Tooling Procurement Verification Protocols and Part Approval Risk Management
Verify tooling geometry with dimensional capability audits under steady-state continuous thermal conditions before releasing final capital purchase payments.
Mold Wear
Meaning
Surface degradation happens when the repeated injection of abrasive resins or the mechanical clamping of metal components gradually erodes the precision surfaces of a tool over many cycles. This mold wear changes the dimensions of the cavity and leads to the formation of flash, where molten material leaks between the parting lines. It governs the quality of the final part and determines the point at which the tool must be removed from production for refurbishment.
The process continues throughout the life of the tool but accelerates when high glass content materials or high pressures are used. Monitoring this erosion is necessary to avoid the production of scrap.
Degradation Mode
Abrasive forces from the flowing material and the chemical attack from cooling gases slowly remove the protective finish of the steel. While mold wear progresses, the sharp corners of the tool become rounded and the surface texture may become pitted or scratched. Mechanical wear also occurs at the sliding surfaces, such as pins and slides, which can lead to galling if lubrication is insufficient.
The high pressure required to inject the resin forces it into every small gap, gradually widening those gaps through a process similar to sandblasting. Over time, the parting line of the mold loses its perfect seal, allowing material to escape and create thin edges on the molded parts. These changes are often microscopic at first but become visible as the tool reaches its cycle limit.
Production Constraint
Manufacturing efficiency drops as the machine must be stopped more frequently to clean off excess material or adjust settings to compensate for dimensional changes. When mold wear becomes significant, the cost of post-processing the parts to remove flash can exceed the value of the components themselves. The increase in part weight due to the enlarged cavity also leads to higher material costs over large production runs.
If the wear is uneven, it can cause the parts to stick in the mold, leading to longer cycle times or damage to the ejection system. Quality control becomes more difficult as the process window narrows and the risk of shipping non-conforming parts increases. Eventually, the tool can no longer produce parts that meet the required tolerances and must be replaced or repaired.
Maintenance Interval
Preventive strategies involve regular cleaning, lubrication and inspection to extend the functional life of the expensive steel assets. By tracking the number of cycles and monitoring part quality, engineers can predict when mold wear will reach a critical level. Coatings like titanium nitride or hard chrome are often applied to the cavity surfaces to provide a harder barrier against abrasion.
When a tool is sent for repair, the worn surfaces are usually welded and then machined back to the original specifications. This maintenance ensures that the production line remains consistent and that the tool can achieve its expected lifetime volume. Proper storage and handling between runs also prevent secondary damage like rust or accidental impact.
Maintaining detailed records of every repair helps in identifying the root cause of premature failure.