Ordering Disc Springs What we need to quote, and what to consider in your design
We deal with design engineers, engineering contractors, maintenance staff and procurement offices. Each has a different level of understanding and access to information, and we work appropriately with whoever contacts us. Sometimes the requirements are very specific and detailed, sometimes less so. Either way, we will take you through all the key questions, considerations and alternatives.
What to Send Us
Where clients know exactly what they want, we keep the interaction simple and easy. We will not patronise you. The more of this you can give us, the faster we can quote.
The disc spring
Nominal dimensions De × Di × t (and l0 or t′ if known), or a drawing, or the size you are replacing.
Quantities
How many disc springs or stacks, whether this is a once-off or a standing order, and when you need them.
The stack
Number of packets and the configuration of each packet (discs in series and in parallel),.
Loads & travel
Preload (working load) and its compression, and the design (final) load and its compression.
The duty
Static or dynamic, and the expected number of cycles. Whether the stack absorbs shocks or applies a load.
The environment
Operating temperature, corrosion or chemicals, and whether the springs must be non-magnetic or carry an electrical current.
Disc spring size
Pick the inside diameter first. The lists then show only the sizes we list for it.
Stack configuration
Operating temperature
The temperature of the assembly decides the material. Give the highest and lowest temperatures it will see.
Your contact details
Review and send
This opens your email program with the request below, addressed to info@reliable-pressings.co.za. Attach any drawings, then press send.
Critical Engineering Applications
Where the cost of failure is high, we will work with you to confirm all the design specifications and risk mitigation actions.
We support multi-million-dollar engineering projects that demand exacting performance, with disc springs in extreme stack configurations that must absolutely meet the design specifications. In these cases we request, and will verify:
- the preload (working load) and its compression;
- the design (final) load and its compression;
- whether the application is to absorb shocks or to apply loads;
- whether the application is dynamic or static;
- the nominal dimensions of a single disc spring;
- the stack configuration: the number of packets and the configuration of each packet;
- the ambient operating temperature;
- the corrosiveness of the environment and any exposure to chemicals;
- whether the disc springs must be non-magnetic, or will carry an electrical current.
Bespoke vs DIN EN 16983 Disc Springs
DIN 2092 (calculation) and DIN 2093 (dimensions and quality requirements) were recently replaced by DIN EN 16984 and DIN EN 16983. These have been interpreted to draw a boundary around the dimensions allowed within the standard, which strictly defines what a DIN EN 16983 (formerly DIN 2093) disc spring is. You’ll be surprised how many disc springs technically fall outside the DIN standard.
As with DIN 2093, DIN EN 16983 divides disc springs into groups by the thickness of a single disc (t), and each group has three dimensional series, set by the ratio of cone height to thickness (h0/t) and the ratio of outside diameter to thickness (De/t).
The constraints that define this narrow range of dimensions have never been explained. But if you spend some time with the calculations the standard provides, you can see that within the standard’s range of dimensions, the real-life results measured against the theory are consistent, reliable and predictable. As we move out to more extreme dimensions, the calculations become less predictive but, oddly enough, the springs often have far better fatigue life… one for the conspiracy theorists, perhaps?
The DIN EN 16983 limits
- 16 ≤ De/t ≤ 40
- 1.8 ≤ De/Di ≤ 2.5
- 0.4 ≤ h0/t ≤ 1.3
We abide by these limits for DIN EN 16983 disc springs, and tell you when a bespoke design falls outside them.
Thicker Is Seldom Better
There is a misconception that if a disc spring must carry a greater load, you should just make the material thicker. We get these requests often. The problem is that the stresses induced in a thicker disc spring become greater than the yield strength of the base material, and the springs just won’t last, or their operating range must be reduced.
We aren’t trying to sell more disc springs when we suggest that thinner disc springs in parallel are better. We advise this so that your disc springs last! This is why, whenever a “thicker” disc spring is requested, we supply all the stress calculations over the full travel of the disc spring.
Our website menu follows the basic structure of how we describe what we do. We support our clients across the value chain for all the products we manufacture. Apart from the actual manufacturing, most of what we do are services that we provide, either formally at our clients’ request, or informally and unprompted, as part of our internal quality and risk assessment processes.
