Too often, plastic processing companies only use purging compounds when absolutely necessary. But waiting until the last minute to purge your machines often leads to unexpected production delays and decreased profitability.
Adopting proactive, preventive purging procedures not only saves you from a considerable amount of downtime, but also helps protect your injection molding machines from carbonization and color streaking.
The key is to not let your machines reach the point when a purging compound isn’t sufficient for a thorough cleaning. When that happens, a manual screw pull is necessary, which results in hours of additional, often unplanned, downtime. A preventive purging program helps reduce production downtime going forward.
Taking a proactive (rather than a reactive) approach to cleaning your machines has many benefits, including:
- Preventing the buildup of contaminants such as color and carbon
- Reducing excessive purging time and material consumption at the end of a production run
- Preventing unnecessary screw pulls (for mandatory screw pulls, preventive measures reduce the time and effort required to pull and manually clean the screw)
- Minimal scrap and rejection rates during job changes, as well as production
Here are two ways to protect your machines from carbonization:
1. Purge Periodically
To ensure the quickest, most efficient changeovers, it’s important to purge your machines on a periodic basis. The frequency at which you do this depends on the materials you’re processing, but a general guideline is to purge every two to three days. For production runs lasting weeks or months, purge once every week or two weeks instead.
It’s also important to rely on data, such as percent defects, to determine when you should purge your machines. Periodic, preventive purging helps protect your machines from carbonization and removes deposits that tend to build up over time.
Since carbon is extremely hard to clean due to its chemical attraction to metal, a stronger scrubber is needed to reduce carbonization.
Glass-filled purging compounds are perfect for thermoplastic injection molding machines because they’re designed to provide superior scrubbing of carbon and color deposits while leaving behind less residue.
2. Seal Machine And Hot Runners At Shutdown
One of the best preventive measures for dealing with contamination is to seal the screw and barrel with a thermally stable purging compound before extended machine shutdowns occur.
Residual polymer degradation can delay machine startup and create unnecessary material waste. The sealing process displaces the heat-sensitive production material and protects the surfaces of the screw and barrel from oxidation.
When the barrel is sealed and the heat is turned off, the purge that is left in the screw and barrel peels away from the screw as it cools, pulling carbon away. When the barrel heats are brought back up and the sealant material is purged out, the screw and barrel are clean and ready for production, which improves efficiency and machine utilization at startup.
To protect your injection molding machine from carbonization, you must take a preventive approach to your purging procedures. Failing to do so will likely lead to machine downtime, increased scrap rates and decreased productivity. Instead of killing your profitability, take proactive measures to maximize efficiency at your facility.
Learn more about how purging compounds impact your production efficiency.