Lotem 800, exposing problems.

[Petkovski]

Hi. Im new to this forum, and searching i found a lot of questions and helpful answers, so i thought you guys might help.

Im working in a printhouse as a graphic designer, prepress and it geek. Recently they brought up the Lotem 800 with the Brisque workstation. I can't believe they brought that shit and sold the trendsetter 800 III quantum. I think the boss is having a hard time managing resources.

Anyways, I'm new to this lotem so i started configuring it and learning it. It's a model with 24 diodes, and on this machine only 17 are active, they need to be changed. After several tests, i noticed that on screen sets below 175 lpi, we're talking about 150, 133 and below, some strange lines are appearing all over the exposable area on the plates. I want to notice that these very thin and fine lines can also be found in very fine halftones or transparent colors, (20%K, 50%M etc etc.). On print, they look terrible.

Is this an issue with the non-working diodes? Also, i had to slow down the drum speed to around 600 - 800 rpms, since on higher drum speeds the lines were more intense. (How much is the maximum drum speed anyway?)

So... does anyone had this problem with the lines? I can't connect the dots through my head how is this related to the non - working diodes, or to the wokrking ones either? Maybe it's an issue with something else?

Also, how much do this diodes cost, and is there anywhere in Europe available to buy? Do they need to change one by one, or a whole array of 12 + 12 needs to be changed.

Please give me some advice.
Thanks.

 

[ansoft]

These line may be caused because of the white oil felts supporting the head. They need to be silicone oiled and replaced every year. From your message I understand that you don't have problem on 175lpi, but you experience problems on 150 and 133lpi. It is very very strange. Do you use these lpi on different resolution from 2540dpi? Please verify the screen set!
Luck!

Ansoft

 

[ansoft]

Laser diodes of Lotem 800V are very very robust.

 

[PACH]

Hi. Im new to this forum, and searching i found a lot of questions and helpful answers, so i thought you guys might help.

Im working in a printhouse as a graphic designer, prepress and it geek. Recently they brought up the Lotem 800 with the Brisque workstation. I can't believe they brought that shit and sold the trendsetter 800 III quantum. I think the boss is having a hard time managing resources.

Anyways, I'm new to this lotem so i started configuring it and learning it. It's a model with 24 diodes, and on this machine only 17 are active, they need to be changed. After several tests, i noticed that on screen sets below 175 lpi, we're talking about 150, 133 and below, some strange lines are appearing all over the exposable area on the plates. I want to notice that these very thin and fine lines can also be found in very fine halftones or transparent colors, (20%K, 50%M etc etc.). On print, they look terrible.

Is this an issue with the non-working diodes? Also, i had to slow down the drum speed to around 600 - 800 rpms, since on higher drum speeds the lines were more intense. (How much is the maximum drum speed anyway?)

So... does anyone had this problem with the lines? I can't connect the dots through my head how is this related to the non - working diodes, or to the wokrking ones either? Maybe it's an issue with something else?

Also, how much do this diodes cost, and is there anywhere in Europe available to buy? Do they need to change one by one, or a whole array of 12 + 12 needs to be changed.

Please give me some advice.
Thanks.

The maximum drum speed is 900rpm.
Laser diodes are expensive . You need a technician with a Spicer to relace the diodes.
Which diodes are faulty?
The faulty diodes do not work so have no effect on the output.
are the lines arround the Drum? Top to bottom of the plate?
Shame about the Trensetter as a 24 beam Lotem800 is slow compared to a Quantum.

 

[Petkovski]

Here are the specifications on the screen set
175 is at 100 resolution and frequency of 5.something
150, 133 and below are on 80 dpm (i think it's dpm) resolution

i think that diodes from 2 to 17 are active, don't know i have to check tommorow at work.

about the lines, there are everywhere from top to bottom on the exposable area. and there are striclty uniformed and parallel.
the lines are vertical H... first we thought it was the plate developer, but we tried developing plates in several partner companies. no luck. we tried different plates too.

so basically, what happens if i some of the diodes are dead? is it ok to put the machine at the optimal speed, let's say 850? even 900? because i think that higher speeds produce more lines.

also, i really need some info from where i can buy diodes and how much they cost? we plan to update the whole set with brand news.

thanks for your help! really apreciate it!

 

[PACH]

Here are the specifications on the screen set
175 is at 100 resolution and frequency of 5.something
150, 133 and below are on 80 dpm (i think it's dpm) resolution

i think that diodes from 2 to 17 are active, don't know i have to check tommorow at work.

about the lines, there are everywhere from top to bottom on the exposable area. and there are striclty uniformed and parallel.
the lines are vertical H... first we thought it was the plate developer, but we tried developing plates in several partner companies. no luck. we tried different plates too.

so basically, what happens if i some of the diodes are dead? is it ok to put the machine at the optimal speed, let's say 850? even 900? because i think that higher speeds produce more lines.

also, i really need some info from where i can buy diodes and how much they cost? we plan to update the whole set with brand news.

thanks for your help! really apreciate it!

Many things can cause lines on plate:
Take the back cover off and clean the V groove ( this is where the head moves)
On the bottom Left and Right handside of the Dynamic Optics) you will see White pads that need oiling with Silicon oil
Problem could come from the Brisque: TSP board; fragmented files ( do an FSCK on the Brisque)
In the Lotem you could have a faulty LDD board ( this is the Laser driver board)
Faulty DDB board ( big board in the L BOx where the diodes are)
Could be a Lead screw problem/ Stepper motor/ coupling to the Lead screw.
As I said that the diodes are expensive and the technician needs a splicer as the fibre cable needs to be fused. Where are you? Maybe you can find help in your country.

