What Does Injection Molding's Parting Line Mean?
                     What Does Injection Molding's Parting Line Mean? 
 
All plastic injection molding manufacturer components have a separation line that 
may be seen. When a mold's two parts are clamped together, a line separates them. 
Although molds must totally seal during the process, a faint visible line is always present 
on the finished product. The size and appearance of the line are determined by the 
plastic type and mold design. 
Parting Lines 
 
The term "parting line" describes a line on an Injection Molding component that is 
produced where the two halves of the mold converge. The end result is a thin, 
occasionally imperceptible line on the portion. This line often has little impact on the 
part's overall dimensions or shape, but it can be visually evident to varied degrees, 
depending on the mold finish, the type of material, the color of the material, and the 
processing conditions. There are a few strategies to reduce the visibility of this line on 
the molded item, but since injection molding uses a mold that has two sides, it is 
impossible to totally prevent it. The shape of the part will often determine the parting 
line. The separation line should be placed in such a way by the mold designer that it 
produces the most strong tooling design while also being least obvious. However, the 
part's design frequently places limitations on the user.  
 
The parting line should typically follow the part's outside contour and allow all of its 
features to pass through the tooling in the direction that the mold opens. The locations 
and directions of the draught required to release injection molded pieces from the mold 
will affect where the separating line is located. Due to these factors, much thought must 
go into the part's design in order to situate the parting line where it will have the greatest 
impact on the part's intended use. The location of the parting line will impact the mold's 
cost as well.  
 
A dividing line that lies on a single, flat plane is the simplest and strongest kind. 
However, this kind of separation line is not always feasible due to the complexity of 
many injection molded parts. Since the parting line typically needs to match this 
contour, parts with intricate contours frequently have higher mold costs. By addressing 
these problems during the component design phase, the part designer can frequently 
lower the cost of the mold. A well-designed part from the perspective of injection 
molding has a well-defined parting line that has been created to be as straightforward 
as feasible. 
How Should a Plastic Parting Line Be Set? 
 
Mold function and part function both affect where a plastic parting line is located. The 
mold opens at the separating line, therefore easy ejection from that location is 
necessary. It might also be apparent and have an impact on how well the finished 
component works. 
 
At Moulding Injection, we'll do our best to select the parting line that will allow for simple 
mold operation and a finished product that meets your standards. The separation line in 
the figure to the left follows the edge of the plastic injection mold design and moulded 
component. The mold's seam was located here. The placement and configuration of the 
separating line around the edge of the part, as shown, is frequently optimal. 
 
Contact Plastic Injection Moulding France for all your moulding injection requirements. 
Why Does Injection Molding Use a Parting Line? 
 
Because of how plastic part molds work, an injection molding parting line is needed. To 
allow plastic to be injected into the middle, the mold's two parts can be brought together. 
Even though the mold seals very firmly, as it opens to reveal the part, the area around 
the seam will have a very slight parting line. The separation line is something that needs 
to be taken into account and planned for with every mold, even if it could be extremely 
minute depending on how tightly the mold fits the material. 
 
What difficulties may a parting line present? 
 
Plastic separation lines present certain difficulties in the injection molding process, as 
with anything else. Here are just a few issues with parting lines that injection molding 
experts frequently run with. In addition to silicone replacements, a set of earbud 
headphones. 
Preventing Parting Lines on Parts Made of Liquid Silicone 
 
Working with liquid silicone rubber (LSR) parts is more difficult. Molten LSR can 
produce more flash, or thin extra plastic, along the parting line because it can fit into 
narrow spaces. Although it is more challenging to get it right, well-designed LSR parts 
will have a parting line that is narrower and less obvious. These earbud covers are 
constructed of LSR (right).