Optimizing the punch/laser cutting combination machine

Grippers on SPM’s newest punch/laser combo machine remove a blank from a nest. Special Products & Mfg.

Enter the shop floor at Special Products & Mfg. (SPM) (No. 39 on the 2024 FAB 40), and you’ll see a range of cutting technologies, but the automated ones stand out—especially the four AMADA automated punch/laser combos. The Rockwall, Texas-based contract metal fabricator purchased its first combo more than a decade ago, and programmers and operators have learned a lot during that time. Laser Cutting Of Stainless Steel

Optimizing the punch/laser cutting combination machine

Much can be gleaned simply by observing the parts on pallets, the scrapped skeletons, and the sheets that still go through a manual shake-out operation. Over just a few days SPM can process hundreds of disparate orders, all strategically grouped by gauge and grade, to get the most out of material and machinery.

Automated punch/laser combos stand apart from other blanking technology. The machines can punch, form, tap, and laser cut, but they also offer a plethora of options for part, slug, and internal cutout removal. Suction grippers lift and stack parted-out blanks, but finished pieces as well as internal cutouts can be sent down chutes as well. Combine this with automated systems that monitor usage and change out punches and dies from magazines or carousels carrying dozens or even hundreds of tools, and you get the Swiss Army Knife of blanking.

SPM has both automated fiber laser cutting along with its automated punch/laser combos—so which parts go where? “With a punch/laser combo, you can run anything that you run on a punch and anything that you run on a laser. But if you don’t utilize that capability of both the laser and punch, you can run out capacity really quickly.”

That was Bo Carroll, SPM’s engineering manager who has been programming and perfecting punch/laser combo jobs since the fabricator installed its first machine in 2009. Over the years, he’s optimized programs and worked with SPM personnel and even directly with customers on how to design parts and take full advantage of the technology.

He works to ensure the turrets have sufficient clearance for the company’s many form tools. They have full press raises after every hit, and it’s for a good reason. Yes, programmers could hover the punch very close to the sheet surface. That’s great for punching efficiency—until the machine crashes because of a high form tool. (SPM’s latest machine can accept upform tools that give more clearance, and greater clearance overall for forming between the turrets.)

That work has resulted in a product mix that varies widely, but for the most part, the punch/laser combos take the brunt of production work, running all day and unattended into the night.

Carroll has spent years making the process as flexible, but also as stable and error-free, as possible. And the devil’s certainly in the details. For instance, the company makes good use of the machine’s in-process tapping station, with an integrated air-blow that cleans the tap threads and the surrounding metal.

This works much better than old-school in-the-turret tapping tools that could leave small puddles or droplets of oil on the metal surface.

“In a combo, you need to be careful about leaving tapping oil on the blank. When you start to laser-cut that, the table can catch on fire. Earlier on, I actually wrote a detailed procedure on how to run a tapping tool safely, without risk of fire. Fortunately, with the latest tapping technology on the combos, we don’t need to deal with that anymore.”

One of four AMADA punch/laser combos at Special Products & Mfg. processes a nest. All are fully automated, with automated loading and part sorting and stacking. Special Products & Mfg.

Talk about trial by fire, literally.

Over the past decade, programmers at SPM have worked to optimize their combo programs, most of which are static nests for production work. They’ve learned to push the technology’s limits while keeping the process stable enough for lights-out operation.

Consider a potential cut sequence for combos: Punch the internal features; laser-cut internal features as needed (with cutouts evacuated down a chute); create the forms (embosses, louvers, short flanges), laser-cut the profile, then remove the part. When possible, programmers at SPM always form as late in the cutting program as they can.

“The sequence here differs than on a traditional punch,” Carroll explained, “not just your order of cuts but where you make those cuts. On a manual punch press, you make your X cut [parallel to the clamps] closest to the clamps last. But with automated part removal, you want that farthest laser cut in the Y direction [perpendicular to the clamps] to be the last cut on the profile.” Cutting in Y allows the blank to stop moving and gives the optimal clearance for the grippers to move in and retrieve the part.

