Heatset web offset - conventional or alcohol dampening?
I am in process of searching a pre-owned or used 546mm cut off heat set web with 880mm web width. I have located a Toshiba 1989 model. The machine's optical condition is nice with splicer, Toshiba press control for ink and register. The price is also affordable for me. But the machine doesn't has no chopper, no auto register and it is conventional dampening machine.
This is my first heatset web offset machine. I need technical advise and help in deciding whether I can go for conventional dampening heat-web offset machine.
- Can conventional dampening web offset machine can print a solid reverse type printing of 175 lpi with perfect register.
- Is conventional dampening system is a succesful system in heatset web offsets without any head aches for printer.
- Moreover few suggest that auto register is a must in fast web offset machine since it avoids mis-registration during production.
To everybody's attention : I am very new to web offset printing, I have machines with conventional dampening and alcohol dampening in a sheet fed but for web offset I have no idea. So all type of suggestions regarding heatset web offset are welcome. Please assist me if Toshiba is a good brand or I should stick wiith Mitsubishi and Komori. Pls guide.
Waiting for kind technical advise to decide my purchase.
If it was me, I would be more concerned about the lack of auto-register than any other consideration. Is Toshiba willing to provide parts for this press? As for the dampening, conventional dampening requires more work than continuous dampeners but I have observed many presses (mostly Hantchos) with conventional dampening producing top-notch work.
A pet peeve of mine: There is no such thing as an 'alcohol dampener', the correct term is continuous dampener.
Daniel T Roll
Web Offset Presses
In my opinion buying a Harris/Heidelberg/Goss or Komori are the better Web Offset Presses,
and that the press be fitted with a RGS (register guidance system) also a goodCombination Folder plus a Continuous Dampening System, well almost the last Bell and Whistle - A Zero Speed Splicer
Next we come on to the Dryer then the Chill Roller Assembly
Komori bought the web press division of Toshiba Machinery in 2001
Last edited by Alois Senefelder; 03-23-2011 at 04:00 PM.
Conventional or continuous dampeners in heatset web offset
Dan, thanks for the correction and your comments. So conventional(molten) dampening is not a problem, thats a relief but you feel auto-register is must. Am I right? Can you please explain me how auto register is a much needed facility? Is there chance for misregistration after making ready? Kindly explain.
Originally Posted by Dan Roll
I guess that buying a web depends a lot on who you are competing with. If your runs are short, an automatic register system is a must in my opinion. These things make a lot of corrections during the press run that a pressman would be to busy to even see the need for.
Daniel T Roll
Misregistration is more likely than being in register. There is no "after making ready" in web. You fire the thing up and make color and register adjustments while running. You wash blankets while running. The object is to never stop.
Originally Posted by shalomshalom
My experience has been such that I wouldn't consider a web press without automated color control, either. Web presses are just wild in comparison to sheet-fed. Control is fleeting and illusory.
Look good and hard at how the plates are hung. Are the register controls indexed, so that they can be returned to "zero" easily? Are the angle-bars controlled by motors, or do you have to unbolt them and move them by hand?
PAY ATTENTION TO THE BLANKET WASHING SYSTEM!! This is CRUCIAL! A good, automated blanket washing system will quickly pay for itself in greatly reduced waste. Remember, you're washing blankets on the fly, so the whole time you're washing blankets you're producing unsellable product.
1) Molleton covers soak up water in much the same way as a bath towel ------ once they're too wet , it takes along time for them to dry. This phenomenon results in the gets-wet, stays-wet problem. The large water storage capacity of these roller materials is disadvantageous because it increases the response time of the dampening system.
2) Read the PDFs I have posted - Thread: Registration or doopid - Dates of posting
01-26-2009, 02-14-2009 also read PDF posted 12-02-2010
Conventional dampening is horrible IMHO. Not only do you have molleton covered ductors that need to be changed out regularly, you HAVE to run a sleeved waterforn to hold the water while the ductor is in limbo. Any linear water system; continuous brush or conventional or otherwise is going to need to run water stops or fingers to control water on the ends when not running a web thats full width. The problem with elastic sleeves and molletons is that the ends that you run dry will pretty much be destroyed by ink and they need to be changed when switching to a wider web. At least with brush dampening (or any continuous dampening system) you don't have to run sleeved waterforms.
Auto register is a must, there are plenty of companies that can retrofit a press with motorized register controls with a closed loop register system (Web Printing Controls, Quadtech). Closed loop color can also be retrofitted, especially if it already has remote ink keys, but they can also retrofit the fountains with motorized ink keys as well. Any 3 ink form, 3 vibrator press is going to hold color well so closed loop color isn't an absolute necessity.
I wouldn't want any press that didn't have auto register, continuous dampening and at least remote ink keys. If the press is cheap enough, it can all be retrofitted. I've run an old Hantsho that had been converted to Baldwin spray dampening, GMI remote inking and closed loop color, with Web Printing Controls auto register. At the end of the day, it's still a Hantsho, but it's a hell of alot better than I'm sure it was when they first put it in.
I have run a lot of web presses, both with auto and manual registration. Manual is fine for comic book type printing. But if your looking to get into commercial printing then auto is the only way to go. Conventional dampning is great since alcohal has voc problems and will get you in trouble with the enviromentalist. You don't have to have a chopper folder, cause you can get around that. You don't have to run sleeves or molliten covers in my opinion.
Last edited by jamfor; 06-30-2011 at 11:19 AM.
This is one of those things where terminology gets used differently all over the place. "conventional dampening" is that what uses water ductor and sleeved water form. You CAN'T run these systems bareback as they are known as "feast and famine". You need to cover a ductor with molleton because it needs to retain water when it swings off the pan roller. You need to cover the water form because a bareback would be dry when the ductor swings off the vibrator. Some people refer to any system that's not spray as conventional, but that's not really correct. Though, I have worked on presses with spray dampening that were nearly impossible to run without sleeved water forms.
Originally Posted by jamfor
"alcohol dampening" refers to any dampening system that runs bareback water forms. I guess when continuous feed dampening systems (brush, spray, duo-trol, dahlgren, etc.) first came about they were probably running on fountain solutions that were designed for conventional dampening. They needed a "wetter" solution so adding alcohol to existing fountain solutions was the way to go. Nobody actually runs alcohol anymore, and you don't need to, Modern fountain solutions are designed not to. There are alcohol substitutes that definately do decrease the water feed rate, but the ones I've used caused way more problems than it was worth.
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