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Major issues with what seems like splay marks. Material way in spec in terms of moisture. When purging excess steam comes out of the feed - no manifold leaks present. Any ideas??
This is seen across 3 machines - 3 tools on all same material. 2 drop valve gate.
Kayl33
A little more information would be helpful, What are your drying temperatures? What are the barrel temperatures settings on the machine and what are the temperature settings for your manifold and gate drops. When purging excess steam comes out of feed clearly sounds like a moisture issue which would be common across any number of machines, which prompts me to ask what type of dryer are you using? A hot air dryer or one with desiccant? What level of moisture are you seeing. Sorry for all the questions, But from what you have described it sounds like moisture is the problem.
Course, yes. Drying temp is 85c dehumidifier dryer. Barrel temps are at 275-295 melt is around 280c all within material data sheet. Moisture check on material checked pre moulding sub 0.18 again within material spec. HR set to 290 6 zones. It can be inconsistent it terms of the splays/silver streaks appearing. Very random. Appreciate the reply!!!!!
Hi,
What is dwell time, tool temperature, do you have condensation or tool leaking....?
"Steam" can be from stabilising component also. How many % of cylinder volume you inject and what is cycle time?
You can test, "just for fun" longer drying (6-8h), higher drying temperature (up to 100C), increase hot air throughput. Datasheet is just for guideline, often is wrong when you have additional additives inside.
Where is possition of splay marks (close to gate or obsticle)?
Hi,
No leaks. Potentially condensation. Tool temp it 60c both FH - MH. Residence time is approx 5mins across barrels of 105mm and 80mm. Yes, already tried the increased temp and time. It’s so inconsistent as it’s running again and ok. “Splay” appear across the part not always as close to the gate though.
Thanks
You can try to reduce residence time in the material hopper or increase temperature at the material feed (flange). One more option is to increase tool temperature (im working with PA 66 but with fire retardant on 90C).
Please check also diameter of machine nozzle and tool inlet. sometimes the splays can come from big shear, try to reduce injection speed. Please check also front of melt on short shot parts. If you will have a "bubles" on the front of melt, please check, if backpressure is working on the machine. Backpressure setting value must change plastication time. If not, please check servo valve (replace it) or control card.
My experience: PA+GF,the barrel and nozzle temperature from the material supplier is 280 degree.the surface is awful,while the temperature decrease t0 235-240 degree,all is ok.
also many times,my ABS injection with slays on surface,and lower temperature solve this.
So my conclution is to try the low temperature as far as possible.
Greetings;
I was taught many years ago that there were two main causes of splay, heat and moisture. The old school way to tell is you could smell the heat splay and not moisture. Grab a part right out of the mold and smell the splay. I have found it to be true.
Most of the advice above will solve your heat source.
Scott
So your 'splay', should be the UV stabilizer being damaged or consumed in the barrel due to the high barrel temps, mold temps, and residence time. I've seen this many times when running UV or FR resins. As long as you can fill the parts, you need to start working the temperatures down until the issue goes away. Either that or run a reverse barrel heat profile. Lastly, get a press with a smaller screw diameter.
Rick