Of course, exceptions abound, like anything else in precision sheet metal. For instance, what if an internal profile requires a laser cut very close to a form? In this case, the punch might complete some internal features, followed by the laser, then forming by the punch, then back to the laser to cut the profile.

“Our machines also have height-sensing capabilities,” Carroll said, “so we’ve actually laser-cut over the top of forms. But you really need to optimize the sequence, and the feed needs to be slow enough to give time for the sensors to detect the sheet and raise the cutting head. But it is possible.”

Again, specific programming strategies can change depending on the nest and, for that matter, the attributes of a specific combo machine model. As Carroll explained, the best way to learn is to look at the machine in action, see how the clamps move the sheet, and how the work interacts with the punch and laser.

Like conventional punch presses, combos clamp and move the material throughout the cutting cycle. The toolpath sequence must ensure skeletal integrity so that the machine never loses its home position.

As John Ripka, application technician at Mate Precision Technologies, explained, “Since the width of a laser cut is narrower than a typical parting or slitting tool, parts can be nested much closer together.” He added, however, that because the combo moves the sheet like a standard punch press, programmers need to take skeletal integrity into account.

Glen Shuldes, applications engineer at Wilson Tool International, concurred. “You need a fair amount of integrity so the sheet doesn’t move during the forming process,” he said, adding that this can mean jumping back and forth between forming and cutting with punching or the laser, depending on part geometry and tooling available.

Developing a punching and laser cutting strategy on a combo machine hinges on the part mix and a shop’s tooling library. SPM has thousands of tools, and the magazine in its latest combo machine can hold several hundred. Special Products & Mfg.

At SPM, if a part has numerous internal cutouts near a formed feature, a programmer might choose to laser-cut or punch some internal cutouts, form immediately thereafter (when sheet integrity is optimal), punch or laser-cut the remaining internal components, then laser-cut the part perimeter before the grippers remove the workpiece. Because slugs and internal cutouts are evacuated, and no microtabs are left on the part perimeter, the piece can skip deburring and can go right to forming, welding, or assembly.

“You can definitely run into skeleton integrity problems,” Shuldes said. “As the clamps move the sheet and stop abruptly to start cutting, the sheet wants to keep moving.” Inertia rears its ugly head, and the remaining sheet ends up being slightly off from where it should be.

Flimsy or distorted skeletons can wreak havoc on process stability. One way to avoid this is to have no web section at all. This is where common-line cutting comes into play. As Jason Grand-Lienard, SPM’s plant manager, described, the part removal automation in combo machines is sometimes ideal for punching straight part perimeters along a common line. For certain part geometries, common-line cutting probably wouldn’t be practical without that automated part removal. As long as parts are removed immediately after being parted out, the process remains stable.

Carroll added, however, that common cuts at SPM usually produce skeletons with large windows—some look like large picture frames. The window shows the area of common-line cutting, while the frames provided enough rigidity, so the clamps could move the remining skeleton to the offload area without curling and getting caught in the brush table.

Also, common-line cuts at SPM are punched, not laser cut, since the laser-cut edges SPM produces are usually specified to very close tolerances. This can be especially true when complex press brake work is involved.

The way part removal works on some machines adds another layer of process stability. The grippers usually hover over a part during the final laser cut, then grasp it immediately after the profile is cut. Sometimes, though, programmers instruct the grippers to hold the piece as the laser cuts the part perimeter. This keeps the part stable and mitigates any bowing or distortion effects as the blank is released from the skeleton.

SPM primarily uses the chute on its combos for laser-cut internal features, but it also can be used for part evacuation, as long as the potential of part scratching isn’t an issue. As Wilson Tool’s Shuldes described, a similar cutting and forming sequence can apply: Cut as much as you can (via the punch or laser) before the forming operation, but not so much that you create sheet integrity issues. Perform forming, any remaining cutting, “then open the trap door and make your last cut,” Shuldes said, “so the part falls cleanly down the chute.”

