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Although paper is often just a vehicle for information people have very strong views on what it should look like. A newspaper on green-lined computer paper, or a novel on cash register tally-roll might be functional but they are unlikely to be acceptable.
For most tasks most people are adopting a standard compromise – A4 80 gram white "photocopier paper". Even with such a boring material paper can cause an amazing amount of trouble to printer users an support engineers. More information on how paper works might sometimes be helpful.
Most paper is made largely from wood fibre. Parts of the wood break down in the pulping process to give a cellulose adhesive that holds the fibres together. Other vegetable material can be used - cotton, hemp, and ice fibre for instance. High quality papers might also contain a woven material holding the sheet together –traditionally linen.
Polishing and sizing are often used to give a finish. The sizing applied to the outside of paper contains a certain amount of kaolin (white clay) and this is held within the fibre mat. British paper types tend to contain ather more kaolin than US papers because there is a traditional demand for higher levels of polish. Polishing is done by running rollers at a different speed to the paper transport and gives a shiny gloss finish. Too much gloss can be distracting, creating reflections from the page. The finish also changes the way paper handles ink. Kaolin will absorb liquid before it can disperse through the fibre, but a highly polished surface may slow absorption so that ink smears.
The wood –fibre in paper is often chemically bleached, perhaps using chlorine or sulphur dioxide. Chemical brighteners might also be added – a brightener tends to flouresce slightly towards the blue end of the spectrum – the same principle used by some washing powders. Coloured papers will also incorporate a dye. Many papers are vulnerable to breakdown by environmental factors- newsprint will yellow if exposed to light and microbes will often invade, particularly if the material gets damp. Paper cannot easily be kept dry because the fibres are often hygroscopic. When paper is damp the kaolin on its surface will tend to bind sheets together, and fibres may break lose from the sheet interfering with ink-flow.
Paper is generally made in large rolls one or two metres wide by a continuous process and cut to the required shape.
Print works often use web-feed - the paper roll is fed through the press intact, printed, then folded and cut. Continual feed through the printing process allows very fast printing if the ink is absorbed quickly into the paper although it can be difficult to get registration right for the cutting process. Web feed suits newspaper production very well.
Print works can also use sheet feed. The sheet feeders on a professional press tend to be vacuum assisted, very fast by comparison with office laser printers and take paper in A0 reams.
Office and home printers normally take paper cut to shape.
Paper Cutting. 
The latter stages of the cutting process generally involve a stack of many sheets of paper being cut simultaneously. The cutting can be done by a guillotine, a saw, or by a water-jet.
Guillotines will obviously bend the edges of the paper in such a way that they will curve slightly and may be difficult to separate. Sawing will bend edges less systematically but will make dust, some of which will penetrate into the paper stack and re-appear during use. Water-jets are the most expensive cutting devices but make no dust. Dust in the paper and bending of the edges can have a marked effect on printing processes. A common reason for engineers to be called out to printers and copiers is that users have changed the grade of paper used.
Paper Grades.
Printer users have quite a lot of incentive to try out different papers. For instance in the market for A4 80gsm copier paper there is commonly a three-fold price difference between papers, with bulk unbranded supplies of available for under £1.50 per ream and a single ream of "quality" paper costing £4. Since the best bargains are bulk-buys organisations can find themselves burdened with large quantities of paper that will not feed through machines reliably. Who carries the burden of this problem can depend on the exact terms of copier and printer maintenance contracts. Maintenance contracts tend to have exclusion clauses to deal with issues like this.
There are about five main printer technologies - bandprinter, dot matrix, thermal, laser and inkjet. In principle, any printer can take any paper shape - for instance a bandprinter could have a cut sheet feeder (although they never do). There are laser printers that cope with continuous forms and many digital print systems take web-feed paper. However there is a tendency for older bandprinters and dot-matrix machines to use continuous forms whilst lasers and inkjets use cut sheets around A4 size. A3 laser and inkjet printers are readily available but usually significantly more expensive.
It is possible for a printer to work with no real knowledge of the shape of paper- but only if the layout requirements are very basic. Most users want the text to begin at the top left of a page and just about fill the space but leave a margin, then to skip to the next page. Users do not want any part of the print to go beyond the page - which would mean they lose information . A lot of this process could be controlled by the computer if there was a way for the printer to communicate with it. Traditionally however, printers are output devices and don't communicate much back to the computer. The printer iself needs to know at least where the top of the first page is, where the right margin is and how long each succeeding pages is. The printer must be given some basic information about the shape of the page and it needs a sensor to detect the top of a page.
VFU & Control Languages.
Twenty years ago it was common for printers to have a "formatter tape". Users would have sales invoice, purchase order, stock control and other pre-printed stationery and would load the correct tape into the printer at the same time as the stationery. The printer controlled layout using information on the tape. VFU tapes could do clever things like putting the right text from a database in the right boxes on a form with very little programming.
