RUST PROTECTION & O-RINGS
In one situation I experienced, the tool was properly cleaned, sprayed with rust preventative, and pulled from the press; but the water leak was not noticed, allowing the water to accumulate inside the clearance holes. With the tool sitting in storage, the water leaked into the diamond-polished cavity and caused major damage. Some will ask: How could this occur with the tool properly pulled, cleaned, and sprayed with a rust preventative? Well, not all rust preventatives are the same. I have used numerous brands over the years and am surprised that some even are used in the industry.
There are numerous reasons why people choose a specific brand or formula: cost, what they have always used, not fully understanding the pros/cons, or just pure opinion. I bring this up only for you to consider whether the rust preventative you are using is contributing to any of your issues.
The viscosity varies with the brand of rust preventive. Some prefer to use a more liquid style that is more visible. I have found that these types can sometimes cause startup issues with scrap and labor to clean the cavities before starting the mold for production. The more liquid versions can sometimes also break down the greases used on the tool and contribute to bleeding, scrap, and downtime for cleaning.
For years I have used a dryer version, which does not break down grease, provides a more protective rust barrier, does not require cleaning the cavities at startup, and reduces startup scrap with the rust barrier being removed after a couple of shots. When there is a need to transport molds through different climates, I use a more robust protectant. (Cavities can also have coatings applied to protect against rust if the issue is chronic.)
One other aspect of rust prevention is using a good shutdown procedure. When running a mold with a chiller, you are at risk for rust from condensation if not shut down properly. When the mold is done running or going to sit idle, it should be brought up to room temperature and have a protectant applied immediately.
Maintaining the water connections and O-rings should also be considered. Water connections should be observed for leaks during preventive maintenance (PM), and if any leaks are observed in production, the issue should be addressed as soon as possible. O-rings in the water connections will fail over time and most molders do not have a procedure to replace them pre-emptively, so the first evidence of a bad O-ring is a leak.
When running molds with higher water temperatures (above 180 F), the water lines should be hard-plumbed using fittings with a tapered sealing surface, versus the standard water coupler connection using O-rings. This will reduce the chance of a worker injury from a high-temperature water leak.
I would recommend that O-rings inside the tool be replaced at each PM. And if any observations indicate an internal water leak in the tool, that should be addressed as soon as possible. One thing a toolmaker does not like are components or cavity inserts corroded with rust, as these can be very difficult to remove.
The article comes from China injection mold manufacturer - Mold Best Assurance Company Limited, website is www.mbamoldanddesign.com
