TL;DR

Recoater streaks create density voids in the build layer. Inspect the recoater blade for chips or debris, clean the blade edge, and check for spatters in the build plane before resuming.

What you might see

visible parallel streaks in the powder bed after recoating
density inspection shows voids in the built part
recoater blade shows visible chip or notch
build failure alarm on layer quality monitoring

Likely causes

Tap to mark as ruled out

Recoater blade edge chipped from contact with a spatter bead or raised melt edge
Metal spatter deposited in the build plane obstructing the blade path
Recoater speed set too high causing turbulence in the powder bed
Powder particles sintered into the recoater blade edge from proximity to the melt pool

Required tools

Replacement recoater blade (EOS-specified for the powder type)
Oxygen detector
Magnification loupe
EOS-approved build plane clearing tool

Safety first

Metal powder used in additive manufacturing is a fire and explosion hazard. Follow the EOS powder handling safety procedures and never expose hot or partially sintered powder to air.
Verify the build chamber oxygen level before opening. Inert gas build-up inside the chamber can cause asphyxiation.
Wear a P100 respirator and nitrile gloves when handling metal powder. Do not use compressed air to clean metal powder spills.

Procedure

7 steps · ~30 min

1
Pause the build or stop at the end of the current layer if possible.
2
Follow the EOS inert atmosphere chamber opening procedure. Confirm the oxygen level is below the safe entry threshold before opening the build chamber.
Warning: The EOS M series uses inert gas (argon or nitrogen) to prevent metal powder oxidation. The build chamber atmosphere can displace oxygen. Verify oxygen level with a detector before opening. Metal powders used in additive manufacturing are a fire and explosion hazard if exposed to air while hot.
3
Inspect the recoater blade edge visually for chips, notches, or sintered powder. Use a loupe or magnification.[1]
4
If a chip is found, replace the recoater blade with a spare of the correct type for the powder being used.[1]
5
Inspect the build plane for spatter beads or raised material in the recoater path. Remove any obstruction carefully with the EOS-approved clearing tool.
6
Run a manual recoater stroke and inspect the powder bed surface before re-starting the build laser.
7
If the build has progressed past the affected layer without interruption, evaluate whether the defect location is in a critical zone of the part. Consult your quality procedure for build continuation or rejection.

Sources

EOS EOS M 290 / M 400 Metal Additive Manufacturing general technical documentation, EOS
EOS M 290 / M 400 operator and maintenance documentation, recoater system inspection and blade replacement (general)

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