Additive Manufacturing III

Question 1

Direct Metal Laser Sintering

Answer 1

• Scanning and sintering metallic powder using a focused laser beam (fibre laser) that causes the powder to sinter (fuse or melt) and solidfy in the shape of a layer of the prototype.
• Use of true production material, near-net shape process.
• Category - Powder bed Fusion

Question 2

DMLS - Process Characteristics

Answer 2

• Layer thickness 0.02-0.04mm
• Process takes place in an inert nitrogen atmosphere <1% oxygen to stop the metal powder oxidising when heated by the laser.
• Temperature of build chamber up to 200C; sintering is achieved with high powder laser (200W-1kW)
• Requires support structure which acts as support and to take heat away from the workpiece.

Question 3

DMLS -Process Characterisitics

Answer 3

• Surface finish & accuracy:
• Good surface finish
• High accuracy
• Recommended wall thickness (min) 0.3mm
• Easily machinable:
• Spark-erosion
• welding
• Shot-peening, polishing, coating
• Heat treatment

Question 4

DMLS - Advantages

Answer 4

• All metals are recyclable; use only what you sinter!
• Near net-shape process, producing parts with high accuracy and detail resolution.
• Good surface quality and excellent mechanical properties.
• Constant development and release of new materials onto the market.

Question 5

DMLS -Limitations

Answer 5

• More complex process than Selective Laser Sintering with regards to designing support structure & orientation.
• Parts need to be cut from the steel plate (usually using Wire-EDM); increase to cycle time & labour costs.

Question 6

DMLS - Materials

Answer 6

• Aluminium
• Stainless and maraging steel
• Cobalt chromium alloys
• Nickel alloys
• Titanium
• Bronze
• Powder size(between 36-65 micrometeres).