 

[Petkovski]

Many things can cause lines on plate:
Take the back cover off and clean the V groove ( this is where the head moves)
On the bottom Left and Right handside of the Dynamic Optics) you will see White pads that need oiling with Silicon oil
Problem could come from the Brisque: TSP board; fragmented files ( do an FSCK on the Brisque)
In the Lotem you could have a faulty LDD board ( this is the Laser driver board)
Faulty DDB board ( big board in the L BOx where the diodes are)
Could be a Lead screw problem/ Stepper motor/ coupling to the Lead screw.
As I said that the diodes are expensive and the technician needs a splicer as the fibre cable needs to be fused. Where are you? Maybe you can find help in your country.

im in macedonia. several experts came from bulgaria and serbia, and none of them had any clue.

 

[Petkovski]

huh.... i've read your post again and again... the problem could be practically everywhere, its a complex system. but anyways really thanks for the advice.
p.s. does no one knows how much these diodes cost??

 

[ansoft]

Dear Petkovski,
I dare to give you several advice:
1. Work on 2540dpi=100dpmm on this Lotem 800V. The lpi is whatever you want-175lpi, 150lpi, 133lpi.....etc.
2. Switch on all the diodes from the registry. If there is a problem with a diode the Lotem automatically will decrease the laser diodes numbers and will write you a message for working with reduced number of diodes.
3. If the problem is in laser diode driver-it needs replacement.
4. If the problem is in the DDB, which is not very common problem-it needs replacement.
5. It could be problem in the Brisque's disk drives. Please check the disks.
6. Laser diodes in Lotem 400 and 800V and 800V2 are very robust. For these years I am a service engineer, I have never changed a laser diode on such a machine. I have changed a laser driver, but a laser diode-never!
7. As PACH told you, clean the V groove and check the white pads. Oil them with silicone oil. It seems to be this problem.

It is a complex system, but you can manage.

Good luck!

 

[Petkovski]

Thanks... I will start this week to sort out this mess, and step by step i'll try anything and i keep you updated!

 

[nemo]

This thread is a month old, but if you still have the problem, follow Pach's advice:
"Take the back cover off and clean the V groove ( this is where the head moves)
On the bottom Left and Right handside of the Dynamic Optics) you will see White pads that need oiling with Silicon oil"
The lines you see are caused by vibration due to friction between pads and V-groove surface causing gaps between two consecutive swaths - wipe the V-groove clean and use the a bit of the silicon oil which came with the machine to lubricate it.
Do not use generic silicon oil as it may damage the V-groove surface - extremely expensive to replace.

 

[Armya Inc]

Thanks... I will start this week to sort out this mess, and step by step i'll try anything and i keep you updated!

This is called banding Issue. The Banding issue or thin lines on the plates are because of gaps caused between Laser beams. Replace the diodes, the issue will be resolved.

 

[VladCanada]

... and no word has been said - are there Negative or Positive plates?
So that could be either "banding" or laser modulation (some laser is ON for a short period of time with no reason to be ON) issues.

 

[Armya Inc]

... and no word has been said - are there Negative or Positive plates?
So that could be either "banding" or laser modulation (some laser is ON for a short period of time with no reason to be ON) issues.

It is a positive Plate

 

[Fii]

The same problem here, on Lotem 400F,24 diodes in array, positive plates. We cleaned the V-groove, repleaced pads, oiled screw and groove - problem still here. Also there was a problem wit diode array, diode nr 13 was almost dead, reasonably it could be the cause, when it died, and also working with 12 diodes only stripes were there, especialy on yellow seperation.
We got new diode from Kodak, that arrived in its antistatic plastic casing, but not attached to metal bar in casing and, bended contacts - 400 euros(or even more) straight to trash can. Ok, no big deal, it was not hard to replace #24 to #13. Basicaly, that canging process isnt such complicated you just need optics fiber soldering station and some tools, basicaly long ph0 screwdriver.
But, those bloody stripes ar still there, and there is no change after all of those procedures.

 

[diggs30]

hi we had similar problem over here after we were blamed because or plates and processor , the problem ended up been something on laser head scraping the plate , or something touching the plate when it was all vacuum down as the lines were dead straight

cheers
dirk

 

[Quicko58]

We saw similar problems on a Lotem with fine lines at random in the direction of drum rotation. In our case our plate/processor was being blamed. After extensive investigation into the processor & finding nothing wrong there, I had to prove if the Lotem was the cause.

By turning the plate through 90 degrees before processing you can narrow the issue to either the setter or processor. In our case this proved the Lotem was the culprit. On investigation the Kodak engineers discovered an intermittent problem with the lead screw and once that was rectified, the problem went away.
john

 

[KevinC@EFI]

By turning the plate through 90 degrees before processing you can narrow the issue to either the setter or processor. In

Just to add to this: depending on your plate size and processor size, often just turning the plate 10 degrees or so is an easier/better way to distinguish imaging-created banding from processing-created banding (or even scratching). 90 degrees is often fine, but may also be too wide for your processor or get confused with banding in the other direction.

 

[kala]

Faced same problem

Here the solution :

1. if lines appearing on all the rulings then its related to non-working laser problems.
2. if its ok with 133 & 150 then change the expose settings for 175 its ok
3. if 175 ruling is the problem try the plate with fresh chemical and see the result if the lines are not visible in naked eye and its visible in printing then its related to expose settings

regards
kala

 

[gthevath]

Hi,

We getting rain kind of artifact on the plate with Lotem 800V.
Please see attached image.
Could it be TSP or DDB boards causing the lines?



Thank you,