How to keep the kerf clean

Oct 14, 2024

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Since flatbed fibre lasers can process parts faster than ever, bottlenecks in part sorting are inevitable.

Whether a shop is using automated part picking or is clearing a skeleton by hand, it’s critical that the parts be easily removed and require minimal post-processing. Canadian Fabricating & Welding spoke to a few machine tool manufacturers to learn how they are helping companies achieve cleaner, more manageable parts in any thickness.

Production flow will be interrupted if parts are welded onto the sheet. Maintaining a clean cut around parts is essential, especially if the part picking processes are automated. Ensuring the cutting process is producing high-quality parts with little to no burr is key.To help manage cutting parameters, AMADA has developed its Laser Integrated System. Originally developed for its REGIUS machine, it has since been rolled out across all of its laser models.

“The system includes i-Nozzle Checker, i-Optics Sensor, and i-Process Monitor,” said Jean-Philippe Nadeau, blanking product manager, AMADA CANADA. “I-Nozzle uses a camera to check the quality of the nozzle, ensuring it’s still concentric. If it needs to be switched out, it does so. It also centres the laser beam automatically.”

The i-Optics Sensor checks the protection glass on the cutting lens.

“It automatically detects any kind of light reflection change on that glass and reports on the cleanliness of it,” said Nadeau. “It lets you know if cleaning or replacements are necessary.”

I-Process Monitor analyzes the beam conditions while sheet is being cut to detect whether the sheet is being properly processed. It then adjusts on the fly and continues cutting. If the cutting head collides with material, a sensor detects that and will stop the machine, check the integrity of the head, and either change the nozzle or recenter the laser and go back to the cut.

TRUMPF has two approaches to monitor laser cutting, the first being Active Speed Control, which looks at the cut in real time to ensure it is clean.

“Whatever feedback the laser gets from the material, it compensates for by either slowing down or speeding up, so it is constantly doing that,” said Brett Thompson, laser technologies and sales consulting manager, TRUMPF Inc.

That technology can be found on the company’s highest-performance machines. For all other units, it has a tool called Smart Rerun, a less interactive process monitoring system.

Avoiding welded sheets is a function of having the right kerf width for the material type and thickness. AMADA’s Locus Beam Control (LBC) technology is one method of managing this. It manipulates the laser beam to create an infinite number of locus patterns. The beam pattern is adjusted for each application. AMADA

“It works off voltage readings,” Thompson explained. “It can identify when a cut is lost. And if a cut is lost, it allows the laser to go back to the cut and try to separate it again.”

AI technology on Mitsubishi’s GX-F Advanced series of fibre lasers uses both a light sensor inside the laser head and a microphone on the side of the head to monitor and adjust the cut.

“The laser rates the cut in real time” said Nick Plourde, project specialist at MC Machinery Systems, the North American supplier and servicer of Mitsubishi lasers as well as laser automation systems, press brakes, and machining equipment. “The machine is able to monitor the cutting process in real time and make necessary adjustments to increase productivity, stabilize or regain the cut as well as track the condition of the nozzle and replace it automatically if necessary. This active monitoring provides stable and efficient processing while maintaining part quality. High part quality contributes to successful sorting.”

Avoiding welded sheets in the first place is a function of having the right kerf width for the material type and thickness.

AMADA’s Locus Beam Control (LBC) technology is used to manage this. The LBC technology manipulates the laser beam to create an infinite number of locus patterns. The beam pattern is adjusted for each application.

“Depending on the material type and thickness, the pattern of the beam will change to widen that kerf as necessary,” said Nadeau. “Using this, we have a productivity mode where we can achieve cutting speeds with a 6 kW that are more common for 9-kW models. And the great thing about the technology is that when you have part picking automation, you can play with the kerf width to help open that gap to make the part picking smoother, so that parts won’t catch on the skeleton when it’s lifting.”

TRUMPF’s Brightline Fiber is one approach to this. The technology is equipped with two fibre-optic cables that allow operators to switch between beam modes.

