[Misc] Riso GR 3750 Masters Smaller than Image on Glass

[barrywilder]

Hi,
I have a Risograph GR3750. I have two drums, one which I converted to blue and one black. They are both the same size: Riso GR(w). The blue drum creates 11"x17" masters without any trouble. The black drum produces only 8.5" x 11" masters, though it is large enough for 11"x17" masters. The master extends only to the middle of the drum, and then it is cut. When I create a new master, the screen on the machine displays 11"x17" as the size.

Also, strangely, sometimes when I create a new master with this drum (not with the other), I receive instead a severely cropped section of the previous master.

Is there some kind of setting on the drum itself that is making the masters smaller than they should be?
Any help would be greatly appreciated.
Thanks,
B

[barrywilder]

Re: Riso GR 3750 Masters Smaller than Image on Glass

Some additional information:

I opened up the scanner bed to look at the master roll. It appears to be burning the whole image, but just amputating it halfway for some reason.

[ddude]

Re: Riso GR 3750 Masters Smaller than Image on Glass

Riso made drums for the 3750 that would only produce 8 1/2 x 11 masters-this sounds like the drum you have. Look at the drum screen under the applied master and compare it to your other drum-you may discover that the screen only extends 8 1/2, and the rest of the area is solid metal.

[barrywilder]

Re: Riso GR 3750 Masters Smaller than Image on Glass

Hi, Thanks so much for your response. I just want to double check if your theory really is the case. I've attached two photos. One of the label that specifies it is a GR(w) and one of the side of the drum screen that is not printing. It does look like mesh, and there are even traces of ink in the printing area that seem to suggest it printed 11x17 at some point. Any thoughts?
Thanks,
Barry
Drum Label.jpgDrum Screen.jpg

[rjfellizar2468]

Re: Riso GR 3750 Masters Smaller than Image on Glass

Please check position of actuator locating on the drum lips. This actuators determines the position of the drum before cutting. Refer to the Blue drum. Also check the drum PCB it has dip swicthes. It has 6 dip switch this determines the color and size of the drum. Refer to manuals or get info from old black drums you have. Before you create new master please check the master roll if it has perporation on it, cut those area before start to print new one to avoid double image.

[Iowatech]

Re: Riso GR 3750 Masters Smaller than Image on Glass

Hi, Thanks so much for your response. I just want to double check if your theory really is the case. I've attached two photos. One of the label that specifies it is a GR(w) and one of the side of the drum screen that is not printing. It does look like mesh, and there are even traces of ink in the printing area that seem to suggest it printed 11x17 at some point. Any thoughts?
Thanks,
Barry
[ATTACH=CONFIG]22749[/ATTACH][ATTACH=CONFIG]22750[/ATTACH]

If I interpret the second picture correctly, as in the ink stops coming through the screen at the bottom of the drum, that is an 8.5X11" drum.
The drum screen (the cloth looking stuff) will go around the drum like any other drum, but like ddude said there are no holes in the metal drum shell underneath the drum screen in the unprintable area.
A point of interest if you are curious, if I remember correctly the drum print size and color labels should be on the top front drum cover if the drum was set up properly. The label in the first photo shows that the drum will indeed work in a Risograph GR line machine that uses "W" sized drums, but gives no indication of what the size of print the drum is capable of.

[ddude]

Re: Riso GR 3750 Masters Smaller than Image on Glass

Usually the 8 1/2 x 11 drum, even though it is "W", will say "A4" or "A4W", giving an indication that it is made for short paper only.....of course, this could have been removed. I do agree with rjfellizar2468, you may have an incorrect switch setting.