A medical molder just submitted this interesting question…
In our attempts to optimize, we are often asked by the tooling engineers to put different temps across sections of the tool. An example would be operating core temps at lower temps than the rest of the tool. We try to keep the tool at the recomended temp for the material instead. What would be your opinion on the correct method?
As a general rule, the best cooling is one which provides the most consistent part cooling. This means your entire part should cool down consistently.
You can often encounter many complications when you try to run different temperatures on the same half of the tool (unless the tool is relatively large such as automotive applications). The additional cooling in one zone will often cool the zone next to it. This can often result in erratic mold temperature fluctuations in the warm portions as it will often reduce the return coolant temperature causing the controller to act as though the mold is cooler than it really is. This can be done… but it requires extensive monitoring over coolant flows and coolant temperature coming in and out of the thermolator, and it is unlikely to get the result you desire.
In truth, areas in the part such as cores, bosses, and thick sections often need additional cooling. Ultimately, adjusting the temperatures in any specific region of the tool will have minimal affect on the transfer of heat.
The best way to provide additional cooling is through increased heat transfer. This can be done in many ways… (1) You can increase the coolant flow to a particular coolant line, which should be verified through the use of a flow meter (2) You can use more heat conductive steels or materials such as beryllium copper in the regions which need more cooling (3) You can additional cooling lines in the areas which require more cooling (4) You can also use more efficient cooling techniques such as water bubblers, baffles, and thermal pins.
When optimizing a process, always look at the entire process and experiment with different temperatures, speeds and pressures. The material suppliers recommendations are just that ‘recommendations’ and can be bypassed when necessary.