Processing in a part today and ran across something that didn't make sense. It is a small encoder cover running in a 75 ton electric Sumitomo. It has a heated sprue in an H-Frame carrier. Mold is sub-gated. Part is 20% glass filled PC. I got the part to 98% full with hold pressure and time set to zero. Went to add hold time and pressure on to finish up a process study and the part came out short. Thought it was weird. So I let it run some more parts thinking it might be an oddity. Well they were still short. Thought well maybe I forgot to add time to my recovery delay. Nope 7 seconds of delay time. Ran them without hold time and pressure and back to 98% full. Ran the recovery delay up to 25 seconds and it still did the same thing. Part with zero hold time and pressure comes out to 7.54 grams and holds a cushion of .315" (which is the VPT point). The part with 5 seconds of hold time and zero hold pressure weighs in at 6.49 grams and the cushion is .295". All other process parameters are the same. Seems a little weird to me. I emailed Sumitomo and hope they answer soon, but track record of them answering back in a timely manner isn't good so I figured I would see if anyone else had a good idea on this one.
Reply With Quote