- Created: 19-01-22
- Last Login: 19-01-22
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PLMHYdkki58
What is Injection Molding:
Injection Molding is a manufacturing process for producing parts
in large volume. It is most typically used in mass-production
processes where the same part is being created thousands or even
millions of times in succession.
Why Use Injection Molding:
The principal advantage of injection molding is the ability to scale
production en masse. Once the initial costs have been paid the price
per unit during injection molded manufacturing is extremely low. The
price also tends to drop drastically as more parts are produced.
Other advantages include the following:
Injection Molding produces low scrap rates relative to traditional
manufacturing processes like CNC rubber machining which cut away
substantial percentages of an original plastic block or sheet. This
however can be a negative relative to additive manufacturing
processes like 3D printing that have even lower scrap rates.
Note: waste plastic from injection molding manufacturing typically
comes consistently from four areas:
The sprue
The runners
The gate locations
Any overflow material that leaks out of the part cavity itself (a
condition called “flash”).
A sprue is simply the channel that guides molten plastic from the
nozzle of the injection molding machine to the entry point for the
entire rubber injection machine tool. It is a
separate part from the mold tool itself.
A runner is a system of channels that meet up with the sprue,
typically within or as part of the mold tool, that guides the molten
plastic into the part cavities within the mold tool. There are two
principal categories of runners (hot and cold) which you can read
about here.
Lastly, the gate is the part of the channel after the runner that
leads directly into the part cavity. After an injection mold cycle
(typically only seconds long) the entirety of the molten plastic will
cool leaving solid plastic in the sprue, runners, gates, part
cavities themselves, as well as a little bit of overflow potentially
on the edges of the parts (if the seal isn’t 100% right).
Thermoset material, such as an epoxy resin that cures once exposed to
air, is a material that cures and would burn after curing if one
attempt is made to melt it. Thermoplastic material by contrast, is a
plastic material that can be melted, cool and solidify, and then be
melted again without burning.
With thermoplastic materials the material can be recycled are used
again. Sometimes this happens right on the factory floor. They grind
up the sprues/runners and any reject parts. Then they add that
material back into the raw material that goes into the injection
molding press. This material is referred to as "re-grind".
Typically, quality control departments will limit the amount of
regrind that is allowed to be placed back into the press. (Some
performance properties of the plastic can degrade as it is molded
over and over). Or, if they have a lot of it, a factory can sell this
re-grind to some other factory who can use it. Typically regrind
material is used for low-quality parts that don't need high
performance properties.
Injection Molding is very repeatable. That is, the second part you
produce is going to be practically identical to the first one etc.
This is a wonderful characteristic when trying to produce brand
consistency and part reliability in high volume production.
Injection Molding is a manufacturing process for producing parts
in large volume. It is most typically used in mass-production
processes where the same part is being created thousands or even
millions of times in succession.
Why Use Injection Molding:
The principal advantage of injection molding is the ability to scale
production en masse. Once the initial costs have been paid the price
per unit during injection molded manufacturing is extremely low. The
price also tends to drop drastically as more parts are produced.
Other advantages include the following:
Injection Molding produces low scrap rates relative to traditional
manufacturing processes like CNC rubber machining which cut away
substantial percentages of an original plastic block or sheet. This
however can be a negative relative to additive manufacturing
processes like 3D printing that have even lower scrap rates.
Note: waste plastic from injection molding manufacturing typically
comes consistently from four areas:
The sprue
The runners
The gate locations
Any overflow material that leaks out of the part cavity itself (a
condition called “flash”).
A sprue is simply the channel that guides molten plastic from the
nozzle of the injection molding machine to the entry point for the
entire rubber injection machine tool. It is a
separate part from the mold tool itself.
A runner is a system of channels that meet up with the sprue,
typically within or as part of the mold tool, that guides the molten
plastic into the part cavities within the mold tool. There are two
principal categories of runners (hot and cold) which you can read
about here.
Lastly, the gate is the part of the channel after the runner that
leads directly into the part cavity. After an injection mold cycle
(typically only seconds long) the entirety of the molten plastic will
cool leaving solid plastic in the sprue, runners, gates, part
cavities themselves, as well as a little bit of overflow potentially
on the edges of the parts (if the seal isn’t 100% right).
Thermoset material, such as an epoxy resin that cures once exposed to
air, is a material that cures and would burn after curing if one
attempt is made to melt it. Thermoplastic material by contrast, is a
plastic material that can be melted, cool and solidify, and then be
melted again without burning.
With thermoplastic materials the material can be recycled are used
again. Sometimes this happens right on the factory floor. They grind
up the sprues/runners and any reject parts. Then they add that
material back into the raw material that goes into the injection
molding press. This material is referred to as "re-grind".
Typically, quality control departments will limit the amount of
regrind that is allowed to be placed back into the press. (Some
performance properties of the plastic can degrade as it is molded
over and over). Or, if they have a lot of it, a factory can sell this
re-grind to some other factory who can use it. Typically regrind
material is used for low-quality parts that don't need high
performance properties.
Injection Molding is very repeatable. That is, the second part you
produce is going to be practically identical to the first one etc.
This is a wonderful characteristic when trying to produce brand
consistency and part reliability in high volume production.