Assist gas is essential in fiber laser cutting, and for more than one reason. Not only does it assist in removing the molten material (slag) in the kerf, the gas, be it inert or active, also provides additional energy to aid in the cutting process. Unfortunately, gas is one of the costliest consumables associated with laser cutting.
Manufacturers that have switched from CO2 to solid state know they’re reducing costs in a number of areas, including electricity use. Fewer moving parts in the solid state laser also means less downtime and fewer repair and replacement costs. And solid state offers more compatibility to cut a variety of materials, including reflective metals. But what about the assist gas costs associated with fiber lasers?
Trumpf has the answer with its recent technology that helps manufacturers cut back on the costs associated with assist gas, especially nitrogen, while also making faster, cleaner cuts.
Because of the traditional distance between the nozzle and cutting surface, users in the past turned up the gas pressure to push the slag out of the kerf, increasing gas consumption. Trumpf’s Highspeed Eco, however, was developed to address that.
The Eco difference
In a standard solid state laser configuration, the nozzle remains a safe distance from the cutting material, minimizing the chance of collision. However, because of that distance, users have to turn up the gas pressure in order to push the slag out of the kerf, which results in increased gas consumption.
Trumpf engineers wanted specifically to find a way to process mid-thick carbon steel with nitrogen in a way that is an improvement upon oxygen cutting performance and also isn’t prohibitively expensive – as nitrogen cutting often is. According to Brett Thompson, sales engineer at Trumpf, cut quality on thick carbon steel cut with nitrogen has traditionally been poorer cut on fiber than on CO2.
“We really needed to address cost per piece and how much nitrogen is being consumed,” Thompson says. “With the normal process, the cubic feet per hour [of gas] consumed by cutting an individual piece is fairly substantial.”
So the team at Trumpf began looking at a way to confine the gas and aim it more effectively into the kerf. The result is Highspeed Eco, which involves a sleeve that fits into the nozzle that touches the top of the material being cut, thereby trapping the gas, which drastically reduces the amount of gas lost.
The sleeve also allows users to run gas at lower pressures, which is why Trumpf can tout 70 percent less gas usage while leveraging the Highspeed Eco. At the same time, the more concentrated focus of gas on the kerf allows users to dramatically increase the feed rate without affecting quality.
“The idea behind the Highspeed Eco is capturing that gas within the sleeve and actually creating a seal on the surface,” Thompson explains. “We call the sleeve the touchdown nozzle. It’s physically making contact on the surface of the material, which causes all of the gas to be trapped and forced through the kerf, so the amount of gas that needs to be used is quite a bit lower. On 1/4-in. material, we’ve seen cut speeds that are about double.”
Tip of the part
The process of forcing gas through the kerf is nothing new. Trumpf’s patent isn’t on the process, obviously – it’s on the dropdown sleeve. In terms of the overall Highspeed Eco, three components are involved: the base body, the sleeve and a pin that allows users access to the sleeve when it needs to be replaced. Thompson says the sleeve only comes in one size but that it works with any thickness of material.
When the assist gas is turned on, it forces the sleeve into the touchdown position. A reverse flow lifts the sleeve back up into the nozzle – referred to as the zero position – when the nozzle moves to another position. The cushion of gas allows the sleeve to move; bowed sheets, surface contamination and even diamond plated material doesn’t cause an issue, as the sleeve simply moves like a shock absorber over the surface of the material.
“That gives you a system that is very reliable,” Thompson notes. “We’re not talking about something that’s just a marketing gimmick – we can cut fast without a lot of gas. This is something that is practical for a customer to use.”
Thompson explains that the problem with other solutions that use a fixed nozzle position, which has a large nozzle that covers a decent amount of area, is that it sits just off the surface, so any surface contamination, tip-up or sort of interference from the material is going to cause the operation to crash.
“The program is always stopping and you’re constantly having to replace nozzles,” Thompson says of the crashes. “It’s just not a good way to process material, especially if there isn’t anyone around to push the stop button on the machine in the event of a collision. Where our patent lies is in the retractable nozzle. It rides on a cushion of gas, so it sits on the surface, but if you go over a piece of debris on the surface, the nozzle will actually move.”
This movement is important, especially when working on uneven terrain. The sleeve also tilts, so there are no issues as it goes over piercing spatter residue.
“It’s very flexible and forgiving in that regard,” he says of working around debris.
The predecessor to the Highspeed Eco is the first-generation version, the Highspeed. The Highspeed technology is unique in that it uses a bi-flow nozzle, which allows a percentage of the assist gas to run through the middle of the nozzle along with the laser beam. The remainder of the gas forms a secondary flow around the middle flow, which is concentrated into the kerf, knocking away the molten material in a more efficient manner than traditional solid-state laser processes using nitrogen.
As seen on page 13, Trumpf has videos that compare the traditional fiber laser, Highspeed and Highspeed Eco cutting the same material. The Highspeed technology uses 40 percent less gas and is 100 percent faster than the standard laser configuration. The Highspeed Eco technology cuts at the same speed as the Highspeed option, but uses 70 percent less gas than the standard process.
Thompson says the Highspeed Eco solution isn’t targeted at any particular industry – it is something that is available to anyone who is interested, so long as they have a Trumpf 5-Series laser, though the company is currently working on making Highspeed Eco compatible with other Trumpf laser lines.
“Anyone who has one of those machines is the target audience,” he says, “because they’re all going to benefit from it.”
Thompson says that since the technology became available last year, he’s had customers tell him they’ve replaced three machines with one Highspeed Eco-equipped machine.
“These customers are doing a lot of 1/4-in. carbon steel,” he says. “So you’re getting a lot more throughput, even relative to an 8-kW machine. But you’re also able to justify those costs because it’s making the part so much cheaper. We’ve had really good feedback on it.”