Sheet metal solutions

By Nick Wright

Water heater manufacturer cuts scrap and setup time with SigmaTek’s nesting software

November 2012 - In boxing, repeated blows to an opponent represent the brawn behind a victorious bout. But without a set strategy to efficiently guide each punch to the right place, precious energy, and possible victory, are wasted. Similarly, the right hardware and correct force will deliver perfect punches in sheet metal. With smart, easy-to-use nesting software, machinery operators can be confident their equipment will guide each punch where it’s needed, minimizing processing time, scrap and energy.

At Milwaukee-based manufacturer A. O. Smith, installing nesting software on its turret punch press has cut the time  in half it takes to program punching, compared to its previous software, speeding the production of its gas and electric commercial water heaters. The company added SigmaNest from SigmaTek Systems LLC, Cincinnati, on its 40-ton Muratec Motorum 2548 CNC punch press at its plant in Renton, Wash., in March 2011. The Motorum 2548 has 44 stations including four auto indexing.

Before using SigmaNest, A. O. Smith had difficulty nesting parts with its previous software, says Joseph Thomas, manufacturing engineer at A. O. Smith’s Renton facility.

“On the shop floor, machine operators are able to load a full 48 in. by 120 in. piece of sheet metal, and punch several parts at once, using the nesting function,” he says. “Before SigmaNest, the machine operators would have to take time to shear parts to size and then punch, shearing parts one by one.”

A. O. Smith uses SigmaNest for mostly square and round-through hole punching programs needed to create sheet metal jackets and control boxes for its large water heaters. It also punches aluminum jackets used on its heat pump line. The Renton plant fabricates higher-capacity commercial heaters for hotels, schools and correctional facilities.

“The square punching is used mostly to notch corners of sheet metal pieces that require a press brake operation in the next manufacturing process,” Thomas says. Those pieces make up the square jacket on water heaters ranging anywhere from 150 gallons to 5,000 gallons. The round-through holes are used on a wide range of heaters, from five gallons to 5,000 gallons. 

A. O. Smith makes louver slats and electrical conduit knockouts for some parts, as well. To create these forms, the user has flexibility to manipulate the punching sequence.

A. O. Smith is accustomed to being flexible and evolving with demand. Founded in 1874 as a small machine shop in Milwaukee, A. O. Smith originally made parts for baby carriages, then grew to offer bicycle components. In 1899, one of the founder’s sons perfected the manufacturing of a pressed steel car frame. Eventually, A. O. Smith became the largest independent supplier of car frames in North America, according to the company. It patented the method of glass lining tanks for residential water heaters in 1936, making hot water affordable for homeowners. Now, it supplies residential and commercial water heaters in more than 60 countries.

Nesting workflow

A. O. Smith fabricates its tanks with several types of materials, all purchased in 48 in. by 120 ft. sheets. The metals include 16 gauge and 18 gauge cold-rolled ASTM A366 steel, 18 gauge 304 stainless with No. 4 finish, and 16 gauge and 18 gauge aluminum with 3105 mill finish.

To accurately punch all the materials, SigmaNest is set up with two preset configurations depending on the job: part punch and nest punch. A. O. Smith uses the former for the bigger sheet metal jackets, which are typically one piece. The smaller control box pieces are nested together, in which case nest punch would be used. Once the CAD/CAM operator initiates SigmaNest and selects nest or part punch, he can import a .DXF file that defines the part geometry. 

“Importing several .DXF files at once and the ability to keep everything together in one workspace is very efficient,” Thomas notes.

A. O. Smith easily imports multiple .DXF files at once and visualizes the nest pattern to create tops and bottoms (A) for small electric control boxes, and their sides (B).

The software also features a built-in 2-D CAD system that makes creating or manipulating geometry simple. From that point, the operator can set the punching to auto tool.

“This will take the tools loaded into SigmaNest’s library, and the software will decide how the geometry should be punched,” says Thomas. In some cases, the punching tools must be changed slightly to accommodate the right punching operation. “The operator then manipulates the punching sequence to ensure that no floating scrap is left on the punch machine turret.”

James Lindsey, product manager at SigmaTek, says other punching software often requires pre-programming for exactly where punch hits need to be. But SigmaNest can accomplish on-the-fly nesting, reducing potential tool overlap or tool allocation conflicts on the machine. 

“You don’t have tool conflicts station to station,” Lindsey says. “We have automatic nesting with tool hits. So as you’re automatically nesting the parts, it’s applying the tool hits as it’s laying down the parts instead of requiring the parts to already have the tooling on it.”

A. O. Smith’s CAD/CAM operator can also create punch programs from SigmaNest and send them to the punch press days before the part is needed for manufacturing. Then, when the operator is ready, he can recall the program, run the job and perform other tasks while the machine runs.

“For our high volume water heater line, the nested sheet metal parts are punched early in the week,” says Thomas. Those parts can keep manufacturing busy through the week. Parts for its lower volume line can be punched on the day of assembly.

Scrap scruples

Scrap reduction has been a major benefit of SigmaNest, saving A. O. Smith labor and material. Its operators don’t have to manually shear sheet as often as before because the machine can load sheet, nest the design and punch parts. With the shear, operators would have to shear sheet to size, which would leave behind more scrap. Now, A. O. Smith has realized a significant savings in scrap material costs, Thomas says.

SigmaNest flags operators with a warning if it recognizes areas of the sheet that will end up becoming floating scrap. 

“You might punch out a part where there’s a little sliver or part or corner that got punched out and it’s just a little extra piece of material that didn’t get punched,” says Lindsey. If the floating scrap gets underneath a desired part, for example, the machine or tool could be damaged if it accidentally punches through two sets of material or puts extra side load on a tool. 

“Scrap is usually one of the first big factors we help customers with,” he says, noting the scrap is curtailed through the nesting process itself, more of a byproduct through the tooling function. “Just reducing the overall scrap ratio, we’re pretty effective at doing that.”

Added benefits

Along with scrap reduction, SigmaNest is intended to trim labor as well as seamlessly integrate into a customer’s business software. SigmaNest can pull jobs directly from the business system. If the geometry doesn’t exist, it can automatically retrieve and import it. Job reports are then fed back into the system when punching is complete.

Thomas says the software’s SolidWorks module and ability to accept PDF files for blueprints were unexpected benefits that have streamlined operations. Substituting tools without having to reprogram an entire job is key, as well.

“We like to call it the three Ms: manpower, motion and material,” Lindsey says, referring to the areas SigmaNest targets for improvement.

For A. O. Smith, customer service and technical support have been there when needed. 

“They are very helpful and resolve issues as soon as possible,” says Thomas. “They are able to remotely access my computer and troubleshoot any issues as they arise.” 

He adds that SigmaNest offered a three-day training class before A. O. Smith started using it. “They were very professional and took time to adjust class material for punching related to A. O. Smith.” FFJ

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