Joel JS
20th January 2017, 03:24 PM
Hello to all,
I am having difficulty on understanding root cause of splay with a Polycarbonate job. (machine is 1000 tons, recommended heat profile 510 to 550 in the rear, 550 to 590 front.... using 20% of the machine shot capacity)
Job would start up after purging and would be pressure limited and only fill 95% of the part. As the material heated up, viscosity lowered, I was able to fill out the part and run good parts, for a limited time. I could make about 10 good parts, (with about 90 seconds cycle time.)
Then splay would appear on the bottom of the part, and at this time the material flowed even easier. As it ran the next few shots the splay would get a little worse, always at the bottom of the part, and the material continued to flow easier, so much so that I would stick the part in the mold if not careful. The splay was getting worse and making bad parts.
I would stop the press, purge out the machine, and restart. The exact same sequence of events occurred ...... pressure limited short parts, then 10 or 12 good parts....... then splay would start with increased "flow-ability" of material.
Since we were only using 20% of the barrel shot capacity, and was able to make good parts I believed I was fighting a material residence issue. I was running 550F in the rear, and 575F in the front. I lowered the rear barrel heats to 530, allowed to cool, and purged again.
Restarted, and I got the exact same results. Sample was stopped.
Afterwards we found the dryer air cone had fallen out of place, so wondering if wet material was the culprit? I kick myself for not checking the moisture content, but at the time thought I was fighting a material residence issue.
(Job does have a hot manifold, it appeared to be working fine. No external signs of any issues.)
So, my question is ....... was I fighting wet material, or is the material residence time too long? We don't have a lot of machine options and are wondering if it is worth another try in the same machine.
Thx - Joel
I am having difficulty on understanding root cause of splay with a Polycarbonate job. (machine is 1000 tons, recommended heat profile 510 to 550 in the rear, 550 to 590 front.... using 20% of the machine shot capacity)
Job would start up after purging and would be pressure limited and only fill 95% of the part. As the material heated up, viscosity lowered, I was able to fill out the part and run good parts, for a limited time. I could make about 10 good parts, (with about 90 seconds cycle time.)
Then splay would appear on the bottom of the part, and at this time the material flowed even easier. As it ran the next few shots the splay would get a little worse, always at the bottom of the part, and the material continued to flow easier, so much so that I would stick the part in the mold if not careful. The splay was getting worse and making bad parts.
I would stop the press, purge out the machine, and restart. The exact same sequence of events occurred ...... pressure limited short parts, then 10 or 12 good parts....... then splay would start with increased "flow-ability" of material.
Since we were only using 20% of the barrel shot capacity, and was able to make good parts I believed I was fighting a material residence issue. I was running 550F in the rear, and 575F in the front. I lowered the rear barrel heats to 530, allowed to cool, and purged again.
Restarted, and I got the exact same results. Sample was stopped.
Afterwards we found the dryer air cone had fallen out of place, so wondering if wet material was the culprit? I kick myself for not checking the moisture content, but at the time thought I was fighting a material residence issue.
(Job does have a hot manifold, it appeared to be working fine. No external signs of any issues.)
So, my question is ....... was I fighting wet material, or is the material residence time too long? We don't have a lot of machine options and are wondering if it is worth another try in the same machine.
Thx - Joel