British-born Mike Young has been a specialist in high-definition graphic & industrial screen printing for more than 30 years. He is a SGIA Fellow, a member of the Academy of Screen Printing Technology, recipient of prestigious Swormstedt Award for technical writing. He is also a frequent contributing writer to trade publications, SGIA Golden Imaging Award print judge, legal expert witness and a popular speaker at industry events. Mike is creator of the internationally known Troubleshooting Chart and published several technical books on advance screen printing techniques, including The Register Guide about achieving print excellence. Mike has conducted business in India (Mumbai) previously and he operates Imagetek Consulting International, a Connecticut USA - based consulting firm, that trains and troubleshoots screen printing operations worldwide. He can be reached at mikeyyoung@aol.com

PART I : AUTOMATION & CONFIGURATION
The very idea of researching different manufacturers, brand names, model types, sizes and various configurations of ancillary features and options - all within a budget, is enough to put off the most harden buyers. However, this article will help to sort out various press types and their capabilities so that you can begin your mission with eyes open and find the machine that best suits your needs and budget. Find out first hand before you invest what the benefits and drawbacks are of different press types, styles and configurations. Once these have been chiefly understood, the review of standard features and popular options assessment will ensure the buying process can be better managed with a lot more confidence.

For many, buying new screen printing equipment is much like hunting for a new house or factory. I use the root of the verb “hunt” for buying because a greater amount of time is spent literally hunting (searching and evaluating) then the physical buying part, which occurs just once but only after a suitable piece of equipment has been found. In my line of work, I see the method of buying a press is strikingly similar to that of acquiring property, such as a house or suitable factory to moving into, particularly for the first-time buyers. For many, the task can be painful and a stressful process, but it could be made a little more pleasurable if one understands the basic concepts and features that are fundamentally needed in a printing operation - separating those that are not required.

People may initially be quite excited about the prospects of looking for another house or factory (press) but only to find later that the task can be very exhausting, frustrating and daunting to perform (too many presses available all claiming to be better and out perform one another). In other respects, buying a new screen printing press is one of the most important and heaviest investments a company can make, not unlike a new house or factory. But the similarities don’t stop there. When looking at a house or factory (press), one has to make sure it is the right size (handles maximum sheet size), of the right type (level of automation), has the desired amount of rooms (needed features) and all the other details that can turn a house/factory into a home/ production environment. Similarity goes further than the product itself, by evaluating city services, local conditions and other amenities (supplier’s after-sales service and spare-parts support). Even those experienced in buying houses/factories (presses) begin to start looking into greater depths and perhaps specific customisation than those of the naïve first-time buyer. This is when the family’s furniture and carpets (production equipment) must fit the rooms (floor space) available - just as a new press has to accommodate customers’ requirements. House/factory and press buying (hunting) alikeness are very real in very way.

A stressful job and challenging, perhaps, but it does not need to be that way. In my experience, I do not think for one minute anyone actually enjoys going through the buying and evaluation process, particularly if they start out with no idea of what they want - which is perhaps more typical than not. However, if the “thought process” and “equipment evaluation” of press suitability are similar in nature to that of aquiring property, then thinking in those terms may make the equipment decision-making process just that little easier to face with fewer mistakes. Doing your homework on printing equipment will make buying task more enlightening and encouraging to conduct if they are suitably guided with some insightful tips from the outset.

As with seeking new property, when looking for a new screen printing press, one should have a good idea of what their objectives are even though they may not be a 100% clear on what types of equipment it will take. Sounds simple enough but many people end up buying property nothing like they originally wanted, paid more then the can really afford and often far from the desirable location. How many times have we heard this before? This is precisely what happens when buying new printing equipment. Perhaps with 35% of all equipment acquisitions, buyers wished they made the “other” decision shortly after their final choice had been installed ! Why ? This is a shame but true.

One must first have a good idea as the investment involved since this alone determines the level of equipment to consider. Size, level of automation, style and features are then closely followed, but not limited to, ‘market/customers’ specialisation, location, suitability today and longterm needs (desired growth plans). Then one has to understand the pluses and minuses of various features and desirable options. If features and options are taken without due consideration, one will inevitably pay more then they should for devices never used. Conversely, one can easily shortchange their operation by neglecting to take advantages of the benefits that some features yield in favour of their particular operation.

