A few weeks ago, my colleague Ben wrote about how EX Grade can be used to facilitate painless screw pulls. But while EX gets a lot over coverage for it's performance during screw pulls, I find it to be as-if-not-more useful in preventing screw pulls. I had a customer contact me a couple of Mondays ago in a bit of a panic. They are custom injection molding shop that runs a lot of different materials. They had inadvertently left a glass filled nylon in the barrel of the injection unit over the entire weekend. With the heats on. Not good.
They were able to get the screw turning and had ran some of their normal purge compound through but could not get most of the degraded material purged out. The screw was wrapped at the feed-throat. They had taken the nozzle body off to make it a little easier to get the charred and degraded material moving through the screw but were struggling. The screw still seemed to be a lost cause.
The Process Engineer I was working with was at his wits' end and was looking for some help. He wanted to know if there was anything they could try before giving up and having maintenance pull the screw. I told him about EX Grade and that his maintenance department should have some in stock. EX grade is currently used in their preventative maintenance program. They pull screws annually to inspect and check for wear. Before they pull the screw, maintenance always purges with our EX grade to make cleanup easier. (EX used before a screw pull will allow you to peel any remaining material off the screw without needing wire brushes or grinders).
I know from past experiences, if the EX Grade cannot clean the screw, nothing will, and you will have to pull it out. EX is the strongest cleaner on the market, so we decided to try to purge first. I asked the PE to contact his maintenance department and see if they had any EX in inventory. Good news! They had a little more than half of a 50-pound bag. They started feeding the EX through the feed-throat. It slowly started cleaning the wrapped portion of the screw. Making its way down the barrel, it finally started coming out the front of the screw. It dragged huge chunks of dirt-like degradation as it went. It slowly improved from a muddy looking purge to a nice bright white. He was thrilled!
A screw pull was diverted. The machine was put back into production. The process technicians were re-trained to the shut-down procedure. Life is good again.
The PE ordered a bag of EX to keep under his desk. Not for everyday purging, but for those unexpected but inevitable moments when something has gone wrong.
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