GRAFIMPEX

GRAFIMPEX
Equipment & Solutions for Newspaper and Commercial Printers

Wednesday, February 8, 2017

MAILROOM AT NAVBHARAT PRESS-INDIA BY STALLION


Mailroom consisiting of Newspaper stream lifting Vertical Belt Conveyor, 70 Feet Horizontal Conveyor, Vertical Drop, Dump Gate, Compensating Counter Stacker with Laser counter

Monday, January 16, 2017

RUBBER ROLLER MAINTENANCE & PROBLEMS

Any printing machine is desired to deliver optimum performance.  In any machine the printing section is considered the important section, the process of ink considered the important section, the process of ink transfer to the surface becomes the vital point for quality outputs.  Thus in a way the "Rubber rollers" which actually transfer the ink can be treated as the heart of the printing machine.
The print quality can be heavily hampered if proper attention is not paid towards the rollers, as it is directly associated in ink transfer.  But that's not all the rubber rollers not maintained properly leads to other indirect losses, some of them are :-
  • Heavy downtime due to defective printing caused by faulty rollers.
  • Frequent replacement of rollers.
  • Plate wear due to incorrect quality of rollers.
  • Wastage of proper printed matter due to uneven inking.
  • Scumming due to defective dampeners.
This number can go on increasing, but the message if this exercise is to emphasize the importance of the Rubber Rollers.  Without proper care they can eat up a substantial amount of the profit and many time it is not even recognized!!!
The most expensive thing in printing is "DOWNTIME" of the machine.  It can cost a substantial amount of money per day and one of the common reasons for it is Defective Rollers or Rollers requiring change.Thus it is very necessary for printers who strive for quality should understand the methodology of proper use and care of the Rubber Rollers.
PRINTING PROBLEMS CAUSED BY FAULTY ROLLERS
  • Scum- Scumming is the appearance of unwanted inked are in the non-image area.  One of the important reasons for scumming is inadequate supply of water to the plate.  Dampening rollers should be soft & should be capable of supplying very thin even layer of moisture to the plate.  Hard or uneven Dampening Rollers will provide inadequate or uneven water giving rise to scumming.
        
  • Image wear- A hard dampening or Plate Inking roller will cause rapid wearing of plate.
       
  • Dot Size- A hard or glazed roller gives dot elongation or dot again.  This effects in getting sharp image with full color value.
       
  • Skidding- Due to accumulation of dried ink film, roller becomes glazed.  Glazed rollers are poor in traction of ink.  Thus when they strike the plate which is having greater surface speed than a roller a skid is produced, in turn causing a streak across the plate.
       
  • Stripping- Ink Rollers refusing to hold ink is called stripping.  These are two main reasons for stripping.  There are two main reasons for stripping.  Loss of affinity for ink in some areas is due to (a) Film of dried ink on the rollers, (b) Desensitization of copper rollers.
       
  • Uneven Corrosion- Rollers with roughed up sides does not allow full size printing.  Hence accurate setting and proper inking is not possible on these rollers.
      
  • Belling- Dampening rollers tend to "bell" at the edges due to constant pull of the hose on the edges.  The hose tends to shrink while drying and thus exerts a pull towards the center.  It upsets the pressure and distribution of water.  It causes bowing of roller and uneven wear of roller.
       
  • Swelling- A roller absorbing ink, cleaning solvents and chemicals becomes tacky or swollen.  It gives rapid drying of ink.  A good roller should have low ink absorption rate.
      
  • Hickeys- These are white spots appearing in solid image areas.  They are caused by hardened specks of ink, dried gum, dirt etc. and hamper the print quality.
      
  • Ghosting Repeat- It is a faint image outline in printed matter caused by poor ink film recovery on the plate by rollers.  It is an indication of poor ink storage capacity in the roller.
      
  • Worn of Journal ends- This gives uneven inking, skidding, due to run-out or excessive play between the journal ends of bearings of a roller.
HOW TO MAINTAIN YOUR ROLLERS IN TOP CONDITION
  • Rollers should be cleaned thoroughly with a roller wash especially at the end of every day's work.  This will prolong the life of the roller and minimize the hardening effect.
       
