LEC 8

• Removing supports

• Depowdering

• Debinding

• Seperation from build platform

• Heat treatment

• Sintering

• colour

• surface roughness

• assembly

• Binder Jetting

• Powder Bed Fusion

  
  

• Powderbed Fusion

• Materialextrusion

• Directed Energy Deposition

Not binder jetting:

• not melted jet,

• can be taken out of powder bed

• PBF

• Material Extrusion

• Directed Energy Deposition

• Materialextrusion

• Binder Jetting

-> work with polymerbinder, which needs to be removed

-> Both work with greenparts, composite material parts joined together by polymeradhesion

-> metals need to be fused

• all

• removing material from the AM part using conventional manufacturing processes (milling)

• directed energy depostion

• Depowdering

• Stress Relief Annealing

• Buildplatform seperation

• Removal of support structures

• Machining to reach required dimensions

• Removal of Support Structures

• Debinding

• Sintering

• Machining to achieve the required dimensions

• Curing

• Depowdering

• Debinding

• Sintering

• Machining to achieve required dimension

• Builtplatform seperation

• Annealing (Wärmebehandlung)

• Hardening

• Machining to achieve the required dimensions

• carefull and complete removal of the powder to

  • free printed part

  • remove of dangerous substances (small powders)

• Tools:

  • Vibration

  • Rotation

  • Compressed Gas

  
  

• at some processes part is conencted to build platform

• careful to not damage

• tools:

  • saw

  • Chemically

• solvent debinding:

  • removes part of the polymer binder using a solvent

  • remains must be removed with thermal debinding

• thermal debinding:

  • removes remaining binder by heating

  • critical parameters:

    • temperature & duration

    • debindinng method & parameteres depend on material combination

• debinding temperature:

  • must be high enough to burn out/ decompose the binder

  • to low -> binder remains

  • to high -> risk of damaging the green part

• three stages:

  • initial Stage:

    • low temperature

    • sinter necks form between particles

    • Little/ no desification

  • intermediate stage:

    • higher temperature (70% of meting temperature)

    • sinter necks grow larger

    • Density increases significant from 70%->90%

  • Final stage:

    • temperature is held constant

    • Pores shrink and close

    • final denstiy reaches about 92%

• Sintering parameters determined by:

  • material composition

  • particle size

  • powder packing

• required for DED, PBF-LB/M

• removes residual stresses

• prevents stress induced cracking

• Temp: 550-600°C

• Temperature held till part reaches homogenious temperature

• optional / required post process

• lower am process accuracy -> higher machining requirements

Tools :

• Milling

• Drilling

• parts kept at high temperature and pressure for extended periods of time

• grains become larger -> reduces anisotropy

• number and size of pores reduced

• part shrinkes significant

• removes material using abrasive/ polishing tool

• manual & automated

• clean between steps to prevent caking