28.5 AN EXAMPLE OF AN FMS CELL
28.5.1 Overview
A workcell has been constructed using one light industrial robot, and one NC milling machine. Some automated fixtures are also used.
All of the devices in the workcell are controlled from a single Sun computer. This is an engineering workstation with UNIX. Thus, it is capable of multitasking (running more than one program at once).
Software drivers, interfaces, and applications have been developed, to aid in teaching and demonstration.
The following pages will describe the interfacing in the workcell, as an example of the connection between process control computers and a plant floor computer. A project in development will be discussed for networking Plant Floor (and higher) computers.
28.5.2 Workcell Specifications
Workcell Layout
Devices:
A five axis, articulated robot arm
Communicates over an RS232 serial data line
Interprets a language called RAPL
Uses a pneumatically controlled gripper
The robot controller is 8088 based
3. DYNA-Mite Milling Machine
A 3-axis 2.5D milling machine
Uses a proprietary NC code
Can be run locally, or remotely (over RS232 serial communication lines)
Programs may be executed as they are entered, or when they are completely ordered
Can handle objects of dimensions 6" by 5" by 4"
Can machine plexiglass, wax, aluminum, steel (at low feed rates)
Has a maximum opening of 4 inches
Has a maximum travel of 1 inches
Controlled by a pneumatic solenoid
Pneumatic solenoid controlled from CRS-Plus robot controller
A former undergraduate student project
Activated electronically by the CRS-Plus robot controller
6. Fixtures (for making customized keytags)
These are highly specific to the task being performed
Parts Feeder - Provides a structured environment so that the robot may easily pick up the parts.
Robot Gripper - Designed to provide a reasonable reach into the vice (and parts feeder), and to firmly grasp the workpiece.
Vice Fixture - Designed to hold the workpiece at a level fixed height, and has a location for drill through of the keytag. This part does not effect the travel of the vice.
28.5.3 Operation of The Cell
Developed/Proprietary software in the workcell
2.1.4 - Example of Robot and Vice Software Driver Use
NC code Example (for the Dyna Milling Machine)
An Example of the Dyna Mill Software Drivers
A User interface for Workcell Control
Actual Communication with devices, via a report window
Workcell Programming window
Advantages:
UNIX Based system allows easy control of cell in modes which are both parallel and/or concurrent
A blend of high level computers with low level devices allows for a very modular system, with a variety of computing resources.
Synchronization of processes is very simple.
Allows rapid reconfiguration of the workcell.
This workcell will perform all of the basic CAD/CAM/CIM functions.
The hierarchical design of software tools has simplified the development of new applications.
Disadvantages:
Many Equipment manufacturers have not considered this type of control (they prefer stand alone modes), and thus their machines lack self calibration features, and software is made to be user interactive, and batch, but is not very friendly for software applications.
Requires technical people to operate the equipments.
