Rubber parts manufacturing process
There are a few process to manufacture rubber parts such as compression molding, injection molding and extrusion etc. You should choose the reasonable manufacture and qualified manufacturing process based your budget, quality and demand. We will talk about the different manufacturing process first as below.
Rubber compression molding for rubber parts manufacturing
Rubber compression molding normally used to manufacture heat cured plastic resin such as silicone, EPDM and NBR etc. Sure TPU and TPE have the heat cured series type. Rubber compression parts molding is commonly use to make keypad, phone case, automotive key case, rubber gasket and rubber cap etc.
Rubber compression mold normally have no so complex structure as the plastic, there is no ejection pins as the injection mold. Sure on the compression mold to manufacture the rigid resin such as bakelite, there is ejection pin and ejection plate as the plastic injection mold. Normally there is only top plate with cavity and bottom plate with core for the compression molding mold. Sure we can make the sliders on the compression mold. On the rubber compression molding process, it is to use the hand to take the rubber part out of mold and have to use the hand to remove the flash from the mold as well. Except for this rubber compression molding have following advantage:
- Reduce lots of mold cost compare to injection mold, sometimes the compression mold cost is 1/50 of injection mold cost
- It is easier to make the complex rubber part even if there is big undercut what you think it is not possible to use the injection mold to manufacture, but rubber compression can make that possible.
- Use the single cavity compression mold to have the rubber prototype made is very good solution to save cost and have the rubber parts as the quality of production.
- It is easier to have qualified surface finishing, normally you do not worry about lots of defect you faced on injection molding such as flow mark, jetting mark and short shot etc.
- Designer have more imaginary space to design the rubber parts as the compression molding process can make the thicker parts out even if the wall thickness is not consistence.
- It is easier to change color by using rubber compression molding, normally there is no additional cost to change colors
- Easier to have family mold
More information for the compression molding process, you can review the article “silicone compression molding” understand more.
Rubber injection molding
Rubber injection molding is most like the plastic injection molding. But we should pay more attention to optimize the rubber molded parts ejection system. Sure the venting system is also very important on injection mold manufacturing. If we can not design a ejection system for the rubber molding mold, then you destroy the ejection system. I Hedy have saw a few guys have the ejection system, but during the production, it is not useful for the ejection.
Rubber compression molding is commonly used to make rubber gasket, rubber end cap, rubber connectors, rubber cap and over molding rubber handle or enclosure parts etc.
If the rubber shore hardness is very low, normally it is not necessary to design the ejection system. So the experience to do the rubber molding production is very important. I have a few suggestion as below:
- You had better to use the big ejection pin instead of the small ejection pin, put the ejection pin the area where it is most possible location to ejector the rubber parts out.
- If it is possible, you had better to use ejector plate with ejector pin. This is to have ejection area for the rubber parts.
- Use the side gate instead of the sub gate if it is acceptable by your customers. Some of rubber resin is good to use the sub-gate without jetting on the gate, you have to review the resin specification before the mold design.
Before you design or manufacture the rubber injection mold, you have to read the rubber resin specification first. Normally the rubber resin supplier offer the guide for you to design the rubber.
Compare the rubber compression molding, what is the advantage of rubber injection molding?
- If you have good ejection system, no need to bring the rubber parts from mold with hand, it is possible to have the automatic rubber parts manufacturing.
- No need to remove the flashes by hand.
Rubber extrusion molding process
Rubber extrusion molding is one of cheap manufacturing to manufacture the rubber tube and rubber gasket etc. For example, your refrigerator door gasket is made by this process. It is very simple mold to extrude the rubber parts.
There is thermoset and thermoplastic rubber extrusion molding. In South of China, thermoplastic rubber extrusion molding is more than the thermoset rubber extrusion molding