How to increase the pressure of compression springs under the same external dimensions

In order to ensure that the "compression spring external dimensions unchanged" in the case of increasing pressure, the best way is to enhance the hardness of the compression spring products, can be used to tempering (control the time and temperature of tempering), that is, often referred to as the burning of the spring (the above viewpoints originated from: Dongguan City, Lee, Manager of the creation of Precision Machinery Company, Limited, is for reference only).