We buy automatic labelers for two reasons, speed and alignment, right? So how good of alignment can we expect? To a large extent, we can answer that by looking at your products and labels. Since bottles show this the best, I will use those as examples.
Let’s start with a round glass bottle, like a wine bottle. Hold a straightedge vertically against the side of a bottle and you will probably see a gap at the center of the bottle. Most glass bottles are hourglassed to some extent, and when you apply a label to that, one of two things typically happen: either the label forms a wrinkle horizontally across the center, or the label spirals slightly up or down because it adheres more to the slightly tapered area below or above the “waist.”
With most plastic bottles, you will see the same gap under a straightedge; however, the soft sides of the plastic bottle will conform to the straight labeling mechanism so wrinkles are avoided. You still have the same problem, though, of there being a greater circumference and therefore more bottle surface to spread the label over at the top and bottom of the bottle than at the center.
The bottom line of all this is that if you don’t have perfect straight-sided bottles, your label positioning will vary from bottle to bottle and lot to lot. Misalignment of the two ends of a label where they wrap around a round bottle and meet at the back can vary as much as 1/8” even with the perfect labeler setup. You can tweak your labeler and might improve the situation, but when you get into a different lot of bottles, you’ll probably have to tweak it again.
Oval and F-style bottles have the same problem, but to a much lesser extent. For the most part, your setup tweaks will maintain a fairly consistent label position.
If you were to machine a perfect sample bottle out of a solid piece of material and run it through your labeler, you would probably see perfect labeling. I have seen this done twice, and both times, hours of tweaking a setup without success were reduced to a few minutes with essentially perfect repeatability.
So this long-winded post is all my way to tell you how to answer your own question: lay a straightedge along your product surface. If you see daylight under it, then you should expect label placement variation. If not, then any decent labeler should provide repeatable positioning within ±1/32”.
I'll have a more technical and detailed post for this later.
Monday, January 19, 2009
Wednesday, November 5, 2008
Achieving the Best Label Alignment
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.
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.
Sunday, November 2, 2008
Wednesday, October 29, 2008
How To Stop a Wandering Label Web
If your label placement is wandering around on your product, you may see that the label web is walking back and forth on the peel edge, or you may see that the rewind roll is spiraling one direction or the other. Either of these can be symptoms of roller misalignment in your labeling head.
First, it is important to make sure that the problem is not in the relative alignment between your labeling head and product. Watch the label web while you dispense labels into the air with no product in position. If your labeler dispenses onto a vacuum pad, be careful to give the label time to dispense completely off the web before removing it from the pad. If your label web has suddenly quit wandering, then you need to correct the alignment between your labeling head and product. Do not follow the instructions below, or you will just make matters worse. If with no product, the label web is still walking sideways, then proceed with the instructions below.
Next, let’s get the easy fixes out of the way. Check that your labeler is threaded the way the manufacturer’s instructions show. If your threading is wrong, then all bets are off. If you don’t have the manufacturer’s instructions, email me a photo, and I’ll show you the correct threading. Check to see if any rollers or other parts are wobbling around on your labeler, and if they are, tighten them and retest the machine.
Now, if we’re going to do this, let’s do it right. Line up the label web where you want it. Measure the distance from the labeler backplate to the near edge of the web along its entire path, making adjustments as necessary so the web edge is in a plane parallel to the backplate. Is the web against both the supply and rewind backing disks? If not, then bring them both into the same plane. Typically, they are held in place by either a collar underneath the disk or set screws through the hub outboard of the disk. (It is common for the supply roll disk to get knocked in from repeated slamming of label rolls into it.)
Every surface that the label web contacts must be exactly perpendicular to the backplate. Look at each roller that the label web goes around, and try to move it. Some lower-priced labelers use bushings instead of bearings, and they’ll wear out on the inside. If you can wiggle the rollers on their shafts, you may need to replace the roller assemblies.
Look at the peel edge. Is it worn down unevenly? If so, replace or sharpen it.
