Basic Principles of Riser Sleeve Design

Casting riser sleeves are primarily used on cast steel parts. They are only used on a few thick, large gray cast iron and ductile iron parts. During the cooling and solidification process of molten metal, the volume shrinks. The volume shrinkage of a casting is approximately three times its linear shrinkage. Therefore, the volume shrinkage of cast steel is usually considered to be 3-6%, and that of gray cast iron is 2-3%. However, due to the graphitization expansion during solidification of gray cast iron and ductile iron, some volume shrinkage can be offset. Therefore, if the wall thickness is uniform and the mold is highly compact, riser sleeves are usually not required. If the volume shrinkage of the casting is not compensated, shrinkage cavities, depressions, or porosity will form on or inside the casting. In severe cases, this often leads to the scrapping of the casting.

The principle for calculating riser sleeve dimensions is to first calculate how much molten metal needs to be compensated for. This portion of molten metal is usually assumed to be a sphere, and its diameter (denoted as d₀) is calculated for riser sleeve calculation. The effective feeding distance for riser sleeve-fed castings is defined by a certain range, denoted as L. For plate-shaped parts with a thickness of h, L is typically 3~5h. For rod-shaped parts, L = (25~30)√h, where h is the casting thickness.

Basic Calculation Method for Riser Sleeve Size

The most common method is: Riser sleeve diameter D = d₀ + h

The reason is that it is assumed the riser sleeve and the casting solidify at the same rate. The solidification process proceeds from the two surfaces of the casting inwards. When the casting is completely solidified, the riser sleeve has solidified to the same thickness. At this point, a hollow shrinkage cavity remains in the middle, with a volume exactly equal to the volume of the feeding sphere. This portion of molten metal feeds into the casting during solidification.

When a hot spot exists in the casting, h can be replaced with the diameter T of the hot spot. That is: D = d₀ + T

Another important part of riser sleeve design is the riser sleeve neck. The riser sleeve neck is the connection channel between the riser sleeve and the casting; the molten metal in the riser sleeve is fed into the casting through the riser sleeve neck. Therefore, there are requirements for the cross-section of the riser sleeve neck. Typically, the diameter of the riser sleeve neck is taken as dⱼ = (0.6~0.8)T.

The riser sleeve height H = (1.5~2.5)D. The height H should also be higher than the height of the area requiring feeding; otherwise, it becomes reverse feeding, where the casting feeds the riser sleeve, which must be avoided.

Other Calculation Methods

A commonly used empirical calculation method is to directly multiply the diameter of the hot spot circle by a coefficient without calculating the amount of molten metal requiring feeding. For example:

Simple casting: D = (1.05~1.15)T. Simple shape, relatively concentrated hot spots.

Complex casting: D = (1.40~1.80)T. Complex shape, for example, with many ribs connecting to the rest of the casting.

Intermediate type: D = (1.15~1.40)T, falling between the above two.

Casting production conditions vary greatly, with too many factors involved, making all calculation formulas approximate and conditional. Often, a single formula may not be applicable to all situations. Therefore, formulas often include coefficients with a wide range of values for users to choose based on their specific circumstances.

Choose Xinda, for Precision Casting Quality

Xinda has been deeply involved in the casting industry for many years, leveraging its profound technical expertise and advanced engineering capabilities to provide customers with customized high-quality casting solutions. Our professional team is proficient in the core technologies of riser sleeve design and dimensional calculation, enabling us to accurately optimize riser sleeve parameters for castings of different materials such as cast steel, gray cast iron, and ductile iron, minimizing defects such as shrinkage cavities and porosity, ensuring that every casting meets stringent quality standards. From riser sleeve optimization for complex and thick parts to one-stop casting design and production services, Xinda is always your trusted partner for improving production efficiency, controlling costs, and ensuring product reliability.