Is it the grid lines that are not printing?
I suspect you have the Canon TS6100, 1200 dpi vertical, not the beast. If I look at Why can’t I set my own height in rows? I see that Calc uses Twips as measurement (1/1440 inch, approx 0.02 mm). This should be sufficient to define a line with width 0.05mm.
Looking at the printer specifications a little more, it is a CMYK printer, that means the actual nozzle that deposits a single colour has a vertical resolution of 300 lines per inch (divide 1220 by the number of nozzles, 4). That equates to a resolution of 0.08 mm, enough to skip an entire line if only one colour is used for printing.
The resolution would be to either:
- set a border for printed cells of minimum thickness 0.1mm
- use full colour printing for the grid, the printer will emulate black for those lines that the black nozzle will skip. That could be:
- In Tools > Options > LibreOffice > Print untick the box Convert colours to greyscale
- In the printer driver , untick Greyscale or Print in Black or similar. You might need to change your defaults or printing profile.