Gear pump
Working principle:
The operation is mainly based on the principle of increasing and decreasing the volume, corresponding to the increase and decrease in pressure between the suction and repulsion zones.
There is an expanded volume in the inlet side of the pump, it allows the material to flow into the chamber. When 2 gears rotate, the glue will be taken from one side to the other side. As the gear teeth on the discharge side of the pump are interlocked, the volume decreases and the fluid is pushed out under pressure.
Disadvantage:
1) When the pressure of one side is big, the glue would be pushed backward. Therefore, it is not suitable for large flows, or frequent start and stop
2) 2K glue ratio can not be changed, for example, if your ratio is 10:1, you cannot change it to 5:1, 4:1. The change will affect the pressure loss of the pump, which leads to the incorrect pump ratio
3) Controllable variable is limited because the metering pump controls the amount of material through controlling the rotating times
4) Only suitable for the low viscosity glue without stuff or pigment
– The stuff in the glue may damage the gears in the mixing process
– Some glue suppliers may add silica sand, aluminum oxide, silica powder, in order to reduce cost, increase hardness, or increase heat conduction. If density is around 1g/cm³, it is not suitable to use this pump
– High cost for maintenance as this type of pump needs to be replaced once it is worn out to ensure the accuracy
– Suitable for only low accuracy demand on gluing dispensing
Advantage:
– The cost is cheap
Recommended materials:
– Only suitable for transparent glue without stuff
– Suitable for low viscosity glue, low density
– Suitable for non change glue mixing ratio, or change in small range (1:1 to 3:1)
– Suitable for non-large flow gluing
Screw pump
Working principle:
When the motor runs, it will drive the screw bar rotating in a sealed chamber. Vacuum is then created in the inlet section as a result of the movement of these screws. Because of the vacuum, fluid is pumped into the pump via the inlet valve. As the fluid enters the pump, it also moves with the rotation of the screw due to the difference of pressure. Finally, the material is discharged from the outlet valve and moved to the desired location.
Disadvantage:
(1) More easy to be wear than gear pump (when the screw rotate and push, there is friction between glue and screw)
(2) Once the screw bar wears out, it is hard to repair
Advantage:
(1) High accuracy
(2) Suitable for big flow gluing
Recommended materials:
– Suitable for additive and density glue
– Suitable for non change glue mixing ratio, or change in small range
Duplex Cylinder plunger pump
Working principle:
The pushing bar creates reciprocating motion inside the cylinder. A pressure difference between the external fluid pressure and the cylinder’s internal fluid pressure can suck fluid into the chamber. Then the plunger moves upward, the internal fluid pressure becomes higher and fluid is delivered into the delivery tank or other desired location.
Advantage:
(1) High accuracy, and the mix ratio can be changed on a larger scale
(2) Low-maintenance design as the bar doesn’t touch the tank surface, even if there is stuff in the glue, no wearing caused
(3) Unique design of anti-back flow device, even if one side pressure is too much, it won’t back flow
(4) Suitable for frequent start and stop dispensing
(5) Pump with an anti-crystallization system that is feasible for Polyurethane adhesives
Disadvantage:
(1) Cost is more higher
(2) Construction is more complex
(3) Size is much bigger and more heavy than the gear pump and screw pump
Recommended materials:
– Can be used with a variety of glues
Single Piston Pump
Working principle:
The working principle is similar to the Duplex Cylinder plunger pump. Through the plunger move forth and back, the pump sucks and pushes out the glue. To control the glue volume by changing the seal room volume.
Disadvantages:
– As there is only a single piston pump, non-continually gluing, long stop time, which affects gluing speed (When the piston pull back, pump reversing, dosing will stop)
Recommended materials:
– Can be used with a variety of glues
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