bottom solid layers on, but not for first layer?

[bourgoynestudio]

I am trying to print hollow, single perimeter parts that are open at the top and/or bottom, but I need to have bottom solid layers (1) and top solid layers (1) on so that overhanging surfaces get printed. My problem is that Simplyfy3d will force fill the bottom (first layer) and top (last layer) as well, even if I start the print a couple layers up from the bottom and end before the last layer. I am printing very big parts, and have to cut the tops and bottoms of the printed part off, which is a huge waste of print time and material. I have at times resorted to shelling the part, but it can be tricky getting just the right shell thickness to have only one clean perimeter printed, without having a second one added for the inner shell wall, and is not a simple task to model well.
So is this possible?

I guess what I really want is for simplyfy3d to not heal my meshes, and print a single perimeter only where there is actual mesh, not worrying about inside or outside or any of that, but sill filling in tops and bottoms where the geometry creates them. This would also be very useful when I want to add internal supports, and don't want them to be ignored as part of the inside of the part.
Is this possible?

[jimc]

Yes in your process, one if the last tabs there is a slicing behavior section which has all these settings

[bourgoynestudio]

I have tried every combination of options I can find in that tab, but it always gives me a filled first and last layer. What am I missing?

[JoeJ]

Can't you just set the top and bottom solid layers to zero? (see the Layer tab)

[bourgoynestudio]

When the bottom solid and top solid layers are set to zero, it leaves gaps in overhanging geometries, for example, where the tops of a figure's shoulders curve toward the horizontal. It will print one perimeter, leaving a gap with the previous layer's perimeter. It treats those steps overs as "tops", leaving gaps in the shell. This doesn't work when printing a single perimeter, because you have unsupported paths. I'm trying to print with the absolute minimum of material. It works great with 1 top and 1 bottom, as the step overs are filled with short zigzags that bridge away from the supported paths, except it fills in the first and last layers too.
So I need it to print tops and bottoms, just not on the first and last layers.

[dennisjm]

Use multiple processes set to each print a portion of the model.

On the middle processes set bottom layers higher and on the very bottom layer set it to 0.

[bourgoynestudio]

It would seem that any process that has bottom solid layers checked on will put in a solid bottom at the first layer it starts, regardless of where it is in the model. I don't think that'll solve my problem, unless I'm missing something.

[jimc]

no it wouldnt. maybe though i am not really understand what your trying to do. your part should be printing exactly how you have it modeled. if you dont have a bottom on the model then it wont print one unless you have the raft on or the model has an error in it somewhere. maybe it would help if you could post up a pic or two or even and example model or factory file.

[bourgoynestudio]

Let me explain it this way. I have a figure sculpture that is too tall to print in one part. I want to print it as a hollow shell using an absolute minimum of material as fast as possible. So I print it as a single perimeter. I don't mind some imperfections, but need a reasonably continuous surface, so tops and bottoms are required for areas such as under the arms and the tops of shoulders. If I cut it into different sections, either as separate stl files (with either open or closed meshes), or as separate processes printing certain layers, I end up with the bottom and tops of each section being printed solid. I have to cut these out before assembling which is a waste of time and material. I have been modeling the meshes as hollow shells to avoid this, with an inside wall and an outside wall, but that is a very complicated process prone to many many mesh errors because inside corners can end up being projected outside the outer mesh. Also if the wall happens to get just a little too thin it does not print at all.
What I really need to be able to do is print a single perimeter with tops and bottoms on, but not for the first and last layer. If that were possible, it would save me a huge amount of time and trouble.

[dennisjm]

Just what I said before.
Add a 2nd process on the piece you want to print.

For the 1st process, tell it to stop printing at 1mm or whatever. In that process turn off the bottom layers.
Then in the 2nd process change the settings however you need for the rest of the model and tell it to start printing at 1mm.