How metalworking manufacturers decide whether to fabricate or stamp

May 7, 2019 3:06 pm

Here are 10 determining factors that fabricating and stamping companies should consider

THE FABRICATOR APRIL 2019

By Kate Bachman

Metal fabrication job shops are the Swiss Army knives of manufacturers. Projects may walk in the door that are as varied as imaginable from the ones coming in the day before. “You never know what you’ll be asked to make,” fabricators typically say. “You have to be prepared for anything.”

Certainly, metal fabricators competing with global manufacturers do not want to turn down a customer. More tools in the toolbox boost a manufacturer’s ability to handle whichever quantities, timetables, and part complexities are required. Fabricators that are also equipped with stamping capabilities—or vice versa—are well-positioned to handle nearly any request.

Need prototypes? We can do that. A short run of 200 by Tuesday? Sure. Then, once you finalize your design, a million parts three months from now? You bet. We can do all of those. No reason to go anywhere else.

»Manufacturers with both stamping and fabrication capabilities must decide which process—or which combination of both—to use to produce a part. Photo courtesy of Kapco Metal Stamping.

But having that broad capacity poses another quandary: Which process path do you use? What indicates whether a job should be run on a stamping press or a laser and turret press or press brake?

Stamping or fabricating? How do you make that determination? Stamper/fabricator manufacturers ACE Stamping & Machine Co., Racine, Wis.; General Stamping & Metalworks (GSM), South Bend, Ind.; and Kapco Metal Stamping, Grafton, Wis., share their perspectives and approaches to this conundrum.

ACE Stamping & Machine Co. Vice President James Haarsma said, “How to determine which route to take is one of our biggest challenges. This is something that I battle every day.”

GSM President and CEO John Axelberg said, “When selecting the manufacturing method for a particular part, we try to propose the lowest-cost option, taking into consideration lead time to production and total volume over the product life cycle.”

Kapco Vice President Mike Kenny said, “For each part we look at annualized volume, geometry, size, features, tolerances, material, equipment requirements in tonnage and size, and our customer’s tooling ROI as the key decision points that drive which particular processes are deployed. Choosing fabrication, stamping, or some combination thereof is the result of identifying the most competent processes to yield consistent, defect-free parts at the lowest total cost.”

1. Cost

Cost is the pivot point that all other factors revolve around. Manufacturers leverage each of the processes’ strengths to achieve cost efficiencies.

Kenny cites stamping’s capability to combine several operations in the press as one way it can tip the scales in its favor. “If there are opportunities to combine additional operations, such as fastening, tapping, extruding, coining, or part marking, in a stamping press stroke, often the reduction in part cost will offset the investment in stamping tooling and help drive the decision,” he said.

For long runs and circular shapes, stamping is still the fastest game in town. Photo courtesy of Kapco.

Stamping can be automated, requiring less labor input per part than other operations, such as a manual press brake, he added.

2. Part Volume

Part runs are certainly one of the key considerations in determining which path to take. Haarsma said, “Volume is usually your first indicator. So we use a cutoff point of 6,000 a year. If an annualized part run is 6,000 or more, usually we want to stamp it.” Machine time is part of that decision, and so is lead time. “At 15,000 parts a year, it’s going to eat up all my machine time on a turret or laser. Our lead times are going to be too long as well.”

Haarsma qualified that break point, saying that it is just a rule of thumb. “We might stamp parts with only a 3,000-a-year volume, depending on other factors.”

Kenny was reticent to adhere to a hard-and-fast rule on volume. “Identifying upfront the volume, life cycle, and design dynamics will lead the team down the path, but there is no defined rule of thumb.” When pushed, he did cite a cutoff number. “In general, parts with volumes of 5,000 or more annually will get a look for a stamping operation,” he said.

Axelberg refrained from pinpointing a cutoff volume at all. “We never draw a line in the sand. We try to learn as much as we can about our customer’s needs and objectives and present more than one option if the choice isn’t clear. There is no set number that applies across the board, because every part comes with a unique set of conditions. That’s what makes this business so interesting!”

3. Timetable

Launch lead time and product development may result in a part’s life cycle starting as a fabrication and ending as a stamping, Kenny said.

Axelberg explained how the customer’s timetable is a major driver. “A lot of it depends on when the customer needs the parts,” he said. “For one of our big customers, we’ve made runs of 20,000 pieces of good-sized parts on a laser and press brake just because they were needed in six weeks. There was no way we could build a die in that time.”

