Insufficient resin color changes may lead to significant production inefficiencies such as wasted, contaminated products and increased scrap rates, and certainly, unnecessarily long downtime between production runs. Operators taking purging shortcuts and “autopurging” may be saving time today, but extended machine downtime tomorrow is far more costly.
You know the importance of uptime and its impact on your bottom line. Learn these three fundamental tips to maintain your efficiency and maximize your profitability.
Periodical purging is your greatest defense against unnecessary downtime.
In order to prevent carbon from developing in your barrels and contaminating your products, you must use the right purging compounds and procedures for your machines. Once carbon is developed, it can’t be removed without a screw pull and manual cleaning, which requires much more significant machine downtime than proper purging.
There are many variables that go into what purging compound is best, including the resin you use, their processing temperatures and more. Using the most appropriate purging compound is critical to mitigating the risk of color and carbon contamination.
Of course, using the right purging compound is of little benefit if you’re not using the right amount, implementing the maximum safe screw speed and backpressure and keeping the screw completely forward while purging, when using a mechanical type purging compound.
Make proper purging procedures a priority to cut down on the unnecessary downtime that’s hurting your bottom line.
With an appropriate grade of heat-stable purging compound, seal your screw and barrel weekly to prevent oxidation from developing.
Typically done upon shutting down for the weekend, sealing the screw and barrel ensures that heat-sensitive resin left from your last production is displaced by a purging compound to prevent oxygen from entering the barrel. If your screw and barrel are not sealed properly, this oxygen leads to carbonization (how quickly depends on the resin).
Additionally, molders should run another barrel of purge on Monday mornings, before starting a production run.
Taking such preventative measures decreases the need for screw pulls and additional machine downtime.
Using a glass-filled grade purging compound – EX grade, for example – is a much more efficient way to clean thermoplastic injection molding machines and extruders than screw pulls. It requires significantly less downtime, and because of the strength of this grade’s glass-filled composition, it does a tremendous job of scrubbing carbon and color deposits.
Unlike a screw pull, which can take anywhere from two to eight hours, running one or two barrel capacities of a glass-filled purging compound may reduce your machine downtime to 20 minutes.
By taking a preventative approach to purging – from sealing your screw and barrel to running periodic purges and using the most suitable purging compound – you maximize your uptime, maintain your efficiency and increase profitability.
Learn how to reduce machine downtime with five quick purging compound tips for your injection molding application.