Product category:
Metering pumps and dosing systems
News Release from: Intertronics | Subject: Pneumatic dispensing
Edited by the Processingtalk Editorial
Team on 28 January 2008
Improving dispensing using pneumatic
valves
The simple pneumatic dispensing machine is generally low cost and almost ubiquitous, dispensing single part adhesives, coatings, sealants and inks
The pneumatics improve the application of materials like single part adhesives, coatings, sealants and inks, by enhancing a manual process to one which is more controlled and repeatable, while health and safety benefits include less mess, less exposure to potentially hazardous chemicals and fewer RSI issues These systems work by filling an industrial syringe or barrel with the liquid material
This article was originally published on Processingtalk on 24 Feb 2006 at 8.00am (UK)
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Pulses of air then push the liquid out of the other end, usually through a dispensing needle or tip.
The quantity dispensed can be varied by the size of the needle orifice (from as small as 0.15mm), the pressure applied and the time of the air pulse triggered by footswitch, finger switch or automation.
They may be hand-held or mounted on positioning robots or rotary tables.
Further reading
Clean precision in volatile dispensing situations
Intertronics have solved the problems of dispensing many materials with the VD510 Diaphragm Valve, designed for precise flow control of low to medium viscosity materials (under 10,000 cps)
Mixing and degassing in one process!
Mixing and degassing of materials such as precious metal pastes or optical adhesives is generally a two-part process taking a long time - but adhesives specialists Intertronics have changed all that
Less than 1% variance is often easily achievable, and 0.1% not uncommon.
Digital timers further improve accuracy.
For industrial liquid dispensing, pneumatically controlled valves are robust, accurate, can be cycled quickly and in many cases can be implemented at low cost with the following benefits:.
1) Increased accuracy - critical applications in areas such as microelectronics or medical devices requiring higher levels of accuracy and repeatability, validation and fine tolerances.
2) Challenging materials can be handled, e.g Cyanoacrylate adhesives (very low viscosity) and thermally conductive RTV silicone adhesives (very high viscosity).
3) Volume - the largest dispensing barrels are typically 55ml in volume: For higher daily volumes, some form of larger reservoir is needed.
4) Automation - a valve can be fixtured to a robot and provide better stability than a dispensing barrel.
Liquid is fed through a hose, to the valve actuated by a pulse of air pressure.
The amount of material dispensed can be varied by the size of the needle orifice, the pressure applied to the material reservoir and the time of the air pulse determined by a pneumatic dispensing controller.
The exception to this type of operation would be a positive displacement valve, such as a screw valve, where precise micro-deposits can be controlled by the rotation of an auger screw.
One of the main advantages of dispensing valves is that they snap closed, with a positive cut off of material flow, either by spring or reciprocal air pulse.
Some designs inherently "suck-back" the material, reducing the "string" effect.
There are quite a few options when it comes to choosing a dispensing valve, and a plethora of materials which might be dispensed through them.
Finding the optimal match is quite complicated - material rheology and reactivity needs to be understood, valve capability identified and proven, and the final outcome defined.
Further information regarding Intertronics products can be found on their website.
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