Plotter not plotting lineweights with autocad

[cadmaster77]

i own a ricoh aficio w2400 wide format printer (copy, scan, print)... i cant get it to plot in lineweights... (some lines are thicker than others).. when im in autocad, it visually looks correct on the print preview... when it actually prints all come out the same thickness... i tried making a pdf then printing that.. but the same thing happens... the pdf looks correct but prints wrong.. i also installed a HDI driver from the ricoh website but it didnt fix it... any suggestions?

thanks