“This is particularly important on thicker materials because without a wide enough kerf, it can be difficult to remove those parts,” said Thompson.

Another technology that MC Machinery offers to optimize part quality and lower nitrogen consumption is the new, patented Agr-Mix blended-gas nozzle. Standard nitrogen conditions on thicker materials can produce a narrow kerf, which can make parts difficult to pick. The nozzle technology not only reduces burr and nitrogen consumption but also produces parts with a larger kerf, which are easier to remove with automation, Plourde said.

While oxygen creates the widest kerf, it doesn’t result in the fastest cutting speeds.

To avoid part tip-up while also simplifying par picking, TRUMPF has created a non-joint process, creating a narrower tab by lowering the laser power output without stopping the laser's movement. TRUMPF

“That’s when having the option of the Agr-Mix is an advantage. The material being cut determines what gas mix will work best for part sorting,” Plourde said. “In very thick materials, you need to use oxygen to get a manageable kerf for part sorting. But as material gets thinner, that changes.”

The part sorter itself also can help with part removal. Plourde noted that MC Machinery’s ASTES4 part sorting software is designed to search for the centre of mass on each part it picks to ensure it lifts straight away from the skeleton. And the ASTES4 has an AI component that detects if a part is being gripped properly.

“Although the ASTES4 can still sort parts with a narrow kerf, you will still benefit from a larger kerf for more stability and better productivity,” Plourde said.

Avoiding part tip-up on a sheet is a critical concern to not only ensure that parts don’t fall between slats but also that no collision with the laser head is possible. Tabbing the parts to the skeleton is the traditional way of addressing this issue.

“Tabbed parts allow you to create a micronest within a nest,” said Nadeau. “This can speed part picking and also post-processing. For instance, you may have a group of the same part that has a simple bend in it. Tabbing those together, you can also process them as a group on the press brake with one stroke instead of bending each individually.”

Part size determines if it needs to be tabbed onto a sheet or together with other parts.

“Customers, of course, will adopt tabbing as they see fit. Some will cluster parts, others will keep parts tabbed into a skeleton,” Plourde said. “In our ASTES4 High-Speed Advanced laser automation system, we have two offload carts for skeletons, so it’s possible for a customer to separate skeletons. Those with parts remaining in them are unloaded into one while empty skeletons go in the other as all other parts are picked out by the automation system.”

This is especially beneficial for shops running lights-out—it’s easier to locate parts the next day, and the system shows any parts missed during processing.

One way that TRUMPF is managing this challenge is through the creation of nano-joints. This capability is enabled by the company’s beam management system.

“Using that system, we can monitor the beam and control to +/- 1 per cent of its power output,” said Thompson. “This means that even on our 24-kW laser, we can scale that power down to a really low level at a very specific point in time, creating a tab that might be a quarter of the thickness of the material. It means we can program how thick or thin we want that joint to be and can place it anywhere around the part. At the same time, the laser never stops moving, it just ramps the power up or down. It results in a process where there is no pause in the processing time. And if you are removing parts by hand, it’s very easy to do because they are barely attached. It also allows common-line cutting to be managed very easily.

AMADA has a new method to anchor parts on the skeleton without using an actual tab that it calls a "soft joint." Essentially the laser cuts an "L" pattern relief on the sheet on each side of the part which creates a control stress in the material that applies pressure to the part to hold it in place. AMADA.

“The technology has continually improved since we first introduced it because we’ve managed to control it better and better. We’re at almost half of what the original limit was on how thin those joints could be.”

AMADA has a new method to anchor parts on the skeleton without using an actual tab that it calls a “soft joint.” Essentially, the laser cuts an “L” pattern relief on the sheet on each side of the part. When the part is cut, this relief creates an “L” shape that creates a control stress in the material that applies pressure to the part to hold it in place.