If considering your second or third press, oneshould already have a good idea of what is required from experience and then lead the final closing negotiations in your favour. Those who have this sort of experience should know what they are talking about and have at least have some ideas of what they are looking for with their next press - often much more than equipment suppliers do themselves. This distinction is important to note for first-time buyers. It is possible the supplier knows less about your needs than you do yourself. This is the case where the blind leads the blind ! The reason for mentioning it is that once the chosen press is installed - your company has to live with it - good or bad ! It is not like sending back a litre of ink or a hundred sheets of paper wrongly ordered, thus the reason for some 35% unsatisfied new equipment owners. Just a little bit of homework will ensure the final decision is with the group of happy contented owners.

In this 3-part article, we shall cover levels of press automation; the most common mechanised “flatbed” standalone single-colour press types (operational styles) available, main features/major options as well as marketplace suitability. One thing this article cannot cover is choice. As with any house or factory, it is only in the eyes and mind of the beholder can make that final decision. The goal here is simply to arrive at that choice expeditiously - without confusion.

In the real world, there exist many underachieved operations solely because they badly need some form of automation and features to move up towards the next plateau in their business. Likewise, there are others who are not competitive enough solely because they are overly automated, spending too much valuable production time doing setups than actually printing, thereby costing themselves out of the market.

Whatever the custom criterions used to settle on the final choice in the evaluation of screen printing equipment, it should cover at least seven separate determining phases in the decision-making process:
• Speciality: Recognise each in-house print speciality and decide what the new press ideally should handle (realising no press can handle everything).
• Automation: Determine the level sought against present capabilities (support, skills, typical techniques employed, etc.), as well as future needs.
• Investment: Determine an agreed “price range” (not a fixed price) affordable and willing to invest, which should include other indirect needs (structural alterations, installation, training, support, etc.).
• Selection: Examine suitable models, styles and sizes to meet the above criterions competitively and used them for positive comparison purposes (such as apples-to-apples rather than apples-to-oranges).
• Practicality: Review affordability and need once again, then training, after-sales support, longterms plans, etc., have been finalised.
• Suitability: Narrow successful brands down to final choice and if appropriate, obtain the informed opinions of production management and lead printers.
• Close: More important than final price or discount - negotiate terms that best suits your company and situation. Since these are management-made decisions and each phase speaks for itself, this article will concentrate only on the ‘selection’ process to better prepare decision-makers in their role as smart capital equipment buyers.

AUTOMATION LEVELS
All screen printing presses are made to different degrees of automation to meet specific throughput and labour requirements. In general, it is usually accepted that greater the automation - greater the hourly production speed, so too investment and therefore more suitable for frequent long run jobs. As we shall see, this is not necessarily true for every operation although it is commonly accepted as such.

Interestingly enough, level of automation has no direct bearing on print quality except that once a press has been optimally setup, other than routine checking and possibly fine-tuning on-the-run, it should continue to print that way without variance. Automation strictly relates to the degree of effort an operator actually puts into running the whole job once production has started. While one can reasonably argue that a fully automatic press may print in register more precisely (within tolerance) than manually registering each sheet by an operator, actual print quality and finish characteristics nevertheless depends exclusively on the quality of screen used as well as press setup (make-ready) procedures and available features. In other words, while an automatic may print in perfect register at incredibly high speeds, they could still be rejected as bad prints !

Here lies the important lesson in equipment economics; greater the investment outlay - greater the potential loss due to waste and longer downtime. That statement was not intended to put anyone off from buying automatics, but a realitycheck for the ‘smart’ buyer that greater automation will always require, by definition, a more efficient operation to reap in the benefits and return on investment. Therefore, it should be understood that the level of automation has little to do with quality but rather it is directly related to greater p r o d u c t i o n throughput. Although some OEMs (Original E q u i p m e n t M a n u f a c t u r e r s ) provide cross-breeds, known as hybrids (to make things more confusing for buyers), there are four distinct levels of automation and presented below in order of sophistication:

Small Format Floor- Standing Manual Printing Table with Vacuum

• Manual We start with this type, not so much to discuss it as a model but for the degree of automation comparisons. As the name implies, a manual press (more often referred as a hand-printing table), are either benchtop mounted (usually for small sizes) or floor standing and are made in every shape, style and size configuration possible. While some are better made than others, their commonality is that they are all manually operated in every form, with the exception of models where the vacuum automatically activates/deactivates the as the screen is lowered/raised. The screen is normally hinged and counterbalanced from the rear of the print table to provide a ‘swing hinge’ or clamshell style operation while a few adopts the parallelogram principle. The screen is simply raised and lowered manually during the print cycle by the printer.

