There are 6 steps in plastics injection molding process steps as preparation, setup, mold closing, injection, cooling, mold opening and remove product. I will explain these process in this post.
I. Preparation.
+ Prepare the mold. We need check mold before assembling in to injection machine. Mold need clean carefully, assembly status. Does each part have crack, bite? Do we assemble ejector pin, or angular core pin mistake?
+ Prepare plastic material: We need dry material to remove moisture. Dry time is different for each material.
+ You need calculate material weight following quantity of product.
+ Prepare cooling channel, jig, insert.
II. Setup.
+ Assemble mold into the injection machine, cooling system, set temperature for the core plate and cavity plate. Then, configure ejection system of the mold, mold opening distance in the injection machine.
+ Prepare working area, worker, equipment, robot to do injection molding process automatically.
+ Connect resin from dry system to feeder hopper of injection machine.
+ Remove old resin in the nozzle.
+ Setup injection condition follow working manual.
III. Plastic injection molding process steps.
Source of this picture: custompartnet.com
1. Clamping process.
Before injection machine push molten plastic into the mold, each half of the mold is attached to the injection machine. The clamping system will clamp cavity plate and core plate. This force will skip injection mold always closing under high pressure of injection process. If clamping is small, the mold can open under high pressure. It is cause of flash, step.
+ How to calculate of clamping force.
F(ton)={A(cm²) x P(kg/cm²)}/1000
F = clamping
A= molding product reflection area
P = pressure in the mold.
You can read this post for clamping force calculate as follows: injection molding calculate clamping force
2. Injection process.
2.1 Injection filling process.
Nozzle will move to contact with injection mold at sprue.
Screw will move forward to push molten plastic in to the mold. Molten plastic will go through mold by way: sprue -> runner -> gate -> cavity.
2.2 Gate seal (Gate closure) process.
This is the process from injection completion through gate sealing (gate closure).Holding pressure (secondary pressure) is applied during cooling and solidification of the gate. This process used to improve sink mark, short shot.
3. Cooling process.
Water or oil will use for cooling channel. As the plastic cools, it will solidify into the shape of the desired part.
4. Plasticizing resin.
While the product cools, screw of injection machine will move back to prepare material for a new cycle.
5. Mold opening and remove product.
When resin cools enough, mold will open and rob of injection machine will impact to ejector plate then push sample out of the mold.
6. Gate cutting and parking product.
After we get sample, it will move to gate cutting machines then parking for next purposed.
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