Mechanica Technical Solutions
Home | Contact | About
Manufacturing Processes > Non-Traditional Machining > Abrasive Jet Machining(AJM)

 

Abrasive Jet Machining(AJM)

 

Process description

Erosive action of an abrasive in a fluid is focused to a high velocity (150–300 m/s) jet through a sapphire nozzle. The abrasive and fractured particles are carried away from the cutting area by the jet.

Materials

  • Suitable for brittle and/or fragile materials.
  • Refractory metals, titanium alloys, ceramics, metallic honeycomb structural materials, acrylic, composites, glass, silicon and graphite.
AJM

Process variations

  • Two systems for introducing the abrasive to the jet stream:
    • Entrainment system: pressurized water jet pulls in abrasive particles into the stream, they are mixed in a tube and exit the nozzle.
    • Abrasive slurry system: mixing of fluid medium and abrasive particles takes place prior to pressurization in a separate chamber to create the slurry. Higher wear rates throughout the equipment experienced using this system, but less expensive.
  • Fluid medium: either water or a gas (air or CO2).
  • Abrasive types: aluminum oxide and silicon carbide use.
  • Tungsten can also be used for the nozzle, but has a higher wear rate than sapphire.
  • Nozzle orifice can be round or square.
  • Water jet machining: very high pressure focused jet of water used for cutting food, leather, paper and foamed plastics.
  • Chemical jet machining: uses a single jet of etchant for deburring.

Economic considerations

  • Production rates moderate.
  • Material removal rates low, typically 15mm³/min.
  • Penetration rate ranging from 10 to 1200 mm/min.
  • Removal rate depends on the hardness of material and process parameters.
  • Material utilization poor. Scrap material cannot be recycled.
  • Can be fully automated using robots. Added flexibility.
  • Small power requirements needed.
  • Economical for low production runs.
  • Tooling costs high.
  • Equipment costs generally high.
  • Direct labor costs low to moderate, depending on degree of automation.

Typical applications

  • Through-holes, slots and profiles in hard, brittle materials
  • For cutting, slitting, drilling, contouring, etching, cleaning, deburring and polishing
  • Electronic component etching
  • Etching and cutting glass
  • Cutting metal foils

Design aspects

  • Features limited to profiles, holes and slots.
  • Depth of cut can be increased with jet pressure.
  • Blind holes not possible.
  • Long holes have tapered walls.
  • Slot widths ranging from 0.12 to 0.25mm.

Quality issues

  • No heat and therefore no heat affected zone. Part free from metallurgical effects and residual stresses.
  • Minimal dust, toxicity and fire hazard, but high noise levels.
  • Less than 1mm focus length from work should be maintained so no loss of definition and stray abrasion occurs.
  • Minimal tool dulling.
  • Inclination of jet angle to work can be less than 90°, but at increased jet divergence on work, and therefore less control over material being cut.
  • Abrasive size, slurry composition and flow-rate important control variables of the process for consistency.
  • Abrasive slurry cannot be recycled due to abrasive grit blunting reducing effectiveness.
  • Abrasive can become embedded in work surface.
  • Surface detail good to excellent.
  • Surface roughness values ranging 0.1–1.6 µm Ra.
  • Surface roughness depends on abrasive particle size.
  • Achievable tolerances ranging ±0.001–±0.013 mm. (Process capability charts have not been included. Capability is not primarily driven by characteristic dimension.)

costing