The printer registers the sheet, lowers the screen and prints with a hand-held squeegee blade, raises the screen and pushed the ink back with the same blade in readiness for the next print cycle. Some manual tables are fitted with a one-arm squeegee attachment, which is also counterbalance from the rear with weights and prints side-to-side, to make life a little easy on the operator, particularly with large print sizes.

It should be pointed out that the difference between ‘manual’ printing to that of any ‘mechanical’ means, regardless of automation, is the lack of uniform consistency from print to print. Every manual print stroke yields a slightly different result, even by experienced printers, due to varying squeegee pressure, speed and true print angle (blade deflection at the contact point with the substrate). Highlighting the difference further, once printed, the ink is pushed back by the squeegee blade inconsistently. With a mechanical press, all of the inbuilt tasks of the floodbar (known also a floodcoater or scraper blade) such as pressure, speed, angle and balance are fixed and repeated precisely during each cycle. If one is looking for consistency, precision (usually closetolerance) and repeatable results, manual printing is not the best way to go, especially for industrial applications that requires repeatable and controllable results.

That said some unbelievable results are routinely printed everyday manually, although mostly accomplish by dedicated artists and skilful serigraph specialist by this means. For many operations, hand printing tables provides everything a company needs but when it comes to something more demanding, some form of automation usually proves more beneficial.

• Semiautomatic - (half-automatic)
While it would seem that the word ‘semi’ implies something is not wholly or fully as it related to the level of automation, many owners and printers alike often refer to their semiautomatic press incorrectly as an automatic. Usually, I have found the intent to say one prints with an auto is nothing more than an innocent slip in terminology.

By definition, a semi-automatic press means the machine literally runs by itself except for sheet handling - both prior to and after printing. In other words, the press operator only has to feed, register and remove the sheet for drying after printing. Everything else on the press is carried out automatically including adjustable dwell times between each function as required. A print cycle is usually activated with a foot pedal, a switch on the control panel or timer with foot pedal override. The act of removing a printed sheet manually to the dryer or drying rack is the reason why this type of press is called ‘half-automatic’. In a number of busy operations or for certain jobs, two operators are used to run the press ; the second to assist in unloading the printed sheets. Although this method of operating with two people cost more to run, it can speed up productivity.

As one can imagine, half-automatics come with in an assortment of models, styles and sizes, at various levels of sophistication as well as a wide range of features and options - which will be addressed separately. Terminology used for press automation was not devised to confuse, but rather to clearly state the operational style of a press purely by its mechanical sheet handling capabilities during routine operation. It does not, however, describe the press style since virtually all presses can be automated beyond belief in one form or another.

• Semiautomatic - (three-quarter automatic)
This is very similar to its half-auto cousin just described except the press has a built-in sheet takeoff system that automatically removes printed sheets from the press. All the operator has to do is to feed and register the sheet - thus the ‘threequarter’ category classification. After printing, sheets are removed and transported to a dryer conveyor belt. Take-off systems work in conjunction with either mechanical grippers or overhead suction device, and can function from the rear or sides (left or right) depending on the press model and format size.

While mechanical grippers are chiefly the industry standard with 4-post presses, when it comes to productivity worldwide (as they are usually self-adjusting for varying substrate thickness), it has three disadvantages although considered minor by the majority of users. All gripper openings have a certain restriction as to the range of substrate thickness it can take without mechanical adjustments (if at all possible) or causing damage and can be difficult to function properly with curly or wavy heavy materials. Then the image is usually required to be positioned away from the centre for auto take - off and offset to one side if using the press default mechanical sheet side guide.

Despite them being minor issues, they may be a concern for those wanting to print a much wider range of thickness on the same press, or printing uncontrollable wavy substrates or simply desiring to centreline the image to produce distortion-free prints for critical results. Mechanical grippers can further be a hindrance with large 4-post presses when printing small size sheets. Operators have to reach over to the back of the print table to position sheets on a datum-line against the mechanical edge stops for the take-off system to function. Other than the necessity to position substrates edges precisely on an imagery line for the take-off to fulfill its role, the datum-line has no other significance throughout this article.