The tapes often broke, they could be difficult to program, and they made printer operation more difficult than necessary.
A later generation of printers generally had some paper size switches. These were convenient if they were well labelled or if you knew where the manual was. The next step was to input parameters from the control panel - which could become quite confusing.
Printer control languages improved things. The computer can be told it's parameters and given page layout information by the computer.
In today's market printer makers tend to ship a Microsoft Windows print-driver with some support software that can override or change printer internal settings. Of course this rather assumes that everyone uses Windows - and significant part of the market actually don't. Some knowledge of the kinds of paper used is necessary to set the printer correctly.
A4 paper will be familiar to most people in the UK and Europe. The standard paper sizes start with A0- this is vast (one square metre and only common in end-use for charts and plans). Take a piece of A0 and fold it in two halfway down the long side and that makes A1. Do the same again and that makes A2. Repeating the action makes A3, A4 and A5, these are the sizes seen in common use. In Europe A4 has gradually replaced older paper sizes such as manuscript and foolscap.
In the US paper sizes such as "legal" and "letter" persist.
Some professions have great affection for odd old paper sizes – the legal and accountancy professions are especially keen on tradition. Most ecent laser printers can cope with most common page sizes - but not necessarily on every tray.
Inkjet printers tend to be most pernickety about paper. Inkjets with a straight paper path can commonly handle anything from 80 gsm to 150 gsm material (copy paper to light card) but they very often can't deal with anything exceptional about the surface finish.
There are exceptions to every rule and some inkjet printers can manage to print on completely rigid surfaces like CDs. To match inkjet cartridges, some CDs have a paper-like surface.
Laser printers quite often have an "S" shaped path from their main feed tray so they are usually tollerant of paper from 80 gsm to 120 gsm and possibly to 180 gsm from the front feed tray.
There will certainly be a printer that can cope, but it may not be a mass market device, so it might be costly
Tractor Feed.
Tractor feed paper has a row of sprocket holes down each margin spaced at 1/2" intervals - no other spacing has been common in recent times. Sheets are not detached from one-another but folded in alternate directionsat perforations, making a fan-fold stack. Usually there are 2000 sheets of single part paper in a box - or 1,000 sheets of two-part.
The industry standard size for tractor feed listing paper is 14", wide enough for 136 columns at 10 columns per inch, and for 272 characters at 20 cpi – useful for spreadsheets.
80 column paper usually has a fine line of perforations down the margins to allow users to separate the tractor feed holes, producing paper approximating to A4 and improving the look of reports
The printer grips the paper by sprocket-pins. Some low cost printers had sprocket-pins fixed on the left and right of the platen, which meant that only one size of paper could be used. More usually the sprocket-pins are carried on two adjustable tractor blocks that can be positioned to handle any width of paper.
The tractors can be positioned after the platen, or before it.
Pull Tractors.
Tractors are traditionally placed after the platen - where they are called "pull tractors". This means that the paper is under tension as it feeds through the print position making it less liable to wrinkle. If the paper wrinkles as the printhead passes over it the characters will be mal-formed, but much worse is that the head will generally tear the paper, crumple and tear the ribbon and possibly bend and jam printhead needles. Avoiding paper-wrecks is therefore quite important.
But there is a problem, with a pull tractor at least one sheet of every printout has to be wasted. This does not matter too much if the average printout is 10 or 20 pages long, but if the printer produces one page warehouse picking lists every few minutes wasting half of the paper becomes irritating.
Push Tractors.
"Push tractors" are placed before the print-position, either below or behind the platen. It can be more difficult to load the paper into a push tractor, but once it is there the paper can be torn off at the perforations the moment it has left the print station. Push tractors allow continuous feed paper to output a single sheet at a time, so that dot matrix machines can be used in work such as producing despatch notes, point-of-sale invoices or pharmaceutical labels.
Listing paper has never been very satisfactory to users, its purpose is to make printer design simpler, but the paper is clumsy and the tractor-holes look ragged. It is possible to apply any of the print technologies including laser to continuous sheet paper, but the market now favours cut sheet paper. sheet on demand printing with cut-sheet paper is simpler.
Tractor–feed remains supreme in one market, multi-part business forms. The advantage of a multi-part form is that it makes two (or more) copies of everything it does.
Multi-part paper can be handy organisationally - for instance the customer gets the top copy of a delivery note, the picking staff get another and a third copy goes for the administration record. The computer may say one thing, but handwritten notes by the picker may show something else. (Lots of businesses have difficulty making computer stock records and reality converge).
Multi-part has the advantage that it is usually forensically verifiable - a customers copy can be shown to correspond to a carbon copy. Verifiability is usually obvious - their white copy says exactly the same thing as my yellow copy. Werification can be much more detailed. Most impact printers have slight errors in character formation and a true copy repeats the pseudo-random pattern of errors - which its highly unlikely any forgery could do.
