Engineering Insight

By: Norbert Sparrow

Microcomponents and machined tubes must meet exacting mechanical specifications and quality standards to satisfy the demands of medical device OEMs. Consequently, the processes used to manufacture the parts must adhere to high levels of precision and consistency. XL Precision Technologies (Stockton on Tees, UK; www.xledm.com) produces approximately 900 000 stainless-steel tube components and assemblies each year, and demand continues to rise. To meet customer requirements, the company has relied on laser technology supplied by Rofin Baasel UK Ltd (Daventry, UK; www.rofin.co.uk) for micromachining and welding applications. It recently added a StarWeld Select system from the same company to “increase production capacity and add flexibility,” says Tom Graham, Managing Director.

The StarWeld Select from Rofin Baasel, which is headquartered in Germany, is an ergonomically designed and fully integrated laser welding system. It incorporates four precision axes that can be controlled manually by means of a joystick or under full CNC operation.

The system’s multimode operational capability enables the use of different techniques for product development, prototyping and full production runs. For example, the laser welder can be used manually to align and tack component subassemblies or semi-automatically under joystick control for manual deposit welding or prototyping new and complex welding geometries. Full CNC operational mode provides the functionality required for large batch and continuous production runs. This versatility is prized by XL Precision Technology, which cites two applications where the system has made a key contribution.

One application involves a component for a minimally invasive surgery (MIS) instrument that comprises four tubes and two spacers. “The part is produced in two stages,” says Graham. “The first operation requires welding the
circumference of a tube longitudinally to a larger tube.” The smaller tube has an outer diameter of 1.2 mm; the larger one measures 1.6 mm OD.

Two subassemblies from the first operation are then placed in a custom fixture with two spacers. Laser welds are performed on both sides of the fixture to complete the assembly. In CNC mode, the laser welder achieves a dimensional tolerance of ±0.030 mm on the finished assembly.

This irrigation tube may look like a simple part, but the acute welding angle makes it an especially challenging component to produce, according to XL Precision Technologies.

Irrigation tube presents welding challenge
XL Precision also produces an irrigation tube that requires the use of the StarWeld Select machine. “At first glance, the tube looks like a relatively simple part,” says Graham.“But it has a 2 mm outer diameter and an acute welding angle, making it an especially challenging component to produce.” The welding operation requires a combination of accurate positioning, precise control of welding parameters and complex component manipulation.

Graham cites the recent addition of the Rofin laser welding system as one more critical element in the company’s toolbox that will allow it to continue to accurately and repeatably manufacture products that meet its customers’ most challenging specifications. XL Precision also has the only Rofin Baasel laser machining centre with four-axes control in the United Kingdom.