non convetional machining, as similar as electro chemical machining

1. Shaped Tube Electrolytic
Machining
Nisarg Shah (11BIE021)
Dhruv Patel (11BIE024)
Rajat Patel (11BIE025)

2. Electrochemical Machining
• Electrochemical machining (ECM) is a Non-traditional machining
process that relies on the removal of work piece atoms by
electrochemical dissolution.
• The machining current passes through the electrolytic solution that
fills the gap between an anodic work piece and a preshaped cathodic
tool.
• The electrolyte removes the dissolution products, such as metal
hydroxides, heat, and gas bubbles, generated in the interelectrode
gap.

5. • Shaped tube electrolytic machining (STEM) is based on the dissolution
process when an electric potential difference is imposed between the
anodic work piece and a cathodic tool.
• Because of the presence of this electric field the electrolyte, often a
sulphuric acid, causes the anode surface to be removed.
• After the metal ions are dissolved in the solution, they are removed by
the electrolyte flow the tool is a conducting cylinder with an insulating
coating on the outside and is moved toward the work piece at a certain
feed rate while a voltage is applied across the machining gap. In this way
a cylindrically shaped hole is obtained.
Introduction

6. S.T.E.M

7. • STEM is, therefore, a modified variation of the ECM that uses acidic
electrolytes.
• The process is capable of producing small holes with diameters of
0.76 to 1.62 mm and a depth-to-diameter ratio of 180:1 in electrically
conductive materials.
• It is difficult to machine such small holes using normal ECM as the
insoluble precipitates produced obstructs the flow path of the
electrolyte.

8. Process Parameters
• Electrolyte:
Type: Sulphuric, Nitric and Hydrochloric Acids
Concentration: 10–25% weight in water
Temperature: 38°C (sulphuric acid) and 21°C (others)
Pressure: 275–500 kPa
• Voltage:
Forwar0d: 8–14 V
Reverse: 0.1–1 times the forward
• Time:
Forward: 5–7 s
Reverse: 25–77 ms
• Feed rate: 0.75–3 mm/min

9. Process Capabilities
• Hole size: 0.5-6mm diameter at an aspect ratio of 150
• Hole tolerances: 0.5-mm diameter ± 0.050mm
1.5-mm diameter ± 0.075 mm
60-mm diameter ± 0.100 mm
Hole Depth ±0.050 mm

10. Advantages
• The depth-to-diameter ratio can be as high as 300.
• A large number of holes (up to 200) can be drilled in the same run.
• Nonparallel holes can be machined.
• Blind holes can be drilled.
• No recast layer or metallurgical defects are produced.
• Shaped and curved holes as well as slots can be produced.

11. Limitations
• The process is used for corrosion-resistant metals.
• STEM is slow if single holes are to be drilled.
• A special workplace and environment are required when handling
acid.
• Hazardous waste is generated.
• Complex machining and tooling systems are required.

12. Applications
• Because the process uses acid electrolytes, its use is limited to
drilling holes in stainless steel or other corrosion-resistant
materials in jet engines and gas turbine parts such as:
• Turbine blade cooling holes.
• Fuel nozzles.
• Any holes where EDM recast is not desirable.
• Starting holes for wire EDM.
• Drilling holes for corrosion-resistant metals of low conventional
machinability.
• Drilling oil passages in bearings where EDM causes cracks.

13. Thank You!!..