There is no way to print on multi-part paper except using an impact printer - which means dot-matrix or bandprinter technology. The nature of business processing tends to produce batches of print so loading and unloading tractor feed is not unduly inconvenient.
It is actually quite difficult for a normal print-works to make a multi-part pre-printed business form. Printing companies naturally expect to handle single part good quality web feed or cut sheets. They need some different equipment to handle light-weight tractor feed. Normally each part except the last will be made of carbon-less copy paper, which has microscopic ink capsules embedded in its weave. Each part will be overprinted with the outline of the form and they must then be bound together, the tractor margins are usually used to do this, either with a very light adhesive or by perforating the paper so that it holds together.
The price of pre-printed stationery can be surprisingly high, typically £200 or more for 1000 forms - 20p per sheet. These costs are often much higher if artwork and plates have to be made – rising so that little change will be seen from £500. Long print runs bring the price down to something like 3p to 5p per form depending on how many parts the un has.
Accounting Software & forms.
Because it can cost a lot to set up pre-printed stationery accounting software houses often do this for their customers. In fact this can often be where a substantial part of the profit for a software business lies - the accounts package is a license to sell special accounts paper.
Software houses own the copyright on their pre-printed forms. Customers cannot simply take the design and get it re-printed, even if they felt the substantial setup prices were justified. If the design of software makes a pre-printed form necessary then software houses can charge a substantial premium for it. Perhaps it is no surprise that some software simply will not operate effectively without pre-printed stationery.
Businesses often just bear the costs of pre-printed stationery - after all if the average invoice is £100 and each order needs one delivery note, one invoice and one reminder at 10 p each then that is just another business cost. One the other hand printing the information on plain paper might cost 2p each. If there are 10,000 orders per year the saving is £2500. With 100,000 orders the saving is a wage bill.
Cut sheet handling is more demanding than tractor feed. The printer has to pick up one sheet from a stack and aim it precisely into the feed ollers.
The first computer printers to provide cut-sheet handling as standard were laser machines, which work in a similar manner to photocopiers and largely copied their mechanical construction. The primary selling-point for early laser printers was quality of output, so their ability to use good quality paper was important. Automatic cut sheet feed was available for daisy-wheel and dot-matrix printers as an add-on option at a substantial premium price.
Cut sheet feeders hold a neat stack of paper in a tray. The tray will have adjustable spacers to ensure that the paper stays in the correct position. Under the paper will be a lift plate which keeps the paper pushing upwards. At the "exit" end of the tray the paper is often pressed up against one or two hinged catches that obstruct its escape as long as nothing pushes it. These are the paper separators.
The other type of separator is a cork or rubber pad under the pickup oller. This pad has sufficient grip to keep lower sheets from feeding so only the sheet directly driven by the roller moves.
When a sheet is to be fed it is held up against one or more rubber rollers. These pickup rollers are often shaped like a "D" and the flat side faces the paper until the moment a sheet is to be fed. As the rollers rotate they engage the paper, pushing against it. The paper is held back by the separator and will distort slightly, breaking away from the stack and moving further into the machine where it is engaged by other rollers that carry it through the remainder of the process.
Controlling the action of the pickup and other rollers requires a sequence of actions. The paper is kicked out, then the pickup rollers stop. The feed-rollers now take over - the paper must be held under enough tension that it does not slip, but not so much that it will be distorted as it travels through the machine. The tension must be very even or the paper will skew to one side or another. Quite often there will be a series of guides and paper gates all of which must be correctly adjusted. This is what makes cut sheet handling more complex and prone to failure than tractor feed.
Some early cut-sheet feeders by firms such as Rutishauser used dedicated microprocessors and motors to achieve the action, making their feeders quite expensive (£400 plus). More recently, printer manufacturers tend to have incorporated a cut sheet feeder into the design, or to make the printer processor and line-feed motor do much of the work. The feeders for Epson’s LQ series printers were fairly cheap because they were entirely mechanical, with the timing actions being produced by rotating the platen forwards and backwards to engage different mechanisms through planetary wheels. The only problem is that non-powered cut sheet feeders tend to be slow because of all the platen movement needed to engage a variety of sun and planet gears.
Laser printers with high work-rates can usually be a component in a stack of cut-sheet paper trays which can also incorporate duplex units (double sided printing), output collators and bookbinding.
The design of cut sheet feed mechanisms has now been refined to the point where they are quite reliable and cheap to produce. Because people tend to prefer their work on neat, crisp standard A4 paper, most laser and inkjet printers make no provision for any other sort of output.
One thing to watch out for with extra trays is their paper specification. It is quite normal to find that a printer will take 150gsm paper but that add on trays take nothing heavier than 120gsm or less. As the paper-path gets more complex the paper range it can cope with diminishes.
