Choosing the right manifold

Manifolds are common auxiliaries used in a plastic injection molding shop. They are key components in mold water cooling circuits. Their primary purpose is to route water from the chiller or cooling tower to the water passages that are used to cool the mold cavity. The two major types of manifolds are water trees and engineered manifolds.

Water trees manifolds are dedicated to a specific molding machine and consist of a long pipe with tee’s elbows and fittings. Hoses run from the water tree to the cooling ports in the mold. These hoses can become a safety hazard and the time it takes to attach each line to the cooling ports is not an efficient use of time. This type manifold is not practical when more than two or three cooling ports are required.

Engineered Manifolds are designed to be used for water distribution on a specific mold. These manifolds are usually made of aluminum, brass, or stainless steel. Engineered manifolds can be mounted directly to the mold eliminating the need for several long hoses running from the chiller. A engineered manifold can be mounted directly to the mold and a single hose is used to transfer the chiller water to the mold and coolant lines are neatly run to dedicated ports. With only one main supply line and all the coolant lines dedicated the engineered manifold makes for a safer environment and greatly reduces downtime needed for the changeover of the mold.

The material used for a manifold is a very important part of the decision making process. The wrong material can be detrimental to the success of a project. Let’s take look at the three major material used in the manufacturing of manifolds.

Aluminum: A lot of people use aluminum because of its relatively low cost and is easily machined. Some major disadvantages of aluminum are that brass and aluminum are dissimilar metals. When brass fittings are used, galvanic corrosion can erode the threads that create leaks and an unsafe environment. Many plants have acidic water and the harsh water can also erode aluminum. Because aluminum is soft it is very easy to cross thread when installing fittings, resulting in damage to the manifold and costly repair.

Brass: Brass manifolds are not affected by galvanic corrosion but are very expensive. They are cost prohibitive unless you have a small project with low flow and very few ports.

Stainless Steel: Many people think of stainless steel as a cost prohibitive alterative to aluminum but in reality stainless steel manifolds are about the same cost as aluminum. Stainless steel manifold will corrode when exposed to harsh water environments and are not affected by galvanic corrosion when using dissimilar metals. This makes stainless steel an excellent alternative to aluminum