Compression springs are constructed to oppose compression along
the axis of wind. Thus From writing pens to railroad cars, compression
springs function to fill a variety of project needs, from the
everyday to the unique. They can be wound in constant or variable
pitch along their length, be constructed of stacked spring elements,
and can be straight, conical, or have a variable diameter. The
very important parameter that should be considered while ordering/buying
any compression springs are the dimentions those include outer
diameter, inner diameter, wire diameter, free length, and solid
height, spring rate and design unites (english or metric units).
Terms :
Free Lenght
The overall length of a spring in the unloaded position.
Solid Height
The solid height is the length of a compression spring when
under sufficient load to bring all coils into contact with adjacent
coils.
Spring Rate
The spring rate is the change in load per unit deflection, generally
given in pounds per inch or Newtons per millimeter (N/mm).
Material
for Compression Spring:
Common materials include stainless steel, high carbon steel
wire, alloy steel or music wire, nickel base alloy wire, brass,
and hard drawn. Spring steel is a standard industrial grade
of steel specifically used for spring making. It exhibits good
elastic and return properties. Music wire is a common and relatively
inexpensive high-carbon steel alloy used for spring manufacture.
It is cold drawn and offers uniform tensile strength. Stainless
steel exhibits good corrosion resistance for specialty applications.
Exotic metals and their alloys with special properties and applications;
include such materials as beryllium copper, beryllium nickel,
niobium, tantalum, and titanium.
Configuration Options
for compression springs include straight coil, ground ends,
closed or squared ends, and die spring.
Straight
Coil Configuration
Streight coil is a standard coil type for compression
springs. Other coil types are hourglass, conical and barrel
types.
Die
Springs
Die Springs are
helical compression springs generally of rectangular section.
They can carry roughly 30% more load for the same deflection
than can be carried by a round section. They are not solely
used in dies but find application in clutches, brakes, farm
machinery and aircraft mechanisms.
Closed
or Squared ends
In a closed or squared ends configuration the ends of the compression
spring where pitch of the end coil is reduced so that the end
coils touch.
Ground
Coil Ends
A compression spring that has ground ends has one end that is
ground to provide a flat plane.
Compression
Spring Principle:
Spring rate can be measured by taking the difference
in force at 80% maximum deflection and 20% minimum deflection
and divding by the difference in deflection. The spring rate
tends to be constant over the central 60% of the deflection
range. Because of end-coil effects, the first 20% of deflection
range has a considerably lower spring rate. The final 20% of
deflection shows considerably higher spring rate. When designing
for a particular spring, design for critical loads and rates
to be within the central 60% deflection range.
Design
Limitations
• If the spring will set solid (compress all
the way, so that all the coils touch each other) at the limit
of its travel, the diameter of the wire times the number of
coils cannot be greater than the space allowed, unless you want
the spring itself to act as a mechanical stop to the motion.
• Springs that operate in a high-temperature environment
(like for instance inside an engine) will need to be made slightly
longer to compensate for the fact that the heat may have an
effect on the length of the spring. The section on finishing
will tell you more about this.
• As a compression spring assumes a load and shortens,
the diameter of the active coils will increase. This is only
a problem when the spring has to work in a confined space.
Please contact
our engineer to discuss your compression
springs requirement.
