“We’re often engineering custom systems designed to meet specific and unique end goals of the customer,” says Greenerd engineering/operations manager Tim Wilson.  

That process can at times lead Wilson and his team of engineers to collaborate with researchers at nearby University of New Hampshire (UNH) to conduct engineering calculations and perform process simulations, long before the first machine layout is developed. Such was the case for a line we spied on the Greenerd shop floor, just weeks away from customer delivery. The automated line, described by the principal engineer on the project, Ben Richards, fabricates electrical splices. The process starts by feeding coiled aluminum wire in two diameters, which vary by about 1/16 in. The wire moves through a straightening operation and then a cut-to-weight operation—“The length of the wire blank is not the key measurable,” stresses Richards.  “Rather, it’s the weight of the final blank that we must maintain to within a tight tolerance.”

Blanks, 1 to 2 in. long, then fit into fixturing cups, custom engineered so that they can hold both diameters of wire. These cups then travel via an infeed conveyor to a hydraulic press, on the way passing by a lane diverter, which separates the blanks into two lanes to optimize throughput. Each lane has its own shuttle equipped with 170 fixturing cups.

Forming operations for the process—described by Wilson as not really punching or extruding, but more of a hybrid operation—include removing any ovalization from the blanks so that they’re perfectly round. Tolerances are as tight as ±0.002 in. on the critical overall diameter of the parts. The process includes adding dimples and then holes at each end of the aluminum blanks; putting an OD chamfer on the outside of the part; and then filling each part with dielectric grease and capping them off for shipping.  

“We had to design the line to handle 26 different sizes of parts, with varying hole diameters and configurations,” Richards explains. “While the target production rate was 60 parts/min., we engineered it to achieve a maximum throughput of 75 parts/min.”

Automating Part Movement

Notable is the custom-designed hydraulic press that features a unique shuttle that moves the parts through, capable of handling both wire sizes. “And, the customer wanted quick changeover from one part size to the next,” emphasizes Richards, who also describes a set of alignment fingers engineered to center the fixturing cups at each shuttle station. This setup enables the same cups to be used regardless of wire size, while still ensuring precise alignment during forming.

“Use of the alignment fingers, along with a few other features, allowed us to achieve a changeover time of less than 1 hr.,” Richards says.

Diving into the upfront engineering that went into ensuring the line’s ultimate success when installed at the customer, Richards notes the use of a great deal of sensors on the line to ensure part quality. “There are sensors on the infeed conveyor and the diverter,” he says, “and we use fiber sensors that look across the forming punches in the press to ensure that the parts release from the punch, and check that the punch remains in its retainer.”

But perhaps the biggest challenge with the project, Richards recalls, was calculating the press force needed to form both sizes of the delicate aluminum parts. “The customer had been using a very old machine and old tooling to make these splices,” says Richards. “A lot of modifications had been made over the years, and so the process specifics were fuzzy. That led us to work with our partners at UNH to help us determine the right forming forces for the job.”

Greenerd’s engineering team used the existing tooling as a baseline but had to make significant redesigns to allow the setup to work on its new process.

Wilson explains further: “We pulled in UNH researchers to help us determine the required forces for what we call an indirect extrusion process. UNH then can use the data, which we were able to verify, in its efforts to further develop its simulation software.”

Also noted: The customer has a 300-A limitation on the amperage it could use to drive the process, “so we couldn’t just throw more power at the job,” Wilson says. “That led to an iterative fine-tuning engineering process of checking and verifying tonnages. We also had to adjust the process to accommodate for heat buildup in the tooling during the process—the longer the line runs, the more heat generated, which gets absorbed into the tooling and can significantly affect part ejection. That then led us to pay close attention to the lubricant used, and also goes back to the concern over the volume and weight of each blank.”

The other big challenge, as previously noted, was engineering the shuttle setup to handle both wire sizes, “which led to multiple redesigns of the shuttle system,” Richards notes.  “Again, the idea was to spend as much time in engineering as possible to ensure that our process would work before we ever started building the system.”

Automated Beam-Punching Line

Next, we looked at a beastly automated production line near completion on the Greenerd shop floor designed to fabricate I-beam sections that ultimately would be assembled by its customer into large, sturdy storage racks for a variety of applications. The line replaces a semiautomated process using an aging hydraulic press to punch bolt holes into the beams.

“For this very custom and highly engineered line,” explains Greenerd applications engineering manager Tom Lavoie, “the task is to simultaneously punch six ¾-in.-dia. holes in structural-steel beams weighing as much as 3000 lb.; plate thickness ranges from ½ to ¾ in. Along with the surface quality of the resulting holes, also critical is hole alignment to ensure quick and easy assembly downstream.”

Again, upfront engineering and development before starting to construct the punching line was vital. The resulting beam line is 170 ft. long and features two 300-ton hydraulic presses to punch the holes. It includes a system to rotate the beams during processing to present the I-beam plates to the tools, and a laser-inspection system that works in concert with an engineered centering device to keep the beams centered in the line as they convey from press to press.  

The Greenerd engineering team, led by Mike Josefiak, developed a four-stage conveying line to index the beams, each stage measuring 35 to 45 ft. long and employing chain-driven roller conveyors. Along each stage are cylinders that fire as needed to keep the beam centered. Servo-driven shuttles ultimately move the beams into each press, held in place by pneumatic grippers. Once the beams are in place in the tools, a laser range-distance sensor scans the beam for length, and a second laser sensor at the entry end of each press locates the leading end of the beam, to direct the punching process. 

“The line will replace an old 375-ton C-frame press at the customer,” Josefiak points out, “that has no automation. Along with improved throughput from the automation we’ve designed in, the use of gib-guided presses on this new line will hold much tighter tolerances on hole size and edge quality.”

Sand-Casting Clean Up

Last but not least, another unique machine we spied and nearly ready for delivery highlights the flexibility of hydraulic presses themselves. The setup: a 10-ton hydraulic press equipped with a two-station die that fixtures sand-cast plumbing fittings. While the customer currently hand-grinds the parting lines and gates from the castings, trimming them in the press will improve productivity by some 300%. 

“In addition,” explains Wilson, “press trimming the parts improves part surface finish, and helps the customer prevent injuries to operators tasked with laborious and tiring hand grinding.”

During each press stroke, the top edge of each of the two tool stations encapsulates the part to keep it from shifting, and so the part does not compress at all. The tool then drives the knife edge through with minimal surface compression and shaves off all excess material. Tooling is A2 tool steel, hardened to Rc 62.  “And, there’s no taper on the knife edge,” says Wilson, “so the customer can easily resharpen it inhouse.” MF

See also: Greenerd Press & Machine Co.

Technologies: Stamping Presses

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