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EBW is a machine controlled process, with welding carried out in vacuum with no filler material, resulting in exceptional weld quality and repeatability.
Weld speeds are typically 1-2 metres/min and result in deep, narrow welds requiring less than 5% of the heat input needed for a comparable depth TIG weld.
The remarkably low distortion resulting from EB welds means precision parts can be finished machined prior to welding, even ground gears.
Click below to see a short video explaining how the process works.
What is the difference between EB and Arc welding?
Arc welding melts metal by applying heat via an arc or plasma faster than it can conduct away until a molten pool is achieved. On thin materials, <2.0mm, the heat source is moved along the joint leaving the melted metal to fuse together. To weld thicker materials it is necessary open the joint to a “vee” of around 90° and to add filler metal, usually in the form of a small diameter rod, which is added to the molten pool of metal to fill the “vee” and so achieve the required joint thickness.
This is a relatively slow process, with weld speeds of 20-30mm/min, and applies a substantial amount of heat to the top surface of the joint, resulting in distortion as the welded metal cools and shrinks.
E B welding uses a focused stream of electrons, which can focus typically 4KW of power into a spot of 0.5mm diameter. This power concentration is so intense that it instantly melts the metal, not just to a liquid but to a vapour. Because conduction is now a minor factor deep welds can be produced at very high speeds. 10-15mm weld thickness at 1000mm/min are typical. As a result, total heat input for EB welding is less than 5% of that required by Arc welding, with resulting much reduced distortion.
Is EB welding equipment expensive and if so how does it compete with conventional welding?
EB equipment is expensive; £300,000 to £2,000,000 is typical, subject to the size of machine. There are several areas where the advantages over alternative processes are so good that it is not difficult to justify the cost.
First is repeatable weld quality; E B welding is mostly carried out in a vacuum with no filler material. Parent metal is being re-melted in vacuum to produce the weld.
The process can now be fully programmed to ensure consistency
Second, weld speed; EBW can weld thick sections 100 times faster than conventional processes.
Third, welding of dissimilar metals; this enables combinations of materials for optimum cost or performance to be joined; a steel hub to a bronze worm gear; a bearing metal to a toughened shaft; magnetic to non-magnetic.
Fourth, because of minimal distortion, even parts as accurate as finish ground gears can be welded together.
What is the difference between EB and Laser welding?
They are both high energy density welding processes. EB welding still produces the deepest high quality welds, but because it is normally carried out in a vacuum the size of the vacuum chamber limits the size of assemblies and speed of the overall weld cycle time.
Laser, which uses highly focused light does not need a vacuum, but still needs controlled atmosphere to weld high strength materials. It is very successful for low power, high speed welds for electronic and thin metal joining, where fibre optics can be used to deliver the light source.
Who invented EB welding?
In 1950’s, Zeiss in Germany were experimenting with electron microscopes and found they could melt metal. They developed the first useable high power EB welding machines, but sold the patents to concentrate on their core optics business. The basic principles of their original design are little changed today.
Why isn’t EB welding more widely used?
Whilst small chamber low power EBW machines are a similar price to a mid-size CNC machining centre, larger work chamber high power machines come with seven figure price tag and require significant expertise in development and control of processes. To justify the level of investment involved requires a major production demand.
This why companies like EBP exist, because we realise that there are thousands of potential applications, which, by themselves won’t support the investment on in-house equipment
The other problem is that EBW is one of a wide range of hi-tech processes available to the design engineer, such as high speed 5-axis machining, additive manufacturing (3D printing), precision casting, ect, all vying for attention. You have only to look at the range of applications that we at EBP are involved in to get a flavour of the potential including;
underwater weapons, satellite valves, motors and structures, motorsport gearbox and suspension, deep water instrumentation casings, hip joints, aero-engine assemblies, critical pressure vessels for defence, commercial, motorsport, radar arrays, electronics enclosures and many more.