Continuing our blog series on getting a better glue pattern on your Gartech Glue System, part 2, we’re covering the technique for checking a glue wheel shaft for bearing runout. When a pattern appears uneven along the length of the tab, it might mean there’s bearing failure, or runout. Runout lets the wheel drift but can be easily checked and repaired at the plant level or during a routine service call.
These techniques are valuable on any of our glue systems, regardless of how worn it’s become. Every glue system is built to last, repairable, and interchangeable with new and old parts.
Let’s Begin
Remove the glue shoes and glue wheels from the glue unit and wipe down the surface of the glue shaft and mounting plate. The cleaner the surfaces of the glue wheel shaft and glue shoe mounting plate, the more accurate your reading will be.
NOTE: When mounting the shoe, it is important that its mounting bolt also be the correct length. Too long of a bolt pushes against the surface of the glue unit housing. This causes bowing in the glue shoe mounting plate, leading to improper setting of the glue shoe, premature wear, gluing issues and eventual failure of the mounting plate. Measure the height of the glue shoe from the mounting side to the face where the mounting bolt goes through. Add 1/4″ to that measurement, and that’s the length of bolt you’ll need. Ex: A shoe that measures 3″ in height requires a mounting bolt that is 3-1/4″ long.
Checking Bearing Runout on Upper Glue Shaft & Housing
One way we check for bearing runout is by using a dial indicator. If you don’t have much experience with this tool or if it’s been a while, this WikiHow article provides a step-by-step understanding of How to Read a Dial Indicator.
Since we’re testing bearings in the mechanical glue unit on-site, we don’t want to take apart more components than necessary. By removing the glue wheels and glue shoes, we’ve removed enough pieces to obtain an accurate reading. You can check the glue wheel for runout this way, too, but here we’re focusing on the glue wheel shaft and bearings.
We’ll begin by attaching the GAR-GU-2067I Magnetic Indicator Mount to the same adjustment nut that holds the glue shoe to the mounting plate; using a 7/32” Allen wrench and 3/8-16 x 1” flat head cap screw. If you don’t have the magnetic indicator mount, let us know. We’ll send it to for the price of shipping. Or, during your next service call, you might coax one out of Service Tech Mike in exchange for a cup of coffee. It doesn’t even have to be the good stuff. He just likes coffee. While he’s on-site, he can show you how to use an indicator if you’re a visual learner.
Quick tip: On a flat head cap screw (bolt), the overall length includes the head. On a socket head cap screw (bolt), the length excludes the head of the bolt. The height of the head is always the same as the diameter of the thread when dealing with standard thread sizes. So, a 3/8-16 bolt has a 3/8″ tall head. Its head diameter is always the thread diameter multiplied by 1.5, or 150%.
The head of the bolt should not be higher than the surface of the GAR-GU-2067I magnetic indicator mount. This causes misalignment where we want the indicator to have a steady connection, so be sure it’s threaded all the way into position.
An indicator on a magnetic base can now be affixed to the GAR-GU-2067I magnetic indicator mount and positioned to check the glue shaft for runout. The magnet in the base will connect with the mount you’ve installed.
Prior to testing, ensure the shaft has been wiped down and is free of any burrs or scarring in the area being checked. Flaws and build-up can provide a misreading on the indicator. We’re looking for the most accurate reading possible, so you aren’t replacing good parts.
Rotate the shaft clockwise and counterclockwise, allowing the indicator to read the shaft without striking the glue shaft key.
NOTE: Acceptable runout should not exceed .0025” (provided the indicator is not reading a scratched, scarred or pitted surface).
If you see more runout than this, you might ask a colleague to double-check you. If it’s still present, consider replacing the C0-fit bearings inside the housing first. As they wear down, their fit decreases and loosens the stability on the glue wheel shaft. It’s a lot like going a month without exercising and feeling a little soft in the middle. New bearings can often takeout the runout in the glue wheel shaft. Sadly, no one has developed a similar device for exercising.
For a complete breakdown of the parts and how they fit together, refer to this blog entry.
During our final inspection of these assemblies, we allow .0015″ runout in-house. Once the glue system runs a while, it isn’t uncommon for the bearings to warm up and give a heavier reading.
Checking Bearing Runout on Lower Glue Shaft & Arm
Because both the lower glue wheel and lower glue shoe move, we have to use a different method for inspecting the bearings. The two components pivot off the same fixed point, meaning they move as one. This lets you run different thicknesses of box, and also lets the wheels drop out of contact when not performing a glue cycle.
NOTE: The lower arm pivots up and down, meaning the lower glue shoe mounting plate and lower glue wheel shaft pivot too. When performing this operation, please keep fingers away from the pocket where the lower arm mounts into the mechanical glue unit. This is a pinch point but one that can be avoided 100% if you’re paying attention, respectful of the equipment in the plant, and mindful of your plant’s safety policies. The Gartech Glue System should never be under power of air or electric when performing this operation, and there’s no reason for fingers to be in the pinch-point area.
