 On average, Mold Craft gains three hours of uptime on every changeover of its 200-ton Lester and its two 150-ton Newburys.  Three dozen lures in different colors, and very variable customer orders, mean a lot of changeovers. |
Time and money spent during multiple mold and material changes are reduced dramatically when a purging compound is added to the mix.
Take a look at those fishing lures (see photo), and if you're a fisherman, stop dreaming—this is about molding plastics. In one of our Basic Elements articles (March 2004 IMM, immnet.com/articles/2004/March/2338), we talked a lot about the why and how of purging with compounds vs. materials.
Mold Craft Products (Pompano Beach, FL) found out for themselves what they could save in terms of hard cash, and what they could gain in terms of increased uptime.
Fish or Cut Bait
Mold Craft makes three dozen lures, and the amount of color diversity is obvious. Production of the flexible PVC lures is done with two 150-ton Newburys and a 200-ton Lester. Process temperatures range from 400ºF in the front zones to 280ºF in the rear.
Three dozen products running on three machines and responding to variations in orders means mold changes, without a doubt. And even more to the point, color changes. Purging is a must, especially when light color follows dark, or to remove powdered pigments to run dispersions.
Purging frequency varies with production and order variances, as you would expect, plus Mold Craft purges each machine about once a week as part of its preventive maintenance program. It had been using polyethylene mixed with liquid additives to do the purging.
When Mold Craft took a calculator to the purging task, it found that cost-per-purge was $445. This worked out to $66,750 annually. Besides that, downtime caused by purging could reach 285 minutes, nearly 5 hours. The in-house purging material used varied from 10-100 lb, with the average around 40 lb.
Compound Savings
Mold Craft decided to try purpose-made purging compound—two of them, in fact, both from Shuman Plastics' Dyna-Purge family. Dyna-Purge M is made to purge a variety of resins from barrels and screws across a temperature range of 350-600ºF. Dyna-Purge V is made specifically for rigid and flexible PVC at temperatures of 320-400°F.
The move was a positive one. The maximum cost to purge decreased by 44%. The annual savings from that was $29,950. The time to purge decreased by a whopping 67%, on average knocking 3 hours off the procedure.
That also meant 3 hours added to production time—but you knew that. Mold Craft also found that, besides being faster, the Dyna-Purge compounds cleaned more thoroughly. There is far less resin wasted on restart waiting for clean parts.
Mold Craft is no longer using large amounts of in-house materials or regrind for purging. Instead, it's used to make lures. Might even be finding a bit of time to go fishing.
Dyna-Purge, Shuman Plastics Inc.
Buffalo, NY
(716) 685-2121
[email protected]
www.dynapurge.com
Mold Craft Products Inc.
Pompano Beach, FL
(954) 785-4650
www.moldcraftfishingproducts.com
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