Blow Molders: Cut Changeovers and Scrap with Smarter Purging

Blow molding has long lagged behind other plastics processes when it comes to efficient purging. For many plants, color or material changeovers take anywhere from 8 to 24 hours. That kind of downtime drags down productivity, raises costs, and threatens delivery schedules. Fortunately, purging compounds have advanced significantly. Today’s purging solutions let blow molders save time, reduce scrap, and improve consistency without overhauling processes.

Why Traditional Methods Don’t Cut It

Many blow molding plants try to bridge the gap by using the next production resin or relying heavily on regrind. At first glance, this approach seems economical—but in practice it often leads to longer purge times, carryover of old color or residue, carbon buildup, and defects in finished parts. Over time, these “DIY” purges accumulate hidden costs in material waste, lost production, quality failures, and even emergency maintenance.

How Purging Compounds Make a Difference

Asaclean® offers several kinds of purging compounds that match real blow molding challenges. Chemical purges, mechanical grades, and purging concentrates are formulated to work in low flow zones like accumulator heads and flow lines. They can even hold the parison—helping during extrusion blow molding. These compounds allow you to run through heads without tearing machines apart. They clean screws and barrels thoroughly and make screw pulls easier when needed.

On average, blow molders who switch to Asaclean® purging compounds achieve about 64% savings in scrap and downtime in extrusion blow molding and about 61% in injection blow molding settings. That translates to tens or hundreds of thousands of dollars saved per year for many plants. ([turn0view0])

Best Practices for Blow Molding Purges

To get the best results, there are a few key practices to follow:

• Clean the extruder before the accumulator head. If the accumulator is dirty, color streaks or die lines are likely to appear.
• Use a “fill‑and‑push” strategy in the accumulator: fill to full capacity, push out 25%, then 50%, 75%, and finally 100%. This sequence helps flush residues from low flow zones.
• Apply something like a “Disco purge”—changing screw speed, stopping and starting screw rotation—to improve cleaning effectiveness in the internal screw surfaces.
• Select grades matched to your needs. For example, chemical grades or purging concentrates do better in low flow or barrier layer lines. Mechanical grades shine when you need strong scrubbing and high shear.
• Seal your machine with a shutdown‑approved grade during extended downtime. That helps prevent resin from degrading or oxygen from causing residue buildup inside hot runners or flow lines.

Real Savings, Real Impact

Numerous blow molding operations have made the switch and realized major improvements. One packaging plant reported that implementing the right Asaclean® grade cut their changeover time roughly in half, while also lowering scrap rates significantly. They saw cost reductions that made purging compounds well worth the investment. It wasn’t just about faster changeovers—it was about stability, fewer defects, and improved overall line efficiency.

Another customer said they saved over 60% in combined scrap and downtime costs by using purging compounds designed for their specific blows molding setup. These savings grew as the purge program rolled out to more lines in the plant.

Key Takeaways

Blow molders do not have to tolerate long changeovers, high scrap rates, or frequent defects. Purging compounds tailored to your process make a measurable difference. When the accumulator head, flow lines, screw, and barrel are cleaned properly, parts improve, changeovers are faster, and less material is wasted.

If changeover times of 8‑24 hours are hurting your budget, it is time to explore better purge programs. Asaclean® can help diagnose, recommend proper grades, train your teams, and deliver solutions that generate real savings.

If someone on your team isn’t yet convinced of the full value of purging, let us help. We’re happy to walk through the impact across your plant and show you how much more efficient, safer, and profitable things can be.