a manufacturer of hot runner manifold systems and controllers—agrees that there has been a resurgence in the use of aluminum tooling in recent months. We have had increased inquiries as to our experience and products offered for aluminum tooling.. This is a cycle we (along with our industry) have seen before.

It seems about a decade ago there was a similar buzz in our industry. The major differences today are that new aluminum grades have increased performance and reliability, faster machines and software are available for designing and producing the molds, and a better understanding of the requirements of aluminum tooling and knowing the production goals give mold manufacturers a better direction.

When you combine the above with early involvement (mold design phase) from the manifold supplier and moldmaker, the mold can be designed once to use standard manifold components that are typically lower in cost without sacrificing performance,This is also the preferred method for all mold builds. Unfortunately it’s not the industry standard—yet.

Currently when molding with aluminum tooling the most common solution for a runner system is the cold runner,,The reasons vary but the most common are cost and the general opinion ‘simple (overall design) is always better,With aluminum tooling having lower volumes in most cases, it becomes harder to justify the added cost of a hot runner manifold system.
However, hot runner systems have a number of benefits that are not realized in most cases,

The general issues are: higher cost, nozzle tips freezing off completely (stopping flow) and damage to the aluminum tooling from installation and thermal expansion. In most cases, the added value of having a similar process in prototype and production can be significant but not considered.

To offset the cost of a hot runner manifold system, early communication and planning can allow the hot runner system to be recycled from the aluminum (prototype) tool into steel (production) tooling. Recycling prototype manifolds into production is possible as long as drop locations don’t change. Using valve gates increases cost but opens up the processing window and can reduce cycle times.

Using a nozzle sleeve or cooling bushing as a thermal isolation barrier is one method to prevent nozzle tips from freezing off, Oles adds . The sleeve isolates the colder aluminum from the increased temperatures of the nozzle tip,

This creates the ‘layer’ of thermal isolation so the tip can flow and then freeze off completing the cycle and starting over again. Another variation of this application is to use the ‘cooling’ bushing to ‘warm or heat’ the gate point instead of cooling it.

By warming the gate point area it decreases the delta in temperature from the bushing to the nozzle tip. The result is easier and consistent start-ups for molding.
With standard equipment found in most injection molding plants, you can warm water to approximately 160oF, This requires a separate circuit, and we don’t recommend looping more than three bushing onto one circuit (depending on shot volume and material set temperatures).

The last thing you want to see is someone climbing into the press and taking a torch to the gate point in the aluminum tool because the gate has frozen off. Using aluminum increases the thermal demands on the nozzle tip area. Aluminum displaces the heat at the point of contact with the nozzle tip quicker than steel requiring the nozzle to heat cycle more often.

An additional benefit from the nozzle sleeve or cooling bushing is a replaceable gate point. Replacement would take the place of reworking the aluminum mold in the case of damage allowing leakage,When using aluminum damage can occur during the assembly process (of a cold sprue or hot runner system) because the aluminum has a lower hardness than the components being installed.

Sharp edges from components installed are the likely areas damage can and will occur if not handled with great caution. When using a nozzle sleeve or cooling bushing, once installed it does not need to be removed. The nozzle interfaces with the sleeve rather than the parent aluminum. The result: preventing damage to the aluminum tooling.