Generally speaking, labelers will present labels the same way every time. The best way to test this (and the first thing that you should test) is to trigger the labeling head multiple times with no product present. Use a pencil to draw a line on the peel plate along the edge of the label web and watch that as the labels go by. Also make a mark at the label gap. Either lay a straightedge along the leading edge of a label and use a pencil to extend that line beyond the label web, or stretch a rubber band across the peel plate above the label gap (not rubbing the labels) to give you a reference for the repeatability of the label stop position. Trigger some more labels with no product present and watch how much variation you get as the label web goes by. There should be next to none. If that is the case, then any misalignment problems you have are not caused by the labeling head. If you do have variation, then you must fix your labeling head before going any farther. Look for help with this under How to Stop a Wondering Labelel Web.
So once you have your labels coming out repeatably, the next step is presenting the products equally repeatably. On an automatic system, watch your products as they approach the labeling head. If you can see the top of the product bouncing to one side just as the label starts to dispense, you are guaranteed to have label placement variation. I see this often with round bottles bumping into wrap belts and other bottles bumping into peel plates. (If your labeler has a top hold-down belt, watch for a bump entering into this belt.) You should be able to bend over at one end of the conveyor, sight along the tops of the bottles, and not see any sideways movement or vibration the entire length of the conveyor.
Matching up the label and product is the third and final step in getting your label position repeatable. If the label is dispensing at any speed other than that of the product surface going by, then you are likely to get random variation in where the leading edge of the label sticks to the product (as well as wrinkles and web tears). Set the labeling head to match the speed of your wrap belt if you have one, or your conveyor if not. The idea is to have the product surface going by the labeling head under control at a constant speed, and then lay the label on that surface at the same speed. Once you match the two speeds, you should get a very repeatable label position.
Now that your label placement is repeatable, is it straight? The key to getting the label at the angle you want is to get the leading edge where it needs to be. The rest of the label will follow. That’s why any little sideways bump of the bottle will throw off the alignment of the entire label. If your label is aiming uphill or downhill on the side of the product, or spiraling up or down on a round product, you need to tilt the labeling head up or down to correct that. To determine which direction to make the adjustment, think about the leading edge of the label. Which way does it need to tilt? If the leading edge is tilted downhill, then you need to tilt the labeling head uphill (and then you will have to lower the entire head to maintain the same height).
Those are the four steps to getting a repeatable straight label position on your products. Any one of these steps could be greatly expanded upon, but it’s impossible to address every potential source of variation. Most important is to get your repeatability down first. Run enough products through at each of the above steps to see the full range of variation you’re getting. If you have too much variation at any one step in particular, look around for what is causing it. It may help to read Reasonable Expectations For Labeler Alignment. If you still need help after that, give me a call at 800-331-7140 or email me at jdawson@su-solutions.com. I may be able to help you eliminate that last bit of variation.
Wednesday, November 5, 2008
Sunday, November 2, 2008
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