eXtendo®
Thermal Printer Family
Part No. D-684-124
Mod. No. 4 270919 HW1
page 21 of 33
5.6.
Paper Supply
5.6.1.
Hengstler Paper Roll Holders
Hengstler offers two paper roll holders for use with the eXtendo® family of thermal
printers. One is a small holder intended to position 100 mm rolls of thermal paper in
various positions behind or below the printer. The second paper roll holder is intended for
paper rolls up to 150 mm diameter, and otherwise has similar characteristics to the 100
mm version. Both paper roll holders usually come with a paper pre-end sensor installed.
5.6.2.
Designing Your Own Paper Roll Holder
It is sometimes desirable for customers to design their own paper roll holder in order to fit
in the available space, or to tailor performance to their specific needs. Based on our
extensive experience in designing printers, we would urge you to consider the following
topics and implement your design with care.
Large Diameter Rolls:
When using paper rolls over 100 mm in diameter, a “dancer bar”
should be considered. This usually takes the form of a spring-loaded arm under which the
paper is placed before feeding it into the printer. As the printer starts to print, slack is
taken up from the paper roll. This starts to lift the arm against the spring, which puts force
on the paper roll and starts it moving slowly. As more printing takes place the roll gradually
accelerates until it’s up to printing speed. Without the dancer bar, slack paper would be
taken up until it was suddenly no longer slack. Now the printer must accelerate a large,
heavy paper roll from zero speed to full print speed in essentially no time. This usually
causes the paper advance motor to stall or the paper to slip against the platen, causing
shortened characters until the paper roll is up to speed.
Spindle Friction:
Another important consideration is spindle friction. As a paper roll
rotates, it slides against the spindle that holds it, assuming a fixed spindle. This friction will
tend to impede the paper roll’s free motion, and is dependent upon the weight of the roll,
the smoothness and material of spindle and paper core. When possible, especially with
paper rolls over 100 mm in diameter, design the spindle so that it can rotate, greatly
decreasing friction and drag.
Catch Points:
More paper jams and transport problems are caused by catch points than
any other issue. Make sure that the paper path is free of anything that can interfere with
free paper flow, especially any sharp edges or “pinch points” into which the paper may
stray and become caught.
Alignment:
Any paper roll holder design must hold the paper square to the printer in all
planes. If the paper is angled in any way, it will enter the printer at an angle and will be
more likely to cause paper jams.
Rigidity:
It is important that the paper roll holder support the paper firmly and not move.
This is especially true in high-speed printing applications and in large diameter paper roll
applications. Many paper roll holders are made from metal too thin to support the heavy
paper rolls they are expected to handle. This results in twisting and warpage while
printing, which binds the paper and causes paper jams. Vibration during printing may also
cause undesired movement of the paper roll.
Shipment:
Do not ship your product with a paper roll mounted in the paper roll holder.
The heavy weight of the paper roll can easily bend or otherwise damage the paper roll
holder or printer, as witnessed numerous times.
