Hai guys know about the allen screws and some bolts by seeing its head
click the following link
"http://www.engineersedge.com/hex_bolt_identification.htm"
Wednesday, January 21, 2009
Thursday, January 15, 2009
Tips for reducing brittle parts of PP
Degradation of PP Material
l Reduce Barrel Temperatures
l Reduce Material Residence Time in Barrel
l Check Barrel-To-Shot Ratio
High Level of Molded-In Stresses
l Increase Barrel Temperatures
l Adjust Injection Speed (Moderate to Slower Speed)
Material Contamination
l Check Color Concentrates Used, as well as Base Resin
l Check Material Handling System, such as Material Feed Lines and Hopper for
Contaminant Materials
Poor Part Design
l Remove Sharp Corners and Use Radiused Corners
l Move Weld Lines Away from Areas Where Strength is Critical
l Reduce Barrel Temperatures
l Reduce Material Residence Time in Barrel
l Check Barrel-To-Shot Ratio
High Level of Molded-In Stresses
l Increase Barrel Temperatures
l Adjust Injection Speed (Moderate to Slower Speed)
Material Contamination
l Check Color Concentrates Used, as well as Base Resin
l Check Material Handling System, such as Material Feed Lines and Hopper for
Contaminant Materials
Poor Part Design
l Remove Sharp Corners and Use Radiused Corners
l Move Weld Lines Away from Areas Where Strength is Critical
Tips to Design runner system.
This system receives molten plastic
from the barrel and guides it into the mold cavity. In consists
of a sprue, runners, and a gate.
a. Sprue bushing/machine contact is usually curved. Radius
of nozzle tip + 1mm is less than or equal to the radius of the
indentation of sprue bushing. And, the diameter of orifice of
nozzle + 1mm is less than or equal to the diameter of the
orifice of sprue bushing.
b. A radius of 1 - 2mm is recommended at the root of the
sprue.
c. 5 - 10mm diameter runners are machined into mold plates.
A polished circular cross section across the parting line is
best due to small surface area, low friction loss, etc.
Machining into both mold halves is difficult and expensive.
A parabolic cross section is simpler machining, but leads to
higher heat loss and more scrap material. A trapezoidal is
another alternative, but causes even more heat loss and
scrap. Alternatively, hot runners can be used which involve
separate, heated manifolds.
d. Runners should be avoided as they complicate issues. Use
a runner only if necessary to fill from thick to thin sections.
If runner must be used, fan gates work the best.
e. Fill cavity with minimum knit lines, multiple gates means
multiple knit lines.
f. Minimize restrictions to flow.
g. Design runners for ease of demolding.
h. Place gate at the thickest section of the part.
i. Place gate at an unseen location on the part.
j. Gates are faced level to parting line to simplify machining.
Start with small gates and slowly increase size. If the gate is
too large the material going through the gate may freeze
prematurely.
k. A radius at the gate/part interface may result in a laminar
flow which will prevent jetting. However, it can also make
gate removal more difficult.
l. Best tensile and impact strength are achieved in direction
of flow.
from the barrel and guides it into the mold cavity. In consists
of a sprue, runners, and a gate.
a. Sprue bushing/machine contact is usually curved. Radius
of nozzle tip + 1mm is less than or equal to the radius of the
indentation of sprue bushing. And, the diameter of orifice of
nozzle + 1mm is less than or equal to the diameter of the
orifice of sprue bushing.
b. A radius of 1 - 2mm is recommended at the root of the
sprue.
c. 5 - 10mm diameter runners are machined into mold plates.
A polished circular cross section across the parting line is
best due to small surface area, low friction loss, etc.
Machining into both mold halves is difficult and expensive.
A parabolic cross section is simpler machining, but leads to
higher heat loss and more scrap material. A trapezoidal is
another alternative, but causes even more heat loss and
scrap. Alternatively, hot runners can be used which involve
separate, heated manifolds.
d. Runners should be avoided as they complicate issues. Use
a runner only if necessary to fill from thick to thin sections.
If runner must be used, fan gates work the best.
e. Fill cavity with minimum knit lines, multiple gates means
multiple knit lines.
f. Minimize restrictions to flow.
g. Design runners for ease of demolding.
h. Place gate at the thickest section of the part.
i. Place gate at an unseen location on the part.
j. Gates are faced level to parting line to simplify machining.
Start with small gates and slowly increase size. If the gate is
too large the material going through the gate may freeze
prematurely.
k. A radius at the gate/part interface may result in a laminar
flow which will prevent jetting. However, it can also make
gate removal more difficult.
l. Best tensile and impact strength are achieved in direction
of flow.
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