Injection Molding

There are two injection molders "Super Hornet" Model 60-PC 100 MINI-JECTOR and  EMCO Model No. 250 Injection Molder both are located in laboratory 109A of the John Mitchell Center.  The parts produced on injection molders can have complex shapes, surface textures, variable cross sections, and other characteristics.  The three functional areas of an injection molder are the injection, mold, and clamping.  

This document describes the operation of the injection molder and related safety practices.

"Super Hornet", Model 60-PC 100, MINI-JECTOR

Operation:  "Super Hornet", Model 60-PC 100, MINI-JECTOR

1.  Turn on the temperature control and allow the machine to get up to the temperature required for the plastic you are using. A lot of the plastics used in the lab are molded at about 350 degrees Fahrenheit.

2.  Fill the hopper with the plastic material that is going to be used.

3.  Feed the plastic material into the injection assembly by pulling forward on the hopper supply knob.

4.  Press the start button for the electric motor and hydraulic pump.

5.  Pack material into injection assembly.
    a. The top control lever moved to the left lowers the ram.
    b. Move the control lever to the right to retract the ram.
    c. Repeat two or three times feeding material each time.

6. Allow a minute or two for the material to become fluid.

7.  Close the mold by moving the lower control lever to the left and hold until the mold is completely closed.
        Safety Note: Make sure your hands are not in-between the two halves of the molds.  If you do need to put your hand in-between the molds make sure the the hydraulic system is turned off and the metal guard bar is hanging between them so that the molds can not close.

8.  To adjust the pressure for injection, loosen the lock nut on the pressure relief valve.

9.  To inject material move the top control lever to the left and hold with the right hand.

10. When the ram is forward the pressure gauge can be read (pressure gauge valve must be open). Adjust the pressure relief valve with the left hand.  For more information on the correct pressure see the instructor or "Regulating the Injection Pressure" in the instruction manual.

11.  Retract the ram and tighten the pressure relief valve lock nut.

12. Now that the set up process is done you can run the machine to produce the parts you need. Just make sure there is plastic in the hopper and you keep packing material into the injection assembly.


1. Wear safety glasses while in the lab.

1.  Shut off the machine when working on the mold.

2.  Electrical work should be done by an electrical maintenance person.

3. Never allow the ram to remain the injection assembly for long periods of time.

4.  Never shut down the machine with the ram in the injection assembly.

5.  Never leave material in mold; remove molded parts and sprue before shutting down.


 EMCO, Model No. 250, Injection Molder

Operation: EMCO, Model No. 250, Injection Molder

1. Turn thermostat knob to medium. This will result in a temperature between 250-300 degrees.  Adjust for correct operating temperature for the plastic to be used.

2.  Align the mold in the clamp so that the sprue hole in the mold is directly under the hole in the nozzle.

3.  Clamp mold in place being careful not to over tighten and that the movement of the clamp does not move sprue hole out of alignment with the nozzle.

4.  Place a small amount of plastic into the opening in the top of the cylinder with the spoon provided (charging the cylinder).  Allow some heating time so the plastic can melt.

5.  Slide the end of the 3/4 inch pipe over the handle. With one steady deliberate motion press the pipe lever down. 

6.  Recharge the cylinder before removing the mold. This allows the shot you just made a few extra seconds to solidify

7.  Unclamp and remove the mold from the machine.  Remove the part from the mold,  break off the sprue and file any flashing that may remain.

8.  Repeat the cycle for an additional shot.


1. Wear safety glasses while in the lab.

2. Be aware of parts or equipment that could be hot.

3. Pay attention to the process at hand.

Prepared by Cory Donovan 3/16/98
References used:
    EMCO Instruction Manual.  Educational Machinery Corp. Box 146, Glenville Sta.-Greenwich, Conn. 06830

    Instructions for Operation of Model "Super Hornet" Model 60-PC 100. (1961, July 1) Newbury Industries, Inc. Newbury, Ohio 
    Steele, G.L.(1997).Exploring the World of Plastics. Illinois: Mcknight Publishing