Tool Tutorial

Morgan Industries G-100T Injection Molding Machine

Overview

The injection-molding machine forms plastic parts by melting plastic and forcing the plastic into a
 multi-plate mold that is held in a powerful clamp. After the plastic solidifies, the clamp is released,
 allowing the finished part to be removed from the mold.
 The basic cycle is clamp, melt, inject, pack, solidify, unclamp, eject.
Clamp:

• Clamp: The two (or more) parts of the mold are brought together and held under pressure by a
   strong clamp.
  Melt:
• Melt: Feed stock material is brought up to melting temperature and becomes a viscous liquid.
   This is often called “the melt.”
  Inject:
• Inject: The melt is forced into the mold cavity, filling it completely.
  Pack:
• Pack: The melt is held at pressure inside the mold until the gate solidifies. (The “gate” is the final
   orifice that material flows through into the cavity.)
  Solidify:
• Solidify: The material is allowed to harden in the mold. As it solidifies, it will shrink. The amount of
   shrink depends on the material and your process.
  Unclamp:
• Unclamp: The parts of the mold are pulled apart to allow the work piece to be removed.
  Eject:
• Eject: The work piece is removed from the mold and allowed to continue to cool. It may shrink
   further as it cools.
  

On the G-100T, all of these processes are manually controlled. This provides great flexibility and
 allows you to use complex molds without having to do any complicated controller programming.
 In injection molding, the key to quality is a consistent process. Since with our machine you are the
 controller, you will get the best results by developing a rhythm and keeping up a comfortable and
 consistent pace as you make parts.

Injection Molder

Safety and Procedures
«

• Some parts of the machine are hot and can cause severe burns
  *
• Hot plastic is sticky and can cause severe burns
  »
• Wear leather or heat-resistant gloves to protect your hands from hot molds and plastic
  «
• The machine has a powerful clamp that can cause crushing injuries. Do not defeat the safety
   interlock, and watch for fingers around the lower platen when clamping and unclamping
  «
• The machine has a powerful ram that can cause crushing injuries. Do not defeat the safety
   interlock. Do not open the feed chute door before the ram has completed its return stroke
  +
• Know what, if anything, your chosen material out-gasses during the melt phase and ensure
   adequate ventilation
  *
• Know the correct process temperatures for your material. Avoid excessive process
   temperatures. Some resins give off noxious fumes when overheated, and all will quickly
   degrade. Excessive temperatures don’t help — imagine melting ice cubes — water at 80°F isn’t
   any more liquid than water at 40°F — so, too, with plastic
  *
• Do not process “mystery material.” It may out-gas unacceptable fumes, or may be corrosive.
  
• Know the properties of your material and obtain a data sheet from the manufacturer, if possible.
  «
• DO NOT RUN SHAPELOCK - it is a very low-temperature plastic not suitable for injection
  molding

Basic Anatomy of a Mold Figure

1
Qrifice

Making parts with an injection-molding el
machine requires that you bring a mold Sprue bush'“&af //
to use with the machine. There are many
 subtleties in mold design, and TechShop
offers a separate mold making class to
dig into those design issues. Indesign; this SBU,
wetool aretutorial only going to covercovers the basic
 parts and nomenclature of a mold.
Sprue
-
Gate
Mold
Mating Ring
Figure 1 shows the cross-section of a el
A
ry
Gap
simple two-part manual mold for a cup.cup:

"

Pactiog Line
fl“‘_’f
CoreBottom

Bottom Plate

The bottom plate has a locating socket 9/16
that centers the mold over the locating Trlocating Seckst
pin on the mold heater.

The core that forms the interior profile of the work piece is, in this case, part of the bottom plate.
 Where the top and bottom plates meet is called the parting line. The top and bottom plates of a mold
 need to meet with correct alignment. In this mold, a simple step is turned in the bottom plate that
 mates with a ring turned in the top plate.

Top Plate

The top plate molds the exterior profile of the part. The locating ring turned in the top plate is milled
 through on each side to provide places to insert tools to pry apart the two parts of the mold. The
 injector nozzle on the G-100T is a 1” diameter ball with a 3/16” orifice. This mold is designed to use
 a sprue bushing (not shown) between the nozzle and the mold. The sprue carries the melt from the
 nozzle to the gate.

Molds should be vented to allow air to escape when material is injected. Vents are typically 0.002”
 deep channels milled along the parting line from an edge or corner where air would be trapped. For
 the class mold, the vents were machined from the edge of the part to the pry gaps for simplicity.