Axelberg added that because the job required a very large annualized volume, GSM worked on a long-run, hard-tooled option that would take over the project when it was ready. “And then in 12 weeks, the part converts over to a stamping. So it starts off soft-tooled and ends up hard-tooled. We do that on a regular basis.”

Axelberg said that to some degree, laser technology has driven the need to take that two-pronged approach. “I think a lot of OEMs have gotten used to the responsiveness of fab shops with lasers and their ability to make almost anything very quickly.” As a result, customers may not start thinking about hard tooling when the product is still in a test phase. Other times the part’s final design has to be worked out. In those situations, GSM will start out using a laser cut/press brake form process and then progress to a stamping tool.

Another reason a customer might not initiate a job in enough time to accommodate stamping tooling is the nature of its industry segment, Axelberg said. “Solar is an unpredictable industry. Projects can be huge, and often because of the complexity of financing and permitting, they’re complicated deals. The date that the project has to go into service is established far in advance. All the other details can really encroach on that final day. So for a lot of these jobs, once they’re finalized, boom, we have to go now—and it’s a lot of parts.”

»Material utilization is a driver, especially when the material is costly. The first drawing shows excellent material utilization using nesting for laser cutting, with only a 1.84-lb./part scrap rate. The second drawing shows material utilization using stamping to blank the part. The third drawing shows the parts blanked and formed in a progressive stamping process. Images courtesy of General Stamping & Metalworks.

Axelberg said that the introduction of high-powered fiber lasers has had a big impact on the calculus unrelated to material type. As recently as five years ago, GSM was building pierce and trim dies to run sheared blanks in its stamping presses. In spite of all the manual handling, the process was still faster than cutting the parts on a laser. “We would run rectangular parts with square corners on our CNC punches because that was faster than laser cutting. Not so anymore. Now we reserve our punches for parts with 3D features that can’t be created on a laser, because the punches can’t begin to approach the profiling speed of the fiber lasers.”

4. Part Size

Kenny discussed another factor: part size. He said that a large part would most likely force the operation toward fabrication rather than stamping. “That is because tool cost grows with each progressive operation in a tool, and a complete tool may require more real estate than the press has available.”

Kenny pointed out that smaller parts have smaller tooling costs, rendering a shorter ROI. “Large parts may require a larger annualized volume to be stamped. Alternatively, we may consider multiple processes, like laser cutting the blank, then hand-transferring it to a form die, or blanking in the die and then forming it in a press brake.”

Haarsma said the limiting factor in size depends on how long the stamping die would have to be to form it, because the company’s largest press bed is 8 feet long. “So for us, if the piece is large, and let’s say it has knockouts, embosses, and lances, what happens is you’re going to need an automotive-type press system—the 2,000-ton, back-to-back presses because your progressive die would become way too long. So on larger pieces with a lot of forming features, size is a limiting factor for stamping.”

5. Shape, Contours, Geometry, Features

Kenny said that, in many instances, the part geometry, features, tolerances, and required equipment specifications in tonnage and size are the leading reasons that Kapco chooses stamping over fabrication.

“There may be certain features, such as holes, sumps, embosses, and ribs, or tolerances that are more advantageous in a servo press, which may lead us to consider stamping them, even for a short run,” he said. “Hole size and location relative to an edge may contribute to choosing stamping or fabrication.”

Axelberg said that some part designs offer no option but to build a stamping die. “Press brakes are designed for bending, not forming. We’ve built draw dies for only a few hundred pieces because of that.”

Haarsma concurred. “For example, stamping is the only process you can form a circular form on.” He added that some high-quantity parts will be run on a turret press because of their complexity.

“I have some parts with a large quantity of pierced holes with a high annualized volume that we do run on a turret press. That’s because of the number of things going out in the part. If we put it in a progressive tool, it would be too long. Most likely, the customer is not going to pay for a $300,000 tool, unless it’s a very high quantity.

“We end up running them on a turret press versus a stamping press because you can put a lot of forms in there, get all the cuts done in one shot. Then you take it to a secondary op to form it, like a 90-degree bend,” Haarsma said.

»This fan component is a good example of a part that must be fabricated on a laser and press brake, rather than stamped, because so much metal is removed and the remaining skeleton would become distorted. Photo courtesy of GSM.

Size does dictate that the part be punched in a stamping press when the form feature is large, Haarsma said. “If it’s a circle or a diaphragm or something, you can’t punch it on a turret press if it’s bigger than 4 inches because that’s as large as the toolholder is. So we have to stamp them just because of the geometry of the part.”

