May 28, 2023

Hardware insertion’s automation evolution in metal fabrication

FIGURE 3. One-piece, quick-change, bowl-feed tooling, stored within the left-hand cabinet, handle both hardware orientation and singulation (ensuring hardware is lined up and spaced correctly). The right-hand cabinet stores different anvils and shuttle plates.

In the middle of the pandemic recovery in 2021, Ron Boggs, North American sales and service manager for Haeger, kept getting the same kind of call from fabricators.

“They kept telling us, ‘Hey, we’re missing fasteners,’” Boggs said. “As it turned out, that stemmed from staffing issues.” As fab shops rehired, they often put inexperienced, less skilled people in front of the hardware insertion press. They sometimes missed fasteners; other times they inserted the wrong fastener. Customer returns and rework mounted.

At a high-level view, hardware insertion seems like a ripe application for robotics. After all, a fab shop might have full-on automation in blanking and forming, complete with towers, part removal, perhaps even robotic bending. All this technology then feeds a largely manual hardware insertion department. Considering all this, why not just put a robot in front of the hardware insertion press?

Over the past two decades, Boggs has worked with plenty of fab shops that have robotized hardware insertion. Most recently, he and his team—including Sander van de Bor, principal engineer at Haeger—have worked on making it easier to integrate cobots with the insertion process (see Figure 1).

That said, both Boggs and van de Bor emphasized that focusing solely on robotics sometimes ignores larger issues with hardware insertion. A robust, automated, flexible hardware insertion operation requires a number of building blocks, including process consistency and flexibility.

Old iron dies hard. Many apply the adage to mechanical stamping presses, but it also rings true for the manually fed hardware-insertion press, mainly because of its simplicity. Standing in front of a manual insertion press, the operator places the fastener and part onto the lower anvil tool. He presses the pedal. The upper punch tool descends, contacts the workpiece, and builds pressure to insert the hardware. It’s all pretty straightforward—until, of course, something goes awry.

“If operators don’t pay attention, the tool will go down, touch the workpiece, and not actually build pressure,” van de Bor said. Why, exactly? “The older equipment has no error feedback, so operators really don’t know.” The operator might not have kept their foot on the pedal throughout the cycle, which in turn could have triggered the press’s safety system. “The upper tool has six volts to it; the lower tool is ground, and the press has to sense conductivity before it builds pressure.”

Older insertion presses also have no so-called “tonnage windows,” a range of pressure in which hardware can be inserted properly. Modern presses sense when these pressures are too low or high. As Boggs explained, because older presses have no tonnage windows, operators sometimes correct issues by adjusting a valve to dial in the pressure. “Some will adjust it too high, others too low,” Boggs said. “Manual adjustment opens the door to a lot of variability. If it’s too low, you’re not installing hardware correctly.” The result: The fastener isn’t secure because it doesn’t mate with the sheet metal as it should. “Pressure that’s too high can actually deform the part or the fastener itself.”

“Older machines also didn’t have counters,” van de Bor added, “which can lead to operators missing fasteners.”

Manual hardware insertion seems simple, but the process can be difficult to error-proof. Even worse, the hardware operation often occurs late in the value chain, after blanks have been cut and formed. Hardware problems can wreak havoc in powder coating and assembly, often because an otherwise conscientious and diligent operator made a few small errors that snowballed into major headaches.

FIGURE 1. A cobot presents a part to a hardware insertion press with four bowls and four separate shuttle plates that feed hardware to the press. Images: Haeger

Over the years, hardware insertion technology has addressed those headaches by identifying and eliminating those sources of variability. Hardware insertion operators shouldn’t be the source of so many problems just because they, say, lose a little concentration at the end of their shift.

Hardware insertion’s first step into automation, bowl feeding (see Figure 2), eliminated the most tedious step in the process: manually grasping and placing hardware onto the workpiece. In a conventional top-feed configuration, a bowl-fed press sends the fastener down to a shuttle plate, which presents the hardware to the upper tool. Operators place the workpiece over the lower tooling (anvil) and step on the pedal. The punch descends, uses vacuum pressure to lift hardware out of the shuttle plate, then presents the hardware to the workpiece. The press applies pressure, and the cycle completes.

This seems simple, but digging a little deeper reveals a few subtle complexities. First, the hardware needs to be fed and presented to the work area in a controlled manner. This is where the guide tooling comes into play. The tooling has two components. One is dedicated to orientation, ensuring hardware exiting the bowl is oriented in the correct way. The other ensures singulation, lining up and spacing hardware correctly. From there, hardware travels down a tube to a shuttle plate, which presents the hardware to the upper tool.

Here’s the complication: The auto-feed tooling—the orientation and singulation tools, along with the shuttle plate—all has to be changed out and aligned with every change in hardware. The different shapes of hardware affect how they feed to the work area, so hardware-specific tooling is just a reality that really can’t be engineered out of the equation.

Because operators in front of a bowl-fed press no longer spend time grasping (and perhaps dropping) and placing hardware, the time between insertions plummets. But with all that hardware-specific tooling, bowl-feeding machines also add changeover. Tooling for an 832 self-clinching nut won’t work for a 632 nut.

To change over older, two-piece, bowl-feed tooling, operators needed to ensure the orientation tool aligned properly with the singulation tool. “They also had to check bowl vibration, air eject time, and how the hose was routed,” Boggs said. “And they had to check the alignment of the shuttle and the vacuum. In short, operators had to check a lot of alignments to make sure the tooling performed as it should.”

