Principe \u00e0 comprendre :<\/h3>\r\n\r\n\r\n\r\n
Injected thermoplastic materials are first heated and then injected under pressure into a mould cavity. Between the plastic phase (soft material) and the solid phase, the material shrinks during cooling. The shrinkage is taken into account in the design and manufacture of the mould. (Overall, a cavity is made larger than the part...so that the right size is reached during cooling...quite easy isn't it?<\/p>\r\n\r\n\r\n\r\n
tol\u00e9rance g\u00e9n\u00e9rale<\/strong><\/h2>\r\n\r\n\r\n\r\nexcept that ....<\/p>\r\n\r\n\r\n\r\n
\r\n- Not all materials have the same shrinkage rate<\/li>\r\n\r\n\r\n\r\n
- Shrinkage is not always the same in length and width of the material flow<\/li>\r\n\r\n\r\n\r\n
- The injection parameters used (pressure, temperatures) have an influence on the shrinkage<\/li>\r\n\r\n\r\n\r\n
- Mould temperature also varies the shrinkage (and also the potential deformation of the parts)<\/li>\r\n\r\n\r\n\r\n
- .... and the list can be much longer...if we also consider that the material supplier also has manufacturing tolerances...as does the mouldmaker...and the moulding company...<\/li>\r\n<\/ul>\r\n\r\n\r\n\r\n
Le retrait \u00e9tant exprim\u00e9 en % de la longueur, on comprend tout de suite que la tol\u00e9rance sera \u00e9galement proportionnelle \u00e0 la longueur du produit…(tout comme c’est le cas pour une tol\u00e9rance g\u00e9om\u00e9trique en m\u00e9canique, qui est proportionnelle \u00e0 la dimension)….ceci \u00e9tant dit, on a d\u00e9ja pli\u00e9 le concept de tol\u00e9rance g\u00e9n\u00e9rale \u00e0 \u00b1 0.2 !<\/p>\r\n\r\n\r\n\r\n
How ISO 20457 works<\/h3>\r\n\r\n\r\n\r\n
The first point to note is that the ISO20457 standard is not fixed like the previous one on existing resins since it takes into account intrinsic criteria of the materials and the types of transformation that can be used.<\/p>\r\n\r\n\r\n\r\n
Are you ready? Let's get to the heart of the matter:<\/p>\r\n\r\n\r\n\r\n
The tolerance grid (TG) to be used, will be based on 5 material \/ process and product criteria combined!<\/p>\r\n\r\n\r\n\r\n
\r\n\r\n- \r\n\u00a0<\/div>\r\nP1 :<\/strong> Which transformation process will we use?<\/strong>
Injection – Compression (1 point)
Extrusion – Soufflage (2 points)
<\/span><\/li>\r\n- \r\n\u00a0<\/div>\r\nP2: What is the stiffness of the material used? <\/strong>(Elasticity module)
> 1200 MPA (1 point)
> 30 MPA (2 points)
> 3 MPA (3 points)
< 3 MPA (4 points)
<\/span><\/li>\r\n- \r\n\u00a0<\/div>\r\nP3: What is the shrinkage of the material used? <\/strong>(see above...)
<0.5% (0 Point)
< 1% (1 point)
< 2% (2 points)
> 2% (3 points)
<\/span><\/li>\r\n- \r\n\u00a0<\/div>\r\nP4: Shrinkage control <\/strong>(by process)
\u00b1 10% (1 point)
\u00b1 20% (2 points)
> 20% (3 points)
<\/span><\/li>\r\n- \r\n\u00a0<\/div>\r\nP5: What is the expected quality <\/strong>
Very accurate (-3 points)
Accurate (-2 points)
Neat (-1 point)
Normal (0 points)<\/span><\/li>\r\n<\/ul>\r\n<\/div>\r\n\r\n\r\n\r\nTG = P1+P2+P3+P4+P5<\/h3>\r\n\r\n\r\n\r\nNeed an example?<\/h3>\r\n\r\n\r\n\r\n\r\n- Injected part (1 Point)<\/li>\r\n\r\n\r\n\r\n
- in ABS (modulus of elasticity: 1600 MPA) (1 Point)<\/li>\r\n\r\n\r\n\r\n
- Shrinkage: 0.7% (1 Point)<\/li>\r\n\r\n\r\n\r\n
- Control of shrinkage (do we have the data sheet?) - (1 Point)<\/li>\r\n\r\n\r\n\r\n
- Commonly used product (normal) - (0 Point)<\/li>\r\n<\/ul>\r\n\r\n\r\n\r\n
TG = 1 + 1 + 1 + 1 + 0 = TG4<\/p>\r\n\r\n\r\n\r\n![\"\"](\"http:\/\/hybster.com\/wp-content\/uploads\/tol_TG4.png\")
<\/figure>\r\n\r\n\r\n\r\nThe standard ISO20457<\/strong>just like its ancestor NFT58000<\/strong>In addition to the above, a distinction is made between dimensions that do and do not include the parting line in the dimension chain.<\/p>\r\n\r\n\r\n\r\n <\/p>\r\n\r\n\r\n\r\n
<\/p>\r\n\r\n\r\n\r\n
Faq Plastics<\/h3>\r\n\r\n\r\n\r\n\r\n\r\nWhat is NFT 58000 french norm ?<\/h3>\r\n\r\nThe NFT 58000 standard defines the tolerances applicable to injection-molded plastic parts, depending on the plastic material, dimension and precision class required by the product specifications.<\/p>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n\r\n\r\n\r\n
