HP LaserJet 2605, 2605dn, 2605dtn Reference page 302

algorithm increases or decreases the current temperature target by some amount which depends
on media type and other factors. The following settings are available for the Fuser control:
●
Paper curl . This setting reduces fuser temperature. The instant-on fuser applies heat mostly
on the image side. This causes asymmetric drying of the paper. When the paper reabsorbs
moisture after printing, the difference between the front and back surfaces causes curl (heavy
toner coverage also causes curl). Decreasing the heating of the paper and toner will tend to
reduce curl (watch out for "cold" offset). Paper curl is worst for lighter papers and in higher
humidity.
●
Heavy coverage. This setting increases fuser temperature. The user's first option should be
to pick a heavier media type in the driver. The defect in this case will be "cold" toner offset in
the fuser. In this case, the toner is not quite melted enough to stick to the paper, so large
patches will stick to the fuser sleeve and then offset 55mm down the page.
●
Toner offset. This setting decreases fuser temperature. The user's first option should be to
pick a lighter media type in the driver. The defect in this case is "hot" toner offset in the fuser.
In this case, the toner next to the fuser sleeve gets too hot and partially separates from the
toner that sticks to the paper. Offset also occurs at a 55m pitch, but it looks more like faint
ghosting.
●
Less/More fusing (-2, -1, +1, +2). These settings provide two levels of decreased fuser
temperature and two levels of increased fuser temperature in case the above adjustments
aren't enough. They can be used to "hunt" for the best setting.
●
Transfer. The transfer bias voltage control in the engine is a complex algorithm depending on print
mode and toner cartridge and humidity. An "increase" or "decrease" in transfer bias means that the
transfer control algorithm increases or decreases the transfer bias by some amount which depends
on media type and other factors. The following settings are available for the Transfer control.
The following settings are available for the Transfer control.
●
Dry paper. This setting increases transfer bias. Some papers (notably Chinese papers)
become highly resistive in dry environments. To get enough transfer current into the paper to
have good transfer, the transfer bias voltage needs to be increased. The range of paper
resistivity in low humidity is so wide that a single standard engine print mode cannot cover all
the cases.
●
Humid paper. This setting decreases transfer bias. All papers absorb water at higher humidity
and become electrically less resistive. This results in transfer defects caused by too much
transfer current. The engine has a humidity sensor and also checks the conductivity of the
ETB in order to estimate the humidity of the media, but this can be inadequate in more extreme
cases.
●
Rough paper. This setting increases transfer current. Rough papers such as cotton bond
papers have a large portion of their surface area spaced away from contact with the OPC
drum by their surface texture. In this case, more transfer current is required.
●
Less/More transfer (-2, -1, +1, +2). These settings provide two levels of decreased transfer
bias voltage and two levels of increased transfer bias voltage in case the above adjustments
aren't enough. They can be used to "hunt" for the best setting. In extreme case (very dry or
very wet), low transfer current defects and high transfer current defects can overlap; that is,
there won't be a defect-free setting. These adjustments can help find the best operating point.
●
Duplex Transfer. Paper which has just gone through the fuser before being printed on the duplex
side is much drier and has higher resistivity than when the simplex side is printed. Therefore, the
engine uses different transfer bias settings for the duplex side. It is common for the duplex side to
278 Chapter 7 The HP ToolboxFX ENWW