Submitted: February, 2005

We are in the process of upgrading our water flow capabilities in our plant, to reduce cycle times. We found out that by increasing water flow in our existing molds we can still get cycle reductions because the molds could use more water than what we were giving them. We were able to double the water flow in the bottle neck circuit to achieve a minimum of 10% cycle reduction.

Recently, a consultant visited us and this topic came up. He was very clear when stating that decreasing water temp would give us more cycle savings than increasing water flow into the mold.

My plant experience has been that by leaving everything equal, if you have to choose between lowering the water temp and increasing the water flow into the mold, the latter would give the better results. The consultant also stated that increasing flow is a common misconception in the industry. We presently run 53°F water and he claims that by running with the original water flow rate and dropping the temperature down to 48°F the results would be better. We will carry out the experiment and find out.

Leaving everything else equal what is best, increasing flow or lowering the water temperature? Is it possible that he is right and that the rest of the industry is wrong?

You asked what was better: more water or cold water.

When adding more GPM's to the mold, at some point the rate of removing heat will diminish as turbulent flow is reduced. One would tend to think colder water may at some point do the same. Filling the cavities when extremely cold can sometimes be more difficult. Reducing the cycle may affect the part dimensions and attribute quality. All of this must be considered.

Performing a DOE as you mention will provide data to support which is more effective. It will be very important to capture accurate water flow and temperature along with as-is Metrology on the parts before starting.

From there the real question is cost. Which is more economical?