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Extrusion Blow Moulding Gap Analysis Advanced
This assessment will give you an overview of you level of knowledge in Extrusion Blow Moulding. You will receive an email with your result as soon as it is completed.
The assessment should take you 10-15 Minutes.
Good Luck!
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Extrusion Blow Moulding overview - Advanced
Please select the best possible answer in the below questions
If you change the temperature setting on the extruder barrel or diehead by 15 degrees C, how long will it take for the machine and plastic temperature to stabalise?
5 Minutes
No need to wait
30 Minutes
1 Hour
2 hours
Heat sensitive plastics such as certain grades of PVC
Should be kept moving through the machine
Degrade rapidly once degradation begins
Can't be left idle in a hot barrel for long
All of the above
The key to making a good parison is controlling the
Plastic flow
Die temperature
Parison cooling rate
Parison inflation
An important step in analysing a parison curl problem is measuring the temperatures of both the diehead and the
Plastic raw material
Mould
Parison
Screw
The transition/ compression zone of the screw increases frictional heat due to...
Pressure
Molecular Bond
Swell
Moisture
Besides shaping the parison, the most important function of the die head is
controlling the production rate
Maintaining a stable melt temperature
Maintaining plastic pressure
Controlling plastic flow
The purpose of the choke in a radial flow diehead is to:
Increase molecular entanglement
Improve weldline strength
Increase the melt-pressure
All of the above
Velocity differences in the plastic flow stream can cause Molecular orientation and...
Film
Splay
Shear heat
Regeneration
The hydraulic oil pressure generated in the accumulator as plastic fills the chamber is called:
Ram pressure
Back Pressure
Head pressure
Plastic Pressure
An increase in accumulator back pressure causes:
A decreased extruder head pressure
Increased extruder output
Increased heat generated by screw rotation
Decreased plastic melting
All of the above
If accumulator ram pressure is decreased, parison sag will:
Increase
Decrease
Not change
Adjusting the Die head opening:
Controls the amount of plastic flowing through the diehead
varies the thickness of the parison walls
Affects the weights of the part
All of the above
Parison programming is adjusting which parison characteristic during parison extrusion?
Plastic wall thickness
Parison length
Parison diameter
Plastic wall temperature
The factor that has the greatest effect on the production rate is the:
Extrusion rate
Cooling time
Melt flow velocity
Various time delays
Ejection time
Swell is an increase in what part of the parison?
Length
Wall thickness
Temperature
Strength
Weight
Variations in the diehead temperatures on each side of the diehead opening can cause variations in
Cycle time
Plastic flow rate
Melt temperature
All of the above
The most important effect of a change in the diehead metal temperature is
The overall melt-flow rate through the die
The overall melt temperature
The overall melt pressure
The melt viscosity next to the metal wall
The process adjustments to correct douganut formation primarily affects
Flow friction
Melt pressure
Screw RPM
Output
To increase Melt Strength, you could
Raise the melt temperature
Enhance the plastic with additives
Enlarge the die gap
Lower the melt temperatures
One way to adjust the die gap setting is to watch the parison drop from the die opening. The parison will
Bend towards the thick side
Sag
Bend towards the thin side
Bend 90 degrees to the thin side
Weak spots that blow out can be as a result of:
A hot pinch-off region
Too high rate of expansion
Impurities in the plastic melt
Misaligned parting lines
Any of the above
According to the Poiseuille fluid flow law, the factor with the greatest effect on the plastic flow rate is
Ram velocity
Plastic Pressure
Gap Thickness
Melt Viscosity
Type of plastic
The changes in diehead body temperature primarily affects viscosity of the plastic
At the entrance to the diehead
In the melt film regions of the die
In the centre of the plastic flow
Throughout the parison
Throughout the flowing plastic
When correcting for any parison melt flow problems, the first condition to check and correct is
Melt temerature variations
Diehead temperature
Meltpressure
Parison extrusion rate
Diehead gap variations
A smaller die gap increases melt pressure and reduces the
Plastic output
Plastic temperature
Parison Swell
Cycle time
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