CONVENTIONAL DAMPENING SYSTEMS
WHAT'S WRONG WITH THE WATER SYSTEM
- First of all I am not going to go through the PH - Conductivity your tap water is screwed dance with you.
you have heard it already and 95% of the time it is BS anyway.
- Is it your pressman? Most likely not. Of course that depends on the level of knowledge you expect from him(or her).
- The symptoms I am going to address apply to all duplicators with conventional systems. Multi, Hamada, Chief. Note this does not apply to Hamada 611 direct feed presses.(No feed board). It does apply to older Ryobi's such as the KR430, or 500's and 500n's.
- Second let's be clear on what a conventional water system is. It consists of a reservoir of water, an aluminum or chrome plated steel fountain roller that is turned every press cycle by a ratcheting pawl arm. It has a water ductor roller covered with a type of cloth, which in most cases is a material known as molleton. This ductor roller is held on the ends by a yoke that is connected to a cam follower(A beaing attached to a small arm connected to the yoke). This cam follower is resting on a cam that can either push the ductor up to the fountain roller and uses spring tension to return it to contact with the distributor(Don't worry that's next) or uses spring tension to contact the fountain roller and the cam to contact with the distributor. This cam cycles once per press cycle as well. The distributor rollor. This is almost always chrome but aluminum can appear here as well. The distributor may also be called the water oscillator as well. Finally there is a water form roller. The water form roller applies the chemically treated water to the lithographic plate. The areas that are non-image or hydrophilic areas accept the water and repel ink from theses areas. The image or hydrophobic areas repel the water and accept ink.
- It all sounds great in theory. It most likely with the exception of factory lemons(Car makers do not have an exclusive it happens to presses too believe me), works out fine.
- The problems come with age.
Deus Ex Machina
- Let's start with the chrome or aluminum rollers. Turn the press on fill it with your fav fountain water mix. I always favored Rosso's unfortunately they are out of business so you are probably using a pink colored universal additive. Which will work fine.
- Examine the fountain roller as the press turns.(Sounds like a soap opera, and sometimes it is!) Is the roller accepting water evenly? If you see areas where water is being repelled this will cause a problem. If this is the case you will want to clean the fountain roller with a continuous dampening system cleaner. After you have drained the water first. If continuous dampening system cleaner is not available, Hurst 116 rubber rejuvenator will work as well. The primary goal is to remove all oil based contaminants from the fountain roller with out leaving any residue.
- Now that your fountain roller has been thoroughly cleaned and is free of residue, you need to apply Gum Arabic to it. This should be done with a cotton pad and you want to make sure that no big drips dry on the fountain roller. Gum arabic is available through some print supply companies but often is not. If it isn't available through them then you can go direct to: Sigma Aldrich, Spectrum Chemical, Fisher Scientific or Merck. One thing, if you do use a chemical supply specify USP grade. If they think you want a Re-agent grade chemical it will cost anywhere from 10 to 100 times the cost of USP grade.
- Ok once the fountain roller is bringing up water evenly. Note the process might have to be repeated multiple times. Also once the Gum is on the roller a water miscible is best use to remove it and then repeat process from start. NOTE AND BE SURE: IF YOUR FOUNTAIN ROLLER IS CHROME A 3-M SCOTCHBRITE WILL DO WONDERS FOR IT. IF IT IS ALUMINUM A 3-M SCOTCHBRITE WILL RUIN IT!
- Ok so now that the fountain roller is accepting water EVENLY ALL THE WAY ACROSS IT! Turn the fly wheel with your hand and bring the molleton covered ductor into contact with the fountain roller. Turn the fountain roller knob on the operator side of the press and look at the build up of water as it comes into existence from turning the knob. Pay close attention from the start. Once the ductor is saturated the water will distribute itself evenly(IF you leveled the press when you put it there).
What you are looking for are areas that are accepting water at a faster rate than other areas.