\r\n\r\nWhat's the difference between NFT58000 and ISO20457?<\/h3>\r\n\r\nThe NFT 58000 standard was published in the 1980s, whereas the ISO 20457 standard is much more recent. Furthermore, the NFT58000 standard is only used in France; internationally, the ISO20457 standard is more common!<\/p>\r\n<\/div>\r\n<\/div>\r\n\r\n\r\n\r\n
\r\nWhat impact do tolerances have on manufacturing costs?<\/h3>\r\n\r\nThe tighter the tolerances, the greater the probability of producing a non-conforming part. It is common to say that to produce a part with a tolerance of \u00b10.1 mm, you need a machine capable of producing parts to \u00b10.01 (i.e. 10 times more accurate).<\/p>\r\n\r\n\r\n\r\n
<\/p>\r\n<\/div>\r\n<\/div>\r\n\r\n\r\n\r\n
Le retrait \u00e9tant exprim\u00e9 en % de la longueur, on comprend tout de suite que la tol\u00e9rance sera \u00e9galement proportionnelle \u00e0 la longueur du produit…(tout comme c’est le cas pour une tol\u00e9rance g\u00e9om\u00e9trique en m\u00e9canique, qui est proportionnelle \u00e0 la dimension)….ceci \u00e9tant dit, on a d\u00e9ja pli\u00e9 le concept de tol\u00e9rance g\u00e9n\u00e9rale \u00e0 \u00b1 0.2 !<\/p>\r\n\r\n\r\n\r\n
How ISO 20457 works<\/h3>\r\n\r\n\r\n\r\n
The first point to note is that the ISO20457 standard is not fixed like the previous one on existing resins since it takes into account intrinsic criteria of the materials and the types of transformation that can be used.<\/p>\r\n\r\n\r\n\r\n
Are you ready? Let's get to the heart of the matter:<\/p>\r\n\r\n\r\n\r\n
The tolerance grid (TG) to be used, will be based on 5 material \/ process and product criteria combined!<\/p>\r\n\r\n\r\n\r\n
- \r\n
- \r\n\u00a0<\/div>\r\nP1 :<\/strong> Which transformation process will we use?<\/strong>
Injection – Compression (1 point)
Extrusion – Soufflage (2 points)
<\/span><\/li>\r\n- \r\n
\u00a0<\/div>\r\nP2: What is the stiffness of the material used? <\/strong>(Elasticity module)
> 1200 MPA (1 point)
> 30 MPA (2 points)
> 3 MPA (3 points)
< 3 MPA (4 points)
<\/span><\/li>\r\n- \r\n
\u00a0<\/div>\r\nP3: What is the shrinkage of the material used? <\/strong>(see above...)
<0.5% (0 Point)
< 1% (1 point)
< 2% (2 points)
> 2% (3 points)
<\/span><\/li>\r\n- \r\n
\u00a0<\/div>\r\nP4: Shrinkage control <\/strong>(by process)
\u00b1 10% (1 point)
\u00b1 20% (2 points)
> 20% (3 points)
<\/span><\/li>\r\n- \r\n
\u00a0<\/div>\r\nP5: What is the expected quality <\/strong>
Very accurate (-3 points)
Accurate (-2 points)
Neat (-1 point)
Normal (0 points)<\/span><\/li>\r\n<\/ul>\r\n<\/div>\r\n\r\n\r\n\r\nTG = P1+P2+P3+P4+P5<\/h3>\r\n\r\n\r\n\r\n
Need an example?<\/h3>\r\n\r\n\r\n\r\n
- \r\n
- Injected part (1 Point)<\/li>\r\n\r\n\r\n\r\n
- in ABS (modulus of elasticity: 1600 MPA) (1 Point)<\/li>\r\n\r\n\r\n\r\n
- Shrinkage: 0.7% (1 Point)<\/li>\r\n\r\n\r\n\r\n
- Control of shrinkage (do we have the data sheet?) - (1 Point)<\/li>\r\n\r\n\r\n\r\n
- Commonly used product (normal) - (0 Point)<\/li>\r\n<\/ul>\r\n\r\n\r\n\r\n
TG = 1 + 1 + 1 + 1 + 0 = TG4<\/p>\r\n\r\n\r\n\r\n
<\/figure>\r\n\r\n\r\n\r\nThe standard ISO20457<\/strong>just like its ancestor NFT58000<\/strong>In addition to the above, a distinction is made between dimensions that do and do not include the parting line in the dimension chain.<\/p>\r\n\r\n\r\n\r\n
<\/p>\r\n\r\n\r\n\r\n
<\/p>\r\n\r\n\r\n\r\n
Faq Plastics<\/h3>\r\n\r\n\r\n\r\n
\r\n\r\nWhat is NFT 58000 french norm ?<\/h3>\r\n
\r\nThe NFT 58000 standard defines the tolerances applicable to injection-molded plastic parts, depending on the plastic material, dimension and precision class required by the product specifications.<\/p>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n\r\n\r\n\r\n
\r\n\r\nWhat's the difference between NFT58000 and ISO20457?<\/h3>\r\n
\r\nThe NFT 58000 standard was published in the 1980s, whereas the ISO 20457 standard is much more recent. Furthermore, the NFT58000 standard is only used in France; internationally, the ISO20457 standard is more common!<\/p>\r\n<\/div>\r\n<\/div>\r\n\r\n\r\n\r\n
\r\nWhat impact do tolerances have on manufacturing costs?<\/h3>\r\n
\r\nThe tighter the tolerances, the greater the probability of producing a non-conforming part. It is common to say that to produce a part with a tolerance of \u00b10.1 mm, you need a machine capable of producing parts to \u00b10.01 (i.e. 10 times more accurate).<\/p>\r\n\r\n\r\n\r\n
<\/p>\r\n<\/div>\r\n<\/div>\r\n\r\n\r\n\r\n
- \r\n