At the Bolton, Lancashire, England factory of trailer manufacturer Indespension, sheet metal cutting productivity has doubled following the December 2016 replacement of a CO2 laser-powered machine with a Bystronic ByStar Fiber 6520 fiber laser profiling center costing nearly £800,000 (approximately $1.3 million; FIGURE 1). The 4kW fiber laser has a 6.5 × 2m capacity bed, making it the largest fiber machine delivered to date into the UK market.
|FIGURE 1. With the ByStar Fiber 6520 fiber laser system, nitrogen is employed as the cutting gas on material up to 5mm thick, above which less-expensive oxygen is used; there is little difference in the quality of the cut edge.|
Indespension's purchasing director Steve Sadler commented, "We cut mainly 43A and pre-galv mild steel, plus some aluminum, from 1mm to 12mm thick. Up to 3mm, the fiber laser cuts three times faster than CO2. It flies through 1mm steel, producing 10 holes/s. The advantage tails off as the thickness increases, but overall the ByStar is twice as fast across all the gauges we process. At a stroke, it has eliminated the bottleneck in our factory that was being caused by the CO2 machine not being able to keep up with our ever-increasing laser cutting workload."
The fiber laser was purchased in part-exchange for an equivalent-capacity Bystronic CO2 model to Indespension supplied in 2009. Sadler confirmed that a good price was realized for the old machine, despite it having worked up to 20 hours a day, highlighting value retention as an advantage of buying equipment from this manufacturer.
At the outset, the main reason for investing in laser cutting was to achieve a greater degree of in-house control over trailer production and save the expense of putting work out to sheet metal subcontractors. Another important consideration was to streamline the prototyping and design process and bring new products to market faster.
"Prior to 2009, during product development we had to buy in one, two, or three sets of prototype sheet metal parts," Sadler continued. "Subcontractors were not keen on producing such small quantities, so the price tended to be high and it took them four to six weeks to deliver the prototypes. If we needed to make a design change and go back to the subcontractor for further prototypes—it could be something as simple as a new set of mudguards—that could add another month or so. Now, we can produce the parts in-house in a matter of days, reducing the lead time for a new trailer from typically six or seven months to less than five, or for a modified trailer from three or four months to less than two."
Sadler pointed out that a decade ago, few trailers incorporated laser-cut features, whereas today they are used extensively. Indeed, products are designed around the considerable capabilities of modern laser cutting machines. One advantage is that machining is so accurate that components fit together precisely and quickly during assembly, without the need for time-consuming fitting-up.
The other benefit is that machining is so fast, especially with the fiber laser, that it is a cost-effective way of taking weight out of components by incorporating numerous holes and slots. It would be too labor-intensive and therefore uneconomical to do manually.
The laser cutting cell operates day and night shifts plus lights-out during the summer months, totaling 18 to 20 hours per day, five days a week. For the remainder of the year, it runs a day shift and lights-out for 10 to 12 hours a day.
Indespension decided not to install automation equipment because it processes a wide variety of sheet sizes, making automated loading problematical. The range of component sizes is also large, ranging from over 5.8m down. Operator attendance is therefore necessary to manage the diversity, so a manual, suction-pad lifting system is used for sheet handling (FIGURE 2).
|FIGURE 2. Sheet handling on and off the ByStar Fiber 6520's shuttle table is performed manually at Indespension using a suction-pad lifting device.|
This presents the company with a problem, however, if a production run involves a nest of only a few simple parts and they are cut from a thin-gauge sheet. The cutting cycle is so quick in the fiber laser machine that the operator does not have time to finish shaking parts from the previous skeleton before the following machined sheet is ready, or to load the next blank onto the shuttle table.
So, the company is thinking about including micro-tags into some sheet metal cutting programs so that profiled parts remain attached to the skeleton, allowing the entire processed sheet to be transferred to an off-line station, where another member of staff can help remove the components.
Of the laser-cut sheet metal parts that go into Indespension's trailers, 80% require folding. Accordingly, when the first laser machine was installed, a tandem press brake from the same supplier was delivered as well (FIGURE 3).
|FIGURE 3. One of Indespension's plant trailers, called Digadoc, showing the large number of laser-cut features and folds required for its sheet metal component parts.|
There are productivity benefits from sourcing the laser cutting machine and press brakes from the same supplier in that all use the same BySoft 7 software. When a new component is designed in Indespension's SolidWorks CAD system and exported to the Bystronic control software, which itself contains powerful 3D CAD/CAM functionality, the model generates a program for laser cutting and a sequence for bending the component, including backgauge position and tool plan, thereby minimizing delay and downtime.
The same software, which has full simulation capabilities, is responsible for nesting the maximum number of parts from a sheet, creating cutting plans and providing an overview of the manufacturing process, including immediate access to production and machine data.
"We are committed to leading the market in terms of innovation, quality, and environmental credentials," Sadler concluded. "The acquisition of the Bystronic fiber laser helps us to deliver on these aims, as well as providing a much-needed increase in production capacity. It also marks our commitment to UK manufacturing, which is an important part of our company ethos."