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Need more production time? Check your dryer

October 1, 2005

6 Min Read
Need more production time? Check your dryer

Three Maguire vacuum dryers replaced 12 hot-air systems. The fourth is for backup.

New drying tech means Yamauchi’s 22 50-ton Arburgs and four 10-ton Nisseis are productive an additional 192 hr/year.

Maguire's vaccuum drying system (See "How vacuum drying works", below).

A switch from hot-air dryers to vacuum drying gave this Belgian molder the expected energy savings, plus 192 hours of added production annually, plus lower scrap and reject rates, plus . . . well, read on.Although resin dryers are called “ancillary” or “auxiliary” equipment, Yamauchi Corp. NV (Hasselt, Belgium) has found a primary role for them in its business strategy. Changing from traditional hot-air dryers to newer vacuum drying helped with four of the company’s bigger challenges.Like other electrical/electronic (E/E) component suppliers, Yamauchi faces intense price competition; pressure to cut costs/raise productivity; stringent customer requirements for quality and consistency; and high energy costs for the foreseeable future.Lower Energy Cost, and . . .The most obvious benefit of the vacuum dryer addresses the energy cost challenge. Compared with a similarly sized hot-air dryer, the vacuum dryer requires 80% less energy to properly dry resin, according to its manufacturer, Maguire. Let’s back up to the productivity challenge. The vacuum dryers take only about one-sixth of the time needed by the hot-air types to dry the resin properly. The other five-sixths are available for molding, as if someone added a few hours to the day. At Yamauchi, that little miracle happens every Monday. (See box, below)The company has gained 192 hours per year of added production by reducing the Monday morning “cold startup” time of its production lines (see Figures 1 and 2, opposite). Yamauchi technical manager Rudi Vermeulen says these hours translate to about e57,600 ($71,600) in additional deliverable product every year.There’s help with the quality and consistency challenge, too. The shorter residence time and greater drying efficiency of the vacuum dryers result in fewer product defects and less scrap.Yamauchi NV is a subsidiary of Japan-based Yamauchi Corp., a worldwide manufacturer of E/E components and much more. It uses 26 of the 40 molding machines in the Hasselt plant to mold polyamide 66 into tiny safety caps for AA and AAA batteries.The company had been using 12 hot-air dryers to dry the resin for those 26 presses. It replaced those dozen units with four Maguire LPD vacuum dryers, three of which are active and a fourth that’s a backup. Vermeulen says energy consumption was reduced by 92%, an annual savings of e15,700 ($19,500). But that doesn’t include an additional e5000 ($6225) Vermeulen estimates is saved by avoiding peak power penalties from the electrical utility. Nor does it include what he calls “dramatic” savings in the energy used to air-condition the plant to dissipate the heat generated by the hot-air dryers.Yamauchi’s analysis shows that switching from 12 hot-air to three (active) vacuum dryers in a PLC-controlled central conveying system saves e2970 ($3700) annually in preventive maintenance costs, and changing from bags to bulk resin containers provides annual savings of e11,800 ($14,700).More and Better OutputVermeulen says that the avoidance of overdrying and the lower residual moisture in the resin provided by the LPD dryers have another benefit. “Since we installed the LPD dryers, we have seen dramatically improved scrap rates through the elimination of bad parts caused by unpredictable drying.” Since the system is still fairly new, precise figures on scrap reduction, increased productivity, and less air conditioning are still being developed. The cost savings itemized above amount to e35,470 ($44,100) annually. Combined with the e57,600 ($71,600) in added production, total savings are e93,070 ($115,700). The investment in the new drying and feeding system was e100,000 ($124,300). Payback thus looks to be a bit more than a year, but actually will be less than a year when the other savings are calculated in.Vacuum-dried resin acquires less of a heat history than in hot-air dryers—typically 85% less exposure to elevated temperature. Speaking of the polyamides used by Yamauchi, Vermeulen says, “These materials are sensitive and can be stressed if subjected to drying temperatures for too long, resulting in burnt, brittle, and discolored parts. Since we installed the LPD dryers, we have seen dramatically improved scrap rates through the elimination of bad parts caused by unpredictable drying.”Vermeulen says the moisture level of the PA 66 arriving at the plant is typically around .3%. “With a hot-air dryer, we can reduce moisture content to the .10-.15% range. The LPD vacuum dryer can achieve levels of .05%.” But not zero. PA dried to a moisture level near zero becomes brittle, which creates serious defects in the finished product. A continuously running desiccant dryer will remove moisture until none is left, so prolonged drying caused by machine stoppage can be trouble.With a vacuum dryer, there is not full vacuum in the drying canister. It retains a thin atmosphere with a minimum of moisture. Moisture levels inside and outside the pellets eventually reach equilibrium at a tiny fraction of a percent, but still above the level where there is a risk of embrittlement.“Vacuum drying makes sense,” says Vermeulen. “It seems excessive to use desiccant beds and regeneration cycles to achieve dry polymer when heated material can simply be put under vacuum to arrive at the same result while saving on operating cost, space, and time.”

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