You can repeat the same steps for checking the upper glue shaft, using the Magnetic Indicator Mount that we used on the upper glue wheel shaft. You can also use a C-clamp and a piece of magnetic material, as shown above. This requires removing the glue shoe mounting plate and adjustment nut.
Why the extra pieces? Aluminum and stainless steel don’t have the carbon content necessary for a magnet to hold. Carbon causes rust, which is the last thing we want on a system that pipes glue and water all day. Any parts on the mechanical glue unit made from carbon steel are treated with a rust preventative to delay this process.
If you’re using the bolt-on GAR-GU-2067I Magnetic Indicator Mount, connect it to the adjustment nut that holds the glue shoe to the mounting plate by using a 7/32” Allen wrench and 3/8-16 x 1” flat head cap screw. Remember, the head of the bolt should not be higher than the surface of the GAR-GU-2067I magnetic indicator mount.
Go ahead and mount the indicator and its magnetic base in a position to check the lower glue shaft for runout. The lower arm that holds the glue shoe mounting plate and glue wheel shaft moves in unison.
Ready? We’re looking for the same problems and info here as were checked on the upper glue wheel shaft.
Prior to testing, ensure the shaft has been wiped down and is free of any burrs or scarring in the area being checked.
Rotate the shaft clockwise and counterclockwise, allowing the indicator to read the shaft without striking the glue shaft key.
NOTE: Acceptable runout should not exceed .0025” (provided the indicator is not reading a scratched, scarred or pitted surface).
If you need to replace parts, we’ve included layouts of the mechanical system in this blog entry.
Alternate Checking Methods
If your indicator is long enough, you can use the sheet guide angle bracket as a base for checking the upper glue shaft, too. The angle bracket that holds the (trombone) sheet guide is already magnetic since it’s carbon-based material. This means the indicator’s base will hold to it without installing another part. You’ll want to remove the sheet guide tube, though.
Do not use the angle bracket of the sheet guide to check the lower shaft as this can cause a false reading due to the movement of the lower arm assembly.
Cleaning the Glue Shoe Mounting Plate
Once all inspection equipment has been removed, working surfaces have been cleaned and, if necessary, the glue shoe mounting plates have been reinstalled, it is important to ensure a clean mounting surface for the glue shoe.
The most important area of the glue shoe mounting plate to keep clean have been indicated with white markers in the above photo. The entire surface of these (4) sides must be kept clean and free of burrs to ensure a tight, flat fit. This includes the corner where the surfaces meet.
Cleaning the Glue Shoe Mounting Area
Just as the glue shoe mounting plate must be kept clean, it’s important that the same area of the glue shoe be cleaned. This is the area that locates the shoe onto the mounting plate and allows it to sit square to the face of the glue wheel.
Gartech does not recommend using a wire brush, wire wheel or metal scrapers (including screwdrivers and hammers) to clean a shoe. If a shoe is not being used, it can be soaked in vinegar to remove excess dried glue. Wiping the surface down and performing general preventative maintenance will also help prolong the life of the shoe in addition to sending worn shoes to Gartech for redressing.
Shoe-to-Wheel Squareness
After reinstalling the glue wheel, glue shoe and, if necessary, the glue shoe mounting plate, it is important to properly reset the shoe and wheel.
Once the surfaces have been cleaned, reinstall the glue shoe to the glue shoe mounting plate and hand-tighten its mounting bolt into the adjustment nut. (This is the same nut we used to mount the magnetic indicator base.)
Slide the shoe against the wheel and, using a 5/16” Allen wrench, tighten the 3/8-16 socket head cap screw while using hand-pressure to keep the shoe against the wheel.
Using the 5/16” Allen wrench, break loose the 3/8-16 socket head cap screw and back away enough to use feeler gauge to properly set the squareness, checking front and back corners of the shoe (indicated in the photo below by red circles—fourth corner obstructed in view) at the same time.
These points indicate where you’ll see uneven wear caused by runout, buildup, or other damage. If you have extra gap at one of these points, even after replacing bearings, you might consider sending it in for a glue shoe redress. If the runout presents in the wheel, we can redress that too.
We covered this topic in an earlier entry too. The proper gap between the wheel and the shoe, the right glue formula, and a correctly-set metering plate lets you achieve a pattern that looks like those in the photos below:
Every Gartech Glue Wheel can achieve this type of pattern, from a 3/16″ to a 5″ glue wheel. We can guarantee that because we’ve proven it in-house and on-site. Before we wrap up, this is a good place to remind you of the importance of running the appropriate glue formula. One reason we’re able to achieve clean, reliable patterns is because we run and recommend the correct glue. Without that, you’re driving a great car on bad fuel. Read our blog entry on glue formulas.