Recently, I’ve seen a rise in calls related to envelope and fusing problems. I see issues with fusers from all makes and models of printers but for the point of this article I’m going to focus on HP fusing assemblies. In this post we’ll review different types of fusers, toners, and envelopes. Given the wide variety of options many different print quality issues can arise and will vary with your printer model.
HP Fusing Assembly History
When I first started working on HP machines back in the late 90’s, the majority of the HP fusers I saw used old technology. The fusers consisted of thermistors, thermal fuses, hot roller, pressure roller, and halogen lamps. They were very reliable, durable, and typically lasted long past their intended life. Getting a label stuck in the fuser simply required the user to remove it. Running a paper clip or staple through it might cause a nick but no serious damage. Envelopes would wrinkle up in the back if not fed properly. Actually, the envelopes would always wrinkle, but a lot less when the envelope tabs in the fuser were set to release some of the pressure. This is the case on models like the HP 5si, 8000, and 8100 series.
The new fuser technology, found first in models like the HP 4L and 4000 series, use a heating element, pressure roller and fixing film. The benefits were that these fusers would use less energy, heat up more quickly, feed envelopes better, and for HP, they are easier to damage so users would have to replace them more often.