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1979 Vintage Cerutti Printing Press

10/02/2017 9:04 AM

I have some technical questions for anyone who is familiar with the modules used in this machine. This vintage has a mix of analog and digital components which takes me way back. In some cases, it is a walk down memory lane, but in another case I am struggling to make sense of the function or as they used to say, the transfer function.

Many of the control modules fall within the definition for "analog computer". Most of the time, I can figure out what is supposed to happen and when. The difficult module has 6 or 7 analog inputs and an analog output but very little information as to what is supposed to happen and when. Sound familiar? It should because I know others of you have faced similar issues where managers just assume you can solve any problem with little to no information to go on. Very frustrating!

Unfortunately this one module, while not critical, has been out of service for some time. I'm not allowed to upgrade it (so far) to newer hardware, even though that is likely to be easier than to correctly guess the exact guess at the transfer function(s) and timing.

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#1

Re: 1979 Vintage Cerutti Printing Press

10/02/2017 10:28 AM

What's it gonna take to put you on the control panel of this shiny new machine today??

http://www.cerutti.it/en/home/products/rotogravure_printing/R98X

...might be able to find something here....

http://www.bohemia-grafia.de/en/machines/print/roll-roll/gravure/000505-rotogravure-printing-cerutti-r28-11-units

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#2

Re: 1979 Vintage Cerutti Printing Press

10/02/2017 11:47 AM

What type of press? Individual unit controls consisted of ink viscosity, registration control and web break detection systems. Does the press have a drive shaft common to all units?

I cut my teeth in a large rotogravure shop that had 5 press lines and one of the lines had some Cerutti units and a Cerutti folder mated with 4 Goss units.

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#3

Re: 1979 Vintage Cerutti Printing Press

10/02/2017 1:48 PM

Can you still operate the machine on a test run with this module in/out, or powered up/powered off?

Would that tell you what it is doing? IHNI...so I will be quiet now.

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#4

Re: 1979 Vintage Cerutti Printing Press

10/03/2017 1:03 AM

Is the transfer function a flying splice at the web infeed, or a flying web cutoff to start a new roll at the rewind? Do you have the electrical schematics for the module? Is the module just a circuit board or a series of individual components (relays, timers, switches, solenoids, etc.)? Is there a PLC involved? Ladder logic? A few more details would be helpful to try to help you out.

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#5
In reply to #4

Re: 1979 Vintage Cerutti Printing Press

10/03/2017 8:01 AM

Thanks for the replies. I wasn't sure if I would get a response. Here is the deal. I have several of these printing presses dating from 1979 to 2012. The newer ones not only have more modern electronics, but they go much faster than the older ones. Unfortunately, upgrading the old electronics is not on the table.

The module in question is known as a 51041 with the name listed as a "Reazione Di Tensione-Correntte" which I believe translates to "Reaction of Voltage-Current". Unfortunately that is not very descriptive for what it does but I may have access to one that works correctly. That is yet to be seen.

It appears to be strictly analog. This circuit appears to operate a roller known as the "dancer" which helps to keep tension on the web when there is a mismatch between the feed rate of paper into the press, and the general speed of the web. There is apparently a couple of missing signals because this subsystem has been abandoned for a while. I'm guessing it can be very touchy and cause more problems than it helps if the circuit gets out of adjustment. I'll get to the details shortly.

The circuit board is a standard size 3.84" by 6.94" and consists of mostly op amps with summing junctions. I'll see if I can insert the circuit drawing in the next post, but I have a meeting to go to right now. Back to you shortly.

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#6

Re: 1979 Vintage Cerutti Printing Press

10/03/2017 9:53 AM

Back again. The first two photos will probably not be very helpful, but it does answer some of the questions.

The transfer function looks something like this:

Just so you know, the guys that came up with this are long retired and unavailable. The new guys use something completely different which I have not seen as yet. I'm at least half a day away from the facility so it makes it a little bit difficult to ask questions. And on top of that, many of the questions I have asked just result in a blank stare. So, no help there.

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#7

Re: 1979 Vintage Cerutti Printing Press

10/03/2017 10:25 AM

That relay that is marked fast/slow actually drops the gain in one amplifier and it is used during normal operation. Beyond that, there are a lot of unanswered questions.

The "Dancer" has a metal rod that is inserted into a coil at one end of the stroke. So far, no one has been able to describe what it does and when so I guess I'm just going to have to climb up on top and have everyone else turn their heads while I'm looking to see for myself. I know that this system is a crude version of an LVDT (sensor) and it is mostly linear but it has no temperature compensation like LVDTs of today have.

