Dispensing Making Money Or Just Making A Mess

Dispensing: Making Money,​ or​ Just Making a​ Mess?
Grease,​ silicone,​ RTV,​ potting compound,​ anti-splatter fluid,​ rust inhibitor,​ marking fluids,​ hot glue .​
All of​ these materials have at​ least one thing in​ common: they’re dispensed on​ a​ daily basis in​ numerous industries across the​ US,​ oftentimes with wildly varying degrees of​ success .​
Our company works with these fluids regularly,​ for a​ wide variety of​ clients .​
In the​ last six years,​ we’ve leaned a​ lot about dispensing systems and how to​ apply them to​ meet the​ needs of​ our customers .​
Here are a​ few key elements to​ consider when facing your next dispensing application.
High Pressure or​ Low?
Time-Pressure vs .​
Positive Displacement
Closing the​ Loop with Flow Meters
High Pressure or​ Low?
The viscosity (usually measured in​ centipoises) of​ our media will determine the​ pressure that it​ takes to​ move it .​
For example,​ dispensing dots of​ Cyanoacrylate,​ (Super Glue) might require no more then 5-10 PSI,​ while flange sealant (RTV) might require 2000 PSI or​ more .​
The exact pressure required doesn’t really matter,​ as​ components are available to​ cover most applications .​
The important thing is​ not to​ mix and match high and low pressure components .​
Sound obvious,​ right? Unfortunately,​ we​ see it​ every day.
Time-Pressure vs .​
Positive Displacement
The accuracy and consistency of​ your particular application will ultimately determine your equipment selection,​ and thereby the​ method of​ dispensing .​
In many applications where absolute consistency is​ not required,​ one of​ the​ simplest methods of​ dispensing is​ time-pressure .​
As the​ name implies,​ time-pressure involves opening a​ valve or​ orifice for a​ given duration to​ dispense a​ fluid at​ a​ given pressure .​
This theory holds that repeatedly opening the​ same valve,​ with the​ same fluid,​ at​ the​ same pressure,​ for the​ same length of​ time will yield similar volumes of​ dispensed fluids .​
Depending on​ the​ particular valve,​ method of​ actuation,​ and repeatability of​ the​ controller or​ PLC,​ this method can actually yield surprisingly repeatable results .​
Applications that involve large volumes of​ material such as​ running a​ bead,​ filling a​ container or​ void,​ or​ spraying glues or​ grease,​ respond very well to​ this method .​
Primary components are the​ valve,​ pressure pump or​ pot,​ and timer,​ oftentimes a​ PLC.
Applications that hinge on​ a​ critical amount of​ adhesive or​ other fluid demand a​ more controlled process .​
Applying dots of​ grease,​ specific volumes of​ glue,​ or​ exact amounts of​ an​ expensive compound are examples of​ where positive displacement (PD) dispensing equipment is​ applicable .​
PD involves filling a​ chamber with a​ media and then using air pressure or​ other force to​ move this media downstream to​ the​ part .​
This chamber and a​ set of​ check valves or​ shut-off plates isolate the​ main supply of​ fluid from the​ part and force the​ fluid to​ be delivered in​ specific packets,​ or​ displacements .​
Main body sizes combined with fine mechanical adjustments allow for tailoring the​ volumes of​ these displacements to​ match the​ needs of​ the​ particular application.
Closing the​ Loop—Flow Meters
If the​ process is​ absolutely critical,​ or​ if​ the​ customer dictates,​ it​ may be necessary to​ verify the​ actual amount of​ fluid dispensed through use of​ a​ flow meter .​
a​ flow meter is​ a​ device that translates fluid flow into an​ electrical output signal .​
This signal is​ typically either pulsed-output or​ analog .​
Some examples of​ flow meters: coriolis,​ positive displacement,​ turbine,​ ultrasonic,​ and doppler .​
Each is​ of​ a​ different design and is​ engineered for a​ particular application .​
Volume (cc’s vs .​
gallons),​ flow (continuous vs .​
intermittent) and viscosity (thick fluids vs .​
thin),​ will all influence the​ type of​ meter that is​ suitable for your particular job.

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