The overall structure of the china printing press is based on two
wallboards. A large number of rollers, shafts, rollers and other parts are
installed between the two wallboards to make the continuous moving substrate
pass through the functional mechanisms such as shafts, rollers and rollers
arranged orderly. In the process of printing, such as tension control, paper feeding,
offset adjustment, water supply, ink feeding, printing (overprint), cutting,
paper feeding, paper handover, numbering, drying, cooling, glazing and various
mechanisms to ensure the automatic completion of the printing process. Among
them, the outside of a wallboard is equipped with various transmission parts to
drive the rollers, shafts and rollers inside the wallboard to rotate, axially
or intermittently, so as to realize various printing functions. On the outside
of the other wall panel, various control mechanisms are installed to control
the printing quality and ensure the smooth printing. Therefore, on the premise
of ensuring the processing quality, the assembly quality of wallboard will
directly affect the quality and accuracy retention of the whole machine. As the
main basic part of printing press, it also affects the quality and life of
various functional parts in the whole printing process. Paying attention to the
research of basic parts is an important means to improve the internal quality of
printing press. In this paper, starting from the existing assembly positioning
technology method, through the calculation of positioning error, the causes of
positioning error of main basic parts are analyzed, and several new assembly
positioning methods for selection are proposed to improve the assembly
positioning accuracy and further improve the printing quality. At the same
time, it also provides the assembly method and means for the printing
enterprises to repair the china printing press.
1� Calculation of coaxiality error
produced by traditional technology
The traditional positioning method of
coaxial accuracy of basic parts mostly adopts mandrel positioning method. In
theory, this method can unify the design datum, the assembly datum and the
positioning datum, and the datum coincidence can improve the assembly
precision. However, due to the shape, position and size errors of the
positioning hole of the wall panel, and the tolerance value of the positioning
part of the mandrel is also given, the existence of the gap will produce
coaxiality error even if the mandrel rotates flexibly. Obviously, with the
increase of the distance between the two wallboards, the coaxiality error is
directly proportional to the distance between the wallboards and the matching
gap. The coaxiality error of large-span printing machine wallboard can not be
ignored because of the existence of gap. Although it seems that the relative
position between the rollers, shafts and rollers can be determined from the common
axis after the assembly of the rollers, shafts and rollers, many transmission,
manipulation and automatic control parts will be in bad working conditions, and
more importantly, the accuracy retention is poor.
In order to establish the relationship
between the gap, wall panel spacing and coaxiality error, the following
constraints are proposed
1). The lower plane of the wallboard is the
support datum and the guiding datum during processing. Therefore, it can be
considered that all the holes in the same position on the two wallboards have
the same height relative to the bearing datum. During assembly, the horizontal
position of the two wallboards is determined by the positioning mandrel;
2). It can be imagined from an intuitive
point of view that the location of the maximum coaxiality error is: the two
ends of one hole contact with the positioning mandrel diagonally, and the
positioning mandrel inside the other hole contacts. Theoretically speaking, the
rotating mandrel should also be flexible at this time; or in the vertical
processing, the combined boring on the workbench (also can be separately
boring), so it is considered that the axes of the two wallboard holes are in
the same direction, but The angle of the large plane of the wallboard is
different, which reflects the consistency accuracy of the pull axis (beam)
parts;
3). Generally speaking, the corresponding
apertures of two wallboards are the same. In order to make the derived formula
have universal significance, two corresponding holes are specially designed as
unequal diameter holes.
2� Coaxiality error
analysis
The coaxiality error of the three basic
parts of the printing press can be calculated by the three relations derived
above.
(1) The formula is a general formula for
calculating the coaxiality error, but it does not include the error caused by
the consistency of the axis and beam.
(2) Formula is a simplified calculation
formula of coaxiality error, that is, the variables in the formula conform to
the reality of china printing press.