Conversely, the alternative suction take-off method could lead to longer changeovers between jobs as the complete assembly needs constant readjusting for each job, as too in many instances temporary edge guides for registering. Although the suction take-off system may resolve some of the gripper systems limitations, suction cups need clear unprinted space on the substrate to work effectively (perhaps 3 cm or more), either found within the print area itself or a clear border around the edge trim margin.

Presses that have integrated grippers take-off systems functions from the rear with 4-posts and on any three sides with clamshells, as with suction systems also. Standalones and after-market takeoff systems are available to operate from the rear or sides (left or right) depending on model and substrate limitations. While this may convert a halfauto into a three-quarter automatic, after-market take-off systems rarely work as well as those integrated originally into the press by the OEM, nor will they necessarily yield higher throughput rates due to slower processing and longer dwell times between each press movement.

• Fully automatic
Now that we have a better understanding of lower automation levels, ‘fully automatic’ literally means the press has the built-in ability to run by itself without any intervention by the operator (other than adjustments on-the-run). Nonetheless, this does not necessarily mean the press (or printing line) runs entirely by itself since that would require an automatic sheet feeder and a stacker at the end of the dryer, truly a ‘one-man operated line’ as it were. Therefore an automatic press, by definition, means it can be ran either as a three-quarter auto (hand fed) or fully automatic (fitted with a sheet feeder). Once an auto-feed has been setup correctly, both feeder and press runs incognito together as one unit. How they actually work and integrate with one another is covered in the appropriate subsections following.

PRESS STYLE CATEGORIES
Not including hybrids or special one-offs, there are generally three distinct styles of flatbed presses available in the way they function: clamshell (swing-hinge), 2-post, and 4-post. They cover perhaps 98% of the world market (excluding sheet-feed cylinder, web/roll-to-roll, multicolour flatbed and textile presses) while the reminder is made up of cylindrical, bottle, CD-ROM, 3-D and other specialised unusual shape presses.

The flatbeds we are referring to are available in an assortment of drives (mechanical, electrical, pneumatic, servo, hydraulic, etc. and combinations of them) and manufactured in a wide range of shapes and sizes with a host of options to broaden their market appeal. While it is not possible to discuss the merits of various drive systems used according to their role in operation and other functions, smart press buyers should nevertheless fully acquaint themselves as to why one press, or function, is made a certain way as opposed to another brand or model. What can be safely stated with certainity is that newer designed equipment are now incorporating the latest technology inexpensively, such as smarter servo drives for greater tolerance and precision in mechanical movement and timing belts to replace cumbersome outdated chains running around sprockets. Noncontact timing discs replacing problematic cams, PLC (Programmable Logic Controllers) replacing hard-wired contractors, AC drives instead of DC and digital preferred over analogue displays are some of the great features now being supplied as standard.

While at the technology phase of this article, do not think negatively if one manufacturer seems to continuously update their press drive system, controller or featured characteristics and other functional workings with newer ones. On the contrary, while it is easy to say they are trying to get things right, I personally would much rather have the latest proven design incorporated in my press, providing it has been properly debugged, than allowing the manufacturer the easy way out by only updating every few years or when forced to. In this respect, do not be afraid of using the latest technology available, if beneficial, and providing it can be properly supported in the field to your operation’s full satisfaction.

At this point, it is very important to stress that no press type or style can be judged better than another brand, drive system or functions being superior. However, capital equipment acceptance for printing can only depend on the need (initial requirement), investment involved (cost), expectation (evaluation), level of competitiveness (risk) and marketplace specialisation. Every body knows that going to work in a Rolls Royce is a better car than a Ford. However, the Ford happens to be a more practical vehicle travelling back and forth to work - even if the other car is affordable. Therefore, a great deal of common sense plays into the decision-making process too.

Depending on model and size, each of the three press styles have their squeegee travelling in three different directions; front-to-back (prints away from the operator), back-to-front (prints towards the operator) and side-to-side. It is most common for clamshells to print front-to-back while the opposite with the 4-post. Some 4-post manufacturers optionally offer the reverse; the squeegee printing towards the back so the operator has unimpeded view of the squeegee blade during the print cycle. (In my view, this is a much better sequence of operation because the press operator can clearly see how both the squeegee and screen separation performs throughout the job for possible in-production adjustments without losing productivity or printing rejects.) Most 2-post models adopt the side-to-side method depending on automation level, which gives operators a superb view of the whole print arena and printing cycle (squeegee stroke and flooding performance). This is very much an added advantage with industrial applications, which we shall review later.

