Selection and description of return spring

Usually in the mold, the spring is mainly used as the auxiliary power of the ejector plate, row position and other movable components, and is not allowed to be used alone. The spring used in the mold has been standardized. The spring commonly used in the mold is the light load blue spring. If the mold is large and the number of ejector pins is large, the heavy load spring must be considered
(1) Preloading ratio
The ratio of spring preload to free length is generally 10-15% of the free length of the spring. The larger the diameter of the spring is, the smaller the preload ratio is, and the smaller the diameter is, the larger the preload ratio is, The preload applied to the ejector plate is not affected by the spring free length. The preload is generally 10.0-15.0 mm
(2) Compression ratio
Generally, the compression ratio is less than 30% – 40%. The smaller the compression ratio, the longer the service life
(3) Spring distribution should be symmetrical as far as possible
(4) The size of spring diameter depends on the space that can be used and the pre pressure required by the die
Several explanations:
(1) The rectangular blue spring is installed beside the compound rod. The inner hole of the rectangular blue spring is small, so it is not suitable to cover on the reset pin. A straight edge (column tube position) should be added inside the longer spring to prevent spring deformation
(2) When the shape of die is narrow and long (the length is about twice the width), the number of spring yellow should be increased by two and installed in the middle of the mold
(3) The spring position should be symmetrical as far as possible. The spring diameter specification should be determined according to the space available for the mold and the pre pressure required by the mold, and the specification with larger diameter should be selected as far as possible
The free length of the spring shall be determined according to the compression ratio and the amount of compression required
L = (B + preload) / compression ratio
B-length of spring after preloading, B = l-preloading amount, usually 10-15mm
Note: the return spring must be embedded in the movable formwork or supporting plate by 15-20 mm. If the calculated length is less than this length, the length shall prevail; if the calculated length is greater than this length, the calculated length shall prevail