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DIMENSIONS & MEASUREMENT TOLERANCES

The pole surfaces of sintered magnets made of VACODYM® or VACOMAX® that have been pressed in moulds usually need to be ground. The tolerance for ground dimensions is i.a. ± 0.05 mm; values of up to ±0.02 mm are possible.

If the surfaces are not to be ground for economic reasons, the tolerances of the thickness in the direction of pressing are typically ±0.2 mm.

The dimensions vertical to the pressing direction are largely determined by the pressing mould, meaning that these surfaces generally remain unprocessed. Typical "pressing tolerances" of these side dimensions are:

Nominal dimensions perpendicular to the direction
of pressing (mm)*

Tolerances (mm)

up to 7

+/-0.10 . . . +/-0.20

7- 15

+/-0.15 . . . +/-0.30

15- 25

+/-0.25 . . . +/-0.40

25- 40

+/-0.30 . . . +/-0.60

40- 60

+/-0.45 . . . +/-0.90

60-100

+/-0.80 . . . +/-1.50

* more precise information available upon request

For moulded parts with a complex geometry a maximum and a minimum sleeve curve is usually stated within which the contour of the pressed part lies.

In the case of parts cut from blocks (i.a. HR quality), the tolerances are ± 0.1 mm. After agreement, smaller tolerances resulting from grinding processing are possible. If dimensions have not been toleranced, we supply according to DIN ISO 2768 m. The maximum dimensions for parts from the 6 series pressed isostatically made of VACODYM are a diameter of 105 mm or a rectangular cross section of 82 x 82 mm2.

Netshape-Parts
As already mentioned above, especially low cost magnets with a pole surface of up to around 6 cm2 in the axial field can be pressed by waiving grinding. Such Netshape-Magnets have the above-mentioned tolerances vertical to the pressing direction. In the pressing direction (= magnetic preferential direction), sporadically measured thickness tolerances of typically < 0.15 mm without a subsequent grinding process are adhered to thanks to special pressing and sintering processes. Care is taken to ensure that the total thickness of the part does not exceed a specific value, meaning that the magnets fit into an assembly gap which, for example, only has to be 0.40 mm bigger than the nominal thickness of the part. Preferred forms are cuboids and bowls with typical thicknesses in the range of 2.2 to 5.0 mm. Our experts are happy to provide advice in the design of the magnet geometry and the tolerances for Netshape-Magnets.

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Last update: 15.05.2013