Page 14 - MetalForming March 2010

Appliance OEM Lovin’ Lubrication
forces to develop a new die preventive- maintenance area where it cycles dies through a rigorous inspection and maintenance protocol. It’s using its press controls and plant-wide networked con- trol software (which we wrote about in 2000) to trigger the PM routine auto- matically, based on attaining a specified number of hits for each die.
A Better Lubrication Approach
The plant’s overhaul of its press- lubrication approach, a project com- pleted a few years ago, helps allow the pressroom’s maintenance team to get to the point where it could accurately pre- dict die life between maintenance cycles, and therefore implement a robust PM schedule. The project saw the press- room switch from spray lubrication to roller-application systems, which result- ed in less die grinding and polishing and more hits between maintenance cycles. It also boosted the confidence of the firm’s engineers that its dies will run as- designed without unscheduled press downtime.
Overall, the switch to roller-applica- tion lubrication systems has led to a 15-percent reduction in die-mainte- nance time, according to process engi- neer Mike Hanson. This has freed up toolroom personnel to perform other tasks, such as investigating new ways to better implement die-protection tech- nology—yet another project underway at the plant to improve OEE. And, increasing its return on investment even more—lube consumption has dropped by at least 25 percent.
“Spraying lubricant on only the top- side of our coil stock as it fed into the presses,” Hanson recalls, “just wasn’t good enough. We could not get enough lubricant to adhere to the bottom of the stock, and as a result we were experi- encing too many splits, particularly on deeper draws. In some cases, we’d even stop the presses periodically during a production run to pour lube onto the bottom die section—not exactly a good way to optimize OEE.”
The 60,000-sq.-ft. Electrolux press- room (recently expanded from 56,000
sq. ft. to make room for a new stainless- steel stamping line anchored by new Stamtec 400- and 600-ton presses) houses two production cells. A lighter- tonnage cell comprises seven presses from 250- to 400-ton capacity that run progressive dies; a higher-capacity cell comprises two 600-ton presses that run transfer dies and a 500-ton progres- sive-die press. A few 150-ton presses round out the lineup.
“All of these presses used to have their own lube-mixing equipment pumped to spray nozzles on the dies,” says plant maintenance engineer Mark
the coil stock. Rollers come in a range of widths from as narrow as 3 in.; users can mix and match roller width to allow the SPR-2000 to control lubricant delivery in zones based on coil width for a par- ticular die.
“We’re processing three material types—bare cold-rolled steel as well as aluminized and galvanized stock,” says Hanson. “Thickness ranges from 0.015 to 0.058 in., with the majority of the material between 0.020 and 0.028 in.
“And, we’re using three different recipes of lubricant,” Hanson continues, “based on material type and thickness. A 5- or 10-percent mixture of lube with water handles most of the material, while a 20-percent mixture flows to the 600-ton presses for deeper draws and heavier-gauge material.”
The Switch to Synthetic
Along with the switch from spray to roller systems for lube application, the firm recently standardized on a new synthetic lube for all of its parts. It had been using a paraffin-based lube on its 600-ton presses, having switched over to a synthetic lube for its lower-tonnage presses a few years ago.
“We believed that the heavier-gauge work and deeper-drawn parts still required the paraffin lubricant,” says Hanson. “However, late last year we tested the synthetic on the 600-ton presses and the roller application sys- tems deposit a nice, even, consistent coat top and bottom that provides the quality and repeatability required.”
One stamping in particular made Hanson a real believer in the roller application system and synthetic lubri- cant: an oven bottom with a 4- to 5-in. draw. “We used to struggle at times forming that part (on a 600-ton trans- fer press),” shares Hanson. “But now the part runs without fail. And, we’ve gotten rid of the mess we used to have from drowning the part in lube.”
An added benefit of the switch to synthetic, says Frauendienst: “It’s much easier and less costly to clean the parts before we send them up to assembly. While the synthetic costs more to pur- chase than the paraffin product, we can
“Press operators can adjust roller pressure pneumatically to fine-tune the thickness of the lubricant coating based on the application.”
12 METALFORMING / MARCH 2010
www.metalformingmagazine.com
Frauendienst. “Now we’re using a cen- tral mixing station with lines running to each press’s roller-application system, to ensure consistent mixes.”
Precise Control
The firm is using Unist SPR-2000 programmable fluid controllers at each lubricant-application system (Unist’s Uni-Roller system) to accurately dis- pense lube to the top and bottom of the stock. Rollers are felt covered; press operators can adjust roller pressure pneumatically to fine-tune the thickness of the lubricant coating based on the application. More pressure on the rollers makes for a thinner coat, and a looser squeeze allows the lube coat to thicken a bit.
Inside of each roller is a dispenser tube the length of the roller, with tiny holes spaced along its length. Each time lubricant injects into the tubes—trig- gered by press stroke—it emerges from the holes in a nice, even pattern across the inside of the rollers for transfer to