Your experience is quite different than mine. At continues dispensing,I noticed that glue dispense volume increase as the material in the syringe decrease. My machine is using air time pressure pump. This is normal for this kind of pump since air is driving the material to go out of the needle. Obviously, more material in the syringe is harder for the material to be driven out, therefore you need more pressure , the lesser the material the lesser pressure is needed. I did simple DOE by marking my syringe into full, 3/4 fill, half fill and quarter fill. From this run I managed to define the pressure needed for each level and attaining consistent glue size. I presented my data to our QA . We agreed that we should have a parameter window on the pressure set up. I placed level meter near the syringe holder to guide our operator when to adjust the pressure . I also placed pressure table guidelines in front of the machine. You may try this experiment , I am not sure if it will work to your line. By the way I am using 30cc syringe in my line . During the line stoppage , I suggest to purge the material for at least 2 minutes .
Ideal solutions to your problem is , Screen Print( should your process allow) or use a volumetric type Pump.
Hope this would help..
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