Why should you service and certify your paper guillotine
It is well known that one of the most important machines used in the print industry is the paper guillotine. It is constantly relied upon to prepare paper for printing or in the finishing process after printing. If a guillotine breaks down then production stops!
It must also be noted that a guillotine can present a high risk to staff and operators if there is no correct training or service procedures in place.
Here is brief outline of some of the important procedures and checks that should be followed when using a guillotine in your business:
Correct guillotine operation and paper handling training for operators. (Including correct and safe method of changing blade).
Reason: Staff operating guillotines without full training present a risk to themselves and can also cause damage to the machine. It is also important to understand how to handle paper correctly to prevent damaging jobs. *An operator suffered a severe cut when a new guillotine blade he was installing fell onto his foot. He had removed the new blade from its case and placed it onto a table to insert the carrying handles. As he did this the blade slipped and fell. The operator had failed to clear the table of other material or to allow sufficient working space for this task to be undertaken safely.
Daily checklist to be followed by operator at the beginning of each working day to insure a safe working area and correct operation of guillotine.
Reason: To insure it is safe to turn on machine in its current state. Check knife carrier is at top dead centre, blade is not exposed past clamp. To insure all guards are in place to prevent injury to staff, including main drive guard and backgauge guard.
3 or 6 monthly calibration of guillotine to insure constant accuracy of production. Including Lateral (left to right difference), Vertical (top to bottom difference) and Actual (actual cutting size is exactly as appears on display). Adjustments all kept within a tolerance of 0.25mm.
Reason: Guillotines regularly lose their accuracy over a period of time from knocking the paper pile against the backgauge before cutting and the constant movement back and forth. Also operators using excessive force with the “Knock Up Block” can cause this to happen. It is vital that a guillotine maintains its accuracy to insure a high standard of work and to prevent problems down the line in other finishing processes.
Yearly service and safety certification of guillotine
Reason: Maintaining your guillotine prevents undue break downs and loss of production hours. Simply not changing hydraulic and gear oils, carbon brushes and clutch brake pads will put a variety of components under extreme stress and will ultimately cause them to fail. Safety Certification of your guillotine insures the safety of all employees using the machine and is safe to use as per “HSA Regulation 2007 – Use of equipment”.
*An operator suffered amputation of part of his thumb when the paper-cutting guillotine he was using overran. He was retrieving a cut stack and was injured when the blade failed to halt on the upstroke and descended part way. This was caused by a failure to maintain the brake, and a fault which occurred on the overrun detection switch. The solenoid-operated safety bolt for the knife carrier was also defective.
The brake defect, overrun switch fault, and safety bolt were all rectified when the machine was subsequently serviced.
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Accuracy and Quality Inspection
Often the question is asked: ”How exactly does a cutter cut?”
In order to be able to answer this question, one must give a two-part response.
First, it is natural for the manufacturer of a machine to know the exact manufacturing tolerances of their product. However, a manufacturer cannot guarantee the quality of the product processed by their equipment once their equipment is in the hands of the user.
Second, it is also natural for the manufacturer to know the standard tolerances related to the use of their machine. At the same time, the manufacturer does not know and cannot control whether the machine is kept in good working order since the tolerances are often due to the use of the equipment, the special requirement of the end-user, and the operator’s know-how.
The question: ”How exactly does a cutter cut?” can only be determined strictly by the user.
In other words, the cut accuracy is affected by many conditions. In this equation, the manufacturing tolerances that are presupposed by a normally functioning machine are not of substantial importance. As described in this book, there are other factors that greatly impact quality.
Therefore, one should absolutely consider two things separately from each other; exactly how the machine is manufactured and how expertly the user can operate with the machine. Before specifications in thousandths, hundredths, tenths or the like are stated, questions must be posed:
How is the quality controlled; the accuracy of an individual cut, a job or a continuous production. In the end the only important question is: ”Does the accuracy and quality of the finished product satisfy the customer?”
There are different quality standards in the Graphic Arts Industry; for example, with the production of art books, the accuracy of tolerances is less important; while with the manufacturing of labels, quality consciousness is very much pronounced in regard to the size accuracy of the finished product.1.6.2.
ChecksNowadays much is written regarding the term quality. Here, in this contest, we are concerned not with the term quality, but with the way that we can check the
quality of our work. Since paper is not a very stable material, it becomes difficult to set boundaries regarding the requirements for quality. Therefore, in determining the dimensional quality of paper, basic measuring and comparative checks have to be considered and included in the results.
Through exact measurements, we can determine that extremely varying air humidity modifies the size of paper. Fortunately, such small fluctuations do not interfere with normal paper cutting operation. However, there is also another side to the coin. The mechanics see again and again that unreliable testing, such as measuring
with a plastic ruler, often controls the dimensional quality of the cut product.
Then if the mechanic comes to the customer and optimally adjusts the machine, the user often cannot understand why its beautiful plastic ruler should not be correct any longer.
Let’s make a test. We cut some flat stock paper, paying attention to good handling and jogging, at 20 cm lengths and bisect it then into two 10 cm long pieces. Afterwards we compare the middle of both strips by stacking one on top of the other. If both sections are equal in length then one should praise the mechanic that made the adjustment. If a difference exists, then we should demand the mechanic to check the adjustments of the machine again. This claim of quality is surely enough on most commercial printing jobs.
In other manufacturing plants, instead of a plastic ruler, quality checks are conducted with the use of expensive optical or electronic measuring instruments specifically designed for production that are able to prove or to uncover dimensional changes while at the same time statistically recording quality fluctuations.
The quality specification, presupposing a properly functioning and properly adjusted cutter, is a mixture of proper handling, appropriate checks and economical work. In order to maintain a good orientation of quality, executed checks and the frequency of these checks in a long production run, as determined by the customer, are as equally important as production.
Checks to to maintain good orientation
Comparison of Over and Under Cut
This basic comparison between the length of the upper and lower sheets must take place under the following conditions:
· Mechanically sound and properly sharpened knife.
· Blank flat paper of the type that is frequently processed, in a size of DIN A4 for instance.
· The stack height should be ¾ the maximum clamp opening of the cutter.
· Clamp pressure adjusted to width and type of the material and the operation conducted by an experienced paper cutter operator or a trained service technician.
Cut a one-centimeter trim on the two opposite sides (parallel cut).
· Afterwards remove the center of the cut pile leaving about one centimeter at the top and bottom.
· The top is put on the lower section and compared together. A falsification of the result would develop if the lower part of the paper pile is placed over the top of the pile. A difference in size between the top and lower parts of the pile would prove that an adjustment of the back gauge vertical position is needed.