5 Tips for a Perfect Shutdown in Extrusion Blow Molding

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Extrusion Blow Molding

While many of our blogs discuss Injection Molding, Extrusion Blow Molding (EBM) facilities also experience their share of processing challenges. They, too, are not immune to contamination issues including carbon specks. 

In fact, from  my interactions with EBM plants over the years, their tussles seem to be on a whole different scale, and proportionally, even more dramatic compared to Injection Molding plants. Most of these shops experience carbon specks on start-ups from poor weekend shutdowns. They tend to have even greater machine downtime and higher amounts of scrapped, un-sellable/unusable parts.

I recently managed a cost-savings purging project with a Manufacturing Engineering Supervisor at Midwestern EBM plant. They were blow molding large, bladder-type parts out of translucent Polyurethane polymer (processed at low temperatures) for both residential and commercial applications. They were chronically struggling with random carbon specks throughout their parts on starts ups from weekend shutdowns.

Depending on the production demand, they were shutting down their machine and restarting it multiple times per month. Their goal was to reduce machine downtime and lower the quantity of scrapped pounds on start-ups.

Based on the nature of the application and low processing temperatures, I recommend these 5 tips for perfect shutdowns in Extrusion Blow Molding:


1.) Select an Appropriate Purging Compound for Sealing
For this application I recommended our excellent shutdown/sealing E Grade purging compound (low temperature/low residue).

2.) Purge the Machine Prior to Shutdown
Use the selected grade to thoroughly clean and remove the Polyurethane from the line before shutting it down for the weekend.

3.) Leave a full-Barrel Capacity of Purge Inside the Machine

4.) Turn off the Heats

5.) Let the Purging Compound Reside in the Machine for the Duration of the Shutdown
This neutralizes & stabilizes the machine preventing oxygen from entering the system.

They conducted 4 separate trials with E Grade purging compound over a 2-month trial period, comparing it to a well-respected competitor. After these trials were conducted, the Manufacturing Engineering Supervisor delivered us a detailed data-driven report, yielding great results.

Using the average of these trials, his report indicated that they had about 180 minutes and 215 lbs worth of scrapped parts on start-ups when using our competitor.  After switching to E Grade, they saw improvements and dropped down to 130 minutes and 170 lbs worth of scrapped parts.  Ultimately, they saved in the neighborhood $4,640 for this one application for each machine in their plant.

Should you like to learn more or have any questions, please don’t hesitate to contact me at bmoore@asaclean.com.

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Topics: Troubleshooting, color contamination, carbon specs, carbon contamination, shutdown and sealing, preventative purging, value added, Cost-per-purge, cost-per-pound, blow molding, extrusion blow molding, shutdown

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