"More Forgiving" Method Expands Capabilities, Flexibility

Do you do a lot of plain cylindrical grinding and wonder whether to switch from hardwheels to belt grinding? Just look at the experience of Mirror Polishing and Plating Company (MP&P), Waterbury, CT and make up your own mind. All the new machines are by Ecotech.

Twenty hours a day, 5 days a week, the company grinds, polishes and plates industrial mill rolls - including challenging thin-wall rolls -- for the paper and film converting market. MP&P has earned such a reputation for quality, turnaround time and good prices that it is in a constant state of expansion - especially for thin-wall work. In response, the 40 man shop just started up one more cylindrical grinder, has another on order and plans to buy two more over the short term.

Moving to Belt Grinding "All the new equipment has belt grinding attachments," says Rich DuPont, vice president and general manager at MP&P. "Compared with traditional hardwheels, belt grinding is more forgiving and cost effective. With it, we turn out quality work more consistently, and with less skill dependency. Put another way, more of our people, of varying skill levels, can productively turn out quality work. With such flexibility, we balance the workload better and improve deliveries."

Mr. DuPont's experience can also give you peace of mind about the "quality issue" with some grinders coming in from China. Their last two belt head machines have been Ecotech model H-147s. Same machines, different nameplate. The one on order is the same machine but with a new brand name: Ecotech H-147/4000. The additional two machines will be Ecotech grinders as well.

"At first, we had the same misgivings about Chinese equipment as the next guy," says Mr. DuPont. "Support, spare parts, workmanship, we'd heard the horror stories. But we decided to take a closer look anyway. Frankly, at a 20-30% price differential vs. similar equipment, we couldn't afford not to."

Obviously, Mr. DuPont is glad they did. Taken together, the switch to belt grinding on the Ecotech machines has cut MP&P's grinding costs about 20%. It also opened up an emerging roll market, simplified operations, reduced risk and enhanced flexibility in scheduling.

After a year's running with the first Ecotech grinder and a couple of months with the second, the quality has been "excellent," Mr. DuPont states flatly. The machines come so fully equipped; MP&P starts them up the day they arrive. He also rates Ecotech's support outstanding. “Quality and 'over-the-pond' support may be legitimate issues in equipment coming from Mainland China,” he adds, “but not with Ecotech grinders."

Small Shop, Global Thinking

"Don’t get me wrong," says Mr. DuPont, "this isn't a commercial for a particular brand of machine. Rather it's a suggestion to not be controlled by rumors or prejudice when shopping for capital equipment. Look into each offering case by case. It's a big, competitive world out there. It offers even the small job shop a lot of sourcing options, provided you think globally and keep an open mind."

Belt Grinding Principles

In principle, belt grinding is much like belt sanding but a lot more accurate and sophisticated. An abrasive belt running on very precise rubber drums replaces the traditional hardwheel and wheelhead. Moreover, the rubber contact drum 'cushions' the operation, making the process more reliable and forgiving. There are fewer things to go wrong. And if something does go amiss because of a renegade grit or operator error, the damage is less serious and easier to fix.

Case In Point

A typical MP&P job is refurbishment of a 12-in. dia by 5-ft long chromium-plated steel pressure roll for a film laminator. Purpose: restore accuracy and mirror finish to the worn rolls. Hardness is Rc64. The process involves stripping off the chromium coating ("pre-grinding"), re-plating and finish grinding ("post-grinding.") Specs are +/-0.0002 in. on diameter and roundness. "Two tenths round and straight, as we say," adds Mr. DuPont. Spec on finish is 4Ra or better.

Pre- and post-grinding remove a total of 0.020 in. on diameter in a series of 0.0002-inch passes, all done with synthetic coolant. Pre-grinding takes about six hours and finish grinding slightly longer. Both involve one belt change, from rough to finish. Turnaround time for the job, including plating, is ten days or less.

Other jobs may involve plain steel or ceramic coated rolls ranging up to 25 in. dia by 160 in. long active lengths. On ceramic-coated rolls, the procedure is the same. MP&P is moving toward belt grinding for all their work.

Why Belt?

Belt grinding improves roll fabrication and repair several ways, according to Mr. DuPont. "First, today's belts are fundamentally of more consistent quality than hardwheels - no renegade grits to gouge a roll surface. Immediately that reduces risk and rework time. On both a unit and per-part basis, belts cost less than hardwheels yet remove material as fast or faster."

That, plus the ease of use of the Ecotech grinders means MP&P can more readily train and use more of their people on the job. This benefits scheduling and utilization greatly.

Even if the operator takes too deep a cut, the rubber contact drum absorbs the excess loads, protecting the workpiece, belt and operator. All the consequences of a damaged wheel running out of balance or exploding simply disappear. "The more forgiving action of belt grinding is especially important on thin wall rolls," Mr. DuPont adds. "When the workpiece wall is only 1/2 in. thick and easily deformable under overload, there's simply less room for error,” Mr. DuPont continues. With hardwheel practice, he had to reserve thin-wall jobs for the two or three most experienced operators. If someone was out sick or on another shift, the job would have to wait. With belt grinding on the Ecotech grinders, the company can turn that type of job over to any of its operators on any shift with complete confidence. The company has done so on the original Ecotech grinder which is set up for belt grinding and hasn't had to scrap a job yet, regardless of which operator is assigned.

Belt changes also go 40 minutes faster than hardwheel changes. That difference alone saves about two hours per job. At eight to ten changes per day shop-wide, MP&P saves 4-5 hours per day in machine downtime and labor vs. hardwheel grinding. That frees enough time to start another job each day and complete an extra three jobs per week. Belt changing is much the same as on a belt sander. Slack the tension, swap belts, re-tension, re-start.

Standardizing On Equipment

Mr. DuPont orders all Ecotech grinders equipped with beltheads and all optional equipment. The basic model H-147 cylindrical grinding machine features a 25 x 160-in. work envelope, six-speed pulley workhead, hydrodynamic spindle and digital readouts. An automatic pick feed reverses the feed at the end of each pass. Behind-the-wheel dressing, wheel balancing and manual swing-down part gauging are built in. Hydro-cyclonic coolant filtration prevents swarf reflux and extends coolant life 16 to 1. Hydrostatic lubrication of table and wheelhead ways provides smooth, precise, non-stick operation.

"With such a simple machine, even less skilled operators can concentrate on finishing the part correctly rather than 'driving the machine'," comments Mr. DuPont. "For our 'one-off' type of operation, we’ve found the ideal balance between simplicity and sophistication, giving us the highest efficiency and machine utilization for quick job changeover. We're making chips 20% more of the time than on comparable grinders, which is as it should be."

Winning Combination, Competitive Edge

"Belt grinding on Ecotech grinders gives us a winning combination of method and equipment for a real competitive edge," concludes Mr. DuPont. "That combination cuts capital cost 25-30% and cost per job by at least 20%, reduces risk and enables us to handle rolls more effectively. That makes financial as well as strategic sense. And whenever you can get the job done for 25-30 percent lower capital investment, your return on capital and balance sheet improve along with the P&L. That's our case exactly. Although I may be the guy helping to keep this going, hats are off to our president, Gary Walband for his decisions to move in the direction of Ecotech and belt grinding.”

For more information, contact Curtis Gibbs

Ecotech Machinery, Inc.,4220 Wayside Court, Lilburn, GA 30047. Phone (770) 279-2001, Fax (770) 279-2102.

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