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S-136 Steel
Meaning
High quality stainless tool steel used in the manufacture of injection molds provides excellent corrosion resistance and polishability for components requiring high dimensional stability and finish. This material is often selected for the production of plastic enclosures for electronic devices because it can withstand the high pressures and temperatures of the molding process. By using s-136 steel, the manufacturer can create molds that produce parts with a mirror like surface, which is essential for consumer products with a premium aesthetic.
The steel is also resistant to the corrosive gases that are sometimes released by plastic resins during the injection cycle. This durability ensures that the mold can produce hundreds of thousands of parts before it needs to be refurbished. It is a preferred choice for the high volume production of smart home devices and wearable technology.
Material Hardness
Strength of the mold is a critical factor in maintaining the accuracy of the plastic parts over long production runs. S-136 steel is typically delivered in a pre-hardened state or can be heat treated to reach a high level of hardness. This resistance to wear prevents the delicate features of the mold, such as thin ribs or sharp edges, from degrading over time.
If the mold material is too soft, the dimensions of the plastic parts will start to drift, leading to assembly problems and a high scrap rate. The toughness of the steel also allows it to resist cracking under the thermal stress of the repeated heating and cooling cycles. Proper maintenance of the mold, including regular cleaning and lubrication, further extends its useful life.
Corrosion Resistance
Protection against rust and chemical attack is the primary reason for choosing this stainless grade over cheaper carbon steels. Because s-136 steel contains a significant amount of chromium, it forms a passive layer on its surface that prevents oxidation. This is particularly important for molds that are stored in humid environments or used with plastics that release acidic byproducts.
If the surface of the mold becomes pitted or rusted, these defects will be transferred to every plastic part that is produced. Using a corrosion resistant steel reduces the need for expensive surface coatings and minimizes the downtime required for mold cleaning. This reliability is essential for maintaining a steady supply of components for the assembly line.
Surface Finish
Quality of the final product is directly tied to the ability of the mold to be polished to a very high standard. S-136 steel is known for its excellent polishability, which allows for the creation of clear plastic lenses or high gloss enclosures. The fine grain structure of the steel ensures that the surface remains smooth even after extensive use.
During the mold making process, the steel is ground and then polished using progressively finer diamond pastes. This labor intensive process is what gives the final plastic parts their professional appearance. If the steel had inclusions or impurities, the finish would be uneven and the parts would look cheap.
This material provides the foundation for the high quality look and feel that modern consumers expect from their electronics.