Hot runners are incredibly useful tools for producing consistent, high-quality parts. But hot runners also have lots of nuances that can lead to even the most seasoned processors overlooking production issues.
Many of these issues start with the manifold and areas where contamination can accumulate over time. These problems aren't easily visible. You may still be running perfect parts for a while while contamination builds up. Eventually, you will be dealing with a major contamination issue that seems like it popped up out of nowhere. The truth is, you just couldn't see it coming. This is one of the reasons we are so insistent on preventative purging being a part of every purge program.
I recently worked with a customer who struggled with this exact type of issue. A process engineer was running PA66 resin with a 50% fiber load. Sometimes they would pull the mold to clean it and other times they had to stop to change the mold. In both situations the same thing happened: the manifold was covered in resin and the next product could not be run. Their initial quick-fix was to try purging with HDPE. This might sound good in theory, but they found it was too runny and wasn't able to remove the previous resin. In fact, it created ongoing residue issues to go with the contamination.
I am all for being resourceful and for trying to fix things. But in this one area, a high-quality purging compound like Asaclean makes your life much easier without headaches or ongoing trial-and-error. After I visited this customer's plant and built them a purge program, they started having painless start-ups without scrap or downtime.
Here are 4 factors to consider if you want to avoid contamination issues with your hot runner:
1.) Difficulty of the Changeover
Look at whether you are processing colors or resins in an order that can make contamination more likely.
2.) Consider MFR
If the next resin isn't stiffer than your previous resin, you will have a tough time pushing out your last production resin.
3.) Manifold Design & Metrics
Understand your mold design and where issues might develop. Track your good parts and try to understand when you usually start running into issues.
4.) Preventative Purging
Start purging between production runs to take care of contamination that might be developing in the mold. Do not wait until you have an emergency situation to purge.
Think of it this way: you wouldn't drive your car until it broke down before you get your oil changed. Take care of your machine and your mold and you will be rewarded with better parts and fewer headaches.
Ready to reduce your production downtime to protect your profits? Learn more about how purging compounds and process efficiency work in tandem.