  • Clean the rollers frequently before the ink starts to dry.  Accumulation of dried ink film will cause Glazing.
       
  • Rollers should never be left for long periods in contact because" flats" can form on the soft rollers.  Moreover if wash-up has not been completely clean the rollers can stick at contact points with the risk of pieces being top of the surface of the roller when the machine is turned.
       
  • Many rollers become useless because of longtime and/or improper storage.  Spare rollers should be rotated with the rollers on the press, at least every six months.  This acts as a sort of seasoning, reliving stresses that are inbuilt in roller.  The replaced rollers should be cleaned thoroughly and after dusting them with talcum powder and covering them up with the black or brown paper, should be rested horizontally on the journals.  The rubberized portion should never contact any other surface. The storage place should be away from direct sunlight and heat.
       
  • While printing smaller jobs on larger machines printers tend to release ink only to cover the print area.  This causes the sides of the rollers to run dry generation high temperature and causing heavy wear on the roller ends due to abrasion.
       
  • While fitting the bearings, take care that you do not bend or damage the journal ends by hammering or forcing.  Check up the journal ends/bearing seats, sockets and brackets for wear or damage.
       
  • Use the correct technique for mounting the hose on a Dampening Roller.  Excessive force may damage the roller by tearing the soft roller from the metal core.
       
  • To avoid "bulging" or "belling" of dampening Rollers place a disc/collar of fibers/plastic, with a slightly smaller diameter than the rubber, at both rubber ends and then sew on the hose ends.  Any pressure or pull exerted now will be on the disc and not on the rubber sides.

Tuesday, February 2, 2016

INNOVATIVE NEWSPAPER FOLDS THROUGH INLINE GLUE APPLICATOR


OGL 22  is an advanced and fully features computer controlled On Line Glue Applicator, developed for Newspaper and Commercial applications.

The machine is fitted in line with the Web offset machine  and allows gluing of running webs at many points along the direction of travel of the web to produce various innovative folding.

In a simple touch screen operation the operator can control the flow and amount of Glue to be applied.

The sophisticated dispensing heads are mounted on easy retro fit enabled brackets for ease of locations on the web path and is connected with  high quality Festo make Glue Pipes. The system features a suck back system to remove the extra glue thereby providing a seamless and neat gluing on the web.

An array of folding options are possible using a combination of Glue Dispensing Heads viz: Butterfly Fold, Panorama Fold, Reverse Fold, French Window etc.

OGL 22 is capable of gluing up to 48 page quarter fold booklets saving huge amount of time and  manpower in bindery for magazine printers.


FEATURES
Handy System for multiple webs.
User friendly Touch Screen to control operation.
Various patterns as dot, dash, continuous are readily available.
Fast and reliable valve for web of speed up to 15mtr/sec.
Different nozzles to suit the gum thickness on the web.
Suck back system, to avoid gum from dripping.
Flow of gum starts at set speed of the machine.
Flow of gum is auto controlled with increase and decrease of web speed & stops at web break/stop or below set machine speed.
Easy Cleaning of the system by water.
Mounting position can be moved horizontally or vertically to get desired results.
Compact system with touch panel controlled.
Local service and support.

 

 

Wednesday, June 4, 2014

Which Stacker to use for your POST PRESS- Log or a Compensating Stacker.



A short comparison with focus on book, directory, magazine & catalog Printers...



Why this comparison?

On every Post Press project we have two challenging choices ahead of us:

1)  What are the right machines for the productions which will be run on the press

2)  How do I layout these machines in order to optimize

ƒ   the available space and the plant logistic

ƒ   the product flow through the system (including intelligent back-up

ƒ   the ergonomics for the operators (easy access, free floor space, safe environment)

This comparison wants to be a help for question 1) with a focus on small and medium presses with limited need of automation where the Post Press mostly consists of a conveying system and either a compensating stacker (optionally with a trimming line) or a semi-automatic log stacker.

Unfortunately we still see plants inefficiently running books, directories or magazine work through a compensating stacker or retail work through a log stacker from where they pile down loose bundles.