Look at the supply and rewind hubs. Are they perpendicular to the backplate? (Are the backing disks in line with the edge of the web?—same thing.) Some supply rolls are mounted to arms that can get knocked out of position. Loosen the mounting screws, line up the supply roll, then retighten the screws. You may find a lot of slop in the holes, so double-check that the support arm is where you want it after you have tightened it. Some rewind shafts move around in a circle. That’s okay if the center of the circle is perpendicular to the backplate.
Finally, look at the drive rollers. These are usually one rubber roller and one metal knurled roller touching each other where the label web goes through. The rubber roller is usually the drive roller that is connected to the motor; the knurled roller is an idler that is spring-loaded against the drive roller. The shafts for these two rollers must be parallel to each other. If they are just the slightest bit out, they will steer the web off a lot. The mechanism that supports the idler roller is probably behind the backplate. Look back there carefully for loose screws, broken springs, or anything else that may give an uneven pressure between the two rollers along their entire length. The roller surfaces may be worn out and need replaced.
The alignment of these two roller shafts is so critical that some labelers provide an adjustment for one of them. You have to test any adjustments here by jogging many labels through (with no product present). A small adjustment goes a long way.
Going through all of these steps should have led you to a straight label web path, which in turn should produce consistent label placement on your products. If you are still having problems, call me at 800-331-7140 or email me at jdawson@su-solutions.com, and I’ll help you find the root of your labeler problem.
First, it is important to make sure that the problem is not in the relative alignment between your labeling head and product. Watch the label web while you dispense labels into the air with no product in position. If your labeler dispenses onto a vacuum pad, be careful to give the label time to dispense completely off the web before removing it from the pad. If your label web has suddenly quit wandering, then you need to correct the alignment between your labeling head and product. Do not follow the instructions below, or you will just make matters worse. If with no product, the label web is still walking sideways, then proceed with the instructions below.
Next, let’s get the easy fixes out of the way. Check that your labeler is threaded the way the manufacturer’s instructions show. If your threading is wrong, then all bets are off. If you don’t have the manufacturer’s instructions, email me a photo, and I’ll show you the correct threading. Check to see if any rollers or other parts are wobbling around on your labeler, and if they are, tighten them and retest the machine.
Now, if we’re going to do this, let’s do it right. Line up the label web where you want it. Measure the distance from the labeler backplate to the near edge of the web along its entire path, making adjustments as necessary so the web edge is in a plane parallel to the backplate. Is the web against both the supply and rewind backing disks? If not, then bring them both into the same plane. Typically, they are held in place by either a collar underneath the disk or set screws through the hub outboard of the disk. (It is common for the supply roll disk to get knocked in from repeated slamming of label rolls into it.)
Every surface that the label web contacts must be exactly perpendicular to the backplate. Look at each roller that the label web goes around, and try to move it. Some lower-priced labelers use bushings instead of bearings, and they’ll wear out on the inside. If you can wiggle the rollers on their shafts, you may need to replace the roller assemblies.
Look at the peel edge. Is it worn down unevenly? If so, replace or sharpen it.
Look at the supply and rewind hubs. Are they perpendicular to the backplate? (Are the backing disks in line with the edge of the web?—same thing.) Some supply rolls are mounted to arms that can get knocked out of position. Loosen the mounting screws, line up the supply roll, then retighten the screws. You may find a lot of slop in the holes, so double-check that the support arm is where you want it after you have tightened it. Some rewind shafts move around in a circle. That’s okay if the center of the circle is perpendicular to the backplate.
Finally, look at the drive rollers. These are usually one rubber roller and one metal knurled roller touching each other where the label web goes through. The rubber roller is usually the drive roller that is connected to the motor; the knurled roller is an idler that is spring-loaded against the drive roller. The shafts for these two rollers must be parallel to each other. If they are just the slightest bit out, they will steer the web off a lot. The mechanism that supports the idler roller is probably behind the backplate. Look back there carefully for loose screws, broken springs, or anything else that may give an uneven pressure between the two rollers along their entire length. The roller surfaces may be worn out and need replaced.
The alignment of these two roller shafts is so critical that some labelers provide an adjustment for one of them. You have to test any adjustments here by jogging many labels through (with no product present). A small adjustment goes a long way.