- Here is where it is imperative observation must be made accurately. If the water appears to transfer evenly that's great. If it does not you must determine the nature of this uneven distribution(This assumes that you have thoroughly cleaned and "ETCHED" your fountain roller. The 'ETCH' being the Gum Arabic. Note there is no actual acidic etching process taking place. Just a poorly applied term. Priming would be more appropriate. Anyway if the the unevenness is in isolated sections the cause is most likely a ductor roller that probably has not been replaced in 10 years if ever. If the unevenness seems to be from one side to the other, than it is likely that: A) The yoke is worn out or needs adjusting
B)If the system operates by using springs to make the ductor contact the fountain roller and cam follower to contact the distributor check and make sure the springs are in good shape.(Note I have only seen one press that does it this way-KR430 all others use the cam and follower to contact the fountain).
- Ok, now I am assuming that you now have a good working fountain and ductor system.
- Now turn the flywheel to make the ductor contact the distributor or water oscillator. Turn the press very slowly and observe the distributor as closely as you did the fountain roller. A) Is it replelling water at all? If so treat it the same way as you treated the fountain roller. Always be sure of what metal you are working with, although 90% of water distributors are chrome.
- Now for the prime suspect - the WATER FORM ROLLER and it's CONTROL ARM.
- For starts lets be good thorough operators and get ourselves 2 pieces of plastic film cut 1" in width. Mount one of the plates that your shop uses on that press and drop the water form in contact with the plate.
- Stick the plastic strips in between the water form and the plate and roll them into the press "BY HAND" turning the flywheel. Ideally this should be done with a completely DRY water form roller. However if it is wet you can still get a somewhat good idea if the roller is set to contact the plate EVENLY! Pull on the strips there should be about 2-3lbs resistance to your pulling and it must be even on both sides.
- If it is not even then you must adjust it.
- I am going to describe the procedure for a Multilith as all other duplicators are adjusted through some variation of the following:
A)On the non operator side there is an eccentric bushing that the water form control arm slides into.
B) It is big and it is made of brass.
C) It is locked in place by a slotted screw(Note this may have been replaced with something else sometime in the past but if you have made it this far you are probably smart enough to figure it out).
D)The big brass eccentric bushing has a slot to turn it with a screw driver.
E) As you turn it you will see the water form move up and down on the non-operator side. Depending on whether it was heavy or light with regard to it's pressure on the plate in relationship to the operator side, adjust appropriately.
- Once you read even pressure on each side be sure your eccentric bushing is locked back down. And check for even pressure from the middle of the roller to each side.
- If the pressure is so high that you have trouble pulling the plastice strips out, or so low that there is no resistance at all(Double check that you have the water control knob in the right position first) you need to adjust the pressure using the operator side water control arm parallel adjustment.
- The water control arm knob has a slotted screw driver end on it. WAIT!
- It also has an Allen set screw holding it in place.
- Loosen the set screw then rotate the control arm which is a parallel eccentric adjustment. Set it to the aforementioned specs.
NOW FOR THE THING THAT IS REALLY CAUSING THE PROBLEM
GOOGLE PLUS PAGE
- So you say you did every thing I said and it still doesn't f$#@ing work. This Kris Johnson is a real A$$H0!!E.
- Ok so I saved the important stuff for last, kill me(Actually I am not kidding I am still involved in printing please kill me!).
- Alright, enough levity. That water control arm, rotate it so you can pull it and the water form out of the press. You will notice that on the operator side the parallel adjustment is about 3/4 of an inch in diameter. If you look at where the control arm inserts into that eccentric bushing on the non operator side you will notice that the hole is about 3/16 of an inch. Whoop dee doo you say?
- The energy used to keep even pressure of the water form to the plate is applied equally to both parts. On the operator side the the energy is distributed amongst 3/4 of an inch of metal. On the non - operator side it is distributed amongst 3/16 of an inch of material. If you examine it closely you will in 99% of all cases find that the hole is elongated on the eccentric bushing making it impossible to ever set the water system right. Replace it or have a machinist fix it.
- Finally, I must add that any one of theses issues can come in concert with each other. The water form roller may have never been replaced in 20 years and the non operator side eccentric bushing worn too. Any combination of these problems is possible. Always remember that replacing the roller covers will not make a worn roller work
- Making your conventional damp system work properly will make you run the press instead of it running you. Of course if you enjoy holding a cotton pad and dripping water into the damp system, ignore this and have at it.
- Good bye for now,