Stripper mold is mold that use stripper plate to push sample out of the mold. It can solve shape cups, containers and lids without undercut. Stripper plate is between core plate and cavity plate. When mold open, ejector system will push to stripper plate and stripper plate push sample out of the mold.
I. When we need use stripper mold?
Some samples have depth so big, if we use ejector pin to push sample out of the mold, sample will have ejector mark. Or samples have inside surface is smooth, we can not use ejector pin. This time, stripper plate is the best way to push sample out of the mold. It is used when ejector pins, pressurized air can not push sample out of the mold. Stripper plate is simple plate, easy to design and marking.
II. Injection stripper mold construction.
- Bottom clamping: Fix mold to injection machine.
- Spacing block. Create space to make ejector system.
- Support core plate:
- Core plate: Fix insert core and make guide system.
- Stripper plate: Fix stripper insert and guide system.
- Cavity plate: Fix cavity insert.
- Top plate: Fix mold to injection machine.
- Cavity insert.
- Bush guide.
- Stripper insert. Push products out off the mold.
- Core insert.Make inside shape of product.
- Guide pin.Guide for cavity plate and core plate.
- Guide for stripper plate: When ejector system push to stripper plate, stripper guide will take it moves forward
- Connecting rod. It is fixed with stripper plate by a bolt.
- Spring: Support push back ejector system.
- Ejector plate. It has holes to assemble ejector pin.
- Ejector back plate. Fix ejectors pin, prevents the ejector pins from disengaging.
III. How to injection stripper plate working?
Stripper mold working is same normal mold with: Clamping, Injection, dwelling, cooling, mold opening, remove product.
I have written more detail about injection molding process at: Plastic injection molding process steps
This post I am going to explain about stripper plate – how it works?
How does it move?
There are 4 ways that it is made:
+ A machines mechanical ejector.
+ Hydraulic pistons within the mold.
+ Pneumatic (air) pistons within the mod.
+ With pull bars.
In this post, I will say about moving by machines mechanical ejector.
As i have written above, stripper plate used to push samples out of the mold. Is it ejector plate? How does it connect with ejector system? It is fixed with ejector plate by a connecting rod and bolt. When the ejector plate moves forward, connecting rod moves forward along with it. This is causing the stripper plate move forward and push molded article. Stopper 20 will prevent moving of stripper plate.
After remove product finished, spring 17 will push ejector plate move back, the stripper plate also returns to the original position.
You can see this video below to understand how it works?
IV. The disadvantages of a stripper plate.
Mould marking with stripper plate is more difficult than ejector pin. If it is not designed and made right there will be constant part quality issues such as flashing. Cycle time will also suffer. It will increase cost of mold.