The stability of K polyurethane cup spraying cannot only look at the "correct A/B ratio" displayed on the controller, nor can the reaction be fully guaranteed by simply lengthening the static mixer.What is really needed is a continuous dynamic control chain: The ratio specified in the formula is the instantaneous ratio of the → A/B → independent metering accuracy of the mixer inlet. The cumulative ratio within a → certain time window is the mixing uniformity and residence time distribution of the → static mixer→. The viscosity, flow rate and atomized → wet film leveling, flash drying, curing and final performance of the mixing material age → rotating cup end in the pipeline after the mixer. Four boundaries must be defined first: Static mixers do not correct mismatches. It can only further segment, reorganize and homogenize the A and B components that have already entered the mixer.If the upstream metering ratio is wrong, the better the mixing, the more evenly the error ratio will be distributed. The cumulative ratio is correct, which does not mean that the instantaneous ratio is stable. Start-stop, color change, flow switching, valve hysteresis, pump pulsation, or short-term shortage may still spray local partial A or partial B material to the workpiece when the total average seems to be qualified. Nominal residence time is not the actual reaction time of each piece of material. Static mixers and downstream tubing have dwell time distributions, channel differences, and dead volumes; materials continue to react during shutdown. Dwell time is in the process window. Too short may result in inadequate mixing; too long may result in increased viscosity of the mixture, increased pressure drop, deterioration of atomization, increased gumming and cleaning loads.Can't take “longer” straight
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