The thing I dislike the most about this is that it was all turned over to a maintenance department who only knows how to swap modules. I can't easily tell what "normal" is supposed to look like. The controls and the press are separated by a wall. Lastly, in 1979, very little was being done to suppress RF noise which radiates from the control panel at a level that I have never encountered. I'm not allowed to fix that either. At least, not yet. That noise comes from the conversion of 3 phase AC to DC with no filtering capacitor what so ever, and some sort of SCR to run DC motors.

I've asked what the I/O pins connect to (as in the next module) and nobody really knows. It seems that the one guy that used to know that died and took that job security with him. But, according to the locals, "He was a really nice guy!"

To make that worse, it seems that some of the equipment that related just to this card has been removed and it just happens to be the only module affected. So, now they just web around this "dancer" and try to work around it. As long as the paper is heavy enough, they seem to be able to get away without using it. It seems to be just one of those things that happens when people leave or die.

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#8

Re: 1979 Vintage Cerutti Printing Press

10/03/2017 10:42 AM

It makes me feel a little bit like the accountant who when asked what 2 + 2 equals, he responds with, "What would you like it to be?"

From what I've seen, a lot of these analog modules are carefully tuned dead art. Many of the components from diodes to op amps used back then do not match up very well with the more modern versions of the same part numbers. Even though the same parts (by part number) are available, they are too different to be compatible with the older electronics. Attempts to "repair" a board just results in an "out of control" response.

Like I said, no one seems to know what "normal" looks like, much less where the inputs and outputs actually end up going. SOSDD! That means SOS, different day!

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#9

Re: 1979 Vintage Cerutti Printing Press

10/03/2017 1:54 PM

I will reply with more info this evening.

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#10

Re: 1979 Vintage Cerutti Printing Press

10/03/2017 11:13 PM

In roll fed rotogravure presses, the tension on the web needs to be controlled. It is (was, as this is all from memory) basically a well tuned wheatstone bridge where the tension of the web determines an output.

The "dancer roller" is just that a roller that moves according to the tension in the web. The dancer roller is on an arm that allows the roller to move up and down according to the tension. The arm that supports the dancer roller is connected to a potentiometer (sp) whose output resistance is relative to the verticle location of the dancer.

When there is no tension on the web the dancer falls to its lowest setting and the resistance of its output rheostat falls to zero. When the tension on the web increases to its maximum, the dancer rises and the output resistance increases as well.

A tachometer measures the linear speed in RPM of the press line, when the known circumference of the gravure cylinders is multiplied by the RPM data from the tach, a feet per minute value of what the press line is calling for is known.

The roll of paper feeding the press line is driven either by direct drive to the roll or by leather belts that "pull" the paper from the roll and feed it to the press. How fast the paper roll is driven equates to the tension in the web.

So... the output of the control is the speed command into the drive powering the rotation of the roll. Speed the roll up and you decrease tension in the web and the dancer will drop. Slow down the roll and you increase tension in the web and the dancer will rise.

So one input is... press line speed, an analog value that scales to FPM of the press demand. Another input would be a feedback tach on the roll. The output from the control is the speed command to the drive powering the roll rotational speed.

Another input would be the remaining diameter of the roll. As the paper is fed out, the diameter of the roll decreases causing the speed command to the roll drive to increase to maintain the desired FPM feed rate.

On the presses I used to work on, we used to run at about 1.5 to 2 FPM difference between press demand and what the roll stands fed the web at.

All of this is from memory of my time as an apprentice and as a 2nd year journeyman real early in my career. Oh so long ago... (late 70s early 80s).

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#11
In reply to #10

Re: 1979 Vintage Cerutti Printing Press

10/04/2017 3:31 PM

Great description! That sounds exactly like what is supposed to be going on. I think the approach that I am studying is a little different, but I can tell that it is a well tuned circuit because nobody seems to know if certain modules are bad or just out of tune.

The digital world is a blessing. It allows one or more software considerations to be available at the same time. These analog devices only have one chance of working correctly in certain devices.

Many thanks for your help. I gave you a G.A. for your efforts.

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#12
In reply to #11

Re: 1979 Vintage Cerutti Printing Press

10/04/2017 3:41 PM

My pleasure...

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#13
In reply to #10

Re: 1979 Vintage Cerutti Printing Press

10/04/2017 4:23 PM

Duh... I forgot to mention that the output resistance of the pot attached to the dancer is also an input.

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