of3.2.2 and3.2.3 and measurements taken in accor
28、dance with2.2. 3.2.2 Thermosetting moulding materials. The shrinkage factor K should be calculated from the mould shrinkage which should be determined in accordance with BS2782:Method640A. 3.2.3 Thermoplastic materials. For these materials the mould shrinkage parallel and perpendicular to the melt f
29、low should be determined on a single cavity mould which would exhibit shrinkage in these two directions. The mould should have a cavity providing a rectangular test piece approximately90mm 65mm 3mm thick and gated on the shorter side with a6mm wide 3mm thick gate. Table 1 Shrinkage factors and dimen
30、sionaltolerance groups for tolerance levels A, B and C 4 Draft Since all tolerances apply to the nominal dimensions on the drawing, the drawing should show the point on the draft taper to which the nominal dimension applies. Figure 2 Non-mould related dimensions Shrinkage factor K Dimensional tolera
31、nce group Tolerance level A Tolerance level B Tolerance level C 0 to 1 130 120 110 1 to 2 140 130 120 2 to 3 150 140 130 3 to 4 160 150 140BS 7010:1988 BSI 02-1999 3 5 Deflection, twist and angular deviation Deflection, twist and angular deviation occurring after removal from the mould depend on the
32、 shape of the moulding, among other factors. For this reason it is not possible to state actual values of tolerances; these should be agreed with the manufacturer. These deformation effects are particularly liable to occur with bulky and large flat items and with anisotropic mouldings and materials.
33、 Table 2 Correlation of tolerance groups with moulding materials Symbol for material Moulding material British Standard for material (if applicable) Dimensional tolerance group Tolerance levelA Tolerance level B Tolerance level C ABS Acrylonitrile-butadiene-styrene (filledand unfilled) 4935 130 120
34、110 UF Aminoplastic moulding material 1322 with organic fillers 140 130 120 with inorganic fillers 130 120 110 MF Aminoplastic/phenolic moulding material with organic and inorganic fillers 140 130 120 CA Cellulose acetate 1524 140 130 120 CAB Cellulose acetate butyrate 140 130 120 CAP Cellulose acet
35、ate propionate 140 130 120 CP Cellulose propionate 140 130 120 PF Phenolic moulding material 771 with organic fillers 140 130 120 with inorganic fillers 130 120 110 Epoxy resin moulding materials 3816 130 120 110 PA6 Polyamide 6 (unfilled) 140 130 120 PA66 Polyamide 6.6 (unfilled) 140 130 120 PA610
36、Polyamide 6.10 (unfilled) 140 130 120 PA11 Polyamide 11 (unfilled) 140 130 120 PA12 Polyamide 12 (unfilled) 140 130 120 PA Polyamide amorphous (unfilled) 130 120 110 PBTP Polybutylene terephthalate unfilled 140 130 120 filled 130 120 110 PC Polycarbonate (filled and unfilled) 130 120 110 PCTFE Polyc
37、hlorotrifluoroethylene 150 140 130 PDAP Polydialkylphthalate moulding material (with inorganic filler) 130 120 110 UP Polyester resin moulding materials 3532 130 120 110 PE Polyethylene (unfilled) 3412 150 140 130BS7010:1988 4 BSI 02-1999 Table 2 Correlation of tolerance groups with moulding materia
38、ls Symbol for material Moulding material British Standard for material (ifapplicable) Dimensional tolerance group Tolerance levelA Tolerance level B Tolerance level C PESU Polyethersulphone (filled and unfilled) 130 120 110 PETP Polyethyleneterephthalate amorphous 130 120 110 crystalline 140 130 120