To reduce the problematic affects of a long squeegee, virtually all press equipment manufacturers tend to traverse their squeegee direction 90 degrees with their large format mode sizes. Although there are as always exceptions to the rule, this usually means printing side-to-side with any press larger than 120 x 240 cm. This type of press, regardless of whether it is a clamshell or a 4-post, is often referred to as a ‘long-stroke’ simply because the squeegee travels along the longest length of the print (with a short blade). The purpose of traversing the blade’s travel with larger format presses is simply to reduce the length of the squeegee blade required. With a 120 x 300 cm print size, it is better technically to print with a squeegee slightly longer than 120 cm than one over 300 cm in length. It is also more effortless to sharpen properly and less expensive for a smaller sharpener.

While print quality is easier to achieve with a shorter blade (less tone dot loss/gain for instance), the only real negative effect of travelling the longest length is the lower productivity since the print cycle will correspondingly take longer to complete. The question of a traversed or nontraversed squeegee, if a choice is offered, should therefore be kept in mind for productivity-hungry production managers vs. the needs of special quality demands. Both equally have advantages and disadvantages to different extremes.

CLAM-SHELL Semi Automatic Screen Printing Machine

• Clamshell Strictly speaking, a clamshell press is essentially a mechanised manual hand-printing table, meaning that the printhead (screen) swings automatically up and down from the rear, while the squeegee stroke and vacuum on/off is automated. Once the printhead is titled high in the upper position, the operator has access for makeready and cleaning even if the model raises less during the printing cycle for a shorter cycle time. The model can be as basic as a handprinting table (offering nothing more than automation itself) or, to the other extreme, ultra sophisticatedly-made for closetolerance work. Because refined models are made by some manufacturers, it tends to easily confuse the press buyer, since they are informed such a press can do this, that or the other, while lesser alternatives may incorrectly claim the very same. Confused? Then you're not on your own ! All will become clearer and make more sense soon.

With larger format sizes, OEMs may give a choice of a conventional printing mode (squeegee travelling front to back) or a long-stroke (printing sideways). As such, one has to decide before purchase on quality or productivity as a priority. A shorter travel distance means the squeegee for a 120 x 320 cm size press will travel less than half the distance so reducing overall cycle time c o n s i d e r a b l y . However, in this orientation, a long squeegee is required, where much print integrity could be lost thereby making halftones, fine lines and ink deposit uniformity from end to end a great deal more difficult to accomplish at any production speed. A shorter squeegee will improve print quality but at the expense of slower throughput rates.

Many clamshell models come with or without an automatic take-off system and operate from either side or rear of the press. Some models may be retrofitted at a later date with a take-off, although in many instances they do not necessarily speed up production. If auto take-off is integrated with the press from new, the grippers must return to the same spot on the table all the time. Therefore, the print table will have a series of mechanical edge guides (along the so-called invisible datum-line) for the sheet to rest up against so that the take-off can function properly.

There are probably more brands, models and types of clamshells available than any other group of presses. Regardless of how they are driven, the prospective buyer would do well to watch for jerky movements, particularly as the printhead rises and descends, as well as excessive banging or vibration. I am always amazed at how printers accept severe banging, cranking and funny noises as being usual and part of the equipment functioning. Other than the vacuum suction switching on/off and squeegee swishing across the screen, there should hardly be a mechanical sound to speak of.

In the industry, clamshells tend to be relegated as a basic or ‘entry level’ press. Printing operations that might have used other styles of presses and varying forms of automation may have made this perception more noticeable. In many respects, this perception holds true due to clamshells collectively are of a lower price and usually more basic than its 4-post counterparts. However, there are two points to consider in this regard. The design of a clamshell press is less complicated and therefore less costly to manufacture in the first place and secondly, perhaps to the surprise of some, there are clamshell available that are sophistically made and engineered beyond the accuracy and repeatability of regular 4-post models. Finally, there are no limits to the format sizes available in a clamshell concept although some models may be limited to certain sizes according to the manufacturers range and marketplace specialisation.

