Dynamic applications, involving large numbers of deflection cycles, will require that in addition to hardened seating faces the guide surfaces must also be sufficiently hard to prevent excessive wear or "stepping". For both support washers and guide elements, a polished surface with hardness of 58HRC is sufficient, and case depth should be 0.60mm min.
A most important aid to efficient and extended life of Disc Spring is the provision of some form of lubrication. For relatively low-duty Disc Spring application, a liberal application of suitable solid lubricant, (e .g. molybdenum-disulphide, grease), to the contact points and locating surfaces of the spring is adequate.
For more severe applications of a dynamic or highly corrosive nature, the Disc Springs will benefits from maintained lubrication, and are often housed in a oil or grease filled chamber.
Disc Spring with Contract Flats and Reduced Thickness:
For Disc Springs with a thickness of more than 6mm, DIN 2093 specifies small contact surfaces at point I III in Addition to the rounded corners. These contact flats improve definition of the point of load application and reduce friction at the guide rod. Contact flat increase spring load which is to be compensated by a reduction in the thickness from 't' to 't'.
Series Stacking: The cumulative effect of bearing point friction of large numbers of Disc Springs stacked in series, can result in the Disc Springs at each end of the stack deflecting more than those in the center. In extreme cases this may result in over-compression and premature failure of the end springs. A “rule of thumb” is that the length of the stacked Disc Springs should not exceed a length approximately equal to 3 times the outside diameter of the Disc Spring.
Stack Length :
When stacking Disc Springs, effort should be made to keep the stacks as short as possible. Friction and other influences make a stack more uneven. It deflects more on the side of the loading. This effect usually can be neglected for a "normal" spring stack, but not for long stacks. If it is longer, the stack can be stabilized by dividing it with guide washers, which as a rule of thumb should have a thickness of at least one and a half times the guide diameter.