Duplex.
One obvious defect with many older and low-cost printers is that they print on only one side of the paper. One sided printing is normal for correspondence where wasting paper has always been seen as a matter of courtesy. Single sided print makes other documents look unprofessional – and of course it nearly doubles paper consumption. Two-sided printing can be achieved by simply putting each page through the printer manually the right way up – which can be confusing because some printers feed the paper upside down.
Recent MS-Windows drivers try to help by having a select-box for all, odd or even pages so that a whole report can be fed back through the machine. Unfortunately this can still be confusing and the risks of a paper-jam ise disproportionately because the paper tends to curl after it has passed through the printer, particualrly through a laser printer fuser.
The ideal way to print double-sided is with a duplex unit which takes the output and directs it through the printer a second time. The duplex unit is much better than messing about trying to ensure each page goes through in the correct order and the right way up, although it still tends to be a bit prone to jamming due to paper curl.
Duplex units have been surprisingly rare for "Catch-22" easons: few users buy duplex units because they are expensive, duplex units are expensive because so few people buy them.
In recent times duplex units have started to become standard on workgroup - type laser printers and even on some inkjets.
Multiple Trays.
Letterhead paper is very widely used to create company image. Almost every organisation has some sort of coloured logo that is to be incorporated in every document in the front page. Letterhead paper is usually pre-printed in colour, it may be on heavier than normal paper and it may be embossed. The page orientation problems of manual duplex printing are also a concern for letterhead, but letterhead is also needed a great deal – often every second page, especially on network printers.
The simplest arrangement is for the printer to have a tray set aside for letterhead and to mark which pages of a document are to use that tray. MS-Windows printer drivers for multi-tray printers offer these choices.
Some organisations have several different letterheads and require a file copy on different coloured paper. Paper-feeder stacks provide for this sort of use. It is worth noting that the cost of the paper feeder trays might well exceed the price of the printer itself – and that the probability of failure rises with the number of trays. A key problem with multiple tray systems is that users get over-ambitious. Trays are generally rated to handle paper grades between 80 an 100 grams – but users persist in trying to put 60 gram copy paper and 120 gram letterhead through feeders. The fact that CSFs will often handle paper grades outside their ating does not mean they should be expected to- often as the machine ages slight wear on components causes it to malfunction and it may not be possible to restore the original beyond-specification workability.
White Paper Offices - Letterhead.
All kinds of pre-printing tend to be quite costly – small firms can find that letterhead costs more than 20p per sheet. Calculating the price of computer printing should probably take these external costs into account.
Some organisations have decided to stop using pre-printed forms altogether – any paper output by the business will have to come from computer printers or photocopiers. The idea is sometimes called a white paper office because fresh white paper is the only kind of stationery used
A good colour inkjet printer can produce reasonably convincing letterhead – although the quality might not match that provided by a professional printer using special inks. The price per page for inkjet letterhead can be around 3-4p, but this might very significantly undercut the price of professional printing.
A colour-capable laser printer with decent sized toner cartridges can produce letterhead and the remainder of a document at the same time for about 3p per sheet - and has all the colour capabilities for doing other things in addition.
The loss of all those nice embossed 150gsm letterheads would be a pity - it really brightens life up to see what government departments can spend money on. Nobody seems to have devised a laser printer with an embossing tool.
White Paper Offices - Forms.
One very important factor in white-paper procedures is that it is easy to correct mistakes. Too often people only find the mistakes in form design when they are already using them and have a 20,000 copy print-run to work through. Long print-runs can also be a nuisance because basic information changes so often – businesses move premises, change phone numbers, change their product lines and ways of operating – each can mean a re-design of the business forms.
Of course using nothing but computer and photocopier output can mean that print quality suffers. Computer output offers a very significant quality advantage that may more than compensate:- each form can be customised to the job in hand and have some boxes pre-printed with information already known to the system.
Printing forms with the data already held can save time re-writing the obvious. Just as importantly the process of transferring information into a computer is usually error-prone, and re-printing the information gives an opportunity for it to be corrected.
Although the idea of a white-paper office has some merit, professional printers are still likely to be needed:
In the last two decades most printers have equipped themselves with computer gear that is more powerful than that on the average desktop. Printers and graphic designers work closely together and tend to come up with a better looking product than an amateur with an inkjet. The better quality inks and stiffer papers used in professional processes are a small part of the overall package.
Most people are swamped with unwelcome paper. The single major cause of complaints to the Data Protection Registrar is unsolicited mail shots. A few weeks of catalogues, trade-press and mailshots can easily mount up into a congealed mass of dead material. In an information-overloaded environment the only way for information to succeed is to look unusual. Professional printers are usually best at making sure a message succeeds.