LIQUID DISPENSER (Amended 10/3/02)

Overview:

Many liquid handling applications, ranging from the bottling of beverages to the processing of chemicals in a laboratory, require a system for the repetitive dispensing of a prescribed volume of liquid into each container in a sequence of containers. This liquid dispensing process serves as the model for the Junior Design project.

Project Scope:

The client, comprising the EGR 3380 course instructors, requests proposals for the design of a liquid dispensing system with the characteristics described below in the User Need Statement. Engineering design teams, comprising EGR 3380 students, shall prepare and submit such design proposals. A proposal will consist of a design report (including appropriate descriptions, drawings, schematics, and analysis) along with the demonstration of a hardware prototype. Intermediate milestone reports and hardware demonstrations will be required as given in the course schedule.

User Need Statement:

The liquid dispenser system should:

• Function: Dispense 20 ± 2-ml of water into each of ten plastic containers without spillage.
• Spillage: Any spillage outside of catch pan will result in disqualification. Unacceptable spillage inside of catch pan is defined as more than 10-ml during one ten-container cycle.
• Water Level: The water is to be drawn from a reservoir, the initial level of which must be below the bottom surface of the containers to be filled. (See illustration.)

• Sequence: The ten containers are to be filled sequentially from the same dispensing spout/nozzle (i.e., water cannot be dispensed through multiple nozzles, either simultaneously or sequentially.)
• Operation: The system operation shall require one electrical switching action for initiation and one electrical switching action for termination. No other operator intervention is permissible while the ten containers are being filled. Exception: The system must have a minimum of four (4) containers in process, or ‘loaded’, at all times. If less than ten containers are initially loaded, an operator may manually insert empty containers and/or remove filled containers, provided an inserted container is not the next one to be filled, or a removed container is not the one most recently filled. Such insertion and removal should in no way affect the operation of the system.
• Setup: The system shall be capable of being setup/assembled and readied for operation within five minutes of the beginning of a testing trial.
• Operation Time: The process of filling the ten containers should be completed within two minutes.
• Reset: The system shall be capable of being reset and initiated for a second trial within one minute of the end of the first trial.
• Size: The system, during operation, shall fit within a cubic space 24 inches on a side. Exception: Power cords and/or other wiring may extend outside the cube as negotiated with the client.
• Safety:
• All parts of the system holding or transporting water must operate over or within a plastic pan or tray capable of containing the total volume of water in the system in the event of a spill. This requirement applies to all stages in the design, development, testing, and demonstration of the system in order to prevent spillage from damaging tabletops and flooring, or from creating dangerous footing conditions in the laboratories, workshops, and classrooms.
• All electrical power – particularly if 120 VAC is used – must be properly grounded, properly insulated from water, and otherwise adhere to applicable electrical codes. Negligence and/or indifference in meeting these requirements, or in reporting violations thereof, are grounds for failure of this course.
• The system in operation shall not present an undue hazard to persons or property. Appropriate safeguards and/or labeling should be in place (for example, for electrical components, pinch points, rotating parts, etc.).
• All fabrication required for the development of the system will be conducted with proper adherence to the general safety guidelines in place for the Engineering Department laboratories and workshops. In addition, specific safety measures will be followed for each tool used in the fabrication process. Negligence and/or indifference in meeting these requirements, or in reporting violations thereof, are grounds for failure of this course.