Here the two main question which help to make the right choice:

ƒWhat will the press print : books – directories – magazines & catalog – inserts – newspapers

What is the degree of automation (manual pocket feeding or stream feeders) in the bindery

Here under a fast and simple guide to what could be the best machine for your operation. It is not a “black or white” choice since space; budget, future plans etc. will also influence the choice:

Compensating Stacker - best for..off the press products“

  • For retail applications, with our without trimming (finished products)
  • For Loose, compensated bundles, 100-250 mm
  • Newspaper printing (direct print, at the end of inserters,..)
  • Builds loose, counted & compensated bundles behind web presses
  • As alternative solution in magazine / catalogue printing to handle WIP


Speed
pagination
sizes
application




<120 .000cph="" span="">
2-128p
magazine-tabloid
heat set + coldest

Semi-automatic Log Stackers – best for „work-in-process“

  • For magazine / catalogue applications (unfinished work-in-process WIP)
  • For book & directory Compressed, counted and secured logs, 450 – 800mm
  • Printing (direct print, at the end of inserters,..)
  • Builds compressed & strapped logs behind web presses
  • Copies in the strapped & stable logs are secured between two end boards



Speed
pagination
sizes
application




<70 .000="" cph="" span="">
4-64p
magazine-tabloid
Heatset + coldest








COMPENSATING STACKER
LOG STACKER
Delivers loose, counted, compensated and unstrapped bundles
Delivers counted, compressed, uncompensated logs secured by two end boards and safely strapped.
100-250 mm bundles height ( in average)
450-800 mm log length on semi automatic log stacker.
No need of consumables for the loose bundles. Possibly need of consumables ( strapping belt/film) to stabilize & protect the pallets
End boards and strapping material needed for each log. Normally no additional cosnumables needed to stabilize & protect the pallets.
The stacks are only shortly compressed in the stacker. After placing the products on the pallet the spine will tend to build up again ( memory effect on the paper). The higher position of a bundle on the pallet the more air will be in the bundle>no uniform bundles
The logs are compressed resulting in completely flat sections with no risk of folded edges. No alternation will happen to the products once they are placed onto the pallet> all products are flat & uniform.
The loose bundles on the pallet are unprotected. They tend to move, especially in the lower layers. Loose bundles are exposed t dust, temperature and humidity. The level of compression also varies with the position of the bundles on the pallet ( with high compression on 1st layer, no compression on last layer).
All products in the log are equally compressed. The products in the log are protected, they can not move ( neither in the log nor on the pallet). The products are not exposed to dust, temperature or humidity.
Slip sheets & pallet film wrapping will protect the loose bundles. This adds costs for labor & consumables. The use of film can lead to folded edges of the sections which can increase the risk of jams in the bindery. Optionally carton corners can be used before film wrapping.
Slip sheets may be used but no film is necessary. No costs for additional consumables. No folded edges of the sections.
Work load of a compensating stacker is higher-higher frequency of bundles which are mostly placed manually on a pallet. Example 7 layers x 14 stacks = 98 movements per pallet.
Lower frequency of logs which can be placed manually ( short logs) or by means of a semi-automatic clamp or a log palletizer on a pallet. Example: 4 layers x 4(6/11) logs = 16 ( 24/44) movements per pallet.
One man operation on compensating stacker behind slower and smaller presses. Two men operation on compensating stacker behind high volume and faster presses.
One man operation on semi-automatic log stacker. One man operation on two fully automatic log stackers ( configuration allowing).
It is difficult to stack pallets with loose bundles w/o damaging the product. Securing the pallets entails additional costs.
Easy stacking of pallets.
Pallets will have to be shrink wrapped if transported to a bindery which is not in house.
Printed products are secure whether to be taken to a bindery in house or outside. Only end boards need to be returned.




Tuesday, September 4, 2012

Offset Printing: The Next Greatest Thing in Blanket Cleaning

Offset Printing: The Next Greatest Thing in Blanket Cleaning: I don't like to promote products, especially ones that are unproven.  But there was a new product released at Drupa by Grafinkontrol for ...

Monday, November 7, 2011

Dot Gain....!!!!!

