Tolerances for aluminium castings

As is generally known, all series products are subject to procedural and technical tolerances.
In the aluminium casting technique these tolerances result from the moulds, the alloys and the casting procedure.
Aluminium alloys to DIN 1725 are used by BOPLA for its enclosures.

Tolerances for Pressure Dia-Castings (DIN 1688, Page 4)

In pressure-die cast parts in light metal alloys the deviations in dimensions are mainly dependent on:

-the exactitude of the dimensions and function of the mould, which in turn is characterised by the degree of exactitude of

-the position of the mould division, characterised by the subdivision into shape-related and non-related dimensions (see DIN 1680, Page 1)

-the shape or size of the casting, characterised by the spatial diagonals and

-the nominal dimensions.

Determining the Spatial Diagonals
The spatial diagonal R is that between the extreme points of the casting.
It is calculated from the nominal dimensions of the prismatic body, which delimits the casting, whatever its shape.



Table 1

Tolerances of dimensions not related to the shape, linear dimensions (lengths, widths, heights, central distances, diameters, roundings)

Spatial
diagonal
area ¹)
Degree
of exactitude
Shape
depen
dency
Nominal dimensions
up to
18
18
to 30
30
to
50
50
to
80
80
to 120
120
to 180
180
to 250
250
to 315
315
to 400
400
to 500
500
to 630
630
to 800
800
to 1000
1000
to 1250
Up to 50 GTA 13 shape-
related
± 0,14 ± 0,17 ± 0,2                      
not
shape-
related
± 0,24 ± 0,27 ± 0,3                      
50
to 180
GTA 13/5 shape-
related
± 0,17 ± 0,2 ± 0,25 ± 0,3 ± 0,35 ± 0,4                
not
shape-
related
± 0,32 ± 0,35 ± 0,4 ± 0,45 ± 0,5 ± 0,55                
180
to 500
GTA 14 shape-
related
± 0,22 ± 0,26 ± 0,31 ± 0,37 ± 0,44 ± 0,5 ± 0,6 ± 0,65 ± 0,7 ± 0,8        
not
shape-
related
± 0,42 ± 0,46 ± 0,51 ± 0,57 ± 0,64 ± 0,7 ± 0,8 ± 0,85 ± 0,9 ± 1        
500 GTA 14/5 shape-
related
± 0,25 ± 0,35 ± 0,4 ± 0,45 ± 0,55 ± 0,65 ± 0,75 ± 0,8 ± 0,85 ± 0,95 ± 1,1 ± 1,2 ± 1,4 ± 1,6
not
shape-
related
± 0,55 ± 0,65 ± 0,7 ± 0,75 ± 0,85 ± 0,95 ± 1 ± 1,1 ± 1,1 ± 1,2 ± 1,4 ± 1,5 ± 1,7 ± 1,9

 

Table 2

Tolerances of Dimensions not related to the Shape for Thickness (wall thickness, ledges, ribs)

Spatial diagonal
area ¹)
Degree of'
exactitude
Shape
dependency
Nominal dimensions
to 3 3 to 6 6 to 10
Up to 50 GTA 13 shaperelated ± 0,15 ± 0,2 ± 0,2
not shaperelated ± 0,25 ± 0,3 ± 0,3
50 to 180 GTA 13/5 shaperelated ± 0,2 ± 0,25 ± 0,3
not shaperelated ± 0,35 ± 0,4 ± 0,45
180 to 500 GTA 14 shaperelated ± 0,25 ± 0,3 ± 0,35
not shaperelated ± 0,45 ± 0,5 ± 0,55
500 GTA 14/5 shaperelated ± 0,3 ± 0,4 ± 0,45
not shaperelated ± 0,55 ± 0,65 ± 0,7

Shape-related dimensions are those in the same part of the tool;
Not shape-related dimensions are those created by the interaction of mobile tool components, e.g. wall thicknesses and base thicknesses or dimensions affected by additives or extenders.

Tolerances for Chill Castings (DIN 1688 T.3)

In the case of raw castings made of light metal alloys in the chill casting process all deviations in dimensions are essentialy dependent on:

  1. the exactitude of the dimensions of the mould, characterised by the degree of exactitude
  2. the position of the mould division, cores, extenders, characterised by the subdivision into shape-related and not shape-related dimensions (see DIN 1680 Part 1)
  3. the nominal dimensions.

Table 1

Deviations in lengthwise dimensions (lengths, widths, heights, central distances, diameters, roundings)

Degree of
exactitude
Shape
dependency

Nominal dimensions

up to
18
18
to
30
30
to
50
50
to
80
80
to 120
120
to 180
180
to 250
250
to 315
315
to 400
400
to 500
500
to 630
630
to 800
800
to 1000
1000
to 1250
GTA 15/5 shape-
related
± 0,45 ± 0,5 ± 0,6 ± 0,75 ± 0,85 ± 1 ± 1,2 ± 1,3 ± 1,4 ± 1,6 ± 1,7 ± 2 ± 2,3 ± 2,6
not
shape-
related
± 0,55 ± 0,65 ± 0,8 ± 0,95 ± 1,1 ± 1,3 ± 1,5 ± 1,6 ± 1,8 ± 2 ± 2,2 ± 2,5 ± 2,8 ± 3,3

 

Table 2

Deviations in Thicknesses (wall thicknesses, ledges, ribs)

Degree of exactitude Shape dependency

Nominal dimensions

up to 6

6 to 10

10 to 18

GTA 15/5 shaperelated ± 0,6 ± 1,2 ± 1,8
not shaperelated ± 0,8 ± 1,5 ± 2,2

 

Shape-related dimensions are those in the same parts of the tool.

Not shape-related dimensions are those created by the interaction of mobile tool components, e.g. wall thicknesses and base thicknesses, or dimensions that are affected by additives or extenders.