Mold debugging & testing
Case: Having designed and built the mold for PSU, designed built for thermal expansion, etc is there an alternate resin any of you have known a mold to debug with that would not require the high heats, braided hoses or oil? I’m contemplating using PC. The goal of this debug is to validate mold mechanics and the make sure all functions correctly before going to the specified resin and services (oil).
It is very common to use PP to test the function of a mould re slide movements venting flash etc. before using the more expensive and more demanding resins. PP is also used at the end of the run to purge along with a suitable purging compound and ensure there are no deposits of the high temperature resin left in the system as can play havoc with a hot runner mold being hung later. There are also wax injection systems available for testing moulds on the bench. I haven’t used one for a long time now. Or the old trick of burning a candle under the sprue. The resulting soot deposits inside the mold can tell you a lot. i.e. mismatch and flash.
If all you are interested in is if the mechanics work, then dry cycling without plastic will tell you that. If you are looking for something more such as obvious mismatch, venting, gate function, fill problems, etc. Then PC is a pretty good choice if run with cooling temps near the top end of what is available with water cooling, that is 195 – 200°F. PC molding behavior is similar to PSU especially in the low MFI grades.
I do want to re-iterate the caution that if you do not test the mold at the intended run temperatures, you run the risk of seizing the mechanical aspects of the mold when you do run it hot.