Slicer Leaves First Layer Empty  

The usual reason for an empty bottom layer is a micro-thin object or edge at or below the bottom of the object, sometimes a calculated difference doesn't match in the umpteenth decimal place due to binary rounding or a chamfer strays a fraction out of line...

The slicer attempts to represent the impossibly thin parts and fails.

A quick and dirty fix is to subtract a large block immediately below the object to mop up any leftovers.

Cheerio,

3mf

If you upload a 3MF, we can check your files and settings.  

Clarifications

I'm not sure you can, because the problem shows up after slicing and normally it opens unsliced.

Here it is anyway: https://we.tl/t-dIoBs92Awm

Here's some pictures too:

Here's a different object pre slicing:

And this is after slicing:

I know it's difficult to show, but the bottom layer just disappears.

Supports

Diem, I'm not sure I completely understand, but there's only one object and then the supports the slicer creates.

Speaking of supports, in the second example I showed in my previous reply, the object is directly on the build plate and again, the slicer cuts off the bottom. I point this out just to add that the problem doesn't seem to lie with the supports.

Sometimes you have what appears to be a single object but if it was designed by taking, for example, a slice from a larger shape, then there may be other remnants of the original shape left in the file causing issues...

As @cwbullet says, if you upload a zipped .3mf of your project we will be able to examine the object and your settings ... and maybe diagnose the problem.

Cheerio,

I have no idea what the issue is or how to fix it, but I do have a work around suggestion for your urgent needs.

If you uncompress the .sl1 file (either zip or tar, I forget which off the top of my head) you'll find that it is a .ini file and a bunch of PNGs. Each PNG represents a layer and they are numbered in order. So you could simply find the first image showing the actual bottom of the print and then replace all the earlier images with a copy of that one. That won't really work for any parts done directly on the plate, but anything with supports and a pad should be fine (the pad will just be a bit thicker). Then you can recompress the directory back into the .sl1 file again.

Yay for open source! 😊 

Unpacking SL1 files

@gnat - thanks for sharing that little nugget of info.

I'm An Idiot

The urgent prints have been printed using my filament printer, which isn't optimal for what I wanted, but it works.

However, after exporting things as a .stl file and opening them with other programs, I saw that it did export the whole object. It was then that I noticed that I am an amateur that has overlooked the lock button underneath the slicing bar thingy, which instantly made the whole object, including the bottom layer visible. As usual with technical issues, it's the human that's the dumbest.

Anyway, I still have no idea why my newer prints fail. I've posted a 3mf file above via a wetransfer link in me "Clarifications" reply if anyone thinks they can help me with that, but I'll try to figure it out myself anyway now that I've gotten past this red herring. Perhaps it's coincide that the older ones worked and it's a hardware issue that I overlooked in troubleshooting or perhaps it really is the files or settings somehow (though I haven't really changed anything about any of them). I'm sure I'll figure out what I'm doing wrong.

3mf file above via a wetransfer

Please zip it and post it here, we tend to be a little wary about external sites.

Cheerio,