DIN 2093 Tolerances
Load Tolerances
Single Disc Spring
The static load F must be determined at the proof test height of the disc spring Itest and not at the spring deflection s which would otherwise lead to a less exact result.
The proof test height Itest is derived from the unloaded free height of the disc spring Io and the theoretical value ho
Itest = Io - 0.75 ho with ho = Io - t
For disc springs with load-bearing surfaces, the Itest calculations must be based upon the nominal material thickness of the disc spring tand notwith the reduced material thickness t'. Measurements must be made during loading of the disc spring. The loading plates must be hardened, ground and polished. Appropriate lubrication must be used during the testing.
The tolerances on Spring load at Itest for normal use are:
Table 7
The tolerances on Spring load at /test for normal use are: Table 7
In order to meet the Spring Load tolerances in some cases it is necessary for the unloaded free height Io to be slightly outside the specified tolerances.
Disc Spring Stacks
Testing of disc spring stacks is accomplished on disc spring stacks consisting of ten (10) disc springs arranged in single series (i=10 and n=1). The load, which is measured during the unloading phase, must not exceed a minimum percentile value of the disc spring force in the loading direction (Table 8). The test point is at a test length of
Ltest = Lo - 0.75 ho
Prior to the testing of the stack, the stack must be compressed with a load equal to twice the nominal spring load F(s = 0.75 ho) of the individual disc spring. The loading plates at the ends of the disc spring stack must be hardened, ground and polished in the exact same manner as the loading plates which are used for testing of individual disc springs. The guiding of the stacks must be in accordance to the requirements for guide rods as described in Chapter 7, and appropriate lubrication of the stack is required.
Figure 34:
Testing of the Disc Spring Stack
Table 8
These load values must not be compared to the measured load values of the single disc spring.
Dimensional Tolerances
Tolerances for the disc spring's diameters are
defined in DIN 7160 and DIN 7161:
For the outside diameter De the tolerance field H 12 applies.
For the inside diameter Di the tolerance field H
12 applies.
For concentricity of the disc spring, the basic
tolerances are defined in the DIN 7151:
Basic Tolerances:
Table 9
Disc spring thickness tolerances tand t':
Table 10:
Unloaded free height tolerances Io:
Table 11:
Heat Treatment
Partial decarburisation of disc springs after heat treatment must not exceed 3% of the material thickness.
To achieve good fatigue strength with minimal relaxation the hardness of disc springs, in materials to DIN 17221 and DIN 17222, must be within the limits 42 to 52 HRC. Group I disc springs should be tested by the Vickers method.
Testing of Disc Springs
Dimensions, Loads and Types
Testing must be in accordance with DIN 267 - Part 5. For the disc spring load F(s = 0.75 ho), the outside diameter De and the inside diameter Di have an AQL (Acceptable Quality Limit) of 1.
For the free height of the disc spring Io, the material thickness tas well as t'and the roughness of the surface finish Ra, the AQL value is 1.5.
Hardness
Testing must be in accordance with DIN 50 103 (Rockwell) and DIN 50 133 (Vickers). Testing must be done at point OM of the cross-section of the disc spring.
Additional testing is allowed in agreement with the customer.