Semi-automatic Dispensers

One of the most commonly used semi-automatic dispense systems is the pressuretime method and this is extensively used for a wide range of production engineering applications. The adhesive is stored in a pressurised vessel and pressure is applied to force the adhesive to the dispensing tip. There are two distinct variations of the pressure-time method  

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Fig. 7.56 A portable semi-automatic dispenser (courtesy Eucid Chemicals, USA).

The use of the mechanical apparatus with its semi-automatic dispensing of indicator and chloroform greatly reduces exposure of the analyst to toxic chloroform vapour, and the use of mechanical stirring also reduces operator fatigue, which in turn makes for better consistency in the results. 

Fiigher viscosity products are typically packaged in cartridges to facilitate dispensing with hand guns and for semi-automatic dispense systems, pressure is applied to the... 

Fig. 7.52 Manual, semi-automatic and automatic control units for dispensing admixtures (courtesy Euclid Chemicals, USA).

Acrylic adhesives can be formulated to have low, controllable viscosity, which makes possible rapid, precise dispensing to parts to be bonded. In addition, rapid curing or setting, without long periods in ovens, makes these adhesives particularly useM for the assembly of various components in automatic or semi-automatic production lines (see Engineering design with adhesives). 

A dispenser is a semi-automatic dosing and filling apparatus, allowing fixed volume dosing by hand. The apparatus consists of a glass cylinder, in which a piston is mounted. 

The fixing reagents are added with twin-automatic or semi-automatic reagent dispensers set to 1 0.01 mL dispensing volumes. Preferably, dispensers should be used that do not require filling via the dispenser nozzle. A suitable double-reagent dispenser is shown in Fig. 4-3. 

The type of application and workplace conditions, such as production rate, dispense quantity and cure speed will determine whether manual, semi-automatic or fully automatic dispensers will be required. 

The cycle time has an important bearing on the investment required to automate the system and the number of operators or workstations that may be necessary. Whether manual, semi-automatic or automatic, the dispensing equipment system specified will depend on the type of application and workplace conditions, such as dispense rate, parts per hour, operator availability and materials handling. Adhesive dispense systems are available for most production lines varying from bench-top applicators to fully automated robotic units with dispense times of <50 ms. 

Semi-automatic units reqnire the control of an operator but use a mechanical, pneumatic or electrical system for dispensing and hence allow a controlled application volume. Semi-automatic emits may also include other features that facilitate adhesive handling and dispensing. 

Most manufacturers of dissolution testing devices offer semi-automated systems that can perform sampling, filtration, and UV reading or data collection. These systems automate only a single test at a time. Fully automated systems typically automate entire processes including media preparation, media dispensing, tablet or capsule drop, sample removal, filtration, sample collection or analysis (via direct connection to spectrophotometers or HPLCs), and wash cycles. A fully automated system allows automatic performance of a series of tests to fully utilize unused night and weekend instrument availability. 

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