Formnext 2016 Additive manufacturing enables fast modification of moulds
Germany - Direct metal deposition (DMD) can be up to three times faster than manual laser cladding. A new technique means laser welding systems can now be equipped with a powder nozzle for automatic layer build-up. The technology promises enormous potential for tool and mould making applications.
Since the start of the 21st century, laser cladding has become established as an effective process for modifying and repairing injection moulds and dies. Now a new additive manufacturing method is combining DMD with a coaxial powder nozzle. In contrast with conventional laser cladding, which usually requires a welder to feed filler wire almost entirely by hand, the new approach is fully automated and said to be highly precise.
The new system uses a powder nozzle which coaxially feeds metal powder into the laser beam and onto an existing surface. The process has been developed by Germany’s O.R. Lasertechnologie GmbH who claim it can be completely automated and is compatible with laser systems outputting as little as 300 watts. It can be used on three-dimensional surfaces and is claimed to be versatile: it can be employed for enhancing surfaces, modifying shapes and completely restoring forming, punching, and injection moulding tools and dies.
HWF, a mid-size tool and mould making company in Eppertshausen near Frankfurt have been among the first to test the technology. One of the challenges that the mould makers face is building up structures measuring 300 x 20 x 20 mm (i.e. with a volume of 120,000 mm3) on hot-working, wear-resistant steels such as AISI H11. In the past, these were built up layer by layer with wire-fed laser cladding to avoid the risks of cracks, deformation and altered metallurgical properties. It would take welders between 60 and 80 hours to complete the task.
Today, HWF uses additive manufacturing and is able to create the same structure by applying layers 250 μm thick at a rate of 5000 mm3 per hour. The procedure can therefore be completed in just 24 hours at a laser output of only 400 watts. Time-consuming finishing by EDM or milling is also said to be significantly reduced.
First, a CAD file defining the addition is loaded into the Orlas Suite, a CAD/CAM software programme developed by O.R. Laser. After dividing the workpiece into virtual layers and determining the best strategy, the coordinate system is calibrated with three characteristic reference points, and the laser parameters are transmitted to the system. Preparations take about an hour to complete. The manufacturing process then takes place automatically.
Close contours reduce need for finishing work
The laser system’s controls permit on-the-fly adjustment of the process parameters to meet changing requirements. Laser intensity can be varied: beginning with a fast build-up, output and powder feed rate are reduced toward the end to create surfaces close to the final contours.
The result is claimed to be a crack-free, high-quality structure optimally fused with the base material, with a hardness of 45-65 HRC. O.R. Laser also say that time-consuming preheating of the mould insert is no longer needed and that base materials are less stressed which reduces the risk of cracks and material undercut that conventional repair methods often cause.
Apart from time savings, the company also claims reduced material costs. Since the DMD process produces geometries that closely approximate the final contours, little follow-up machining is needed.
Markus Fischer, the managing director of HWF, says: “Laser cladding is here to stay in tool and mould making. DMD has made us more productive by letting us take a different approach when moulds change. We have firmly integrated it into our process and CAD/CAM landscape.”