Vinyl shrinkage and crop mark detection.

[ChristianTR]

We have been having issues with the crop marks not being found on Auto-Align. It will find the first one but then the material gets shifted up on its way to the next crop mark and completely misses it. It will do this 4 or 5 times and eventually work (rarely) or it will say "crop marks not detected".

We were curious, since we print at about 42 degrees and cut with no heat, could shrinkage of material cause the crop marks to be in the wrong position? This has been boggling our minds for days we are narrowing it down but cant quite figure it out.

Thanks!

Christain.

 

[StarSign]

Let me guess cutting with a Graphtec?

 

[ChristianTR]

We are using a Roland SC-540.

 

[d fleming]

When I first starting cutting pre printed material (on my Graphtec) I got this error quite often, the better I got at placing the media on the cutter, the better my results became. Now I rarely get it. Sometimes the print may not be as square to the roll as it cou and I have to align the print to the cutter versus the roll. You'll get better.

 

[bob]

Shrinkage is not the problem here. The minute amount of any media shrinkage isn't going to have any effect on anything.

Here is the definitive reason why most any auto sensing rig cannot find registration marks. Pay attention...

When the plotter moves to where it thinks a mark should be, the mark isn't there.

Why does this happen?

Most often it's because the media isn't loaded reasonably square to the marks. That's square to the marks, not necessarily square to the media.

The next most popular cause is that an inch on X and/or Y on the printer are not an inch in that direction on the plotter. In other words, if your printer feeds out what it thinks is one foot of media, does your plotter feed pretty much the same amount for what it thinks is a foot? Likewise for carriage travel.

Never forget that the map is not the territory. The map is the logical image in the software and what is sent to the machinery. The territory is the actual print that comes out of the printer and what gets loaded into the plotter. They are not the same thing. That's why the larger the marks the better the chance of the plotter finding them. Flexi was notorious for not reading the marks until, if memory serves, in version 8 they doubled the size of the marks as well as the search area. That fixed that.

 

[Mosh]

+what Bob said

 

[threeputt]

Bob: I think the OP is using Roland equipment which is both printer and cutter.

OP: When we get these same types of messages on our SP-540 Roland, it almost always is because the tiny little hairwidth arrows are too close to a large block of color.

ie: the eye 'sensor' gets confused and is unable to distinguish between the two. We solve this by covering just a corner of the block of color with a 1/2"x1/2" chunk of vinyl cut from outside the print area.

 

[ChristianTR]

We have been lining up both crop marks on a straight edge on the printer so it should be pretty straight. That's what made us think of shrinkage or it being warped slightly. I cannot see the shrinkage, just a hunch.

Yes, it is advancing around an eighth inch every so often. Sometimes its really bad and ends up an inch away from our crop marks and sometimes its only slightly. It happens on just about everything

We have found that if we don't take the media out or lift the pinch rolls it finds the marks perfectly and cuts them with no problems. So that brings us back to not loading the media straight enough. What do you guys do to ensure your media is straight?

Could the sensor voltage have anything to do with it? It is set at 2.6 currently.

I am printing some labels and the corner of the crop marks are not touching the print and the distance between the two is different on each corner. Is that normal?