39、 filled 130 120 110 PMMA Polymethylmethacrylate 130 120 110 POM Polyoxymethylene (polyacetal) unfilled, length 150mm 150 140 130 filled 130 120 110 PPO Polyphenylene oxide (modified) filledandunfilled 130 120 110 PPS Polyphenylene sulphide (filled) 130 120 110 PP Polypropylene 5139 unfilled 150 140
40、130 filled with glass, talc, or asbestos fibre 140 130 120 PS Polystyrene 1493, 3126 130 120 110 PSU Polysulphone (filled and unfilled) 130 120 110 PVC-U Polyvinylchloride (unplasticized) 130 120 110 SAN Styrene acrylonitrile 4936 130 120 110BS 7010:1988 BSI 02-1999 5 Table 3 Tolerance values on dim
41、ensions Tolerance group (from Table 2) Code letter Nominal dimension range mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm Over up to 0 1 3 6 10 15 22 30 40 53 70 90 120 160 200 250 315 400 500 630 800 1 3 6 10 15 22 30 40 53 70 90 120 160 200 250 315 400 500 630 800 1 000 Tolerances
42、mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm 160 NMR a 0.56 0.60 0.66 0.74 0.84 0.98 1.14 1.32 1.56 1.88 2.30 2.80 3.60 4.40 5.40 6.60 8.20 10.20 12.50 15.80 20.00 MR b 0.36 0.40 0.48 0.54 0.64 0.78 0.94 1.12 1.36 1.68 2.10 2.60 3.40 4.20 5.20 6.40 8.00 10.00 12.30 15.60 19.80 150
43、NMR 0.46 0.50 0.54 0.60 0.68 0.76 0.86 0.98 1.14 1.36 1.62 1.94 2.40 3.00 3.60 4.40 5.60 6.80 8.60 10.60 13.20 MR 0.26 0.30 0.34 0.40 0.48 0.56 0.66 0.78 0.94 1.16 1.42 1.74 2.20 2.80 3.40 4.20 5.40 6.60 8.40 10.40 13.00 140 NMR 0.40 0.42 0.44 0.48 0.54 0.60 0.68 0.76 0.86 1.00 1.20 1.40 1.70 2.10 2
44、.50 3.10 3.80 4.60 5.80 7.20 9.00 MR 0.20 0.22 0.24 0.28 0.34 0.40 0.48 0.56 0.66 0.80 1.00 1.20 1.50 1.90 2.30 2.90 3.60 4.48 5.60 7.00 8.80 130 NMR 0.36 0.38 0.40 0.42 0.46 0.50 0.54 0.60 0.68 0.76 0.88 1.02 1.20 1.50 1.80 2.20 2.60 3.20 3.90 4.90 6.00 MR 0.16 0.18 0.20 0.22 0.26 0.30 0.34 0.40 0.
45、48 0.56 0.68 0.82 1.00 1.30 1.60 2.00 2.40 3.00 3.70 4.70 5.80 120 NMR 0.32 0.34 0.36 0.38 0.40 0.42 0.46 0.50 0.54 0.60 0.68 0.78 0.90 1.06 1.24 1.50 1.80 2.20 2.60 3.20 4.00 MR 0.12 0.14 0.16 0.18 0.20 0.22 0.26 0.30 0.34 0.40 0.48 0.58 0.70 0.86 1.04 1.30 1.60 2.00 2.40 3.00 3.80 110 NMR 0.18 0.2
46、0 0.22 0.24 0.26 0.28 0.30 0.32 0.36 0.40 0.44 0.50 0.58 0.68 0.80 0.96 1.16 1.40 1.70 2.10 2.60 MR 0.08 0.10 0.12 0.14 0.16 0.18 0.20 0.22 0.26 0.30 0.34 0.40 0.48 0.58 0.70 0.86 1.06 1.30 1.60 2.00 2.50 a Non-mould related dimensions. b Mould related dimensions.6 blankBS7010:1988 BSI 02-1999 Publi
47、cations referred to BS 771, Phenolic moulding materials. BS 1322, Specification for aminoplastic moulding materials. BS 1493, Method of specifying general purpose polystyrene (PS) moulding and extrusion materials. BS 1524, Specification. Cellulose acetate moulding material. BS 2782, Methods of testi
48、ng plastics. BS 2782:Method 640A, Determination of shrinkage of test specimens in the form of bars of compression moulded thermosetting moulding materials. BS 3126, Method of specifying toughened polystyrene (SB) moulding and extrusion materials. BS 3412, Specification. Polyethylene materials for mo
49、ulding and extrusion. BS 3532, Unsaturated polyester resin systems for low pressure fibre reinforced plastics. BS 3816, Specification for cast epoxide resin insulating material for electrical applications at power frequencies. BS 4935, Specification for acrylonitrile-butadiene-styrene (ABS) moulding and extrusion materials. BS 4936, Method of specifying styrene-acrylonitrile (SAN) moulding and extrusion materials. BS 5139, Classification for polypropylene plastics materials for moulding and extrusion. BSI 389 Chiswick High Road London W4 4A
