MyPrintingTutorials.com-Printing Tutorials Offset Printing Digital Printing A Guide to Offset and Digital Printing

Most commercial printers print at 300 dpi which is suitable for 150 to 175 lpi. So in order to get a photo printed at 300 dpi the final resolution of the photo after resizing should not be less than 300 dpi. When you resize a photo after scanning the dpi increases or decreases depending on whether the photo is scaled down or scaled up. That is unless you re-sample the photos in Photoshop by clicking the re-sample button. Re-sampling up is not advised unless absolutely necessary and even then the photos should not be re-sampled up more than 10 percent otherwise the quality will deteriorate. Re-sampling down is alright but should be done after the image has been finally edited.

Now if suppose a 7×5 inches photo is to printed at 300 dpi then we have to scan the photo at 300 pixels per inch. However if the photo is to be enlarged to 14 x 10 inches then 300 pixels would not be sufficient as when the size is increased the dpi will go down, in this case, to 150 dpi. So in order to maintain the same dpi the pixels have to be increased. A 14 x 10 inches photo at 300 dpi requires 4200 x 3000 pixels (14×300 = 4200, 10 x 300 = 3000). To get this pixels the 7 x 5 inches photo has to be scanned at 600 pixels per inch ( 4200/7 = 600, 3000/5 = 600).

As a rule when the photo is going to be resized at twice the length and twice the breadth the pixels have to be doubled. So scanning resolution of 300 ppi becomes 600 ppi when the length and breadth of the scanned picture are to be doubled.

Posted under Digital Printing, Offset Printing

Some of the common sizes in which books are published are :

1) 8.5 x 11 inches – 1/4 single demy size used mainly for magazines and souvenirs.

2) 5.5 x 8.5 inches – 1/8 single demy size used for paper backs and other books.

3) 7.25 x 9.5 inches – 1/4 single crown size used for notebooks and magazines

4) 4.75 x 7.25 inches – 1/8 single crown size used occassionaly

5) 4.25 x 5.5 inches – 1/16 single demy size used for very small booklets.

Other sizes

1) 8.5 x 13.5 inches – 1/4 DFC size. used for registers and small threefold brochures.

2) 6.75 x 8.5 inches – 1/8 DFC size used for notebooks

3) 7 x 5 inches – 1/16 of a 22 x 28 inches Board used for invitation cards.

4) 7 x 4 inches – 1/18 of a 22 x 28 inches Board used for invitation cards.

5) 6 x 4 inches – 1/20 of a 22 x 28 inches Board used for invitation cards.

Posted under Book Printing

Macro is another mini offset printing machine company based in Coimbatore, India. The first machine that we bought five years back was from them – the 15×20 Macro Deluxe model. We are still using it. During the course of these five years we had to change some parts such as dampening roller and the plate clamp. We have found the machine to be quite sturdy and reliable. It has 11 inking rollers and two form rollers. Some four color jobs can still be run on it and there is no registration problem. The cost of the machine comes under Rs. 500,000/- It does not need a stabilizer like some other machines. and there is no problem running it on generator power.

Some of the draw backs of the machine is that it is a two cylinder machine and scum is a constant problem. One person has to sit on the back where the plate is and keep on wiping the plate from time to time. Another problem with the deluxe model is that it has a motorized feeder table lifting. The problem with this is that the machine operator has to manually press the table lifting button from time to time as the auto lifting function is very difficult to adjust without stopping the machine. All this hampers the production and thus the day’s total number of impressions may come down.

It seems that Macro is not too keen on improving their offset section. Instead it has gone for manufacturing of thermal lamination machines which has become very successful and they received good responses for this even during Drupa 2008.

Visit their website at www.macroprintindia.com

Posted under Offset Printing

We have been using the Epson 7800 printer for about a year and have found it exceptional in terms of quality. The photo printouts on photo paper are just amazing. The printer has a maximum width of 24 inches. It can print full bleed 24 inches. The color reproduction is quite good. The only draw back is the cost of ink cartridges which may come to about Rs. 3400/- for one. There are a total of eight cartridges – Cyan, Light Cyan, Magenta, Light Magenta, Yellow, Light Light black, Light Black and Photo or Matte Black. The printer can print on canvas too and numerous other media including back lit film. Back lit film from Technova is however not available at present in 24 inches width.

The printer can also be used for color proof copies. It is used in Technova’s Polyjet System also though the maximum dpi of 2880 x 1440 may not be high enough for 150 lpi. The cost of ink at 100 percent coverage comes to about Rs. 40 at 1440 dpi. The cost of the printer is around Rs. 200,000/-

The printer does not have a maximum printing length which depends only on the supply of ink and paper but we have experienced that some complications arise when printing at more than eight feet length. It may be because of the software. I have not been able to find out for sure.

Posted under Digital Printing

At the start of this year we had installed a CISS from SplashJet Print Technologies in Mumbai, India. The continuos ink supply system is VERY VERY cost effective compared to regular inkjet cartridges. The initial cost of setting up the system in your printer is under Rs. 3,000 or something close to that. Each of the four cartridges is connected to containers containing maximum 100 ml of ink. We use a Hp K850 inkjet printer with our CISS. It does not work with all inkjet printers. The quality of the print deteriorates somewhat but it is good enough for everyday office documents. Photos also don’t come out that bad.

The ink containers are refillable. Refillable bottles have inks of 200 ml each. Black Ink is available in 300 ml and 200ml. The four bottles of 200ml ink each comes under Rs.800/- for all four.