6. Tolerances

Another ingredient to throw into the cocktail that dictates hard tooling is tolerances that cannot be held in a turret punch press as well as in a press, Haarsma said. “There are parts that we run into here that are 200 pieces a month. We stamp them because we have 300 holes, for example, that are closely spaced with a +0/-1 tolerance and +0/-2 on the position.”

Stamping drives improved tolerance control and greater repeatability because the tool is performing the work, Kenny said. “Controls and sensors can be added to aid greater control of the process.”

7. Finish, Edge Quality

The customer’s preference for a particular finish can point in one direction, the manufacturers said.

“The edge condition from stamping to laser-cut is definitely different,” Axelberg said. “A sheared edge can be more prone to small fracturing, depending on the type of forming you’re doing. The stamped edge typically is going to be sharper, so often we smooth those edges with vibratory deburring machines.”

Haarsma offered another viewpoint. “Sometimes a customer does not want a laser-cut edge. They prefer a stamped edge which has breakout and rollover, so it’s clean through 70 percent of the material. That’s when you start to get the breakout and rollover, but you can deburr that off. Whereas with a laser-cut edge, depending on the thickness of the part, you’ll start to see the beam frequency; it can affect the finish of the side.”

Kenny added, “With the servo press, breakaway can be improved.”

8. Material Type

The material type that the component is formed of is a factor, although, with the advent of fiber laser technology, not as much as it used to be, Haarsma said. “We stamp titanium, gold, and brass. In the past we were limited. We could not cut titanium, brass, or any of the red metals that are reflective materials with a CO2 laser. A year and a half ago, we acquired a fiber laser that can cut through those reflective materials.”

9. Material Utilization

Raw material utilization is another key decision-driver, Axelberg said. “Certain part geometries may leave a lot of scrap in a stamping die, but virtually none when nested with other parts on a laser.” Often the material cost savings justifies a higher processing cost, Axelberg said, adding, “That break point moves with the cost of steel.

“For example, a part was made from 8-gauge, Grade 50 galvanized. As production volumes started to climb, we hoped to transition it to a full progressive die. Unfortunately, the tooling payback was about 21/2 years because of the poor material utilization relative to the laser process. So we came up with a compromise. We built a two-out blank die to run coil, which matched the laser’s material yield with a big increase in throughput. The forming operation is still done in a two-stage form die in another stamping press.”

»Some parts with circular contours must be formed in a stamping press. Photo courtesy of Kapco.

Kenny said that he finds the stamping process offers better material utilization and lower process cost than fabrication, but coil yield can be another decision point. The company balances lot size with coil changeover to appropriately manage efficiency and inventory, he said.

10. Downstream Processes

Kenny said that stamping offers better process control, which is important for subsequent operations such as welding and assembly.

Conclusion: Having Both Is Better

All three stamper/fabricator manufacturers expressed that having dual capacity has boosted their offerings and ability to retain customers.

“It’s nice to have fabricating and stamping capabilities,” Axelberg said. “I would not want to be a pure stamper. Or vice versa. When fab volumes get really high, or if a die breaks, we can produce the part in a stamping press or a laser and a press brake.”

All three said they quote projects both ways.

“We calculate it a couple of different ways,” Haarsma said. “Fabrication is easier to quote because you have software that does a lot of it for you. Whereas for stamping, I have to do a strip layout to estimate material yields, so that takes a bit longer than fabrication.”

Kenny said that Kapco has supported its customers with both stamping and fabrication technology for the same part at different times in the product’s life cycle. “It is not uncommon for us to produce first parts using fab technology to prove out the part and provide low-volume prototypes until higher program volumes are needed. Then we invest in a stamping die. Alternatively, when volumes reduce to the point that stamping becomes less viable at the end of a product’s life cycle, we will switch back to fabricating the part. Our customers benefit from optimized production processes at low- or high-volume delivery scenarios.”

Axelberg foresees another new technology that may change the “fab or stamp?” vector. “We don’t have a 3D metal printer yet, but I can see that technology significantly reducing the cost of form tools for low-volume parts with complex geometries.”

ACE Stamping and Machine Co., , 800-597-7485, www.acestamping.com

General Stamping & Metalworks, 574-288-0611, www.gsmwinc.com

Kapco Metal Stamping, 262-377-6500, www.kapcoinc.com

»Laser technology has driven the turnaround expectations forward because some laser processes can be executed very quickly. Photo courtesy of Kapco.

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