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ME-542 Manufacturing with Non-metallic MaterialsVISCOMETER (Web Tutorial)
Introduction:
The Facility of Applied Manufacturing Enterprise (FAME) in San Diego State University serves as a training ground for engineering students. It is a practice-oriented program in which technology, business, and scholarship can be integrated. For example, the program provides hands-on experience about the application of polymeric materials and molding processes through the operations of machinery. The manufacturing machines available are widely used in industry such as the viscometer that is being presented on this webpage. Viscometer is a machine to test fluidity of a thermoplastic material that is being used for industrial processes. Extrusion barrel is filled with melted plastic materials, and they are being push down by a metal rod to the orifice, which is located at the end of the barrel. The force and speed of the rod, and the diameter and length of the orifice are some of the parameters to calculate the viscosity. Sketch and Diagram.
Purpose:
This is a tutorial for the viscometer used in FAME located in the facility of SDSU's Engineering Department. It provides the student with a method needed to determine the viscosity of a plastic material and to operate the machine for testing. This website is also intended to promote the Mechancial Engineering Department's Facility of manufacturing processes, providing insights and ideas about student's projects. Lastly, this tutorial benefits students, faculties, and staffs as a quick guide in using the viscometer for future purposes.
Procedure:
"All steps should be followed in the order presented from beginning to end. This tutorial is written in the format as follows: All bullets represent execution key strokes and all italicized-bolded text are pictures of components and controls of the machine. Additional comments and explanations are included in every steps to provide the necessary understanding for the operation."
Test Equipment
All Switches off. Make sure that all major switches such as the preheat, thermal controller, and motors are in the "off" positions before proceeding.
Turn on the main switch This is to power the machine's electronic system.
Turn on the motor switch. This will drive the main motor.
Select an orifice. The size of the dimension of the orifice, such as length and diameter will be used for calculation.
Install orifice udnerneath the extrusion barrel. Screw the orifice using the right size of a screw driver. It is recommended to do this while the machine is still cold.
Insert the thermal sensor chord into the extrusion barrel.
Choose speed. To determine the velocity of the metal rod(plunger) descending into the extrusion barrel. this is the value of the variable, Vel, that will be used for the calculation. It is recommended to start from the slowest rate, then make adjustment if necessary. Note also that the selection of the speed depends on the diameter of the orifice: smaller the diameter, slower the speed: bigger diameter, faster speed.
Set-up the temperature. Select 275 degrees C (starting temperature) using the temperature selector. Turn on the preheat switch as well as the thermal controller switch. Calibrate all the system. Preheat the process for 15 minutes (this will allow the machine to warm-up as well).
Pour material. With the material in plastic pellets form, grab a handfull and pour it into the extrusion barrel. Tomp the pellets using the plunger to accomodate all of them inside the barrel. Make sure that the plunger has space inside the barrel filled with pellets. There should be at least half of an inch available(insert the plunger on top of the barrel to be sure). Then heat the material for three minutes for complete melting.
Install the metal rod(plunger) Attach the plunger underneath the compression load cell.
Activate the rod metal. Press the button in "down" position to move the metal rod. As the plunger moves downward, look up to the load meter and chart if they show any readings.
Take the printout result. The chart should show a graph of a Force versus Time plot. The x-axis corresponds to the force measured while the y-axis corrspond to time.
Use the derived formula to calculate viscosity.
Parameters:
u = viscosity F = force (taken from the graph) Rr = radius of metal rod Ro = radius of the orifice L = length of the orifice Vel = velocity (rate of the plunger's descending speed)
Formula:
u = (F*Rr**2)/(9(pi-squared)(Ro to the 4th)(L)(Vel))
Prepare a pan below the extrusion bar to catch the falling materials in nylon/threaded forms.
Congratulations! You have just learned how to operate one of FAME's industrial machinery.