Posted under Ink Jet Printing

Novadom plates are manufactured in India by Technova. The plates come in Legal, B4 and A3 sizes. They are polyester based plates output through a laser printer such as Hp 5200 laser printer. They may be output through a photocopier also but the result may not be that good. They are ideal for short run spot color printing.

We have been using Novadom plates for a couple of years and they are basically the only alternative to metal plates. They are very cheap compared to the metal ones which comes in about Rs. 60 or 70 per plate. Novadom plates in legal size are available in packets of hundred for under Rs.750/- per packet. The B4 and A3 sizes comes under Rs.15 per plate.

Novadom plates are known as Smart Plate in the US. They are distributed there by Hurst Chemical Company. These plates have the limitations of common laser printer plates  that I discussed in my post under “Difficulties With Laser Polyester Plates.”

Posted under Offset Printing

Autoprint is a mini offset printing machine manufacturer based in Coimbatore in India. It has received several awards for excellence in printing machine manufacturing in India. It may be safe to consider that it is now the best manufacturer in India when it comes to mini offset machines.

At our press we have one single color Autoprint Knight Offset Machine with the optional Kompac Dampening. This is the best single color mini offset machine that Autoprint has to offer at present. We use the machine daily for producing color printing materials. The Knight machine is quite suitable for multicolor jobs in runs within a thousand or two. It has two inking form rollers with a total of 15 ink rollers. The cost of the machine with the kompac dampening system comes under Rs. 800,000/- in India along with all taxes.

Autoprint has come out with its new two color mini offset machine, Autoprint Dion 250. This is a replacement to the Knight 250 CB which was introduced for a short period and withdrawn from the market due to some technical problems. I am yet to receive information on this new product because the sales have really not started at present. The Autoprint Dion is under Rs. 1,500,000 in India.

It may be remembered that Autoprint had ambitiously launched a mini offset four color machine in the Indian market some one or two years back but it failed due to problems such as registration issues. Hopefully they will come out with a good replacement soon. Autoprint is a name that you can rely upon. Their country wide support is excellent with sufficient engineers all over the nation.

Posted under Offset Printing

TechNova is one of the world’s largest manufacturers of digital & analog offset printing plates; printing chemicals; and inkjet, laser and drafting media. It is primarily based in India but their products are available in many countries through their authorized dealers.

In Drupa 2008, Technova launched their Metal CTP System, Metijet and Metijet Plus. Metijet is imaged on an inkjet printer such as Epson 7880 at maximun 120 lpi and then it is baked for a few minutes before being mounted on the press. Metijet Plus, on the other hand, is imaged on the Epson Printer and then it is exposed on an exposing machine before being processed and mounted on the press. It is capable of holding 150 lines per inch.

Currently, Technova’s Polyjet system consists of Polyester CTP and Film to Plate system. The Polyester CTP plates are known as Polyjet Plates which are imaged on the Epson Printer and then baked for a few minutes and thereafter transfered to the press for printing. They hold good registration and fine halftone reproduction. The only difficulty is that the right temperature for baking is hard to get in the beginning. A linearization file has to be applied to get correct output from the inkjet printer.

Technova’s film to plate system includes the InstaDry film. The film holds excellent registration and gives good four color printing plates for the press. They come around 90% close to imagesetters. This film is also imaged on an Epson Printer.

The Epson Printers offered by Technova along with the system are available in 17″ and above widths. The software used is Technova’s Polyrip which is really the Open Rip software.

Technova’s Polyjet System comes under Rs. 600,000 for the 24 inches width Epson printer. The price may have increased now as this is the price that I received one or two years back.

Posted under Offset Printing

a) Background Tint and Unwanted Specks – One of the most common problem with laser polyester plates is background toning caused by toner scatter from the laser printer on the plates. This problem becomes acute when the printer is running out of toner. Printing a few blank pages can help solve some cases where the toning is caused by dirt deposited inside the printer. Blank pages should also be run through the printer after a paper jam to clean the printer.

b) Misregistration – Registration is critical for jobs which demand more than one colour. If two colors are to be printed then two master plates have to be printed, one for each of the colors. Now the colors have to be printed on the plate such that their placement is accurate. Laser printers perform poorly in this. Exceptions are some high end laser printers such as Xante’s Platemaker series. These printers perform exceptionally well with polyester plates but both the plates and the printers are more expensive than the ones we get from vendors like HP for printers and Technova or Hurst Chemicals for plates. Xante uses its own plates known as Myriad Plates. Inkjet plates perform better in registration issues as the plates tend to be more stable and there is no heat as in the case of laser technology which might affect the plates.

c) Poor Printing of Solids – Areas in plates where there are a heavy concentration of a particular ink are known as solid areas. Laser printers again fail in this test too.

d) Stretching of Plates while Running in an Offset Machine – This is yet another problem which occurs with most of the laser plates.

e) Long Runs not Possible : Laser plates are limited to short run production usually in a few thousands. The toner on the plates tends to come off after some thousand impressions.

f) Laser Plates are Use and Throw : Laser plates are difficult for reuse as the toner comes off the plate after one time use.

Posted under Offset Printing

a) Adobe Indesign or QuarkXPress – These are the best page layout software. You may choose either one of the two. They have a lot of features for designing a magazine or brochure or book.

b) Adobe Photoshop – Editing of photos is best done in Photoshop. It is best for photos to be scaled and rotated before placing them in a page layout software. The dpi for the photos should be about twice the lpi at which it would be printed. If suppose the photos are to be printed in Offset at 150 lpi then they should be at a resolution of 300 dpi.

c) Corel Draw and Illustrator – These software can create files in vector format. They are good especially for creating logos.

Posted under Offset Printing