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Steady Hands Heal Wounded Dies

By: Brad Kuvin

Thursday, December 01, 2011
 

As a former moldmaker, Pete Mourouzis fully understands the need for speed and workmanship when it comes to tool, die and mold repair welding. As owner of Wicked Welding, Inc., Dayton, OH, Mourouzis applies his precision-welding skill and knowledge daily to help manufacturers return worn or damaged tools back to service. At his disposal are two welders, in addition to himself; an array of precision micro-tig (gas-tungsten arc) welding systems and traditional tig-welding setups; and two micro-laser-welding systems. Mourouzis and his team perform not only emergency-room repairs on tooling but also enjoy a thriving wellness program that has it included in some of its customers’ routers, performing planned maintenance-welding procedures.

“Half of the work we get in here we turn around in one day, and another 25 percent in two days,” says Mourouzis. “To many of our customers, turn-around time is more critical than price, and that’s where our ability to laser-weld comes up big. While it’s a relatively slow process in terms of deposition rate, if I don’t have to preheat we can turn around work in hours rather than days.”

We walked around Wicked Welding’s 4000-sq.-ft. shop while welders were busy repairing mold tooling, and learned first-hand how the steady-handed team provides local customer Dayton Systems Group (DSG) with fresh carbide-insert stamping tools for its customers in the can-making industry.

Wicked Welding’s Pete Mourouzis has two laser-welding machines at his disposal, to make tooling repairs—an 80-W manual machine (top) for hand-held work, and a 100-W machine with a three-axis rotary fixture table for more precise work. Both require him to perform three actions at once —foot-pedal control of the pulsed laser, right-hand manipulation of the part, and left-hand filler-wire feed into the weld. Shielding gas (pure argon) flows through the blue hose to protect the tiny welds from the atmosphere.

Mourouzis launched Wicked Welding in 2003 after having worked for several years in small injection-mold shops. He spent three of those years running CNC machines and doing assembly work, and the last two as an inhouse welder.

“While others around town can weld as well as I can,” he shares, “what I bring to the table is my knowledge of tool and die applications. I talk the toolmaker’s language and understand how tools work in the press, all of which impacts my ability to offer the right weld-repair solution for the job.”

Wicked Welding’s sweet spot is relatively small tooling—shoebox-sized work weighing a few hundred pounds or less. Mourouzis and the firm’s other two welders will use the micro-tig process when it can, but “trying to tig weld traditional tool steels cold is a recipe for disaster,” says Mourouzis. “Without proper preheat, cracking is inevitable, and that’s where laser welding has proven to be a huge benefit. I can laser-weld without preheating (depending on the size of the repair area), filling small pits that affect the surface finish of the part or restoring worn or damaged cutting edges. Also, as stampers have moved away from stocking several replacement inserts, the value on our services has risen. We’re laser-welding to repair die inserts weekly for our customers.”

“Free-Moving” Laser Welding

Mourouzis launched his company as a provider of traditional tig and micro-tig welding services, and made his foray into laser welding in 2005 with the purchase of a small LaserStar 80-W manually operated machine. In 2008 he added a larger 100-W Rofin model, equipped with a three-axis joystick-controlled table and rotary fixture. Both machines run pulsed-YAG lasers and feature a stereomicroscope and cross-hair for precision beam alignment. By year-end, Mourouzis should have a third laser-welding system inhouse, this one rated to 200 W.

Here’s how LaserStar describes what it calls the “free moving” process of using laser welding for mold and die repair:

“The laser generates a stationary infrared light pulse which is targeted through the microscope’s crosshair. The laser pulse can be controlled in size and intensity. Because the heat generated remains localized, operators can handle or fixture items with their fingers, welding small areas with pinpoint accuracy without causing any harm to the operator’s fingers or hands. This free-moving concept enables users to eliminate costly fixturing devices.”

To maintain these stamping tools for Dayton Systems Group, Mourouzis deposits tiny, precise laser welds to hold replaceable carbide inserts in place.
When we visited the welding shop, customer Jon Ledford, DSG manufacturing manager, was there picking up some recently repaired tools. DSG supplies the can-making industry with production systems, sheet-feeding lines and tooling.

“Welding, for applications such as replacing carbide inserts on our tools, is part of our process, and Wicked Welding is on our routers,” says Ledford. He showed us a few tools that Mourouzis works on regularly, which feature carbide inserts. Says Mourouzis: “Of course, we don’t actually weld on the carbide. But we can make tiny laser welds to hold the inserts in place in the tools. The carbide inserts are lightly pressed into place, then I push the weld beads right up against the carbide. It’s a fine line—put too much heat on the carbide and it will crack, so I try to use the laser to dig into the base material (M4 tool steel) and shove it up against the carbide to lock it into place.”

