A three plate mold has 2 parting lines and three opening type runner opening, runner stripper plate opening, and product opening. One parting line use to remove a runner and one parting line use to remove product. It has three main groups: runner stripper plate, fixed side(cavity plate), and movable side(core plate).
* Advantages of 3 plate mold.
+ Gate location select easy.
+ 3 plate mold usually uses pin point gate so it remove easy.
+ Product and runner can remove separately, it is suitable for automation.
* Disadvantages of 3 plate mold
+ Mold is expensive.
+ Injection molding cycle is long.
+ Injection machine need large stroke.
+ Mold structure is complex, weak durability.
I. Three plates mold construction.
- Top plate.
- Runner stripper plate.
- Cavity plate.
- Core plate.
- Support plate.
- Space plate.
- Bottom plate.
You can see basic function of mold part at two plate mold review plastic molding
II. How does a 3 plate mold work?
Plastics injection molding steps: injection -> cooling -> opening -> remove product. Three processes injection, cooling, and remove products are common. You can read it at plastic injection molding process.
This post I will explain opening process.
* 3 plate mold opening sequence.
There are three opening types in 3 plate mold base.
+ Runner opening
+ Runner stripper plate opening
+ Product opening.
1. Runner opening.
This opening will cut runner from the product. When mold open, fixed side (cavity plate) will slide on support pin by gate cutting spring fore. Gate cutting spring assemble between the runner stripper plate and cavity plate. Product will attach on core plate. The runner lock pin skip runner on the runner stripper plate. 3 plate mold usually use pin point gate so it is cutting easy. Mold will move continuously.
2. Runner stripper opening.
After cavity plate move to end of puller bolts. Puller bolts will move following cavity plate. It pushes runner stripper plate moving so runner stripper will push runner out of runner lock pin. Spring pin will push runner out of runner stripper.
3. Product opening.
After side parting lock is opened. Core plate and cavity plate is separated. Cavity plate will stop and core plate will move continuously. I will create a distance to remove product.
This video below will explain about mold opening sequence.