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Like any piece of machinery or equipment, mold maintenance is critical to the life of the tool and the quality of the parts it produces. It’s also critical to the mold’s productivity and efficiency. No matter how much you pay for the mold up front, it won’t give you a good return on your investment if you do not maintain it properly.

Tim Peterson

December 6, 2010

6 Min Read
Mold maintenance tips: Laziness now means trouble later

Like any piece of machinery or equipment, mold maintenance is critical to the life of the tool and the quality of the parts it produces. It’s also critical to the mold’s productivity and efficiency. No matter how much you pay for the mold up front, it won’t give you a good return on your investment if you do not maintain it properly.

The major issue is having to replace the mold before the end of the product life. Putting off mold maintenance is very shortsighted. Compare it to your vehicle. If you don’t change the oil, perform regularly scheduled maintenance as recommended by the vehicle maker, and generally maintain the vehicle, it will wear out more quickly. It’s the same with tooling. If you don’t take the time to perform regularly scheduled maintenance on the mold, it won’t last.

There are many reasons why mold maintenance is delayed or, in some cases, not done at all. Some molds are put into a dedicated press where they run 24/7 for a year or more, and nobody wants to take the time to pull the mold and interrupt the production run. However, if you don’t take the one shift or so to pull the mold for maintenance, you’ll eventually be down a lot longer. By waiting until the mold breaks down due to lack of maintenance, you keep losing time. This is particularly true with high-volume molds, or molds that run filled engineering-grade materials.

Mold maintenance is something that needs to be considered up front and needs to be built into your capacity planning. Regularly scheduled mold maintenance means you will get longer life out of the mold, and you will maintain your productivity and efficiency. You can’t keep running the mold without preventive maintenance. It may look good on paper, but it just isn’t possible.

Here are a few tips for ensuring a smooth-running tool:
Schedule maintenance. If you are a large supplier on any scale, you need some type of Enterprise Resource Planning (ERP) software to schedule maintenance and alert you when a mold needs to be pulled for maintenance. Many of these computer programs send an automatic notice when a specific mold needs maintenance. These are programs that work with the machine.
Many production scheduling programs allow you to see the machines running in real time, and also include built-in modules that tell you when it’s time to take the mold out for maintenance. Sometimes it’s done by the number of cycles. Some people might ignore those signals, but they run the risk of bigger problems if they do.

Another problem is looking at every tool as being the same. Even if you have mold maintenance software, you can’t schedule every mold for preventive maintenance at the same shot count. The type of material is one major factor. You can get more cycles between maintenance on a mold running polypropylene than you can with one running glass-filled nylon. Mold operating temperature is another factor. Molds running extremely high-heat engineering-grade materials such as Torlon and using hot oil require more frequent maintenance. If you’re using ERP software, you have to set up each mold on a separate schedule according to that particular mold’s requirements.

Most molding operations have a mold maintenance and repair department that can perform routine maintenance and small repairs, such as broken core pins or ejector pins. For repairs beyond the scope of the molder’s maintenance and repair department, the mold may need to be returned to the mold manufacturer.

Grab the low-hanging fruit. There are many simple and easy maintenance steps that you can take. A buildup of gas or resin in certain areas can easily be wiped down. Don’t let buildup occur until you eventually crash something.

Fix, don’t block, faulty cavities. One big issue in high-cavitation tools is the tendency to block off one or more cavities with which there’s a problem or if those particular cavities quit making conforming parts. This is a huge deal with the scientific molding process that many molders use in today’s production environment. It wasn’t such a problem in the days when molding was a “black art” and the process technician could simply turn some knobs and alter the process.

Today, shutting off cavities means you’re changing your process considerably, i.e., changing pressures and everything else. With scientific molding, shutting off cavities isn’t accepted the way it used to be. Additionally, you’re reducing your output and not getting the productivity you need, and all this is the result of poor planning in the beginning and failing to take out and maintain the mold. Because blocking off cavities means you cut your production, it’s a guarantee you won’t have time to pull the mold for maintenance or repairs. You need to see the value in every part that you mold, which makes maintenance a necessity.

Put it away clean. For a company that does shorter production runs, and thus a lot of mold changeovers, one of the big problems is not preparing the mold properly for putting it back on the shelf until its next run. For instance, the automotive industry carries a huge shift in volumes. Many vehicle makers are using the same parts on all platforms, and a lot of custom parts run fewer pieces, so molders for that industry are doing more changeovers and keeping molds on the shelf longer.

Take the time to blow out the waterlines, spray the mold with rust preventive, and make sure it’s production-ready before you store it. If there is a broken core pin or ejector pin, fix it when the mold comes out; don’t wait until you have to run it again. Have a system in place whereby a mold doesn’t go on the shelf until it’s production ready. There’s danger in thinking, “We made it through this run. Why spend the money to fix it now?”

Local support
At Industrial Molds, we’ll sometimes get a mold back in such bad shape that the customer’s in-house shop can’t fix it. Many companies just don’t want to spend the money on preventive maintenance. As OEMs try to get their molds cheaper and cheaper, they also want the moldmakers to throw in maintenance as part of the mold build.

Something else to consider is the service that your local mold manufacturer can provide. If U.S. OEMs and molders keep sending their tool builds to China, they won’t have any local shops to do maintenance. We spend a lot of time—and some of our customers spend a lot of money—fixing offshore tooling.

With the evolution of all the new engineered plastic materials, you can’t just throw grease on a mold anymore and call it good to go. You have to pay attention to the temperature specs. We’re not running tools the way we used to. The maintenance has be more tool specific in today’s molding world. Products are more temperature sensitive, and as temperatures get higher, we have to explore the proper lubricants that can be used on a mold. “Proper” maintenance is as important as just maintenance.

Tim Peterson is VP of Industrial Molds Group (Rockford, IL), a designer and manufacturer of injection molds. Industrial Molds says it will provide a CD with every mold it builds that gives instructions on proper preventive maintenance, a suggested PM schedule, and tips for keeping its molds in tip-top shape for a long, productive life.

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