Going through all of these steps should have led you to a straight label web path, which in turn should produce consistent label placement on your products. If you are still having problems, call me at 800-331-7140 or email me at jdawson@su-solutions.com, and I’ll help you find the root of your labeler problem.
Wednesday, October 22, 2008
Reasonable Expectations For Labeler Speed
There are a lot of misunderstandings and misrepresentations about labeler speed—more accurately termed as throughput—and a corresponding number of disappointments after purchase and installation. Many factors influence your ultimate labeler speed, but these are not often considered when specifying or selecting a labeler. Preparing yourself with a complete understanding of all these issues may prevent any false expectations and disappointments with your new investment.
If you are new to labeling and considering a semi-automatic labeler, you can get a pretty good idea of what your actual throughput will be by simulating the process. Gather up a quantity of product in the same form that the operator will see them: a case of 24 bottles, a tote of widgets, a loose pile of bags, or whatever. Carry them to the place where you will set up your labeler, pick up one product, pretend to label it using the actual hand motions required to operate the machine (this part will probably take 1/2 to 3 seconds with a semi-automatic machine—ask your supplier), place it into a "completed" case, tote, or pile, and repeat this process until you have completed at least ten products. How long did this take? Divide the number of products you labeled by the number of minutes it took (or the number of seconds divided by 60), and you will have the number of products you can label in one minute. Multiply by 50, and you'll have the number of products labeled per hour (allowing 10 minutes for micro-breaks like stretching, sneezing, etc.) You may feel silly doing this, but in my opinion, this will give you the most accurate throughput prediction possible. If you choose not to do this and then are disappointed by your actual throughput after buying a labeler, don't go crying to your supplier telling him his machine is too slow.
This exercise should point out several important points:
With all that said, on a semi-automatic machine a person can usually label approximately 15 round bottles per minute, 10 front-back bottles per minute (if the labels alternate on the liner), or 20 flat single-label products per minute while they are actually labeling—not hauling product around.
Fully automatic labelers have the same issues if you are manually loading or unloading them. A labeler may be capable of 120 products per minute, but if you can only load it at 40 ppm, that's the throughput you'll get.
Automatic labelers in line are a different story because you have automatic conveyor feeding via a conveyor. If your labeler is rated for 120 parts per minute and your conveyor is providing parts that fast, then that’s the throughput you’ll get. Until it’s time to change labels. Make sure you allow for 2-5 minutes down time for replenishing the label supply roll.
When looking at labeler throughput, just as important as the motor speed on the labeler is the stability of your products. If you are labeling empty bottles, it may not take much to knock one over and start a domino effect. Even full bottles can have this problem—water bottles are notorious for this. Bottles can easily be knocked over at transfers onto and off of the labeling conveyor, metering wheels, wrap belts, and turns in the conveyor. Make sure you understand how fast you can reliably transport your products before you plan on increasing any speeds.
Print-apply shipping or product ID labels on boxes present a different source of misunderstanding. A print engine may be rated for 12 inches per second (ips) and if your label is 6 inches long, you can print 2 labels per second, or 120 labels per minute…right?
Wrong. First, printing at 12 ips does not give you the same print quality you get at 8 ips. If you are printing bar codes or fine print, you may not be satisfied with the print quality at the fastest setting on your printer; test this. Second, you have to allow time for the tamp pad to cycle out and back between labels. If your applicator can cycle in ¼ second—which is quicker than typical—and you are printing at 8 ips, your 2 labels per second is now down to 1 label per second, or 60 labels per minute.
But wait, there’s more. For you to hit this theoretical throughput, you need to have your previous box out of the way and the next box in place every second. I won’t go into the many sources of variability to this, but trust me, the timing will vary. You need to plan on the maximum barcode scan/data transmit/print-apply cycle time and the minimum distance from the leading edge of one box to the leading edge of the next. You’ll be doing well to label 30 boxes per minute.
