- Blister. A blister is a raised area on the plastic surface, very similar to the medical condition of the same name. …
- Burn Marks. Burn marks are generally caused by problems similar to blistering. …
- Burrs. …
- Embedded contaminates. …
- Flow marks. …
- Lamination. …
- Sink marks. …
- Short mold.
What is short mold?
A short shot is
the incomplete filling of a mold cavity
which results in the production of an incomplete part. If a part short shots, the plastic does not fill the cavity. The flow freezes off before the flow paths have completely filled.
What are the plastic molding defects?
- Flow Lines.
- Sink Marks.
- Vacuum Voids.
- Surface Delamination.
- Weld Lines.
- Short Shots.
- Warping.
- Burn Marks.
What causes plastic delamination?
Too much moisture on the material
, which is usually due to a failure to completely dry the material before using it. During the molding process, moisture becomes steam, which leads to surface delamination.
What are the common defects occur in thermoforming process and suggest remedies?
- Flow Lines. Description: Flow lines are lines, streaks, or patterns that show up on the prototype, caused by the molten plastic passing through the mold or gate. …
- Sink Marks. …
- Vacuum Voids. …
- Surface Delamination. …
- Weld Line.
What are the types of plastic Moulding?
There are 5 types of plastic moulding that is considered to be the most effective and most popular. These 5 types are
extrusion moulding, compression moulding, blow moulding, injection moulding and rotational moulding
.
How do you keep plastic from warping?
Solution:
Increase residence time by adding time to the cooling process of the cycle
. This will ensure the material receives the proper amount of residence time and eliminate mold warping. If the barrel temperature is too low, the resin is not able to heat up to the proper flow temperature.
What causes sink in injection molding?
Sinks are common injection molding defects that occur in thicker sections of molded parts. … The
outer portion of the part that is in contact with the mold steel cools much faster than the internal part
. As the molecules in thicker sections begin to contract, they pull in on themselves, leaving a defect known as a sink.
What is 3 plate mold?
A three-plate mold is
used when part of the runner system is on a different plane to the injection location
. … This second parting plane enables the runners and sprue to be ejected when the mold is opened. In the following diagram of a three-plate mold, the runners will be ejected separately to the cavities.
What does short shot mean?
A short shot is
an incompletely filled mold cavity
. … If the injection rate into a mold for the material is too slow, the thickness of the frozen layer builds up to a point where material can no longer be fed into the cavity, thus creating a short shot.
What is plastic delamination?
Delamination refers to
a flaw where plastic manufactured parts fracture into layers
. … Shrinkage stresses due to improper curing and cooling can cause cracking that leads to delamination, or faults in the injection molding process or machinery can result in this defect.
What causes delamination?
Delamination is caused by
matrix cracking, bending cracks, and shear cracks
. Delamination can affect the compression strength of composite laminate, and it will slowly cause the composite to experience failure through buckling.
How do you solve delamination problems?
- Reduce shear stress.
- Remove excessive moisture. …
- Reduce regrind material.
- Avoid excessive use of mold release agent. …
- Avoid material contamination.
What are the common defects in thermoforming process?
| Problems Possible Causes | 1. Part temperature too hot for proper release | Stretch marks on part 1. Plug assist sticks to sheet and causes freeze-off lines | 2. Cold mold causes curved chill lines around lip of part | 3. Mold temperature varies between cavities |
|---|
What are the common defects of casting?
- Gas Porosity: Blowholes, open holes, pinholes.
- Shrinkage defects: shrinkage cavity.
- Mold material defects: Cut and washes, swell, drops, metal penetration, rat tail.
- Pouring metal defects: Cold shut, misrun, slag inclusion.
- Metallurgical defects: Hot tears, hot spot.
What are the types of thermoforming?
There are two main types of thermoforming:
vacuum forming and pressure forming
. Vacuum forming uses heat and pressure to draw plastic sheets into its final configuration. Once a sheet is heated and placed over a mold, a vacuum is used to manipulate it into its desired shape.
