-The Difference Between Two Plate Mold and Three Plate Mould
What Is a Three Plate Mould?
Three plate mold is also called small gate mold and it’s more complex than 2 plate mold. It has an additional mold plate between top clamp plate and cavity plate, called runner plate, which allows the runner scrap and plastic molded parts released separately.
Another thing is that the three plate mold requires three times opening. The first opening is to break the gate and pull sprue, so the feeding runner can easily take by arm robot or manually by hand.
The stripper plate will move after puller bolts pulled by cavity plate. The second time is called runner opening, which is to release the molded parts.
This opening will make space between the stripper plate and the cavity plate. The third time is to release the product automatically. It is suitable for automation.
3 plate mold is usually employed when the part is too big and need multiple injection points.
Merits and Drawbacks
Three-plate can be more problematic. Three plate mold design has more advantages to locate the gate. It can have a gate located at the middle of the plastic part and allows pin-point gates.
Compared to two plate mold or a hot-runner mold, three plate mold is cheaper to build and less likely to break down. Thermally some sensitive materials are less likely to degrade.
However, it could be problematic as well. Three plate mold requires longer cycle time and long run distance.
Therefore, it needs a bigger injection molding machine. Besides, although three plate mold could help reduce the production cost, it may cost more material because of the runner scrap. It is necessary to use a sprue puller.
What is Two plate mold
Two plate mold is the most typical mold, the simplest mold, and the most reliable mold.
it has a simple construction. Normally it has the fewest number of moving parts including a fixed plate and a moving plate.
Sprue, runners, gates, and cavities are all on the same side of the mold and cold runner and mold cavities on the same plate.
It is easy to design and to build. It has one parting line, A side and B side 2 main parts.
Advantages of 2 plate mold
It is more straightforward to run in production and easy to operate. Because of that, it is also cheaper to manufacture compared to other molds.
Besides, it has minimal operational problems, which means longer lifespan and less maintenance.
It has shorter run distance and fewer limitations, which makes things easy for the operator the set up the parameters of the injection molding machine.
Another great advantage of two plate mold is that it has a shorter cycle time, which could help reduce the cost of products and improve the efficiency of production.
For mass production, it can save money and time. Besides, two plate mold drops the plastic part freely. But after molding, there’s a need to cut off the gate manually.
What’s more, it’s easier to choose a gate shape and location when it comes to two plate mold.
The gating method includes a side gate, direct gate or submarine gate, and side gate and direct gate are generally used.
With submarine gates, parts and runner are separate.
Other than direct gates, gate location is limited to the side of the plastic part, with a few exceptions.
Compared to three plate mold, two-plate mold is much simpler and low cost. Usually, three plate mold is not recommended as it has some disadvantages.
It’s not just because of a much more complex structure but much higher scrap rate and it’s also lack of stability because of a complex mechanism.
It’s random to use for high volume production because it required longer cycle time and bigger injection molding machine as the run distance is longer comparing with 2 plate mold.