2-Post Pillar Semi Automatic Screen Printing Machine

• 2-Post For many, this design concept may not appear to be a 2-post variety at first because of a wide mechanical enclosure in the centre at the back that controls the screen’s up and downward movement. With this equipment style, the longest length of the screen is positioned traversal in the press with the squeegee travelling along its length sideways (side-to-side). Unlike its clamshell cousin but similar to the 4-post, the screen is kept horizontal at all times. Although this type of press is relatively a newcomer to the industry (early 70s in its present form), it has gained a formidable foothold worldwide since the early ’90s. As proof of this assessment, it has probably already outsold clamshells and 4-posts units combined. A powerful statement, perhaps, but it gives credence to the press style, value, quality performance and a fast healthy return on investment. Other than the 2-post being competitively priced against its adversaries as a style, the key benefit from this type of press is that it meets many different small format printers' needs more adequately with full access to the whole printing arena right in front of the operator.

Because the squeegee travels sideways, rather than front to back, the operator can immediately see screen separation and if the squeegee blade or floodbar settings need adjusting with all fingertip controls within view and easy reach of the operator from the sitting or standing position. Due to this exceptional accessibility, make-ready and changeovers are quicker, quality easier to obtain and maintain and jobs can be completed quickly with less fatigue. The printhead moves to the highest position for make-ready and cleaning but with just enough up and down screen clearance during the print cycle for operators to easily remove and insert a new sheet.

This type of press lends itself to print light-toheavy, thin-to-thick and flexible-to-rigid substrates in small format sizes. Sizes are limited, usually up to 50 x 75 cm, although some manufacturers go beyond to market elongated models to some 76 x 150 cm in size. As one can imagine, the key to this type of press is to keep the screen long and narrow so front-to-back of the printing operation is well within the operator’s view and reach. This is extremely important for many operations, particularly with industrial applications that desire a constant view of performance during the print cycle. Models are also available with automatic take-off systems, including conveyor systems that run through the print table for heavy or rigid materials, thus rendering these models three-quarter automatics. Further, it is possible to integrate a mechanical gripper take-off system for thin materials or retrofit one at a later date, with either gripper or suction cups.

Before moving onto the next classification of presses, which is 4-post, they are by definition mainly reciprocating table-types (print table moving in and out). Today, there are 2-post models also available with reciprocating tables, similarly to that of a 4-post, either with or without various take-off systems. Confused ? Then wait, it doesn’t get easier for the smart press buyer ! Some models come as standard with a fixed table (nonreciprocating), with side or rear take-off and with squeegee running front-to-back or side-to-side.

In truth, the degree of creativeness in designing and engineering between press OEMs have spread so much that the mixed of styles, levels of automation and features run across the whole spectrum. It appears almost any configuration of models, styles and automation is possible. While it undoubtedly gives the marketplace a much greater group to choose from, it can also send the press buyer into a world of utter confusion.


To cut through all the pros and cons of styles, features and options, consider for a moment basic price. For example, why buy a press for Rs.2,250,000/- when one at half the price has seemingly everything needed or spend Rs.1,260,000/- yet get the same output and quality as with a Rs.900,000/- model. On the other hand, one would think there must be more inherent benefits in a Rs.900,000/- press than its direct opposite from another supplier for Rs. 750,000/-. If those added benefits prove to be very desirable for your type of operation, then the Rs.750,000/- press does nothing for your company. Just like looking for that new property - it was never meant to be that easy ! However, with a little foresight, there is some relief in the decision-making process if one mindfully analyse all the equipments merits and the marketplace for which the types and styles are most suited - then compare with your specific needs.

Essentially, the 2-post concept was designed for small format print sizes while the reverse with the traditional 4-post presses. If you like, the 2- post filled a void that small 4-post styles could not easily reach due to their high cost. The 4-post smallest size format generally starts where most 2-post sizes finish. By virtual of the fact that 2- post presses are extremely compact by design, accurate and inexpensive, they are by default highly demanded and therefore ideal for smaller print size of almost any quantity and closetolerance work.

Large format 4-Post three quarter automatic with reciprocating(Sliding) Print Table

• 4-Post In the world of screen printing larger than say 60 x 80 cm, this particular type of press, in terms of sophistication, print quality, productivity and print sizes availability as well as it being internationally supported, makes this style the high-end leader in printing operations world over. Its only real challenge today is the multi-gripper or shuttle-gripper three-quarter autos (print table does not reciprocate), which can be transformed into a fully automatic with an auto sheet-feeder (see later).

