10 Questions
What is the role of high-pressure gas streams in the LBM process?
Aiding the exothermic reaction process, cooling, and blowing away vaporized or molten material and slag.
How does surface roughness change with increasing feed rate in LBM?
Surface roughness increases with increasing feed rate.
What is the effect of increasing cutting speed on surface roughness and quality in LBM?
Surface roughness decreases, and quality improves with increasing cutting speed, when other operating parameters are kept constant.
What is the range of achievable tolerances in LBM?
±0.015–±0.125 mm.
What is a key advantage of LBM in terms of material compatibility?
LBM can machine materials that cannot be machined by conventional methods.
What is another advantage of LBM in terms of tooling?
There is no tool, so no tool wear.
What is a disadvantage of LBM in terms of capital investment?
High capital investment is involved.
Why is LBM not recommended for certain materials?
LBM is not suitable for high heat conductivity materials and light-reflecting materials.
What is a requirement for effective operation of LBM?
Skilled operators are required.
Why is LBM recommended for specific operations only?
The production rate is very slow.
Study Notes
Electron Beam Machining (EBM)
- EBM is a metal removal process using a high-velocity focused stream of electrons.
- Electrons strike the workpiece, transforming kinetic energy into thermal energy, melting and vaporizing the material.
Advantages of EBM
- No mechanical contact between tool and workpiece, hence no tool wear.
- Can machine very small holes with high accuracy in various materials (steel, stainless steel, Ti, Ni super-alloys, aluminum, plastics, ceramics, leathers).
- Drilling holes with high depth/diameter ratios (> 100:1) is possible.
- No cutting force is applied, allowing for simple workholding and machining of fragile/brittle materials.
Disadvantages of EBM
- High equipment cost.
- Low material removal rate.
- Limited to small cuts.
- Vacuum requirements limit the size of the workpiece.
Applications of EBM
- Drilling holes in pressure differential devices used in nuclear reactors and aircraft engines.
- Machining wire drawing dies with small cross-sectional areas.
Electron Beam Process Capability
- Holes with diameters ranging from 100 μm to 2 mm can be drilled.
- Holes can be tapered or barrel-shaped along the depth.
- Materials that can be machined include steel, stainless steel, Ti, Ni super-alloys, aluminum, plastics, ceramics, leathers.
- EBM does not apply cutting force, enabling machining of fragile/brittle materials.
- Power densities of 106 kW/cm² can be achieved.
- Conductive and non-conductive materials can be machined.
Material Removal Mechanism
- Material removal rate increases with increasing beam current, pulse duration, and energy per pulse.
Heat-Affected Zones (HAZ)
- HAZ developed by EBM is generally less than 0.25 mm deep.
- HAZ consists of a thin layer of recast material, which may diminish structural integrity.
- Amount of recast and HAZ depth are governed by pulse duration, energy per pulse, spot size, and workpiece thickness.
- Shorter pulse durations reduce HAZ.
Surface Quality/Tolerance
- Increasing feed rate generally leads to increasing surface roughness.
- Surface roughness values range from 0.4–6.3 μm Ra.
- Achievable tolerances range from ±0.015–±0.125 mm.
Discover the benefits of Electron Beam Machining, a contactless process that offers high accuracy and versatility in machining various materials.
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