Sheet metal operators often have unique hardware requirements, be it because of access issues (inserting hardware in hard-to-reach spaces), unusual hardware, or a combination of both. Such setups used custom-designed, single-piece tooling. From this, Boggs said, eventually came the development of one-piece tooling for standard bowl-fed presses. The tool incorporates both orientation and singulation elements (see Figure 3).

“It’s designed for quick changeover,” van de Bor said. “And all the control variables, including air and vibration, the timing, and everything else is controlled by the computer, so there are no switches or adjustments the operator needs to make.”

Locating pins ensure everything stays in alignment (see Figure 4). “Operators don’t have to worry about alignment when they change over. It’s always aligned because everything is pinned in place,” Boggs said. “The tooling just bolts on.”

When an operator places a sheet on the hardware press, he aligns the hole with an anvil tool designed to handle specific fastener diameters. A new diameter requires a new anvil tool, a fact that for years has promoted some arduous batch-production arrangements.

FIGURE 2. Bowl-feeding eliminates the most tedious aspects of hardware insertion.

Imagine a fab shop with the latest cutting and bending technology, all with quick, automatic tool changes that allow for small-batch or even kit-based production. Then the parts reach hardware insertion, where, if pieces require different kinds of hardware, operators resort to batch production. They might, say, insert a batch of 50 pieces, switch anvils, then insert the new hardware in the required holes.

A hardware press with a turret changes the scenario. The operator now can insert one kind of hardware, turn the turret, then reach into a color-coded container for another kind of hardware, completing all hardware requirements in one setup (see Figure 5).

“Depending on how many pieces you have, it’s less likely you’ll miss inserting a piece of hardware,” van de Bor said. “You complete the entire part with a single handling, so you don’t miss a step at the end.”

A combination of bowl-feeding and anvil turrets on an insertion press can make kit-based processing a reality in the hardware department. In a typical setup, fabricators dedicate bowl-feeding for common, higher-volume hardware, then place hardware used less frequently in color-coded containers close to the work area. When operators grasp a part that requires multiple kinds of hardware, they commence inserting, listen for a “beep” from the machine (signifying it’s time for new hardware), rotate the anvil turret, review a 3D image of the part on the controller, then insert the next piece of hardware.

Imagine a scenario in which the operator inserts one piece of hardware after another, making full use of the automatic bowl feed and rotating the anvil turret as needed. Then, after the upper tool grasps an auto-fed fastener from the shuttle plate and descends toward the workpiece on the anvil, it stops. The control alerts the operator that the fastener isn’t the length it should be.

As Boggs explained, “In setup mode, the press descends the ram slowly and records its position. So, when it’s running at full speed and the fastener touches the tool, the system ensures the fastener length is within a specific [tolerance] range. An out-of-range measurement, either too long or too short, triggers a fastener-length error. This, combined with fastener detection (no vacuum in the upper tool, usually caused by a hardware feed error), as well as the monitoring and maintaining of tonnage windows (rather than have the operator manually adjust a valve), creates a robust system ripe for automation.

“A hardware press that self-checks can be a tremendous asset to a robotic cell,” Boggs said. “In automated setups, a robot moves the sheet into position and sends a signal to the press that basically says, ‘I’m in position; go ahead and cycle the press.’"

The hardware press ensures the anvil pin (which fits in the hole in the sheet metal workpiece) is clear. The vacuum pressure in the upper punch is what it should be, so a fastener is present. Knowing all this, the press sends a signal to the robot.

As Boggs put it, “the hardware press basically looks at everything and tells the robot, ‘OK, I’m good.’ It initiates a press cycle, ensuring a fastener is present and its length is correct. It then verifies that the cycle is complete, ensuring the pressure used to insert the hardware was correct, then sends a press-cycle-complete signal to the robot. The robot receives that and knows that everything is clear to move the workpiece to the next hole.”

All those machine checks, made initially for the manual operator, effectively provide a good foundation for further automation. Boggs and van de Bor described further tweaks, like certain designs that help prevent sheets from sticking to the anvil. “Sometimes fasteners stick after the press cycles,” Boggs said. “It’s an inherent problem when you’re pressing material together. When it sticks in the lower tool, operators usually can give the workpiece a little twist to lift it out.”

FIGURE 4. A shuttle plate bolts on with locating pins. Once set up, the shuttle will present hardware to the upper tool, which uses vacuum pressure so it can hold and transport the hardware to the workpiece. An anvil (lower left) sits on one of four turret stations.

Unfortunately, robots don’t have a manual operator’s finesse. “So, there are now press designs that help facilitate workpiece removal, helping to push the fastener out of the lower tool, so there’s no sticking after the press cycles.”

Certain machines have different throat depths that can help robots maneuver the workpiece into and out of the workspace. Presses also can incorporate supports that help robots (and manual operators, for that matter) position the work reliably.

Ultimately, reliability is key. Robots and cobots might be part of the answer, and their integration has become a lot simpler. “In the cobot space, providers have made leaps and bounds to make it as simple as possible to integrate them with machines,” Boggs said, “and press manufacturers have done the development work to ensure the right communication protocols are there.”

But press technology and shop practices—including workpiece supports, clear (and documented) work instructions, and proper training—play their parts too. Boggs added that he still receives calls about missing fasteners and other problems in the hardware department, many of which utilize reliable and yet very old machines.

The machines might be reliable, but hardware insertion isn’t for the unskilled and unengaged. Think back to the machine detecting a length error. That simple check prevented a small error from snowballing into a larger problem.

FIGURE 5. This hardware press has an anvil turret with four stations. This system also has a special anvil tool that helps operators reach hard-to-access areas. Here, hardware is inserted just below a return flange.