unwanted blank margins in raster data

Hi, 

I'm writing a backend for Seiko-Epson label printers. I can successfully 
convert outputted raster data, but always seem to have a blank margins on the 
page. I've set the imageable area in the PPD to the full page size, but for 
some reason the rasteriser (or something) insists on having a margin--which 
is unnecessary.

I've checked my PPD on-line, and cannot see any problems with it.

Suggestions?

Also, the raster header shows the correct page dimensions but the raster 
image always seems to be the same size, regardless of page size chosen when 
printing. Is this normal (obviously I can simply process the data relating to 
the page size, rather than the whole raster image).


TIA
Nigel.