I operated one of these for a couple of years here in the US, what kind of work are you planning on using the Karat for?
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We're looking to buy a used 74 karat, i know very little about this press (other than what i've read and been told by the salesman).
Could really use some impartial feedback. Any users out there?
Is there anything i should be aware of, any major downsides to the press?
We operate a traditional 4 colour litho press, works a treat for us and we'd like to use the Karat to capitalise on the larger sheet size.
Many thanks in advance
I operated one of these for a couple of years here in the US, what kind of work are you planning on using the Karat for?
Back in 2002 I was able to review one of these machines. The following is the article I wrote. Keep in mind this was back in 2002 and some of the issues with the machine may have been addressed, especially concerning the inks.
KBA Karat review 9/10/02
After having a day to watch the operation of the Karat 74 I have come up with the following report.
Start up of the press in the morning requires a few things that are not typical of a conventional press.
First you must measure the blanket height to the bearers each day and enter this value into the press control. The reason for this is that each job you print requires you enter the thickness of the stock in to the press control. By doing this the press automatically sets printing pressure based on the reading you took in the morning of the blanket to bearer height. The main problem with this, which was conveyed to me by the pressman is the fact that he cannot seem to get enough pressure to print on stocks with texture to them. On these jobs the pressman puts in a false value for blanket to bearer height so the press automatically gives more pressure. The pressman also stated the tool to measure the blanket height is also difficult to use when trying to get an accurate reading. I personally tried the tool my self and agree that it is difficult, especially when an accurate measurement to within .01mm is required. This tool is supplied by KBA. Next you have to tighten the blanket which supplies ink to the plate cylinder, there are 4 of these and it takes about 3 minutes to do this. If this is not done there will be slurring on the plate cylinder.
The second thing you must do is add ink. To do this you must install the Doctor blades of which there are 4, this takes approximately 7 minutes. Care must be taken to protect the blades from nicks and your hands from cuts as the blades are extremely sharp. As of now the only supplier of the ink is Sun Chemicals and the pressman informed me the ink is still a work in progress. The ink comes in a tube much like the ones all press maunfacturers use on their automatic ink supply systems. The tubes must be inserted and then the machine pumps it into the doctor blades which run on the anilox roller. It takes about 20 minutes for the ink to fill up the blades/ trough. Typically the ink is kept in the press for at least three days as to keep from taking 20 minutes everyday to fill the blades/ trough. It must be changed at this interval or the anilox roller will become clogged and prevent an even ink flow.
Once this has been done you are ready to image your first job. To do this one must select the job, select the paper thickness. (There is a register screen with different register settings based on different stock types and thickness as this can affect register adversely) paper size, screen type and LPI you want to image at (multiple settings for LPI available at press.) Once this has been done the settings are saved. Next you select a plate loading icon and change plates, then you select an icon to image and start the imaging process.
The first job of the day takes around 16 minutes to image before you start printing, after that it takes about 20 because you have to do a 4 minute blanket wash for each job after the first, prior to imaging.
Setting up the feeder seems to be relatively easy. All that is required is the sheet size be entered into the press control and the feeder automatically sets itself as for the delivery. The pressman informed me that to go from a full size sheet to a 14 X 20 takes approximately 4 minutes. The feeder does have its issues. When the machine was increased in speed to run at 10,000 iph, powder started to fall from the delivery above onto the sheets in the feeder below, which had yet to be fed into the press. To further illustrate this problem the pressman hit the delivery, which runs above the feeder, with his hand to cause what looked like a blizzard of powder to fall on to the feeder. When he finished there was a pile about 3mm tall of powder on the feed table and the feed pile. There where a few paper jams while onsite that had to be cleared, from the orientation of the feeder it was awkward. The pressman does not like the way the feeder and delivery are setup. Having a pressman background myself, I do not feel I could ever get used to this setup. We attempted to run a doubling form while on site but had some issues with the file and a reliable print could not be run, this was our issue not the press. I did run a test form I brought which I could see slight doubling, my guess is this was from the feeder. The pressman informed me that thin stocks were difficult to run (60lb and below) and thick stocks marked on the powder spray bar in the delivery.