Other Features

More sophisticated molds have additional features. Runners distribute material from the sprue to the
 gates in multi-gate or multi-cavity molds. Core pulls are additional parts of a mold inserted from the
 side to create more complex features than a two-piece mold will allow. Ejector pins are used to pop
 the part from the mold when the machine unclamps. Inserts are components placed in the mold to
 become part of the finished work piece.

Using the Injection Molder

The injection molder requires many steps to set it up. It may seem a little overwhelming at first, but it
 will get easier each time you use the machine.

Remove Leftover Plastic and Fill Hopper

Start by checking the hopper for plastic left over from the previous user. If there is plastic in the
 hopper, you'll have to heat up the machine up and purge the hopper before adding your own plastic,
 which is covered a little later on. If there is no leftover plastic in the hopper, fill the hopper with the
 plastic you'll be using.

Preheat Injection Molder
1.

1. Turn ON the injection molder by flipping the switch on the side of
    the temperature control housing.
   




2.

2. Adjust the temperatures to match the material you will be
    injecting based on the chart on the front of the machine.
   



3.

3. Begin heating the
    heater block to the
    correct temperature
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   nozzle and
    heater take
   e e TG about 20 minutes
   T LN to heat up, so be careful not to burn yourself on
    anything while setting up the rest of the machine.
   
   
   



4.

4. Connect the machine to a shop air
    supply, and turn the air on to the
    machine using the valve in back.
   Underneath
the machine are a
booster pump and storage tank.
The booster pump increases the air
pressure to 200 PSI, which is the limit
of the tank. Do not adjust anything
on the booster pump since this could
cause the tank to explode, resulting in
serious injuries or death.



5.

5. Open the material hopper cage. There is a safety device that will not let the machine activate
    the plastic injection stroke when the hopper cage is open, which makes the machine much
    safer while your hands are inside it and in range of the injection nozzle.
   

Set Up Mold
1.

1. Insert the locating bolt into the heater block on the bottom platen. The locating bolt keeps your
    mold centered under the injection nozzle.
   
   



2.

2. Place the riser block onto the locating bolt
    and spin it to make sure the locating bolt in
    the riser stays centered. Depending on the
    height of your mold, you may not need a
    riser block. Make sure there isn’t any foreign
    material on the riser or heater block surfaces.
    The riser block should spin freely about
    the locating bolt and should not rock when
    applying pressure to one side or the other.
   
   




3.

3. Carefully put the two halves of the mold
    together. Any scratches inside the mold will
    leave marks on your molded parts. Place
    the sprue bushing on the top of the mold
    and place the mold on the riser block. Check
    for any gaps or uneven parts resulting from
    misalignment or foreign material on the mold.

    

   
   

4.

4. Adjust the clamp force to 10 tons by
    turning the clamp force knob. Ten tons is
    the maximum clamping force that may be
    placed on the injection nozzle. Depending
    on the design and size of your mold, you
    may need to use more or less pressure.
   
   




5.

5. Adjust the Pilot Pressure to 6.
   
   



6.

6. Check to make sure the upper platen is
    fully raised. If it is not, loosen the four bolts
    holding it in position. Be sure to support the
    upper platen when loosening the last bolt,
    since it is very heavy. Let the platen fall as
    far as it can, then slide the safety cage down
    to reveal the backing bolts at each corner
    and thread them all the way up into the
    machine.
   



7.

7. Raise the safety cage (it may take quite a bit
    of force to engage the catch), then raise the
    upper platen as far as it will go and clamp
    it in place by
    tightening one bolt.
   bolt.
   



8.

8. Remove the
    mold from the
    machine (use
    gloves; it will be
    warm), lower
    the safety cage,
    release the
    safety on the
    clamp knob,
    and push itinit in to
    raise the bottomplaten.
   bottom

   platen.
   

9.

9. Raise the safety cage, place the mold and
    sprue bushing on the riser block to check
    clearances. There should be about 1/4”
    between the top of the assembly and the
    injection nozzle. If there is not enough
    clearance, lower the bottom platen by
    turning the adjustment screw on the side of
    the machine.
   
   





10.

10. Lower the safety cage and pull the clamp
     knob out to lower the bottom platen. Place
     the mold over the locating bolt on the
     riser block. Spin the mold to make sure
     it's centered in the machine. Remove any
     plastic dripping from the injection nozzle with
     needle-nose pliers. Close the safety cage,
     release the safety, and push the clamp knob
     in to raise the bottom platen.
    
    



11.

11. Raise the safety cage and raise the bottom
     platen using the adjustment screw on the
     side of the machine until the mold contacts
     the injection nozzle. Tighten the adjustment
     screw further until the mold does not spin on
     the riser block.
    



