During the SLM printing process, it was observed that the recoater blade constantly touch the parts and as a result less amount of powders were seen to deposit over the printed part. Why would this happen?
It also seems like the protruded part is remelted more than the powder deposited. How to avoid this phenomenon?
Roshan Sebastian The recoater blade constantly touch the parts and as a result less amount of powders were seen to deposit over the printed part. The most prominent reason is WARPAGE
We can avoid it by:
- Provide necessary support material, so that there will be better heat transfer and reduce uneven cooling which further leads to warpage. The base plate should be choosen as per its thermal conductivity values.
- To ensure that a print job begins properly, the initial layers of a print are fused with a substrate that must be removed via Wire cut EDM after the print is complete. However, if the thermal stress of the substrate exceeds the strength of the substrate material, the substrate will begin to warp, ultimately causing the part itself to warp and potentially causing the powder recoater to collide with the part.
- Don’t position your parts parallel to the recoater, rotate them around the Z axis for a better repartition of the recoater force : If you put your part parallel to the recoater, it will be more difficult for the recoater to pass over it in case of deformation. Rotate your part 5 to 45 degrees around the Z axis so the recoater doesn’t pass over a long and flat wall. Given the edges, especially the corners of a part, always start to deform first, it’s always better if the recoater passes over a corner and then the rest of the part instead of facing a long flat wall with two corners at a time. This reduces the probability of a crash and can preserve the quality of sensitive features such as thin walls.
- Avoid putting parts right behind each other: If a part deforms and the recoater touches it, the build might continue although the recoater and/or the part is damaged. The consequences of such a situation would be a deterioration of the powder bed right behind the area of collision. So if possible, when nesting your parts on the build plate, try to add some space behind your parts along the recoating axis.
Bijaya Bikram Samal :
In my case, am not sure it is Warpage and might be the case of higher energy density of the laser beam causing the material to splash out. because i have tried to reduced the laser speed and this issue only tend to get worsen.
What would be the preventive measures in this situation as one sees an increase in the part lumping up due to higher energy density? If I had increased the speed, there would be some cases of porosity occurring, due to the insufficient melting of the sample.
1. Please keep your LED constant, and increase the scan speed and increase the laser power.
2. Keep your first layer as thin as possible so that it will stick with your base properly. Roshan Sebastian
2. This factor seems important as well as the support selection for building the part. There always this mistake that the a thick layer of the powder would always be deposited over the base plate during the process. I might need to use a high power to ensure proper bonding with the base plate.
If a volumetric support is chosen over the regular block support, would the warpage issue reduce up?
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