Grand-Lienard added that toolpath sequence strategies vary with each sheet, and the best approaches build from operators’ observations. Does the remaining skeleton stay steady? Is there any evidence of distortion or curling of the remaining web sections? Are internal cutouts being removed reliably? Are grippers encountering any snags as they lift pieces out of a nest? Asking these and other questions help build a strategy that will keep the combos producing throughout a shift and unattended into the night.

Observe SPM’s machines in action, and you’ll see the punches create the internal part profiles, and all cutouts are sent down the chute. The lack of slats, Grand-Lienard explained, is one of the punch/laser combo’s greatest benefits.

Recently, an operator of one of the company’s automated fiber lasers pointed out one part with an internal cutout that kept getting hung up on a slat. The slats weren’t built up with slag, and the plant overall maintains a regular slat-cleaning schedule. That part’s cutouts just happened to have a shape that was susceptible to tipping. The programmer could have put in a slug-destruct sequence, chopping the internal cutouts into bits that could fall easily in between the slats, but that added cutting cycle time, and regardless, it wouldn’t mitigate the risk of tip-ups altogether. So, for a time, the shop kept those internal features microtabbed in place, there for those at the shake-out station to remove and deburr.

A combo machine can form like a conventional punch press, but determining when to form in the program can depend on the nest. Forms are usually made near the end of a program, but sheet integrity and clearance issues factor into the equation as well. Mate Precision Technologies

Getting rid of the slats—by using that punch/laser combo—proved to be a more robust solution. Today, the piece is cut on the combo using only the laser, then removed automatically and stacked, ready for the next operation.

Cutouts or slugs in general are a big consideration for process reliability. In SPM’s case, laser-cut slugs on the combo drop through a chute, but the reliability of that drop is always scrutinized. Typically, the drops happen without issue, but assist gas from the laser can cause turbulence that can make slugs on light material, like thin aluminum, behave unpredictably. The last thing programmers want is for that slug to end up on top of the material. So, for certain pieces, slugs are microtabbed in place. Yes, they require manual filing, but a little extra manual labor at the shake-out station costs a lot less than crashing an automated machine that’s supposed to run without interruption.

As they do with stand-alone laser cutting and punching, programmers at SPM sequence part programs to mitigate the effects of distortion. Grand-Lienard pointed to one program that uses a series of diamond clusters that create a perforation on a portion of each part in a nest. If the programmer sequenced those cluster-punch hits to occur from one end of the sheet to the other, distortion would ensue, and the position of other features and part perimeters would end up being slightly off from where they should be. Even worse, workpieces would curl and, in short order, create issues for automated part removal.

So, for this job, the programmer uses those cluster punches to place diamond-shaped perforations in alternating quadrants of a sheet, similar to how a stand-alone punch would be programmed. Spreading out those perforations minimizes the distortion and keeps everything aligned for the subsequently punched and formed features as well as the laser-cut part perimeter.

Brush tables on punch/laser combos, combined with automated part removal, allow for some creative programming, including the ability to create negative forms. At SPM, these include certain shallow embosses. In these cases, the brush table provides enough clearance, and the laser can cut the profile cleanly before the part removal automaton grips and removes the blanks. Again, if the blanks weren’t removed immediately after being formed, such forming likely wouldn’t be as reliable and repeatable.

Carroll added, however, that forming in the negative direction on a combo machine must factor in another consideration: the stainless steel roller table section in the middle of the brush table, which accommodates the laser. (Laser cutting directly onto a brush table would be, shall we say, an igniting experience.)

“If you laser-cut in the X direction, and the sheet drags over the stainless rollers and hits a downward-formed emboss, the sheet can jump up and hit the nozzle,” Carroll said, “and you can lose your cut. In those cases, we’ll laser-cut almost the entire part perimeter, then form the downward embosses or bridge lances. Then, we slow the machine down and make that final cut.”

