D from BC said:
Typically, which side of the paper is heated for fusing the toner in
laser printers..?
Is it the back of the paper or is it the front with the toner?
Or both?
On the Canon CLBP460/HP4500 series, both sides are heated. You don't
just want the toner to melt, you want it to run into the paper.
With heavier materials, such as card or transparencies, the transport
slows down so that the medium spends longer in contact with the fuser
rollers and longer in the cooling channel on the way out.
You would have a job designing a roller-type fuser with one hot roller
and one cold one; but there may be other types of fuser, using radiant
heat, which only heat one side of the paper.