This page shows the results of some experiments I made with the Plic3r slicer program. My first experience with Plic3r is documented here: Variable Layer Height. Since then I have made Plic3r my slicer of choice, but I also use Craftware to check the output of Plic3r.

Note that the final prints I showed  in the Variable Layer Height page looked like this:

Notice the little bumps on the surface. They seem to be randomly located all over the place. I found that to be really annoying and wanted to find out what caused them. Doing that was not hard to do. (How I did this is explained below.)

What I discovered was the bumps appear at the end of a layer. What seems to be happening is a small blob of filament gets left behind when the hotend moves from the end of one layer to the start of the next. So to verify this I changed Plic3r’s Seam Position from Random to Aligned. This was the result:

Well, at least the bumps were not random any more. But they were still there. So I switched Seam Position to Aligned and got this result:

No bumps! But I know what you’re thinking: what about the back sides? Well here is the answer:

No bumps there either. So where did they go?

I have not got the faintest idea. But as long as they stay away I’m happy.

Now it may be that they will reappear on a part with different geometry – time will tell about that.  But for now I’ll stick with Seam Position = Aligned and hope for the best.

How to check what’s really happening

One of the tricks I used to figure out where the bumps were occurring was to look at the actual toolpath the hotend was going to make when it printed the part. Plic3r does not have the ability to do this right now, but the Craftware slicer does. To see the actual toolpath with Craftware you just load the Gcode file for the part you are going ot print into Craftware. This is the result of doing that:

The box at the bottom has sliders that let you select any particular print layer, and any particular hotend position on that layer.  Here is a screenshot showing the starting position for printing layer 100:

Note that the Layer slider is set to 100 and the Line slider is set to the far left. This causes the virtual printhead to be shown at the start of layer 100. The text box after the word Line is the number of the line of GCode that positions the printhead.

You can move the virtual printhead around the layer by moving the Line slider. By doing this you can see exactly how and where the printhead will move, and in particular where it starts and ends each layer. Here is a screenshot of the virtual printhead in the middle of Layer 100:

Why is it that Craftware can show this and Plic3r cannot? I made the suggestion to add this capability and got a very precise answer.  You can read the whole exchange here.


Last Update: 24 Apr 2017