Sooner or later, every hot melt application process must deal with unwanted issues. While manufacturers often troubleshoot difficulties on their own, it’s useful to know whether the problem is avoidable—and to learn about the fixes you can try.
This post will list a few of the common problems with hot melt drum unloaders and how to get your machine up and running perfectly again.
As you know, troubleshooting isn’t an exact science. If something is happening with your drum unloader that you can’t figure out, then contact us.
The experts at IMMCO are always glad to help.
1. HOT MELT ON TOP OF PLATEN
The seals are likely damaged or missing if you find hot melt on top of the platen. Replace the platen seals to fix this problem.
It’s also possible for hot melt to pool on top of the platen if the drum unloader’s bleed valve was left open or is stuck open. Give it a check—make sure the bleed valve is closed when pumping hot melt.
2. LOW PUMP RATE
A declining pump rate is one of the most frustrating problems with hot melt drum unloaders. There are several potential causes of a low pump rate. The most likely are:
- Platen isn’t hot enough – it’s either set at too low of a temperature or the heater isn’t working correctly
- Char on the platen, reducing heat flow into the material
- A partially blocked filter (see char problems below)
- A partially blocked hose – possibly a result of char, a failed heating element, or damage to the hose; consider IMMCO’s hose cleaning service
- Low ram pressure
- A leaky seal between the platen and drum
- Worn pump components that must be replaced
If you do not see the results you want, there’s also a chance that cured adhesive is coating the platen. Clean the drum melter to bring the rate back to normal.
Using a lower “Run Temperature” on the platen will minimize cleaning issues. Since Uniflow drum unloaders have nearly 2X the surface area of other designs, they can run at a lower temperature to achieve the same pump rate as competing machines.
3. CHAR IN ADHESIVE
Char is one of the problems with hot melt drum unloaders that happens as the adhesive gets too hot and starts breaking down. Reduce the heat to the platen to keep it from charring the material.
Char will also form if the platen is overly hot when it exits the drum. Uniflow platens switch to a “Standby Temperature” when the platen nears the bottom of the drum. This standby is lower than the “Run Temperature,” so the platen is cooler when it exits, thereby generating less char.
4. HOSE NOT HEATING
There are three possible reasons a hose isn’t heating. First, it could be a failed relay that needs replacing. Second, the heating wire can break—in this case, the hose must be replaced. Third, the RTD (resistance temperature detector) can fail.
Uniflow hoses come with a backup RTD, so if one fails, with the rotation of a switch, you can change to the backup RTD and save thousands of dollars.
5. HOSE OVERHEATING
Check the solid state relay (SSR) when a hose is overheating. The SSR will have to be replaced if it’s frozen.
6. MATERIAL NOT COMING OUT OF BLEED VALVE
There are many reasons that adhesive may not come out of the bleed valve:
- Ram down pressure is too low
- Uniflow offers a high-pressure ram option that reduces bleed time on high-viscosity materials.
- Platen is not hot enough
- Platen is clogged with cured adhesive
- Bleed valve is not opening
7. TOO MUCH MATERIAL LEFT IN THE DRUM
Excess material left in the drum is a design issue. It is common for competing drum unloaders to waste 20 – 40 pounds of adhesive. Due to our unique platen design, a Uniflow typically only leaves 2 lbs of material in the drum.
If less waste is a priority for you, then take a close look at Uniflow’s impressive drum-emptying capability.
8. PLATEN WILL NOT HEAT OR IS OVERHEATING
This heating issue is likely the result of a faulty or frozen solid state relay (SSR); replace it.
9. PUMP IS RUNNING, BUT NO MATERIAL IS COMING OUT
When everything seems to be functioning, but no material is pumping, check the key as it may have sheared and need replacing. If a sheared key is not the issue, then the pump may be running backward. Check the motor’s polarity and reverse if required.
10. PUMP WILL NOT START
Pumps don’t start until the adhesive is ready to flow. Likely, one or more temperature zones (hose, platen, etc.) have not reached the operating temperature.
11. PLATEN IS GOING DOWN CROOKED
A platen that travels cockeyed is no good. Ensure there are no failed heaters causing the platen to heat unevenly. Barring that, it may be that the hydraulic cylinder is leaking and needs rebuilding.
A platen going down crooked could also be an adhesive issue if there’s a large air pocket in the drum’s material.
12. RAM WILL NOT GO DOWN/UP
There are a few problems with hot melt drum unloaders that prevent the ram from moving.
To troubleshoot the ram, check that there’s air pressure, that the down solenoid hasn’t failed, and that the temperature zones are heated above the low alarm setting.
13. MOTOR IS OVERHEATING
Motors overheat when running too slow. To fix this speed issue, try a different gear reducer so the motor can run faster and ensure there’s no restriction in the material flow.
14. CAVITATION
If the material in your pump is cavitating, the pump will make a thumping noise. Reduce the speed immediately or else it will experience a catastrophic failure. Reasons that lead to cavitation include:
- Not enough ram force
- The material requires more heat
- Pump speed exceeds the material melt rate
AVOID PROBLEMS BY BUYING THE RIGHT MACHINE
At IMMCO, we manufacture hot melt dispensing equipment for a wide range of industries worldwide. Our Uniflow drum unloaders are known for their stellar performance, ease of maintenance, and persistent reliability. Click to get a quote.
