Is there a way to prevent this?

[bbinnard]

This is a screen capture of the tool path building the middle deck of a model of the Eiffel Tower. The middle deck extends out from the tower's support structure, and Simplify3D's tool path for this level starts with the support structure (orange) first, and then proceeds to the outside perimeter (blue).

As you can see, this cannot print properly because there is nothing for the perimeter loops to attach to. But of the toolpath started from the inside and worked outward, there would be. But - how to make this happen?

I have already tried both of the Layer tab's Outline Direction options: Inside-Out and Outside-In. The results for this particular layer are the same for each. What happens is the infill structure is done first, then the outside perimeter loops, and then the bridge loops that connect the outside perimeter to the main structure. What's needed is to switch the order of printing the last two types, but I don't see a way to do this.

I can't find a way to post 2 images in the same post, so my next post will show the complete layer.

[bbinnard]

This image shows the completed toolpath for the level in question. The yellow bridge loops are printed last, after the blue perimeter loops. But without the bridge loops there is nothing for the perimeter loops to attach to.

The order of printing is Orange, Blue, Yellow. It needs to be Orange, Yellow, Blue. But how to make this happen?

[JoeJ]

I think you would be better off just disabling bridging for that part of the model. Click on the "Other" tab and then set the bridging "unsupported area threshold" to 999999 to disable it.

Otherwise, I think it's going to do what your describing, since you always want to print the bridging sections last as they are usually bridging between two different parts of the model. So if one part hadn't been printed yet, the bridging wouldn't work. So if you don't like the sequence it is using, I would suggest disabling bridging using the instructions above.

[bbinnard]

Thanks for the instructive reply - now I know more about how bridging works. But regrettably that change did not help; the toolpath is still the same - only the extrusion type and preview color has changed.

Here is a screenshot of that layer partially complete:

You can see it is printing the blue outer shell after completing the orange support material.

Here is the same layer a but further on in the printing process:

Here the bridging material is being added in between the outer shell and the main structure. The difference this time is that it is colored green instead of yellow.

So I am still stuck on how to change the order of printing.

[bbinnard]

I changed the number of outer shell loops from 2 to 6 and said I wanted to print from Inside to Outside. My thought was maybe this would eliminate the bridging and simply print loops from inside to outside. And it seems to have worked. Here is a side view of the start of the overhanging layer:

This is a more oblique view after printing a few more loops

And this is shortly after the outer edge is complete and the "bridging" material is starting to be printed

This looks good to me and I expect it will print OK. Figuring out how all the 3D printing hardware and software work sure is an interesting activity.