Dot gain


Dot gain is a phenomenon that causes printed material to look darker than intended. This happens because the diameter of halftone dots increases during the prepress and printing process. The optical and physical properties of the media and machines used both in preparing the job for print and the printing process itself cause this behavior. Below is an example of what happens when a nice flat tint (left) gets printed on newspaper stock: ignore the fact that the paper is grayish – look at how the dots get fuzzy and a lot bigger.

Simulation of dot gain in a newspaper


Prepress and press operators can try to minimize certain types of dot gain but cannot avoid that dot gain occurs. As such it is also the responsibility of the designer to be aware of dot gain and to anticipate its effect. You typically find dot gain controls in applications like Adobe Photoshop.

Dot gain controls in Photoshop


Dot gain basics

Dot gain is expressed as a numerical value which equals the difference between the wanted value and the resulting value. For instance: if a page has a 50% flat tint as a background but after measuring the printed result, this flat tint is now 65%, the dot gain equals 15%.

•Please note that the convention for specifying dot gain is slightly weird: it is expressed as a percentage at a certain tint. The percentage however is not a real percentage but an absolute value – 20% dot gain at 50% does not mean the end result are halftone dots that are 60% but that the resulting halftone dots measure 70%!
•If no target percentage is specified, it is assumed that dot gain is specified for a 50% tint.
Dot gain is not identical for all the colors used in color printing. There are slight differences in dot gain between cyan, magenta, yellow and black.

Total dot gain is the difference between the dot size on the source file and the corresponding dot size on the printed result.

Dot gain is sometimes refered to as TVI (tone value increase). TVI is a more generic description of the difference in tone value between a requested value and the final output. It is also a more suitable name for processes in which some devices may not actually deliver a dot in the final output.

Types of dot gain


There are different types of dot gain in the prepress and printing process.

Dot gain caused by imaging devices & media

The optical system in computer to plate systems or imagesetters is not always perfectly linear. In order to make sure that the media are exposed sufficiently, the laser beam is a bit wider than needed so that the lines that are exposed slightly overlap each other. Depending on the process (positive/negative), this may cause either a slight dot gain or a dot loss.

Media such as plates or film also can be non-linear: some are but polymer plates for instance can have a dot gain of 5 percent of so.

Mechanical dot gain on a printing press

On an offset printing press ink is transferred from the printing plate to the blanket and from the blanket to the paper. Each time the dots get squashed a little bit, increasing the physical diameter of the printed dot. The ink that is used, the fountain solution, the blanket, the pressure (over/underpacking) and the speed at which the press runs all influence this type of dot gain.

When ink is absorbed in paper, this occurs both vertically (into the paper) and sideways, which again increases the dot diameter. This effect is more pronounced 0n newsprint than it is on coated paper.

Optical dot gain

When light hits the printed surface, it becomes slightly diffused around the dots. The human eye (as well as measuring devices) perceive this as a darkening. Dots appear to be larger than they really are.

Compensating for dot gain

Applications like Adobe Photoshop will automatically compensate for dot gain when images are converted from RGB to CMYK. This is done based on the selected preferences, as shown in the above screen capture of Photoshop CS3′s color settings. Designers need to be aware of this and make sure that their software is configured properly for the printing process that will be used to print their jobs. They also need to be aware that vector based applications like Adobe Illustrator don’t compensate for dot gain. If you draw infographics for a newspaper, you need to make sure that flat tints don’t get too dark in print.

Prepress operators are expected to make sure that plates delivered to the press are linear, with a typical tolerance of around 2%. Workflows and RIPs come with calibration tools to achieve this. If a system has 5% dot gain, instructing the RIP to image a 50% tint as a 45% tint assures that the end result is once again 50%. This process is called linearisation.

Given the fact that so many people supply files that are optimised for sheetfed offset printing with a dot gain between 12 and 20%, operators may tweak other devices such as digital presses to mimic the dot gain behavior of offset presses.

In general higher screen rulings exhibit more dot gain. Vendors of workflow and computer to plate systems sometimes anticipate this: for the very fine dots that are used in screening algorithms such as stochastic screening, they create screen cells that aren’t linear – the 50% dots may for instance be 38% dots. By including a pre-compensation in the screen cells, printers achieve better results with the out-of-the-box set-up and only have to focus on fine-tuning the system to their particular needs.