Over the next few entries, we’re going to troubleshoot some common problems when it comes to getting a proper, clean glue pattern. Gartech founder Jim Garrett’s ideal for the glue wheel is that, when set properly, it transfers the precise pattern of the wheel onto the box.
To achieve this, here are a few things we look for:
- Clean, even lines from properly metered glue.
- No overflow of glue from the shoe.
- “Shiny” sides on the wheel from a proper gap between the glue wheel and glue shoes.
The Ideal Glue Pattern
When the right glue formula is metered properly and the gap between the wheel and the shoe are set, you will get a glue wheel pattern that looks like this:
The question is, “Why doesn’t your glue pattern look like these?”
Here are the most common reasons:
We’re often told that operators or maintenance aren’t given the time for housekeeping or upkeep for any number of reasons. We aren’t judging. We will say this: Poor housekeeping contributes to multiple failures, including messy glue patterns, wasted glue, sloppy work sites, premature damage to parts, and bad boxes. We’ve seen it in your company’s plants and in your competition’s plants. Yes, this line of work is dusty, it’s sticky, it isn’t ideal. Those are valid excuses.
When it comes to correcting glue pattern quality, there are small portions of the glue system that must be maintained and kept clean.
The glue shoe mounting plate is the most common origin point or problem area. Glue build-up on this part causes the glue shoe to mount out of parallel, out of square, or both. The problem this build-up causes worsens the further away it gets from the source. So, 1/32″ of build-up on the mounting plate might create 3/32″ extra gap–or more–between one side of the glue shoe and the glue wheel. Now parts are out of alignment, glue drips from one side, and the pattern is uneven. The grid below shows how the problem worsens.
This problem can be corrected with basic housekeeping. Clean the mounting plate and inspect the glue shoe for uneven wear. In most cases, we can redress the glue shoe and return it to spec. Ignore the problem too long and you’ll either be purchasing a new shoe or, depending on your plant’s budget, stuck trying to make a worn shoe perform like a new one.
Though we manufacture all of our parts with close tolerance, the holding power of a bolt “allows” for parts to be forced into fitting. The problem? They aren’t fitting properly. The moment the glue system starts running with misaligned parts, the part geometry starts changing.
The glue shaft and key are other areas that affect the fit and performance of the glue wheel. Taking the time to clean these areas reduces downtime in the long-run, as well as preserving part life. We talk about that in our next section.
Moving parts wear out. It’s a factor of life, our bodies, and our world. If that weren’t the case, we’d have 90-year-old linebackers and everyone would be driving 30-year-old vehicles with all its original parts. Now we add the properties of glue and the abrasiveness of paper dust to the mix. Running three shifts? Even more wear. It’s expected, no matter how well you maintain equipment.
If the glue wheel looks like it’s running unevenly, inspect the bearings using an indicator. We detail this more in Part 2 of the series.
In the same way that glue build-up impacts the shoe, bearing failure impacts the glue wheel. This is something we check on every service call, in fact. After 25 years of manufacturing glue wheels, years of researching and testing bearings, repeat inspections of every part we manufacture, and even testing whole systems in-house, we’ve seen the damage that bearing failure causes. The tolerance that we allow ourselves in-house is stricter than the tolerance we recommend for running purposes. If an assembly doesn’t meet those tolerances, we scrap it and start over.
Uneven grooving on the metering plate? Wash cycles and housekeeping aren’t being performed as recommended. This includes sharp edges, knicks and burrs on the glue wheel as well as build-up. All of these things act like a pebble against the shoe. With every revolution of the wheel, it’s striking and wearing, all the while building up more with new glue. A brush with nylon bristles–not wire, not copper, not steel–should be used to scrub the wheel. It might be necessary to soak the wheel first. And, again, if the wear is extensive, a redress of the shoe might be necessary. A worn or damaged wheel can be sent in for redress, too.
This starts small, but so did the Grand Canyon. Someone decides they aren’t changing their glue formula. They don’t need to use cold water. They don’t want to isolate a cable. Any pump should work. They don’t have time to run wash cycles or redress parts. Nothing wrong with independence but an irresponsible mindset sets up everyone around them for failure.
Someone replaces a bolt with one that’s a little longer: this creates drag, misalignment, and premature wear along with part failure and poor functionality.
Someone buys an off-brand belt, an unsealed bearing, or starts having a local shop make their parts. Soon, the loose tolerances or wrong ratings don’t withstand running speeds or performance needs. There’s nothing wrong with local shops. Jim’s business began as a local machine shop able to make repairs that got a box plant back up and running. We don’t forget those roots and we appreciate that not all plants receive the same budgets. It becomes difficult to guarantee or warranty a glue system once our parts are replaced.
Let’s take ego out of this equation, as we aren’t faulting operator’s for getting their job done. If anything, we want to make their job better. This is why we have specs for what works best and how we recommend the system being used. The majority of “human error” problems we encounter stem from a determined operator who needs to get an order out but makes choices that create problems.
A metering plate shouldn’t extend past the surface of the glue shoe or have a .020″ gap between the wheel and the shoe. In these cases, either a part is worn or the wrong glue is on the wheel. Removing bolts from the glue shoe mounting plate or leaving the glue shoe or glue wheel loose also creates wear and safety issues. It becomes a tug-of-war between shifts, crews, and individuals. We’ve gone into plants suffering these problems, made the corrections, offered additional training, and watched the system perform. Weeks, days, even hours, later–the same problems come back.
If it’s an issue of lacking training or experience, we offer re-training services as well as user manuals. We’ll also schedule service contracts in the event that a plant doesn’t have time for upkeep. What we want to avoid, above all, are unsafe practices or adjustments that work against the function of the Gartech Glue System.
If you’re seeing glue smearing on the tab of the box, it’s an indication that the glue wheels are set too closely for the board thickness. Adjust the nip and this problem will go away. This will also help eliminate transfer of glue to the opposite wheel if you’re seeing any.
We’ll continue this series later in the week, including covering some of the common problems with glue.