12.

12. Support the upper platen and loosen the side slide bolt. Do not let the platen fall on the mold.
     Place the upper platen on top of the mold and jiggle it to seat it fully on the mold. Tighten the
     four side slide bolts to hold the upper platen in place.
    




.

13. Lower the safety cage and then lower
     the four corner bolts until they are seated
     on top of the platen finger tight. (Using a
     wrench on the bolts may cause the platen
     to become crooked, possibly damaging
     the machine or your mold.)
    



14.

14. Now that the upper platen is in place, it's
     time to adjust the clamping force. Lower
     the safety cage and pull the clamp knob
     out to lower the bottom platen. Adjust your
     clamping force to what you’ll be using
     while creating parts. Raise the bottom
     platen using the adjustment screw on the
     side by a 1/4 turn and push the clamp
     knob. There will be an audible thump
     when the jack screw locks in place at the correct clamping force.

15.

15. If you do not hear a thump while adjusting, check to make sure the jack screw has gone over
     center. If it has not, lower the platen adjustment until the jack screw goes over center, and
     raise it a 1/4 turn at a time
     until you hear the thump. Over center Step 15 Not over center
    Clamp and unclamp
     the mold a few times to
     make sure the thump is consistent.
    consistent.

    Left: The jackscrew is over center,
     contacting the pneumatic cylinder
    cylinder. Right: The jack screw is not quite
     touching and not capable of holding
     the clamping force specified

    specified.

Set Up Plastic Injection

Now that the mold is set up, you can set up the
 plastic injection.
1.

1. Start by adjusting the ram pressure.
    Ram pressure controls how fast the ram
    moves as well as how much pressure the
    plastic being injected puts on the mold.
    Figuring out how much pressure to use is a
    combination of science, art and experience.
    A good starting point is 3000 PSI. Adjust
    the pressure using the knob under the ram
    pressure gauge.
   



2.

2. Remove the mold and riser plate from the
    heater block and lower the safety cage.
    Close the hopper cage to enable the plastic
    injection stroke. Release the safety and
    push the inject knob in. Hot plastic should
    come out of the injection nozzle similar to
    a hot glue gun. This will help purge any
    plastic left over from previous users as well
    as any burnt material.
   



3.

3. Lift the safety cage and clear out the plastic
    using a tool (e.g., pliers) instead of your
    hands. The plastic will be very hot and
    gooey, and may cause severe burns even if
    you’re wearing gloves.
   
   



4.

4. Place the riser block, mold and sprue bushing
    in place over the heater block. Make sure there Step 6
    aren’t any gaps between any of the pieces and that
    everything is centered on the locating bolts.
   5. 
5. Lower the safety cage and press the clamp knob to
    clamp the mold. Double-check the ram speed gauge,
    clamping force gauge and pilot pressure gauge.
   6.
6. Turn the small timer knob all the way clockwise until
    it stops. Do not apply too much force since it is easy
    to break the timer attached to the other side. The
    timer comes in handy when making larger quantities
    of parts and you know how long the injection cycle
    should last.
   
   

Make Some Parts
1.

1. Release the safety on the inject knob and push it in
    for about five seconds. It should take the mold about
    this long to fill and begin to solidify.
   2.
2. Release the knob and wait another five seconds.
    This keeps pressure on the plastic in the mold and allows the plastic to fully solidify.
   3.
3. Pull the clamp knob out to release the bottom platen and raise the safety cage. Carefully
    remove the mold using gloved hands. Twist the sprue bushing several times to sever the
    plastic holding it to the mold and place it back on the heater block to help keep it warm for
    the next part.
   




4.

4. Carefully split the mold halves apart and pop the molded part out. You may need to use a
    screwdriver or other prying implement, but be careful to not damage the mold. You can use
    blasts of air or gentle persuasion with a screwdriver to pop the molded piece off the mold.
    Do not use too much air since it will cool down the mold.

.
6.


5. Chances are, the first part will not come
    out right. It may take a few tries to get
    everything up to temperature and to find
    the right injection time, speed and clamping
    force. Consult the troubleshooting guide
    (locatedfurther at the back ofin this handout)document) and
    adjust accordingly.
   
   






6. Keep the hopper full while using the
    injection molder. If smoke begins to come
    out of the hopper opening, the plastic level
    has fallen too far. Depending on the size of
    your parts, you may need to add plastic as
    frequently as every two or three parts.

Cleanup and Shutdown
1.

1. Scoop out any unused plastic from the hopper. Remove your mold and riser block, lower the
   2.
   3.
   4.
    safety cage, and run a few injection cycles
    to purge any plastic left over in the hopper.
   