A 4-post press is exactly that, it has a frame holding post in each of the four corners that keeps the printhead always in a horizontal plane. During the print cycle, the printhead lifts about 5 cm between each print although it can rise to some 30 cm or more for make-ready and cleaning. The print table slides inwards to the print position and back out to the operator in readiness for the next sheet. In Europe, this type of press is better known as a ‘reciprocating-bed’ printer rather than referring to the number of corner posts it has as in other parts of the world.

A standard print table has built-in raising and falling mechanical edge guides for manually registering sheets. If integrated with mechanical take-off grippers (a few are made with a suction system), it functions from the rear so that substrates have to be positioned likewise against the back edge guides along the invisible datumline. Once printed, the take-off grippers will deposit the sheet onto the press’s transport delivery conveyor for rear exit or to the left or right side straight to a dryer conveyor belt.

Before moving onto the next style classification, there is an additional three-quarter automatic press made, which by their very style must be covered at this time. The secondgeneration of these three-quarter presses, if you like, uses either a shuttle gripper system (grippers reciprocating back and forth rather than the table) or multiple grippers (grippers rotating in a conveyor-like action through the press itself). Both gripper systems are also a requirement for multicolour printing lines - although that press type is not part of this article.

Essentially, these ‘shuttle/multi gripper’ - type presses are still three-quarter autos because they need to be manually fed by the operator, but when matted with an autofeeder, they immediately become transformed into fully automatic presses. To achieve this transformation, the press must be suitably modified to become ‘feeder-ready’ particularly concerning the matter of on-press device to register the sheet automatically (rather than manually) prior to printing. The necessity of interfacing a feeder correctly is addressed in the second part of the series.

With the evolution and creativeness of press designs, this type of three-quarter automatic has effectively replaced the traditional fully-auto model (see next press style) in many instances. All being equal, they require less investment (some considerably), usually less intimidating to operate and production output not too dissimilar for many printing applications. Without a feeder, these presses represents the most productive three-quarter automatics ever made.

• Fully automatic
Almost by necessity, this model employs the 4- post concept and by correct definition it is still a three-quarter automatic press without a feeder (as in deed all cylinder presses are too). The difference is that this press has been designed from the floor up to be feeder-driven, which is discussed in PART 2. Another clear difference between this style of press and the previously mentioned shuttle/multi gripper type is the noticeable esthetical point of it being solidly built. It is perhaps the flagship press in any manufacturers range of flatbeds in terms of reliability and durability. Most fully-autos are made to run around the clock 24/7, breaking only for regular maintenance and service. Of all the flatbed range of presses available, this type eats work continuously day and night and always hungry for more. One can reasonably argue that this is not the case with lesser models no matter how well they are maintained. Although this type of press is indeed the workhorse of the industry, the numbers being installed are sadly dwindling in comparisons to their half-and three-quarter cousins, and currently supported perhaps only by loyal seasoned users.

Historically, this model of automation works by rotating multiple mechanical grippers through the press or by reciprocating suction cups at the rear take-off end (sheet’s leading edge). Regardless of the take-off transportation system, make or size, the sheer wealth of engineering at this level has made these presses all but the stream locomotives of yesterday’s years. While they may no longer enjoy life in quantity, they do in quality production performance and usually provide favourable benefits around the clock for their owners.

To be continued in PART 2.
In the next part of this series, we shall look more closely at the feeding systems required for fully automatic presses, as well as take take-off systems for all press types and configurations. Additionally, to equip the ‘smart press buyer’ with the right tools, we shall also cover standard and optional features that may benefit production and business goals.

Photo Courtesy :
Machine Photographs for this articles are provided by Grafica Flextronica, Vasai.

Editor’s note: In helping readers to familiarise themselves with the wide range of equipment type, style and sizes available, the author originally included brand names and model types where appropriate. However, in fairness to all manufacturers and to avoid issues of commercialism, he decided to remove these references from the final draft since it was not practical to mention brand names in a neutral unbiased manner. Photographs and illustrations chosen to assist the reader for visual familiarisation and were randomly selected by the editorial staff. They do not serve to endorse anything other than to act as a visual aid to the article.

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