Is anyone out there familiar with the Heidelberg KRZ 2 color rotary letterpress? I am curious as to how one of these could be made to work with photopolymer plates? There doesn’t seem to be much information out there about these presses. I would like to get familiar with their operation.
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When I was a student at Sydney Tech., School of Graphic Arts they had one and as year 4 students we ran it. It used Dycril plates which would equal to modern steel backed photopolymer. They were good but the design problem was the common impression cylinder making makeready impossible. Also although wet on wet printing seemed to have some future back in 1969 it never sorted itself out. I think I know someone who has one. As far as I know no one in Sydney actually used one in industry.
i have some dycril plates that were made for me back in the early 1980s, they are very hard but the material falls off the steel backing.
More importamt is the fact that rotary plates must either be exposed on a suitable cylindrical exposure unit, or the original image must be altered, around the cylinder, to compensate for the change in image length when it distorts as it is wrapped around a cylinder; only the base side of the plate retains oringinal relation, and the surface is spread as it wraps. This is already inherant in flexo platemaking, they have software programs and tables based on cylinder size and undercut.
You are getting into areas that are not do-it-yourself, unless final print length is not critical. Print width is unaffected.
Like Lasimp, I set up and ran a two-color Heidelberg Cylinder press in school at RIT. We ran a type form on the reciprocating bed and a second color image on the wrap-around cylinder. I truthfully don’t remember what we did in terms of makeready for the forms, but we did have success in getting the two printed. I think the instructor cautioned us that it was very difficult to get absolute register between the two images as one had to be adjusted in length for the wrapping around the cylinder while the other was printed from a flat form, but for many forms, it was a very useful concept.
It seems the plates we were using were Kodak relief plates, but I would assume you could get a thickness of current polymer plates to run on the unit.
I also ran a KORD press with relief plates (dry offset) which was very successful. I had my students run a four-color process job using plates I had a local newspaper make. No need to mess with ink & water balance.
Most all of them are used as a one color press, put a base in the bed and proceed as usual. The secondary color unit was always trouble, it was easier from a production point of view to run a second + color on the bed, made registration easier, as there is no image stretch. The secondary color cylinder, at least back in the day in germany, used flexible BASF Nylonprint plate. it was mounted with a special doublestick DUPLO tape. But a huge waste of time tryong to register the 2 colors. Albeit a 2 color press, they go for less than a straight one color, as they need more Floorspace and the second color failed.
It seems to me that it would not be hard to build an exposure unit to match the KRZ. You would just have to use your existing plate processor for washing/drying or some other method. I suppose that one could find an extra cylinder for the press you were using, drill holes and plumb it for vacuum. Then you would make a UV exposure unit that surrounds the cylinder. You could secure the plate, then the film, and then a kreen over the whole works, turn on your vacuum and slide the whole cylinder into the exposure unit and your image would exposed at the correct length for the circumference of the cylinder. I understand that projects like this are never this simple. But I am lucky to have engineers, machinists, and welders as close friends. I probably should find a KRZ first, and then learn how to use it before all of this. Also, is it correct that the KRZ has no flatbed but two form cylinders and one impression cylinder? I don’t think that I would wish to bother with a two color press that has a bed and a form cylinder. It is obvious to me that this would create registration problems. But with both forms being rotary I don’t see why you couldn’t hold an amazingly tight register. Providing you can develop your own way to effectively and accurately process plates for the machine, or farm the plates out for a reasonable cost.
Sorry everyone, I feel a little dumb. I am not sure weather the KRZ or RZB has two form cylinders, or one bed and one cylinder. Maybe someone can shed light on this.
Now I’m wondering! Its going back a long time but the press I am thinking of had two plate cylinders and a common impression cylinder. Chain delivery, sheet fed.As I remember it its a KRZ. Heidelberg had a little booklet for the platen and the cylinders. If anyone has one you will find the entire letterpress range in the back for late 60’s.
I found my “Hints for The Pressman” and the KRZ is as i described. (151/2 x 221/8). The KZB was huge in comparison and it looks like each Plate Cylinder had its own impression cylinder with a walk through division. Sheet fed but bigger (28x40)
Ok then it obviously is the KRZ that I am thinking of. Are these common in the US? What would be an appropriate price for one? I think that I would really like to have a press such as the KRZ.
Be careful what you wish for.
Parallel Impression said,
“Folks, don’t confuse the KRZ with the KSBAZ. The KRZ is an all-rotary press, the KSBAZ a flabed with added rotary unit.
I would think photopolymer use is possible with the proper cylinder shell for specific plate thickness. Then you have to allow for image stretch for the mounted plate, unless the plate is exposed in-the-round. This true for the KSBAZ rotary unit as well.
I think the all-rotary presses have a common impression cylinder, as do the flatbed-rotaries. This means any heavy impression that distorts the packing is going to create problems such as image distortion, especially if there is overprinting.”
The thing about Heidelbeg rotary units, whether on an all-rotary unit like the KRZ, or the flatbed-cylinders like KSBAZ or SBBGZ, is the plates are held on plate shells which were designed for specific types of plate. I know they were made for wraparound plates, which might be compatible with the thinnest film-backed photopolymer used today. I’ve only seen those on two-color flatbeds, made for curved stereotypes or 1/4” plates, using a Warnock shell and hooks. To use that today, some bright person might make suitably curved metal blanks and then mount thinner photopolymer plates by adhesive on top. If that idea is in actual use anywhere, they haven’t told the lists. And in my own experience, the second-color unit on a flatbed Heidelberg leaves so little of the cylinder surface available that doing makeready on the packing becomes very difficult.
With the all-rotary presses, they would have been designed for full-size plates covering the entire cylinder (or at least full-length so the plate clamps do their work), rather than spot-gluing a small plate into register (though that may not be impossible). With film and photopolymer costing what they do, the economics of a KRZ suited to larger stock and plates are pretty demanding. It would not be as flexible a press as a flatbed.
iirc Whittenburg recently sold a SBZ to someone who is using the cylinder shell and modern adhesive back plates.
I ran one for many years on & off used to put a steel jacket on the impression cylinder a, cutting forme on the flat bed clamp a sheet of mylar on the rotary cylinder mount a nylo plate on that allowed us to cut & crease and print all in one pass.. btw it was nicknamed the Cane Toad