Plastic Tube extrusion?
Hi. This is my second post in row, but a different topic this time.
I'm stuck at a problem. Coming from a mechanical background, plastics and polymers seems far too alien to me. Though i seem to understand the basic material properties, the processing, and extrusion mechanics are quite complicated, and i'm unable to obtain a model or try a mathematical formulae to understand its design considerations.
In the vast field of Plastic processing, my main concern is - Plastic Tubing.
The plastic is fed through the hopper, the screw compresses and melts the plastic under shear, the plastic exits through the die, it takes the form of the round oval shape- after passing through a particular apparatus for even mixing and melt pressure- and finally exits through a die-mandrel combination. The mandrel controls the inside diameter of the tube, while the die limits the OD of the tube. The spacing between both- die-mandrel gives the thickness of the tube.
After passing through the die- the tube passes through a water bath, for quenching and taking its final form. In some cases, it even passes through a small area of vacuum sizing, where the dimensions of the tube are controlled.
After passing a long channel of water bath- about 10m - 15m in length, it is pulled by a haul-off unit. I can't remember its name, but its basically a belt conveyor pulles arrangement, driven by an Ac motor, which in turn drives a set of gears, and finally a belt conveyor- which pulls the tube from the extruder side, and lets it fall freely at the other side.
The die and mandrel are designed to the approximate dimensions of the plastic tubing. But the speed of this puller - is used to fine tune the dimensions.
So even if i calculate the die- mandrel dimensions for the right size of tube- i find here- that the engineer here has been using the same set of die-mandrel for atleast 2-3 different sizes of tubings.
Can anyone tell me more about this? Is the Young's modulus here? I remember something about the young's modulus, but it was more about steel. Never read anything about plastic there.
Is there a way to calculate, the different speeds of the puller , or Haul-off unit, to get a set of different size tubings from a particular die-mandrel design?
Any reference sites from web would be greatly appreciated. Thanx.
I'm stuck at a problem. Coming from a mechanical background, plastics and polymers seems far too alien to me. Though i seem to understand the basic material properties, the processing, and extrusion mechanics are quite complicated, and i'm unable to obtain a model or try a mathematical formulae to understand its design considerations.
In the vast field of Plastic processing, my main concern is - Plastic Tubing.
The plastic is fed through the hopper, the screw compresses and melts the plastic under shear, the plastic exits through the die, it takes the form of the round oval shape- after passing through a particular apparatus for even mixing and melt pressure- and finally exits through a die-mandrel combination. The mandrel controls the inside diameter of the tube, while the die limits the OD of the tube. The spacing between both- die-mandrel gives the thickness of the tube.
After passing through the die- the tube passes through a water bath, for quenching and taking its final form. In some cases, it even passes through a small area of vacuum sizing, where the dimensions of the tube are controlled.
After passing a long channel of water bath- about 10m - 15m in length, it is pulled by a haul-off unit. I can't remember its name, but its basically a belt conveyor pulles arrangement, driven by an Ac motor, which in turn drives a set of gears, and finally a belt conveyor- which pulls the tube from the extruder side, and lets it fall freely at the other side.
The die and mandrel are designed to the approximate dimensions of the plastic tubing. But the speed of this puller - is used to fine tune the dimensions.
So even if i calculate the die- mandrel dimensions for the right size of tube- i find here- that the engineer here has been using the same set of die-mandrel for atleast 2-3 different sizes of tubings.
Can anyone tell me more about this? Is the Young's modulus here? I remember something about the young's modulus, but it was more about steel. Never read anything about plastic there.
Is there a way to calculate, the different speeds of the puller , or Haul-off unit, to get a set of different size tubings from a particular die-mandrel design?
Any reference sites from web would be greatly appreciated. Thanx.
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