Fiber laser system cuts parts for bicycles

BARNOLDSWICK, LANCASHIRE, ENGLAND – Hope Technology manufactures aftermarket components for bicycles, exporting half of its rapidly expanding production to more than 40 countries. The business, which was founded in 1989, now employs around 130 people and was based on a quest to make mountain biking safer by developing an alternative to cantilever brakes.

Founders Ian Weatherill and the late Simon Sharp, ex-Rolls Royce aero engineers and toolmakers, developed a brake disc inspired by those used on motorcycles. Now, the brakes are manufactured in the tens of thousands annually, along with sprockets, chain rings, and other components that go onto a mountain bike (FIGURE 1).

FIGURE 1. Hope Technology's chain rings and brake discs (inset) are used on mountain bikes.

By mid-2015, one of the company's 70 CNC machine tools on the shop floor, a Bystronic BySprint CO₂ laser cutting machine, was struggling to keep up with the factory's 24/7 operation. So Lindley Pate, works and production manager at Hope Technology, knew that fiber laser cutting was a maturing technology—so the company installed a 4kW Bystronic BySprint Fiber 3015 machine.

"We use relatively thin materials, such as 2mm stainless steel for brake discs and up to 6mm aluminum for some sprockets," Pate says. "For thinner gauges, compared with an equivalent CO₂ source, the fiber laser produces components three times faster. It has made a fantastic difference in helping us to meet the sheer volume of orders."

The machine is equally capable of handling much thicker material. The company often processes 12mm-thick aluminum tooling plate to produce fixtures for other machines on the shop floor.

A further advantage of fiber laser cutting, Pate says, is the high cut quality using nitrogen exclusively as the cutting gas. "The as-machined edges on stainless steel appear polished, so brake discs, for example, need no edge finishing. They go straight to onsite heat treatment," he explains. "This is in contrast to production on the previous CO₂ machine, which left a residue even when nitrogen was used. Oxygen as the cutting gas is not used at all here to avoid the problems associated with oxidation of the cut metal edges."

Pate adds that other factors in favor of fiber laser cutting over CO₂ are more consistent accuracy, less machine maintenance, and more economical running costs, both in terms of the amount of electricity used and the lower requirement for cutting gases. There is now no need to use helium gas at all (which runs all the time on a CO₂ laser machine), resulting in further savings.

Bicycle components cut on the company's fiber laser system are mainly brake disc blanks from 410 stainless steel sheet in soft condition (FIGURE 2). The discs are either one-piece varieties or two-piece assemblies requiring an outer band of the same material and a floating center of 2014 aluminum, which is also cut on the machine. The company also produces sprocket blanks from 7075 aluminum, as well as bike maintenance tools, merchandise such as bottle openers and key rings, and parts for display stands and trophies.

FIGURE 2. Brake discs ready for milling.

Maximum sheet dimensions that can be accommodated on the fiber laser cutting machine's table are 3.0 × 1.5m, which is generally the size used when producing aluminum parts. However, in the case of the specialty stainless steel that the company buys, the mill supplies the sheet in a variety of strip sizes—typically 330–550mm wide by 1000–1500mm long—which is placed transversely across the machine's shuttle table for processing.

The variation in stock was one reason that the company decided not to equip the laser cutter with an automated system for delivering fresh material to the machine and subsequently retrieve the laser-profiled sheets. Another reason, as Pate points out, is that the facility is a low- to medium-volume manufacturer of specialized components that need not only CNC machining, but also a degree of hand crafting—so large-volume manufacturing principles are not appropriate.

Based on design data from the company's SolidWorks CAD network, programming is carried out offline using Bystronic's BySoft 7 software, which has nesting capabilities for maximizing component output from a sheet, according to Pate (FIGURE 3).

Laser cutter programmer Mark Jolly likes the useful scrap cut-down feature in BySoft that cuts big areas of waste material inside a component into several smaller pieces. It avoids the risk of a large piece of scrap distorting upwards, which could damage the laser nozzle traveling 1mm above the sheet. He also appreciates the engraving function that can be called up at the control by backing off the power output from 4kW to 600W.

"We have always believed in making everything in-house from top-quality materials, either solid billet or aluminum forgings," Pate says. "We not only machine everything ourselves on CNC equipment to control precision and quality, but also heat-treat, anodize, polish, and assemble onsite. We are even branching out into in-house carbon fiber production, which will result in handlebars, seat posts, and even a complete bike being available."

"The fiber laser has become an essential tool at the start of the production routes for brake discs and sprockets," Pate continues. "There has been minimal downtime since the machine was installed, which is essential—we only operate one laser, so it has to be reliable, as otherwise production would stop."

This article was supplied by Bystronic UK, Coventry, Warwickshire, England; www.bystronic.com.