   
2. Loosen the four side slide screws to lower
    the upper platen, spin the four corner bolts
    all the way in, and lift and secure the upper
    platen in its fully raised position.
   
3. Lower the bottom platen, turn off the heater
    block and lower the safety cage.
   
4. Turn OFF the air to the machine. Turn OFF
    the machine power, and disconnect the air
    supply at the source.

Troubleshooting
Issue

Bottom platen doesn’t move when
 the clamp knob is pushed in.
Ram

doesn’t operate when you
engage the injection valve.
Lower platen stalls coming down
when disengaged.
Short shots (a short shot is an
insufficiently filled mold).
Cause / Resolution

Is the safety cage all the way down,down, engaging the safety interlock?

Ram doesn’t operate when you engage the injection valve.
interlock?

Is the door to the feed chute closed, engaging the safety
 interlock? Is the pilot pressure high enough?

Lower platen stalls coming down when disengaged.

The safety cage should slide smoothly on the stanchions,
 but sometimes it sticks. When it sticks, it causes the safety
 interlock to trip, cutting off the clamp piston’s air supply. Helping
 the cage down by hand is a quick fix. The most likely cause is
 contamination of the stanchions by over-sprayed mold release
 or other foreign material. Wipe down the stanchions with WD-40
 to remove the contamination and lubricate the stanchions.

Short shots (a short shot is an insufficiently filled mold).

Resin is too cold, doesn’t flow well because of insufficient
 time between shots to fully melt the material, or not gradually
adding material to the barrel on a consistent basis. This is the
 most likely cause of short shots in a well-warmed mold. Wait
longer between shots and feed material at a constant rate.

Resin is too cold, doesn’t flow well because cold drool was
 injected. Solution: Drool freezes in the air as it comes out of
 the nozzle. Don't try to inject it. Use needle nose pliers to pinch
 off and discard it. Molds with runner systems can be designed
 to divert the leading edge of the flow into a “blind alley” so that
 the cold leading edge is parked out of the way.

Resin is too cold, doesn’t flow well because barrel and/or
 nozzle temperatures may be too low. Adjust temperatures
judiciously. It is easy to set the temperature too high.

Mold is cold, shot solidifies too quickly. If these are your
 first shots, the problem may solve itself after a few shots.
 Alternatively, increase temperature of heater block. Note that
 using a riser block will reduce the overall efficiency of mold
 heating, so you may need to compensate.

Shot time is too short. Use a longer shot.

Shot is too slow. IncreaseIncrease injection speed. Increase injection
 pressure. Enlarge gates. Enlarge vents. Enlarge runners and
 sprue.

Trapped air. Add and/or enlarge vents.

Issue

Excessive flash (flash is material
 that squeezes out of the mold
 along the parting line).
Part

won't eject.
Plastic doesn’t inject and escapes
from nozzle seat.
Ram won’t return.
Cause / Resolution

Insufficient clamping pressure. Increase clamp pressure.
 Reduce injection pressure. Change to a material with lower
 viscosity, allowing reduced injection pressure. Increase size of
 gates and vents, allowing reduced injection pressure. Redesign
 mold to have a smaller area at the parting line. Redesign mold
 to include clamping bolts.

Poor platen adjustment. Make sure the top platen is correctly
 adjusted square to the mold. Flash only along one side of the
 part is an indication of a skewed platen. Make sure the platen is
 adjusted to hold the mold securely, and that the adjusting and
 suspension screws are tight. If you are using a mold that is too
 small to contact the upper platen, redesign the mold to 4"x4” or
 larger.

Poor mating at parting line. Re-machine the interface
 between the mold plates for a smoother finish.

Part won't eject.
finish.

Use a squirt of aerosol mold release every few shots.
 Eliminate undercuts. Increase taper. Polish mold. Add ejection
 mechanism. Remember, plastic shrinks as it cools. It will pull
 away from the outside of your mold, and shrink on to the core.

Plastic doesn’t inject and escapes from nozzle seat.

The upper platen is poorly adjusted,adjusted, creating a gap between
 the nozzle and the nozzle seat. Repeat the upper platen
 adjustment procedure.

Cold drool fouled the seat and/or blocked the sprue. Remember
 to discard cold drool immediately before clamping. Clean
 dripping material off the nozzle.

Ram won’t return.

Occasionally, high viscosity or cold material will cause the ram
 to get stuck in the barrel. Use short shots on the ram return assist
 valve until it breaks free. Each shot should be one second. If it is not
 free after 5 or 6 shots, get assistance from a TechShopshop DC.tech.