PART DIFFICULTY OFFSET PRINTING

                                          PART DIFFICULTY OFFSET PRINTING


                                        
                                                                                            By : Berkah Mandiri Mesindo


ON THE PART OF THE PRINTING DIFFICULTY

In The polished plate, it is expected that grain can hold perfectly ink, and ink that does not react with the plate. Tetapj result of polishing, the surface of the plate was certainly no less flat section. although not noticeable, until there is a part that may be less d apat holds ink well. Therefore everything that d apat cause grain damage will affect the image above, misalnye because shear rollers are too heavy, the rotation between the plate cylinder with a rubber cylinder which is not sama.Sifat is not contained in the bimetal and, Trimetal, because on this plate gam bar located at the base of which is sensitive to tin (copper), until the damage as aforesaid may be said no, and if there is damage to the grain occurs k arena other reasons. Damage caused. grain damage for example:

A. PLATE TO BE BALD

1. SPEED ROUND ONE CYLINDER PLATE AND RUBBER

    An equal friction plate cylinder with a rubber cylinder can
occurs when the center line of the plate cylinder mm smaller than the
rubber cylinder, suppose in one round cylinder to 1.25 mm.
(According IGT) .Although the numbers seem small, but sufficient
great to eliminate the grain on the plate, especially when the pressure
each round cause friction (rubbing) equate speed
round plate cylinder. Friction that occurs at the time and place
the same, and consequently grain damaged parts also on
the same place anyway As already explained that the difference
diameter
     between the plate cylinder with a rubber cylinder was ser ing intentional
to cope with the development of the paper, in order to print the war na
can be right next (registers) .In the paper width 80 cm,
development of paper about 1 mm If the location of the  plate 0,2 mm above
bearer and bearer tall rubber cloth, m aka it is not possible to
last color printing plate layout as high as bearer or slightly
underneath that work d apat registers. Of course rubberized fabric must
under the bearer to get enough pressure. Although the
this way will produce good prints, presumably better
not the case. But as evidence that the plates are located O,2 mm
above bearer mean it does not matter. Excess pressure of 0,1 mm above
would be more dangerous than adar-ie difference O,1 mm
between the center line of the two cylinders are appropriate, in accordance with
provisions. Therefore, steps should be taken when changing the line
the middle of the cylinder, the proper pressure can dijaqa way
which has been described.

2. ADJUSTMENT ROLLERS LESS GOOD FORM.

    Rotation speed depending on the rotation of rollers form rol
distribution (conductor) and the tuning on the plate. Turnover ro1
ink (form rollers) on the plate and the conductor must be equal ro1
speed. It is by the person concerned has been taken into account that
rol velocity distribution with the corresponding plate cylinder. But though
Thus printers still have to set the adjustment form rollers on ro1
distribution and plate with tepat.Ini means that the pressure rollers form
on the plate should be the same pressure is on ro1 conductor. If
The roller pressure tothe weight of the roller intermediaries but too light
on the plate, roller rotation symptoms so gliding above
plate and swipe the image on the plate and the image to be damaged and
ink circulation is inhibited, halted due to heavy pressure on
rol intermediaries. Because of the adjustment should be arranged so that the pressure
on rol intermediaries slightly lighter than the pressure on the plate.
If still friction will occur between the form rollers
with rol conductors that are not so harmful. If the relationship
between the form rollers with less back rol conductor, when roller
passing above the cylinder gap will decelerates and cause
images and grain near the plate gripper be damaged.


3. PRESSURE TOO HEAVY.

    Pressure. print on offset printing too much harm,
because due to the ongoing shift will damage the grain and images
above the plate. It does not matter whether the print pressure occurs between
rubber cylinder by cylinder plate or between plate with form
dampening rollers or roller, all of which can damage the plate. Pressure
the weight of that part of the rollers will cause damage to the plate
certain parts, and so bald. Because the printing pressure adjustment
balance would prevent such damage.

4. TOO MUCH WATER (dampening SOLUTION).

    Adjustment of water use are printed with bar ang need
note, that giving too much water causes the plate
gam less sensitive to the bar to the ink and causes the image is not
holds ink well (blind Lopen)

5. WATER TOO ACID.

    The solution is too acid can damage the plate. Because of the addition of
acid in a water bath should not be based on estimates, but should
measured even if I have not add any solution in a water bath.
To measure the acidity. can use a pH meter or with paper
indicator. In his um um acidity needed an equal 5 and 7
(PH 5 - pH 7).

6. MAKING THE WRONG.

    If the plate is less perfect manufacture lead plates can not stand
long time. In making this mistake plate can be caused by
developing ink is not strong too thin to protect the image, up to
when etched so damaged. To resolve this error does not exist
other way, except to replace a new plate.

B. FIGURE MEETING.

1. INK TOO FAT (CONTAINS LOTS OF OIL

    It will be symptoms of greasing because part no
picture over time also holds the ink eg
between point raster (dicht or vollapen) and line
enlarged (aanlopen / verbreden) .This caused no balance
between the water with ink. The pH of the water is too high (less acidic because
size (5 and 7), but the ink is too fat. This situation may
because too many menyampurkan pasta is too fat. If
meeting image for reasons mentioned above, can be seen between
raster point on the plate and rubber cloth as great at au not. If
raster point on the plate and rubber swell, meaning due
ink too fat. But if any enlarged h a point on the fabric
This is due to k arena rubber molding pressure is too strong or turnover
cylinder same.If not because the latter is not immediately
addressed can lead to gam bar so tightly. To overcome this course
Just by reducing the pressure or adjust the balance of rotation
plate cylinder with a rubber cylinder.

2. TOO MUCH INK.

    When giving too much ink will also point raster
enlarged. With the finger back at the paper shifted recently
printed, then the image will be swept away when the ink too much.

3. CHANGES OF RASTER.

    When the dot raster is seen with a magnifying glass look round
eggs (lengthwise) or as no tail, if this is the case only
the fabric which then disturbances on the plate cylinder and rubber,
most likely due to the rubberized fabric too loose. Certain
just rubber cloth should be hardened again.

4. FABRIC RUBBER too loose.

    When the rubber cloth is too loose, then the image will be enlarged due
curved rubber, if the rubber is too curved can be improved
powers which cause friction at the point raster to form
raster back and occurs greasing. To overcome this need
hardened rubber cloth on the cylinder.