Grand-Lienard again emphasized that this is very much the exception rather than the rule. In fact, the fabricator works with customers for ease of manufacturability, so if SPM can avoid downward forms on the combo, it does. The vast majority of forms—including louvers, extrusions, and flanges—are formed upward, usually at the very end of the program before the blank is parted out and removed.

What has become a rule, not an exception, when it comes to clearance is the space needed for certain narrow portions of a blank that protrude peninsula-like into a skeleton web section. “These can be problematic for part removal,” Grand-Lienard said. “We’ve learned to add a punch around those areas to give it space. For instance, we might add a 0.25- by 1-in. punch around those problem-geometry sections, just to give the blank shape some relief for the part removal automation.”

Observe the parts being stacked by SPM’s combo systems, and you’ll see flat pieces interspersed with some formed pieces with embosses and louvers. Still, not every job undergoes automated part removal, and this usually has to do with how the parts stack.

Tall louvers are formed on a sheet with punch tooling. Here, punch/laser combos give the programmer flexibility, especially for thick or abrasive material that can wear a punch form tool quickly. In some cases, the laser can perform the cutting that the form requires, after which the punch tool creates the form. Wilson Tool International

For instance, SPM fabricates numerous parts with tapped extruded holes, placed in such a way that makes stable, reliable stacking impossible. Before long, stacked parts would slide off each other. For this reason, you’ll see these and similar parts being sent to the manual shake-out station.

SPM still sends these jobs to the punch/laser combo, mainly because in-process extrusion and tapping far outpaces a secondary manual operation, even if they require manual part removal at the shake-out station. In these cases, programmers place the microtabs in strategic places, usually near a corner, to allow for easy shake-out and (when possible) to eliminate the need for edge deburring. They also ensure those remaining microtabs won’t interfere with any backgauging requirements at the press brake.

Specific punch tools can help ease the denesting process and, in some cases, be used in conjunction with automated part removal. Imagine you have parts too small for part removal grippers to grasp. A programmer might be able to nest them together (in a “mini-nest”) with a common line and use a punch tool that cuts a groove into the sheet from above and below. “And it often breaks off very cleanly,” Wilson Tool’s Shuldes said, “since you end up with a chamfered top and bottom edge.”

The pieces remain attached and sufficiently stable for grippers to remove. Once sent downstream, workers can snap the pieces apart whenever it makes sense—even after bending, if the blanks happen to share a bend line.

“The answer will depend on how many toolstations or rail locations are available for a product,” Mate’s Ripka said. “Another consideration is how many tools are required that are permanently loaded into the machine.”

He described a hypothetical situation in which a shop might choose to punch 0.250-in.-dia. round holes in 0.060-in. mild steel. Any hole smaller than that, and laser cutting (especially with a fiber laser) is likely to be faster; larger than that, and punching might be the way to go. “That is until the hole size exceeds the maximum tooling size you have,” Ripka said. “At that point, laser cutting would be the better option.”

He emphasized that the example merely illustrates concepts programmers might think about, but in the real world, they need to consider a host of different factors: slug removal, the potential of part removal automation, laser cutting power, and, again, available tooling.

At SPM, programmers punch straight sections, especially for 12 ga. and thicker. At that thickness, the punch can outpace the laser. For thinner stock, the 4-kW fiber laser wins the speed race every time. Carroll emphasized that this decision to punch versus laser-cut depends heavily on part requirements, downstream operations, and, not least, a shop’s tooling library. “At last count, I think we have more than 1,300 special shape and form tools,” Carroll said.

On top of this, its latest combo has a magazine capable of holding and automatically changing out hundreds of tools. Combine this with the machine’s auto-tool-change features and QR codes that track tool usage, and it’s no wonder the fabricator leans heavily on punching in its combo operations.