There are too many different cases to get more specific than this in this post, but for anyone who wants an independent opinion on your throughput capacity or anyone who needs help optimizing your labeling setup to increase your throughput, feel free to call me at 800-331-7140 or email me at jdawson@su-solutions.com.
If you are new to labeling and considering a semi-automatic labeler, you can get a pretty good idea of what your actual throughput will be by simulating the process. Gather up a quantity of product in the same form that the operator will see them: a case of 24 bottles, a tote of widgets, a loose pile of bags, or whatever. Carry them to the place where you will set up your labeler, pick up one product, pretend to label it using the actual hand motions required to operate the machine (this part will probably take 1/2 to 3 seconds with a semi-automatic machine—ask your supplier), place it into a "completed" case, tote, or pile, and repeat this process until you have completed at least ten products. How long did this take? Divide the number of products you labeled by the number of minutes it took (or the number of seconds divided by 60), and you will have the number of products you can label in one minute. Multiply by 50, and you'll have the number of products labeled per hour (allowing 10 minutes for micro-breaks like stretching, sneezing, etc.) You may feel silly doing this, but in my opinion, this will give you the most accurate throughput prediction possible. If you choose not to do this and then are disappointed by your actual throughput after buying a labeler, don't go crying to your supplier telling him his machine is too slow.
This exercise should point out several important points:
1. Your ultimate throughput may include as much product handling time as actual labeling time.
2. A one-person machine may require two people to operate at full speed--one to label, and one to haul product back and forth, tape up cases, etc. (If so, they can alternate jobs periodically.)
3. You cannot simply take the labeler speed that your supplier tells you, multiply that by the number of minutes in the day, and get a realistic throughput.
4. The people who did not point at you and snicker while you did this are your real friends.
With all that said, on a semi-automatic machine a person can usually label approximately 15 round bottles per minute, 10 front-back bottles per minute (if the labels alternate on the liner), or 20 flat single-label products per minute while they are actually labeling—not hauling product around.
Fully automatic labelers have the same issues if you are manually loading or unloading them. A labeler may be capable of 120 products per minute, but if you can only load it at 40 ppm, that's the throughput you'll get.
Automatic labelers in line are a different story because you have automatic conveyor feeding via a conveyor. If your labeler is rated for 120 parts per minute and your conveyor is providing parts that fast, then that’s the throughput you’ll get. Until it’s time to change labels. Make sure you allow for 2-5 minutes down time for replenishing the label supply roll.
When looking at labeler throughput, just as important as the motor speed on the labeler is the stability of your products. If you are labeling empty bottles, it may not take much to knock one over and start a domino effect. Even full bottles can have this problem—water bottles are notorious for this. Bottles can easily be knocked over at transfers onto and off of the labeling conveyor, metering wheels, wrap belts, and turns in the conveyor. Make sure you understand how fast you can reliably transport your products before you plan on increasing any speeds.
Print-apply shipping or product ID labels on boxes present a different source of misunderstanding. A print engine may be rated for 12 inches per second (ips) and if your label is 6 inches long, you can print 2 labels per second, or 120 labels per minute…right?
Wrong. First, printing at 12 ips does not give you the same print quality you get at 8 ips. If you are printing bar codes or fine print, you may not be satisfied with the print quality at the fastest setting on your printer; test this. Second, you have to allow time for the tamp pad to cycle out and back between labels. If your applicator can cycle in ¼ second—which is quicker than typical—and you are printing at 8 ips, your 2 labels per second is now down to 1 label per second, or 60 labels per minute.
But wait, there’s more. For you to hit this theoretical throughput, you need to have your previous box out of the way and the next box in place every second. I won’t go into the many sources of variability to this, but trust me, the timing will vary. You need to plan on the maximum barcode scan/data transmit/print-apply cycle time and the minimum distance from the leading edge of one box to the leading edge of the next. You’ll be doing well to label 30 boxes per minute.
There are too many different cases to get more specific than this in this post, but for anyone who wants an independent opinion on your throughput capacity or anyone who needs help optimizing your labeling setup to increase your throughput, feel free to call me at 800-331-7140 or email me at jdawson@su-solutions.com.
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