Various types of precision dispensing systems
In production processes, user may require to dispense various kind of fluids.
Electronics OEM may dispense two-part polyurethane potting material onto PCB for resistance to shock, vibration and moisture. Aviation component manufacturers dispense fixed amount of thermal conductive adhesive onto heat sinks. Adhesives are being dispensed in many automobile parts assembly facilities. Toys manufacturers dispense optically transparent adhesive to “form” toys’ eyes. Beverages manufacturers dispense large but relatively fixed amount of drinks into bottles. Controlled amount fluid dispensing processes are everywhere.
In this article, we will focus on discussing industrial fluid dispensing processes. A quick summary for general precision dispensing systems are listed:
1. Manual dispensing of 1-part adhesives & industrial fluids
Bottles, barrels, cartridges are available for manual dispensing. Bottles are squeezed by operator for desired dispensed amount. Most of the time, they can be fit with dispensing tips to reduce orifice size. Barrels and cartridges can be dispensed manually using manual dispensing gun too.
Flexible, very low initial investment cost
Repeatability of dispensing results since it depends heavily on the operator.
2. Pneumatic dispensing systems for 1-part adhesives & industrial fluids
For controlled amount of dispensing. Pneumatic dispensing system is a lower cost option yet viable to most of the production processes.
Industrial fluids are stored in standard cartridges or barrels for easy dispensed with used of standard fluid dispensing systems. For process where large amount of fluid is consumed, canisters or tanks are pressurized and fed the liquid into separate liquid line which terminated by precision dispensing valve. Normally, pinch tube valve, needle valve, diaphragm valve are installed, the valve selection criteria are very much depends on liquid flow rate, fluid viscosity and other process limitations.
Reproducible dispensing result. Option to upgrade to automated processes without much hassle.
Not suitable for pasty material dispensing application. It is not a good choice for tight tolerance dispensing application.
3. Manual dispensing of 2-part adhesives
2-part adhesive consists of components A and B, which are usually supplied as one set in two separate containers. The two components are removed from drums by spatula or trowel and weighed in a container with weight ratio that recommended by manufacturer. It is crucial to mix 2-part adhesive homogenously so that its specified cured properties can be assured.
No investment required for systems
Time consuming upfront weighing and mixing process, contribution of human factor may alter performance of adhesive
4. Manual dispensing of 2-part adhesives (with tools)
2-part adhesives can be dispensed with dual cartridge gun if there are delivered in standard 50ml, 200ml or 400ml dual cartridge. Mechanical or pneumatic dual cartridge dispenser has two individual rods that extend into the chamber of cartridge linearly when being triggered. Fixed amount of A and B materials meet at the outlet where static mixer are attached for final stage of adhesive mixing.
Long static mixer are usually picked for low viscosity 2-part adhesive dispensing so that through mixing can be guaranteed. In the event the work is finished or during long break time, it is advisable to leave static mixer in position as the adhesive contained in it will harden and blocked the cartridge. All hardened adhesive must be removed from the outlet opening of cartridge before the next job started.
Process reliability yet low initial investment cost
Not suitable for large dispense volume process due to limited cartridge size
This article covers fundamental part of dispensing methods that are seen in typical industrial applications. There are more sophisticated technology such as robotic system, automated two-component adhesive mixing system, plasma cleaning technology, etc, which we did not present here.