Hot spot

[pabney]

I have recently been getting a hot spot on the edge of our SM52 plates. Not every plate, just every once and a while. Also, this does not appear on our other sized plates. I can find to kinks or anything else wrong with the plate that would cause this. Could this be a vacuum problem? That is the only thing I can think of, and wanted opinions before calling in service. I have attached a pic showing the problem.

Thanks in advance
Paul

 

[DCurry]

Could be that there is a piece of debris on the drum preventing the plate from making full contact, or it could be a clogged hole in the vacuum system on the drum. I used to run a Creo Lotem and if I didn't clean the holes every week or so I'd start to get spots like this.

Could also be that the plate is bent before it even gets to the drum. I've gotten boxes of plates before where this happened, though usually it would be a banged-up corner.

 

[buckeye]

We occasionally get tiny tape balls or gum residue on the drum that come from the four pieces of tape that hold the plates together in the box that they're shipped in. I think it sticks to the edge of the plate sometimes and is then transferred to the drum. It doesn't happen a lot, but it does happen non the less. The hot spots we get are more circular in shape and not what you're getting in the snapshot you provided. As DCurry suggested, it would seem that the plate is possibly getting kinked or was kinked right out of the box.

-Erik

 

[pabney]

No kink in the plate, and I can not find anything on the drum. When they happen they seem to be in the same place and not moving around, so I am going with a vacuum problem.

Not sure how to clean the vacuum holes, or wether I should even try. Any tips on this?

Paul

 

[buckeye]

Not every plate, just every once and a while.

I would think that if it was a mechanical problem, such as vacuum, that it wouldn't be intermittent - but one never knows.

-Erik

 

[DCurry]

Not sure how to clean the vacuum holes, or wether I should even try. Any tips on this?

Techniques may vary depending on what CTP device you have, but on the Creo Lotem I would open the access doors to reveal the drum, install "cheaters" to allow the drum to spin and the vac to turn on. Then I'd go to the console and turn on the vacuum (this way, anything dislodged got sucked up). The machine came with a maintenance kit that contained a device specifically designed to clean the holes - basically a straightened paper clip with a nice handle. Once the vac was running, I just inserted the tool into each and every hole (there were probably a few dozen) and wiggle it around to make sure the holes were clear. If I ran into a major clog, there was a small drill bit attachment I used to twist through the residue and open up the path. When done, I wiped down the drum with a lint-free cloth to make sure there was no debris. Even a very small speck can interfere with plate contact.

As mentioned, that was a Creo Lotem running Fuji PJ plates, and later Kodak Swords. The next place I worked I ran an Agfa Avalon using AzuraTS plates, and in 2.5 years never did any hole cleaning at all.

Is the hotspot always in the same location? Have you tried spinning the plate to see if the hotspot moves? That's a good way to isolate if it's the plate or the CTP.

 

[Raymond Ramirez]

I have recently been getting a hot spot on the edge of our SM52 plates. Not every plate, just every once and a while. Also, this does not appear on our other sized plates. I can find to kinks or anything else wrong with the plate that would cause this. Could this be a vacuum problem? That is the only thing I can think of, and wanted opinions before calling in service. I have attached a pic showing the problem.

Thanks in advance
Paul

What device are you using and plate manufacture.

 

[pabney]

We have a Dart 4300S using Fuji LH-PJ plates. About 5 years old. No problems before now. In guessing this is happening on about 1 out of every 25 plates. Only on one out of 4 plate sizes.

 

[buckeye]

Is the SM52 plate the only one that is .006 gauge?

-Erik

 

[pabney]

Not sure how to translate into gauge, but here is the info that is on the box on our 4 plate sizes.

SM74 - 605 x 745 x 0.3
SM52 - 459 x 525 x 0.2 (this is the problem plate)
GTO - 370 x 450 x 0.15
AB Dick - 330 x 492 x 0.15

The hot spot is always on the edge of the plate, either on the right side or the left side approximately 2.5 inches down from the tail clamps.

Paul

 

[Raymond Ramirez]

Email Me so I can give you some info paul...and possibly walk you through a quick inspection...The plate in question is the 8 gauge

LET ME GUESS...maybe out of focus for that Gauge [email protected]

 

[pabney]

Raymond
Email sent. But wouldn't the focus affect the entire plate as well as all of the plates. I wouldn't think focus would be intermittent.

Paul

 

[buckeye]

Surprising, because our SM52 plates are .15 (.006 gauge) and not .2 (008 gauge).

Thinking out loud here, but did you look at THAT area of your plate processor to see if it could be coming from there? It is odd that it happens every 25 plates or so. Intermittent problems suck.

-Erik

 

[Raymond Ramirez]

OK a quick lesson. If you are drivng down a country highway you notice that the lanes are fairly wide. We drift left to right without going out of our lane. look at the lane as the CTP and our driving is the plate emultion..... outside our left and right lane is out of bounds but the boundry line is faded instead of a solid line. this is called the cusp of the plate (Fail window)....Nonetheless, We now get into the city where the freeways are tight. If we drift into someones lane or go over the line we get shot at or the middle finger....so with this said. The plate is exposing 90 percent of the time but the emultion or the lasers drift a bit this will cause the plate to fail...See the device is doing what its told to do so we cant see any problem unless you know where to look. The only problem is that the plate is our only indication of failer that we can touch and see. We need to verify drum speed and laser power for the plate first then look at focus... if it was a processor issue the processor is going to yell at you for being +/- 2mohs if you have the current ZAC model processor...Which I think you do since Fuji started supplying to there customers with the 4100. series. I am sorry about being so long winded. I can walk you through an exposure test

 

[ansoft]

I experienced the same problem some time ago. The plate edge is just on the vacuum groove of the drum. Sometimes the the drum is loosing vacuum and you get this result. First of all please check your tail clamps. Second- load a plate, open the back cover and check the plate if it is ok on the drum. You will see if there is a problem with the vacuum. You may check the vacuum hoses, but it is a rare problem. Finally, if you set the drum speed with 100 rpm and laser power to 90, everything will be ok.
Good Luck!

 

[Raymond Ramirez]

After going over with Paul over the Phone we have determined that the device was out of focus. for the 8 gauge plate. about 30 tack pulses. We will let you all know how it goes at the end of the week or next week

 

[pabney]

I would like to publicly thank Ray for the assistance. He was very helpful on the phone and I learned a lot. It is a bit to soon to tell if this has fixed the problem, but I am very hopeful that it will.

Paul