In general most feed throat temps are from 95 deg (f) to no more than 130 deg (f). And if you stay within those temperatures it will not bother the drying of the material. We run radel which its melt temperatures go up 640 deg (f) and we ran the feed throat at 120 deg (f).
There are some injection machines that have specific feed throat temperature specs. Husky PET machines are an example. However most injection machines do not. There are several things to avoid. Do not get any part of the feed throat cool enough to cause condensation. Do not let the feed throat get hot enough to let the material soften and clump. Outside these cautions you will usually find little effect of the injection molding process from FT temperature.
The throat temperature should be the same as the dryer temperature. This will ensure you will not get any bridging of the material in the throat. If you do not have hot, dry air to the hopper on top of the throat. You can also get wet material depending on your throughput. I have used hot oil to the throat on materials such as Ultem, PEEK, etc.
I have reviewed lab data on the effect of feed throat temperature on molded parts, there is a direct correlation! You need to keep the feed throat hot enough so that it will never condensate and not too hot to clump. The reason Husky and the high end injection molding machine makers put tight controls on this is because they know it can affect quality. How many machine have you seen where the FT water solenoid valve gets stuck, so they just remove it.