Consult Us Before You Finalise Your Design
Because of their simple shape, the complexity of disc springs in production and in use is very often underrated. Mistakes in a disc spring solution inevitably lead to short operating life and failure, and then it is very difficult to find a better substitute, because the installation space is usually fixed.
We will help you as part of our service, at our expense. It causes much less grief in the long run, and we want you to have disc springs that perform as your application needs.
Spring force
The force of a disc spring is calculated with the Almen and László model. Its accuracy in the expected mid-range of the load curve is very good, yet approximation errors change the results significantly as disc springs get larger. We discuss this in detail on our design page.
Static loading
For static loading, a certain stress level must not be exceeded. The limit is given by the reference stress σOM at the flat position, which should not exceed the tensile strength Rm of the material, to avoid plastic deformation of the spring (setting losses).
Dynamic loading
Most disc springs can only bear a limited dynamic load. Their life depends on the stress range and on the stress level. The number of cycles to expect can be estimated from the fatigue diagrams. Dynamically loaded disc springs must also be preloaded to at least 15% to 20% of the cone height h0 (s1 ≈ 0.15–0.20 h0), to avoid cracks starting at the top inner edge at the beginning of the deflection.
Stacking
Disc springs stacked face to face (in series) add their deflections. Stacked the same way round (in parallel), they add their forces. Parallel stacking adds friction and a stronger hysteresis: the force when loading is higher, and when unloading lower, than calculated. Suitable lubrication (grease containing MoS2) reduces the hysteresis.
We describe a stack by the number of packets it contains and the configuration of each packet. A packet is the smallest repeating group of disc springs that makes up the stack.
Series and parallel arrangements can be combined in one stack to give a progressive or regressive load curve: for example, one that is linear at first and then levels off at a set load despite further travel. Watch the weaker parts of a combined stack, because they are normally pressed flat quickly, which is not allowed under dynamic loading.
Load characteristic curves
The load/deflection curve of a single disc spring is not linear. Its shape depends on the ratio of cone height to thickness, h0/t. If the ratio is small (about 0.4, Series A) the curve is virtually a straight line, and it becomes increasingly curved as h0/t increases.
At h0/t ≈ 1.4 (√2) the curve is flat near the flat position over a considerable range of deflection, which is useful for wear compensation. Above this, the force falls again before the flat position (regressive), the spring can snap through, and it needs to be fully supported. DIN EN 16983 disc springs stay at or below h0/t = 1.3.
Guides
In dynamic applications, the surface of the guide elements must always be harder than the disc springs. A minimum of 55 HRC is advisable, otherwise the surfaces can be damaged. Damage causes uneven movement during deflection, changes the characteristic, and can even start fatigue cracks. The wrong guide clearance can also change the loading in a harmful way.
Stack length
Friction and other effects make a stack deflect unevenly: it deflects more on the loaded side. This can usually be neglected for a normal stack, but not for long stacks. So the length of a stack should not exceed three times the outside diameter. If it must be longer, divide 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. No individual stack should ever contain more than 14 packets.
Material
The best material for disc springs is standard spring steel, which is always used unless particular circumstances call for a special material. Special materials generally have a lower tensile strength and often a different Young’s modulus from spring steel, so their springs usually cannot be designed with the same free height, and the forces are lower. See our materials page.
Temperature
Each material has its own temperature range. Too high a temperature can have a tempering effect, which causes a loss of force and, in extreme cases, plastic deformation (setting losses).
Corrosion
Disc springs can be protected against corrosion by suitable coatings or by using corrosion-resistant materials. These materials are only available in a limited range of thicknesses. Also, almost all high-alloy steels can suffer stress corrosion cracking at high working stresses.
Hydrogen embrittlement
Some chemical or electrochemical processes (such as electroplating) can let hydrogen into the material, which can cause delayed brittle fractures. Heat treatment afterwards cannot avoid this entirely, so processes without this risk are preferred.
Ready to order?
Email us your requirements, or call us and we’ll take you through the key questions.