In most cases, SPM programmers punch when tooling is available and laser-cut the rest. They rarely if ever resort to nibbling special shapes and contours. Aside from a few legacy jobs that use specialty radius tools, the laser tackles nearly all curved geometries.

Not every piece SPM sends through the punch/laser combos is removed with part sorting automation. Pieces need to stack cleanly, and certain formed geometries—like the extruded holes in this part program—sometimes prevent that. Special Products & Mfg.

Material type and thickness specs factor into the punch vs. laser decision as well. Mate’s Ripka described some combo applications that resort to laser cutting more than punching, though just for certain sheets that can be abrasive for punch tooling, like high-tensile-strength material. “The use of punching tools in harder or more abrasive material may affect tool wear more rapidly than others,” he said. “In these cases, it might be more beneficial to laser-cut a large quantity of holes or shapes in that material.”

Shuldes described one hypothetical example where the material being processed is at the upper end of a machine’s thickness capacity. Punches can wear quickly in these scenarios, but adding laser cutting gives some flexibility. For instance, some form tools today can be designed without the punching capability. This helps when, say, trying to use a louver tool in difficult material. A traditional louver form tool does both cutting and forming. In challenging material, though, the laser can perform the cutting while the form tool can create the louver.

SPM’s fiber lasers are the low-volume workhorses, processing automatically generated dynamic nests all day long. When SPM receives jobs of sufficient production volumes, programmers do their best to send them to at least one of the company’s four punch/laser combos—especially its latest one, where the 4-kW fiber laser has effectively shaved hours off production times.

“We’ve had jobs that have historically taken us 14 hours [on punch/CO2 laser combos],” Grand-Lienard said. “Now, they’re taking just seven, so we’re doubling up on our lights-out production.”

The company has worked to perfect its static nests for these large orders, too, complete with clamp repositioning to get the most out of every sheet. Planners also have strategically placed like jobs together, such as numerous small-quantity jobs that all use the same grade of 16-ga. mild steel. Grouping all these jobs together effectively makes one high-quantity order, and with automated part sorting, all the jobs are stacked, organized, and ready to go when people return to the floor. There’s no huge pile of hundreds of random parts to sort through.

Some blank geometries, like those extruded and tapped parts, just can’t be stacked reliably—which is why some jobs still go to the manual denesting table. Again, manual part sorting is a small price to pay for all the efficiencies downstream.

Grand-Lienard pointed to a sparsely populated area of the shop, a place that once housed a multitude of manual drill presses. Just one remains.

“Every time we’ve installed a new punch/laser combo machine, this department has gotten smaller. All the tapping and countersinking and similar operations we used to do here are now done on our combo machines.”

Exceptions will always exist, an immutable fact at any contract manufacturer. Some taps or countersinks might need to happen after blanking or bending or welding. Some nests will inevitably need to be taken out manually. But the parts that people do shake out are optimized for the process.

For parts that can’t be automatically sorted, the combo’s lasers leave minute microtabs on the part profiles, and they’re located for optimal part stability and ease of removal.

A programmer might choose to use a cluster or custom punch, rather than rely on a laser to cut individual features. The decision usually hinges on available tooling and the consistency of the product mix. Mate Precision Technologies

Even better, the laser-cut tabs are much easier to break apart than those left by stand-alone punches—no more prying and hammering, no more manual denesting struggles amid an otherwise extraordinarily automated operation.

Orders move steadily and reliably downstream. And as those at SPM and other precision sheet metal operations have found over the past few tumultuous years, reliability—especially at the primary cutting operation—couldn’t be more important.

See More by Tim Heston

Tim Heston, The Fabricator's senior editor, has covered the metal fabrication industry since 1998, starting his career at the American Welding Society's Welding Journal. Since then he has covered the full range of metal fabrication processes, from stamping, bending, and cutting to grinding and polishing. He joined The Fabricator's staff in October 2007.