“It’s remarkable to see how well it holds the part in place,” said Nadeau. “But if you want to remove it with a part picker, it is not affected by being attached to the skeleton. It adds a few extra cuts to your process, but it is very effective for avoiding tipping, and there’s no concern for part picking applications.”

There are times when it is necessary to remove interior cut-outs that can get stuck in the skeleton, such as a larger round hole in a part. AMADA uses what it calls laser destruction or “slug destruct,” where those items will be cut to allow them fall through the table slats more easily.

“This is just one more tool that makes automated part picking easier, because you don’t want to lift that cut-out off the sheet with the part,” said Nadeau.

Nadeau discussed the importance for shops to consider how nesting will change with automation.

“When you automate part picking, you need to change your approach to nesting,” he said. “Most companies now are just focussed on getting the most out of their sheet and will use many filler parts everywhere. But with automation, your priority needs to be the stability of the sheet. Ideally, you want to have at least 3/8 in. between all your parts to make a seamless operation. The result is additional scrap material, but the trade-off in productivity and long-term cost-effectiveness usually outweighs that cost.”

AMADA’s automated part removal systems are equipped with between one and three unloading tables, depending on the model. Nadeau encourages companies in the process of considering these systems to think more in terms of kits with their nesting.

“Essentially, you want your nest to be similar to how you will lay out the completed parts on the unloading tables,” he said. “This keeps the processing straightforward. In high-mix/low-volume shops, this is not always possible, but it’s a useful goal to have in mind to keep the process as simple as possible. These setups allow you to see a great deal of productivity quickly.”

When investing in new equipment, companies should consider all available options. If part sorting is a critical concern, a flatbed laser cutting machine may not be the ideal system.

Standard nitrogen conditions on thicker materials can produce a narrow kerf, which can make parts difficult to pick. Mitsubishi's Agr-Mix nozzle technology not only reduces burr and nitrogen consumption but also produces parts with a larger kerf, which are easier to remove with automation. MC Machinery

A standard alternative in the market is the laser/punch combo configuration. With its ability to punch and tap forms, laser cut contours, and sort parts efficiently, it can be ideal for the right part mix.

“Because it is removing parts one at a time during processing, there is less that can go wrong in the part sorting process,” explained Nadeau. “Of course, it’s a machine for thinner material. Once you start working with material more than 3 mm thick, it may still be possible to use, but it may not be ideal. But a lot of people who are used to using lasers don’t automatically think of punching capabilities. Although it may run slower than a flying-optic machine, you can also go a lot with it, and in the end it’s a very cost-effective process.”

TRUMPF widened the scope of options with the introduction of both the TruLaser 8000 coil edition and the TruLaser Center 7030.The coil edition is fed, as suggested by the name, directly from the coil. The flexibility of this is twofold: operations aren’t dictated by a sheet size, so it’s possible to choose to operate within a form that best suits the parts in line at one time; and it’s part of a large cell that provides robotic part picking at the end of the line.

The TruLaser Center 7030, meanwhile, is a laser centre that runs somewhat like a punch press in that part sorting is integrated into its operating footprint, with a drop bin for smaller parts and suctioned part lifting for removing larger parts. Like a punch press, it runs on a sheet dragging model, so some material is unusable due to the grippers required to manipulate the sheet. However, productivity savings in terms of sorting and skeleton removal more than offset this concern.

Downtime just isn’t an option today, and the more efficient a fabrication shop is compared to its competitors, the more business it will be able to win and keep. Lasers can help make increase that efficiency. Part sorting ease is a crucial part of that equation.

Editor Robert Colman can be reached at [email protected].

AMADA CANADA, www.amada.ca

MC Machinery, www.mcmachinery.com

TRUMPF Inc., www.trumpf.com

If part sorting is a critical concern, a standard flatbed laser cutting machine may not be the ideal system for a shop. Other options, such as a laser/punch combo, or TRUMPF’s new TruLaser 8000 coil edition shown here, are worth putting in the mix. TRUMPF