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Cutting, positioning and joining in one clamping

New manufacturing solution from weil engineering

Equipping components which carry media with threaded bushings or fittings, replacing hydroformed components by deep-drawn half-shells and building complex 3D assemblies from individual parts direct from the coil – these are the areas of application for CutFusion from weil engineering, the mechanical engineers from Mülheim. CutFusion not only saves a great deal of handling time and effort, it also makes the manufacturing workflow much safer.

The CutFusion method

CutFusion is a fully automatic method where parts or assemblies are processed completely in one clamping. After the component has been clamped in the fixture, its position is known at all times during the manufacturing process. Now the laser can cut holes and contours in the component. Then the individual parts to be joined are positioned with the aid of internal automation, and welded using the laser – in an absolutely reproducible manner thanks to the same clamping.

“The knowledge of position and orientation is the greatest gain when using the CutFusion method,” emphasises Harald Liebhart, Head of Development Laser Cutting at weil engineering. This method provides more product reliability and an optimised manufacturing workflow.

The machine concept

The flexible laser cell FLC offers the constructional basis for the CutFusion method. A cutting optic and a welding optic are both located on a joint drive axis. Each is driven by a separate linear motor. Thus the laser can produce the break-outs with the cutting optic first, then the cutting optic moves out of the working range and makes room for the welding optic, which joins the positioned components.

The FLC provides room for up to three separately driven axes in total. Depending on the application case, the third axis can be equipped with a welding or cutting optic.

Use of a further processing optic can greatly reduce the cycle time in many cases.

Threaded bushings and fittings

Parts which carry media in particular are equipped with various threaded bushings, fittings, screw tubes and flanges. Air-tightness and thus a high seam quality are vital for these components.

The component is clamped in the fixture, the hole contour cut, the fitting added and welded. Since the part is firmly clamped during the processing process and remains clamped, the welding position is identical to the position of the cutting contour and can be approached in a reproducible way.

Processing always takes place in a fixed position: the laser beam always strikes the component vertically from above. Then the fitting is positioned and welded. If further fittings or connection pieces are to be joined in other positions, the fixture moves to the corresponding fixed position before cutting, and the process can be repeated.

The optic is crucial

When a fitting is welded onto a component, the welding optic is guided from the outside in a circle around the joint. In the case of standard optics, this movement means a complex interplay between four axes – connected with overhanging movements of the optic around the join area. This is due to the structure of standard optics: The Z-axis of the machine and the focussing axis with the focus point are parallel and a distance x apart. This means a rotational movement of the optic around the Z-axis leads to a circular welding path of radius x. Conversely, the welding of small radii is linked with large movements. This means a large interfering contour and can lead to access difficulties when welding small fittings onto small components in particular.

Together with TRUMPF Lasertechnik, weil engineering has developed a rotation optic where the focus point is on the Z-axis of the optic. When this optic rotates about the C-axis, the orientation of the focus point remains constant. This allows small contours to be achieved with minimum displacement movements. This is not only beneficial for accessibility, it can be of an advantage for the design of the entire machine.

In the example, a fitting with a diameter of 20 millimetres is to be welded to a component. The rotation optic moves at a welding speed of 2 m/min around the component, the welding time is 1.8 seconds.

In contrast, the standard optic would have to move along a circular path with a radius of 290 mm for this component. This corresponds to a length of around 1.8 metres. Since the welding time should be unchanged at 1.8 seconds, the system would have to travel along this path at a speed of 1 m/s = 60 m/min. This speed makes completely different demands on machine design since much greater acceleration forces are applied.

Turn two into one

It is easier, less expensive and more flexible to build a component from two pressed half shells than to produce it in a hydroforming machine. “This approach is not only predestined for the CutFusion method, it opens up unbelievable potential for the production of function parts,” reports a confident Harald Liebhart. For this application case, the flexible laser cell FLC was equipped with two cutting and one welding optic. The two half shells are supplied to two work stations and clamped there, thus fixing and defining their position. They are trimmed by a laser cut, whereby the laser beam is divided between the two work stations with the cutting optics. Then the cut half shells are positioned and joined by laser. The entire laser output is available for this, increasing the welding speed accordingly.

After this base body has been built, further working steps can follow, turning the two joined half shells into a complex component: The cutting of further break-outs, positioning and joining of muff and fittings or complete functional parts. Thus even complex assemblies are made in one clamping without intermediate storage and transport of the parts.

Tailored parts: Always know where

It is particularly attractive to build a complex 3D assembly from roll-fed material. Just-in-time production in its purest form – made possible by the laser.

The individual parts are cut directly from the coil. A handling system such as a robot, grasps the part directly while it is still being cut. This makes its position and orientation defined and known. This component can be positioned in the fixture and joined without further measurement. The component is picked up exactly once during production and positioned in place directly. This renders every type of measurement, positioning and alignment obsolete and saves time and handling efforts. “Position orientation is the most major saving. It combines four individual steps into one: orientation, measuring, supplying and positioning,” says Harald Liebhart, summarising the advantages.

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