Prevent Hot Runner Downtime with Scheduled Maintenance

Preventative Maintenance (PM) is a critical task that aims to help ensure your mold(s) run at peak efficiency by strategically investing in service and maintenance before things go very wrong and get very costly. A well executed PM program will help improve productivity and avoid costly downtime including unscheduled breakdowns. However, the trick has always been in finding the right balance to optimize your operation. Too little service and you could still incur breakdowns, among other issues, and too much maintenance you end up throwing money away.

The frequency of a Preventative Maintenance Program is very specific to individual molds. There are numerous factors that have an influence on the scheduling of PM. Some of the most significant are materials and how the processing equipment is being operated.

Materials being molded play a big part in how often a hot runner mold will require maintenance.  Some molds can go months with very little maintenance while others will require daily cleaning of the “gas” residue that builds-up on the face of the mold. Aggressive materials that contain “fillers” (glass) or are corrosive can prematurely wear hot runner components.  These types of materials require that the hot runner be manufactured using special materials that protect the system in order to maximize the “runtime” between PM’s. If your hot runner was not specified to process this type of resin grade your maintenance schedule may be more frequent.

If a mold becomes hard to start-up, difficult to maintain all cavities or has required a gradual increase in nozzle set-points, there needs to be a full evaluation completed to determine the “wear” on gate components (both in the hot runner & mold). The condition of the gate may be a clue as to the need for PM. On valve gated molds, flash around a valve pin may require valve pin replacement and/or gate replacement or repair. Molds with a thermal gate also experience wear on torpedoes or liners in the gate components. Sometimes a frequency for PM can be set up based on the shot count.

Training personnel on the shop floor on the proper start up & shut down procedures is also an important factor in keeping a mold performing at its best. All hot runner systems require a “soak time” for heat to penetrate through the system. Just because the hot runner controller indicates that the set-point has been reached, doesn’t mean that everything is up to a temperature that allows you to safely start up the mold. Knowing the material & the hot runner system allows you to determine what the “soak time” requirements are for each mold. Heat sensitive materials may degrade if it’s left to sit at a normal processing set-point for an extended period of time.  Degraded material can lead to major hot runner maintenance.

If the hot runner system is “On”, the mold cooling must be “On”. If the mold is valve gated and has individual pistons for each cavity, mold cooling should remain “On” for a period of time after the hot runner is shut down.  This protects the actuator seals from being harmed by the residual heat from the hot runner as it cools. This becomes especially important if running a high temperature engineered resin.

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Edited by Leafly Mould Provides Injection Mold, Plastic Mold, Injection Molding, Die Casting Mold, Stamping Mold

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