bottom solid layers on, but not for first layer?

[bourgoynestudio]

I have tried that. But as soon as a process with bottom solid layer (1) is started, whatever layer that may be, it prints the first layer of that process as solid, filling in the entire cross section as solid.

the attached file has 4 test parts. One closed mesh, one open mesh, and two hollow shelled closed meshes. Two processes.

[dennisjm]

Hm, I don't have a suggestion then, I thought it would see that the 1st layer isn't a bottom layer but I guess not.

[bourgoynestudio]

Yeah. It was a very good idea, I thought it would work, but it seems to default to solid on the first layer of the process

[dennisjm]

My next suggestion is harder, but is to just cut the model in a 3d program and model it as hollow instead. Annoying and time consuming to get right though.

[bourgoynestudio]

I think I'm going to investigate just going into the g-code and manually deleting the extra movements. I would think the largest sections in the first and last layers would be grouped as one path, especially if I am using retraction at the end of each path.

Or just delete the first and last layers entirely.

[bourgoynestudio]

In the preview mode, is there a way to show the gcode that is being simulated as it is simulated?

[jimc]

ok so i looked at your factory file and i am still confused. you say it prints a solid bottom on all your parts. i look at the mushroom things in your file and they print just as they should. the solid ones print with a solid bottom and the shelled ones on the right print without a solid bottom. so what i am understanding here is that you dont want a solid bottom? if thats the case why not shell the model as you did. if it doesnt print in some ares that because the shell is too thin. thicken up the shell a bit so its thicker than your extrusion width. if you have a shelled model you can slice it wherever you want and print it in sections. to make it easy, anything below the build platform in s3d doesnt print so you can just drop the part to the height you just printed then print the remaining top.

[bourgoynestudio]

I don't want to have to shell them.

With a complex model it adds hours of work, and it involves a lot of trial and error, and doesn't always slice in a predictable fashion. My test parts were very simple, but shelling complex meshes always introduces bad geometry that has to be painstakingly sorted out. Its a real pain. It is also the hard way to work around what a slicer could do very very easily. It would be really simple to be able to just print them with one perimeter, if I could get tops and bottoms , just not on the first and last layer.

[jimc]

ahh i see. well i loaded your sample back up and i can get it to slice no problem, however i want it to. i can slice it where it gives me a bottom or without. i can also drop the model below the bed "x" amount to begin printing at bed level and at that point i can print it with a solid base or without. any combination works and this is using your non shelled mushrooms. for this model i left the top at 1 layer and just toggled the bottom layer on and off and no matter what layer i start printing i can either decide for it to have a base or not. on slicing behavior i also put that on heal, not discard. i dont think it makes a difference with this. no multiple processes needed. if you want to start printing you next piece at 80mm then double click the model and in absolute positioning enter -80mm in the z and slice away

[bourgoynestudio]

But when you print it with bottom layer off, does it still add the paths between the perimeters where the mesh slopes enough that the perimeters no longer stack on top of each other? It doesn't for me, and I understand those areas to be considered the bottom.Compare the bottom of the curved form when printing solid bottom layers on versus off (see screenshot). There is empty space between the perimeters when it is off, there are short zigzags bridging them when it is on, but also a solid first layer.
That is the problem I am having.

Of course, now on further review I see that the path print order is always perimeter first, which leaves them unsupported, so the issue looks like it is moot...