I must state the fact that I have never seen a press come up to color as fast as this machine. With in 5 sheets the color is where it is going to stay, provided a few issues are taken care of, which I will get to later. The machine is also able to print ghosting forms very well as the one form roller it has, which in reality is nothing but a blanket cylinder, carries a constant supply of ink and does not use a ductor. There is some very slight ghosting, although it is very much less then a conventional inking system. It is very important the blanket for this form roller is kept clean and free from pits or smashes as it will show immediately in the printing. As for adjusting the ink you are very limited, there are a few tricks that can be done with the doctor blade to supply more ink overall on the sheet or for that matter less if needed. In the future this kind of ink train with better overall control could be on to something.
As I stated earlier there are a few problems with the inking system that must adhered to in order to produce acceptable printing. Cleanliness must be taken to a new level with this machine. In order to do a color change (Metallic inks cannot be used as they will permanently damage the 6000.00 anilox roller) you must first remove the ink cartridge, which is not an issue in itself, it is the cleaning of the ink supply mechanism which the cartridge attaches to which is the issue. This can take 20 minutes on its own and you still have not removed the ink from the blades/ trough or cleaned the anilox roller which can take another 20 minutes, all for one unit. To clean the doctor blades you must either do it by hand or put it in a machine the pressman affectionately calls the "Dishwasher". The "Dishwasher" is approximately 10 feet long and 2 feet wide. It is basically a big steel tank that the blades are put into and a wash cycle is selected. It uses hot water and possibly some type of solvent (This is speculation I did not ask if there was solvent.) to pressure clean the blades. The excess ink is stored in a tank to be removed when full by an outside chemical company. Last time I checked it was expensive to have what maybe construed as hazardous waste removed. I was told by the pressman that the anilox roller must be kept clean at all times. If it was not, there would be noticeable degradation in the printed piece. Also the edge of the doctor blades had to be perfect without nicks or it would be immediately apparent in the printed piece. The pressman also informed me that on long runs, one he mentioned of 77,000, he noticed color variations later in the run due to the anilox roller becoming clogged. The reason this can happen is due to what is called the ink "sausage". As the trough is filled with ink the anilox roller must continue to spin causing the ink to roll up into what looks like a sausage, approximately 25 millimeters in diameter, running the length of the anilox roller. On conventional ink fountains when the ink is kept in the fountain for long periods of time, the top of the ink begins to dry and form a skin on top. With an anilox system this skin still happens, but not the same way, because the anilox roller is continually turning, causing the outside of the "sausage" to constantly get supplied new ink, also the outside of the "sausage" is what is touching the anilox roller so it is what supplies the new flow of ink to the roller. The problem is the middle of the "sausage", this ink never cycles to the anilox roller so it becomes hard, like the skin of ink in a conventional fountain. If the press is stopped, along with the anilox roller, the ink settles in the trough and this middle of the "sausage" attempts to dissipate into the rest of the ink, not very well I might add and eventually clog the anilox roller. Another note to mention… ink tracks into the yellow unit causing it to turn a muddy color just like on other DI machines. Also the pressman informed that heavy coverage jobs are difficult to run, the press does not seem to supply enough ink. Lastly, for some reason on screen builds and rich blacks the ink does not seem to dry very fast on the sheet. One job I was shown had been printed the previous day and was still wet when a finger was dragged across it.
The delivery seems to have sufficient sheet control for high speeds. The suction slow down wheels where chromed and caused marking of the sheets. This was told to me by the pressman. Other than that the delivery seemed to be fine.
Imaging issues were few, although they were a nuisance. You could not image just one plate. The customer did have a workaround for this. On single color jobs they would only image crop marks on 3 plates and the job to be printed on one plate, this way the other plates could be used again. They were told by KBA if they needed to re-image one plate they could just load the one plate and image all four plates at one time, the reasoning was that the other 3 previously burned plates would burn again in the exact same place. I tried this and found it not to be true, the previously imaged sections turned out to be much darker than the section that had only been burned once. As for adjusting the laser intensity, the pressman had not been trained on how to do this and did not know if it was even possible. The imaging process was relatively quiet, considering only the plate cylinders were turning. The pressman could clean the lens for the laser although it was very delicate and easy to break when installing it.
