A polyimide film substrate pre-heater assembly is provided for pre-heating substrates in an image producing machine and includes (a) plural rollers including a drive roller; (b) a substrate path defining and heating assembly for defining a portion of substrate path; and (c) a belt assembly including a polyimide film belt forming a loop. The loop forms a substrate transport nip against the substrate path defining and heating assembly. The polyimide film belt includes a polyimide film support layer, a puzzle cut seam having inter-fitting teeth and receptacle members, and a fluoroelastomeric overcoat layer for filling and strengthening the puzzle cut seam, thereby preventing the inter-fitting teeth and receptacle members thereof from popping up when the loop is driven over relatively small diameter rollers.