Ledford explains that at one time, brazing was used to assemble the inserts into the tools. However, the process proved messy and slow, and it was difficult to remove the inserts when they needed to be replaced.

“I can tack an insert in place in about 2 min.,” says Mourouzis, “while brazing might take 15 min. or more.”

Hair-Thin Filler Wire

While micro-tig welding requires what most would call thin filler wire—down to 0.010-in. dia.—filler wire for laser welding is hair-thin, as delicate as 0.005-in. dia. M2 filler wire is a favorite of Mourouzis and his crew.

 

A Wicked Welding operator peers through a stereomicroscope to deposit precise micro-tig welds, while feeding thin filler wire into the weld. A gas lens on the air-cooled tig torch, in place of a standard tig-torch collet body, optimizes shielding-gas coverage and improves joint accessibility.
“It’s a fantastic all-purpose filler metal for A2 and D2, as well as M2,” he says. “It’s my go-to-rod unless a customer requests a direct match to the base metal. And we also burn a lot of 420 stainless-steel filler metal—it’s a good match for S7 and H13—as well as M42 wire to weld on powered-metal tool steels.” In all, Mourouzis stocks 40 different types and diameters of filler wire, noting that “my experience (he figures he’s ignited millions of arcs in his time as a welder) allows me to select the right filler wire for the job at hand.”

To laser-weld DSG’s tools, Mourouzis hand-holds the parts in the small laser-welding machine. “I’m performing three operations at once,” he notes: “I have to manipulate the part under the beam with my right hand, feed the filler wire into the weld with my left hand, and use a foot pedal to control the laser.

“We tried to make the tiny welds holding the carbide inserts in place using the micro-tig process,” continues Mourouzis, “but even that precision process deposited excess filler metal. DSG didn’t want to have to mill off any extra material. Also, even micro-tig would cause slight discoloration; laser welds don’t.

When using the lasers to build up weld metal—to restore a cutting edge, for example—Mourouzis can deposit as much as 0.008 to 0.010 in. per weld pass. Yes, it’s a slow process, but “if you only need 0.005 in. on a tool and I don’t have to preheat,” he reminds, “the time savings is significant.” For work as refined as rebuilding a cutting edge, Mourouzis will opt for his larger laser welder and can use its rotary fixture table on round parts.

Adds Ledford: “Laser welding has been a blessing for our stamping tools. Even if one of our customers drops a tool and mars the steel, we can send it here for a quick laser-weld repair. And in many cases, we don’t even have to machine the weld—the tool can go right back in the press.”

Low-Amperage Micro-Tig Has its Place

Micro-tig welding at Wicked Welding is what you’d see at most other precision welding shops—air-cooled torches with gas lenses in place of collet bodies to optimize shielding-gas coverage; pulsed inverter power supplies (Miller Electric 200-A Maxstar and WeldLogic PA-100 units) running DC for most jobs; and finely ground 2-percent lanthanated tungsten electrodes. Shielding gas is pure argon—also the gas of choice for laser welding.

“I use a double set of regulators on one of the micro-tig machines,” adds Mourouzis, “when we’re welding at really low amperages, under 5 A. The twin regulators allow us to really control the gas flow at low flow rates so we don’t extinguish the arc, yet still ensure the required level of shielding.”

In fact, many of Wicked Welding’s jobs require a combination of processes—laser and tig welding. Says Mourouzis: “I’ve had die blocks where we preheated, used conventional tig welding with a large-diameter filler wire to build up an area, preheated again, micro-tig welded on top, cooled the area and then laser-welded around the deposit. An ideal application for such a procedure might be to fill a hole—I can micro-tig to fill to within 0.020 to 0.030 in. from the surface, and then top it off with the laser so that no machining of the weld is required. There’s no over-welding and we’re sure to avoid any pitting or voids.”

Mourouzis is quick to remind that he also takes his tig-welding services on the road—two to three times each month. “We can repair tools right in the press,” he says. “And we don’t just repair tooling—we can perform all sorts of weld repairs throughout a metalforming plant.” MF

 

See also: Rofin-Sinar, Inc., Miller Electric Mfg. Co.

Related Enterprise Zones: Tool & Die, Welding

 


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