Plate changes took about 3 minutes. Loading plates into the magazine took about 30 seconds. All plate loading went fine except the last job where the press control locked up and had to be rebooted 4 times. The optical sensors for the leading plate edge in the magazine had to be kept clean or the plates would not load.
Plate cleaning seemed to work well, this was accomplished by a small rubber wheel that was attached to the laser carriage and ran on the plate behind the laser. It ran on an angle to the plate basically erasing the imaged silicone. I was amazed there were not any scratches while present. The rollers were 40.00 each and needed to be replaced on a monthly basis. The customer had a rather large supply of them. There was also a fine plate cleaning device which consisted of what looked like a large molleton roller, this was removed form the press and not used as it was difficult to keep clean and did cause plate scratches.
The blanket wash roller was somewhat of a sore spot for the customer. When it was working it did a good job, although I felt a 4 minute blanket wash was excessive. The blanket wash roller cleaned both blanket cylinders at the same time, which was an engineering nightmare. The blanket cylinders spin in the same direction to each other at the gap. The blanket wash brush roller fits in this gap. Since there is only one blanket wash roller it can only spin one way, this means it must go against the direction of one blanket and with the other. To do this KBA has a motor mounted inside the roller itself to drive it against the other blanket. This motor has failed 5 times in 6 months, now for the good part… the complete roller must be replaced. The customer was told this roller is considered a consumable item and is their responsibility to replace… at a cost of 6000.00 per roller.
My views of the machine are varied. I must say I like the way it comes up to color and I think its design is kind of cool. The cost is attractive and the printing is acceptable. I consider its printing abilities much the same as the QMDI with the exception it prints on a larger sheet and ghosting is far less. Its footprint on the floor for the physical machine is also attractive to shops with little room, although there are as many peripheral equipment cabinets as its competitor the SM74DI which must be accommodated, including the "Dishwasher". As for the press control, it could use some work, there are too many mouse clicks to do repetitive jobs. My guess is in the future this will be addressed by KBA. Also little things like having to engage the cylinders after imaging seems time consuming when the software could have it done automatically like Heidelberg does on the QMDI. Also the sheet counter is quite possibly the most rudimentary counter I have seen short of a mechanical one, there are no waste sheet capabilities. Once again my feeling is this will be addressed.
The level of press operator will have to be above average. There is much to keep clean and little room for error. I will state that the Pressman claims to have trained an operator without previous press experience to run the press 2nd shift. He did inform me this operator can run the press but does occasionally run into problems a more experienced press operator could handle. The press control was fairly intuitive.
Mechanically the machine is built like a tank. I saw very little wasted room on the machine, it seemed to be well thought out with the exception of the blanket washer, the secondary plate washer and the delivery/ feeder setup. I typically have a good eye for potential mechanical failures and none seemed to stand out on this machine. Even the way the ink blanket/form roller/cylinder applied ink to the double plate cylinder seemed to be efficient in its use of cam and follower to apply ink to the correct plate at the correct time.
Consumables may be costly. Blankets need to be replaced constantly on the ink blanket/form roller/cylinder. As soon as these start to fail it is apparent in print quality. Blankets on the blanket cylinder seem to wear faster than on a conventional machine according to the pressman. The rubber wheels to clean plates of silicone must be in stock at all times. That blanket wash roller could be a huge cost if it is not redesigned and continues to fail.
Last edited by Paul Cavanaugh; 12-10-2009 at 04:39 PM. Reason: Typos
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oh! what a post dear Paul Cavanaugh.........
Keep up the good work.
If you are still looking for a KBA Karat 74-4 we have a machine for sale year 2001 for £15,000 ex. site. Can be seen running.
Anyone know of a independant mechanic in the USA that can take down and install a 2003 Karat 74?
Any can help with the installation of the Brisque RIP for the Karat?
I am also looking for 74-4+L, in good condition. But I have questions and doubts, because of their second hand value.
Probably I'll be the only user of this machine in Turkey. How much does the plates cost ? As far as I know, I'll have to use ink tubes with this machine. How much these tubes cost ? By changing tubes can i print extra colors (such as gold or silver).
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