A technique to avoid warping on large 3D prints

[Jamie Mantzel] figured out his own way of 3D printing large objects without fear of warping. First a bit of background information. When using a 3D extrusion printer like the RepRap or Makerbot, prints that span a large area tend to warp. That’s because these printers lay down one thin layer of plastic at a time. If the first layer cools too much, it will shrink a bit before the next layer is laid down. As that second layer cools it pulls the part toward the center, eventually bowing the part which causes it to hit the extruder head.

After having several prints encounter this issue [Jamie] decided to alter his design so that it wouldn’t cause these stresses. The first thing that he did was to add alternating voids to a layer between the raft and the actual part. You can see these as notches on the bottom the piece pictured above. This takes care of the initial stresses from the first layer. Next, he adds holes wherever he can in the main body of the part. This is especially important on the edges of the piece where the warping forces will be the greatest.

He also moved the starting position of the bed closer to the extruder head. His hope is that this will help the raft bond better, and resist pulling away from the bed during printing.

See his video explanation of his adventure after the break.

[Read more...]

Removing fisheye distortion


Reader [alex] had a commercial plugin for fisheye lens correction and wondered exactly what kind of magic was behind it. Was it actually doing line detection? He dropped in a square grid to see what it spit out. The warped result indicated that the transformation was completely independent of the photo’s content. Using this result as a guide he was able to create a similar transform using Warp and save it as a script. The script generates almost identical results and now he knows exactly how little magic is involved.