Sorry that you cannot print correctly from Lightroom. Which exact version of Lightroom are you using?
Do you need to set margins. Try setting all margins to 0.
After selecting the Printer settings tab on the bottom of the Layout panel on the right side of the screen, you should see a tab called EXPANSION which is located beside the Borderless setting I believe (working from memory, dont have Lr open). Select that tab and then select RETAIN SIZE. That should keep the cell width correct.