Design for Metal Additive Manufacturing – Residual Stress
In a series of videos, Marc Saunders, Renishaw Additive Manufacturing Solutions Centers Director, will discuss key factors that drive the success rate and productivity of metal additive manufacturing builds and some of the critical guidelines that designers should follow to create production components efficiently. This video features key tips to design out residual stress.
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Transcript
00:00:01 [Music] in a series of videos I will discuss key factors that drives a success rate and productivity of metal additive manufacturing builds and some of the critical guidelines that designers should follow to create production components efficiently today I will discuss back to one residual stress residual stress is a natural consequence
00:00:31 of the rapid heating and cooling and the laser powder bed fusion process each new layer is created by moving the focus laser across the bed melting the top layer of powder and fusing it to the layer below heat flows from a hot male pool down into the solid metal below and so the molten metal cools and solidifies this all happens very rapidly in a matter of microseconds residual stresses
00:00:57 can be destructive as we add layers on top of one another the stresses build up and can lead to distortion of the part causing it to curl up at the edges and pull away from its supports in more extreme cases the stress can exceed the strength of the part leading to catastrophic cracking of the component or distortion of the build plate so how do we minimize residual stresses in
00:01:21 additive manufacturing one way to tackle this is by burying our scanning strategy choosing a method that is best suited to the part geometry when we are filling in the central ball part an activity known as hatching we typically move the laser back and forth there are different types of hatching including the meander hatching pattern suitable for small and thin features the chessboard hatching
00:01:43 pattern suitable for large parts and stripe hatching pattern suitable for large parts and offering a higher build rate than the chess pool we can also rotate the orientation of our scan vectors from one layer to the next so that stresses are not all aligned in the same plane a rotation of 67 degrees is typically used between each layer to ensure that it is many layers before the
00:02:05 scanning Direction is exactly repeated heating of the pill plate is another technique used to reduce residual stresses whilst post-process heat treatments can also relieve the residual stresses that have built up my key tips to design out residual stress include avoid large areas of uninterrupted melts be careful about changes in cross section use thicker build plates where
00:02:27 stresses are likely to be high and select an appropriate scan strategy watch out for the next video featuring optimized part orientation for additive manufacturing [Music] you