Wear of Molds

The parts of plastic injection mold wear out due to contact or friction between parts, and in addition, due to glass fibers contained in the plastic resin.
If the shape of the wear exceeds the tolerable range, problems occur such as the mold can no longer move correctly, the mold will be broken, or the shape of the molded product becomes deformed.
The worn out of molds is classified into normal wear and abnormal wear.
Normal wear is the worn out that is caused when parts that touch or slide against each other gradually get worn out.
Although it is technically possible to make it difficult for parts to get worn out, it is extremely difficult to prevent wear fundamentally unless the parts do not contact each other.
Normal wear is classified into initial wear and steady wear.
If the part is replaced with a new part when the steady wear reaches managed scheduled dimensions, it is possible to prevent in advance failures or problems with the molds.
On the other hand, abnormal wear is wear that is not normal wear. There are five typical classifications of abnormal wear.

1. Abrasive wear（abrasive wear）This is the form of wear that can occur easily when there is a difference in the hardness of the materials that are rubbing against each other. The harder material bites into the softer material generating scratches, and causing wear.

2. Adhesive wearThis is the form of wear in which projecting parts of materials hit against each other causing a part to get adhered, and as a result of growth of the adhered part, it becomes a transfer particle, and eventually falls off as wear dust.

3. Fatigue wearThis is the form of wear in which metal fatigue occurs due to repletion of the application and removal of load (repetition of operation and stopping), causing wear,

4. Fretting wearThis is the form in which wear of fine pitching shape occurs on the surface of mating parts.

5. Corrosion wearThis is the form of wear that is caused when a potential difference is generated between metals in a corrosive atmosphere, thereby causing the sliding parts to disappear, resulting in damage occurring speedily due to the addition of friction wear.