Setting Conditions, Producing, and SamplingTHEORETICAL
BACKGROUND
The machine setting at the beginning of each injection molding
processprocedure should be as close as possible to the most
desirable processingconditions. To start with a calculated guess of
the possible process conditionfor a given material, we should also
consider some important factors like:injection molding machine
size, material grades, mold design, etc. Processconditions settings
is influenced by these following parameters: Injection molding
machine Injection mold Material Geometrical parameters of the part
Desired properties of the productData inputs are based on each
stage of the machine work cycle as shownbelow:(
Produce Good Sample Product
Prepare all materials & equipment for running the machine,
e.g., spanner,screw driver, etc. Use previous Mold Setup Chart
& QA product approval, if any, to runthe machine. Try to get
best machine setting for the product & take 3-5 good samplesfor
QA visual & functional check/ testVisual Appearance Checking
One product performance criterion is to check product condition
visually.
_ Be sure that the product is inspected at its front, side &
back._ If defects are noticed, please do the necessary adjustments
until you get a good product
Functionality Checking (Product Specifications)
One product performance criterion is to measure good functioning
ofproduct using some tools & methods
_ Ensure the scale is reset to zero_ Place one full shot on the
scale_ Compare the weight to the standard shot weight_ Product
Dimension_ Warpage or flatness_ Flash, shorts or sink
Machine Setting Conditions and Trial Run
1. Go to the molding machine area.2. Familiarize yourself with
the display of the control panel. Copy theparameter setting
currently in the display panel to your worksheet for thefollowing:
Mold Closing Mold Opening Barrel Temperature Dosage Holding3.
Observe and try to familiarize yourself with the entire injection
moldingprocess cycle.4. Run the machine based on the current
settings and collect samples.PART II Sampling1. Take 5 samples of
the product.2. Check each of the products using Visual Checking and
FunctionalityChecking method.3. Record the results using the forms
found in your worksheet.
Machine Setting Conditions and Trial RunSETTINGS FOR MOLD
CLOSINGSETTINGS FOR MOLD OPENINGSETTINGS FOR BARREL
TEMPERATURESETTINGS FOR DOSAGESETTINGS FOR INJECTIONSETTINGS FOR
HOLDING
THEORETICAL BACKGROUND
INJECTION SPEEDInjection speed is the filling speed of the
molten material in to the mold withthe forward movement of a screw.
Unit: cubic centimeter (cc)/sec.
INJECTION PRESSURE (Pmax)Injection pressure is the term for the
pressure applied to the molten materialwhen a screw moves forward
to inject it from the nozzle at high speed. (unit:Bar )
HOLDING PRESSUREThe pressure applied to the molten material
after completion of InjectionPhase. It pushes further plastic melt
into the cavity before gate freezing.Unit: Bar.
SHOT CAPACITYThe maximum amount of plastic melt that can be
injected from the barrel ofan injection molding machine in a single
shot. Unit: grams of polystyrene.
INJECTION RATEThe injection rate is expressed in terms of the
volume of the molten materialwhich can be injected in the unit
time. Unit: cm3/s.
SCREW SPEEDThe rotational speed of the screw during dosing. It
is expressed in rpm(rotations per minute).
BACK PRESSUREThe molten material is plasticated and kneaded by
the rotation of a screw andtransferred to the tip of the screw,
where the molten material accumulatesand recoils, causing the
backward motion of a screw. In order to suppressthis movement,
slight pressure is applied to the injection cylinder side. Thisis
called back pressure. Unit: bar.
CLAMPING FORCEClamping force (CF) is the force which keeps the
mould closed duringinjection.Required Mould Clamping ForceClamping
force ( F ) in the diagram should bebigger than the force ( f )
which makes themould open during injection