Injection Mold is a Heat Exchanger needs Cooling
As once explained to me years ago by one of my mentors in the plastic injection molding industry, an injection mold is nothing more than a "Heat Exchanger" which receives hot material, thus raising the mold temperature, and then, using cool liquid (Usually water) cools the injection mold to solidify the finished part to the point where it can be ejected without deformation. The science of thermal transfer is well known, however, in the typical design applications for water passages in a given tool, we are often faced with obstacles which prevent the optimum placement of water lines which result in less than adequate cooling conditions, and result in longer cooling cycle time required.
So, to measure both Input and Output water temperatures-------Do you expect to get temperatures that relate to the actual thermal changes that have a direct effect on your injection molded part? It is quite possible that these temperature deltas will only confuse the issue by thinking that these temperatures actually relate to the skin temperature of your part being molded, whereas cooling channels that are placed farther away from the actual part cavity due to mold design restrictions can confuse your expected results. The use of Thermocouples mounted in close proximity to the cavity surfaces can give you a better understanding of the thermal dynamics within the plastic injection mold, but you may find that specific locations in the injection mold do not give you the total picture of the temperatures that affect your entire part during the molding cycle.
Another point I'd like to share on injection mold cooling is the potential for reduced flow. I have traveled worldwide to many molding facilities in US, UK, Europe and China and found that it is quite common for cooling channels in injection molds to be clogged with various mineral deposits that accumulate over short periods of time. In some cases over a few weeks. This of course is a function of local water quality and whatever secondary filtering and/or water treatment that is at the injection molding factory. As you can imagine, the cleaning out of these mineral deposits can be very troublesome and typically requires the use of acids that are indeed risky to use on high quality precision tooling. It is a rather simple process to test for the increased % of flow restriction and may be a more valuable parameter to be used to verify cooling efficiency if indeed you are seeing variations in your parts that appear to be cooling related.
So, to measure both Input and Output water temperatures-------Do you expect to get temperatures that relate to the actual thermal changes that have a direct effect on your injection molded part? It is quite possible that these temperature deltas will only confuse the issue by thinking that these temperatures actually relate to the skin temperature of your part being molded, whereas cooling channels that are placed farther away from the actual part cavity due to mold design restrictions can confuse your expected results. The use of Thermocouples mounted in close proximity to the cavity surfaces can give you a better understanding of the thermal dynamics within the plastic injection mold, but you may find that specific locations in the injection mold do not give you the total picture of the temperatures that affect your entire part during the molding cycle.
Another point I'd like to share on injection mold cooling is the potential for reduced flow. I have traveled worldwide to many molding facilities in US, UK, Europe and China and found that it is quite common for cooling channels in injection molds to be clogged with various mineral deposits that accumulate over short periods of time. In some cases over a few weeks. This of course is a function of local water quality and whatever secondary filtering and/or water treatment that is at the injection molding factory. As you can imagine, the cleaning out of these mineral deposits can be very troublesome and typically requires the use of acids that are indeed risky to use on high quality precision tooling. It is a rather simple process to test for the increased % of flow restriction and may be a more valuable parameter to be used to verify cooling efficiency if indeed you are seeing variations in your parts that appear to be cooling related.