Make sure all auxiliary equipment is turned off, and that the production area has been prepared for the start-up team’s duties. Be sure to provide that team with a list of scrap / downtime issues that occurred during the last shift of the week, so the team’s members are fully aware of potential problems. Press shutdown provides the perfect opportunity for a post-production preventative maintenance inspection. Tiebars, belts, hoses, oil levels, lubrication systems, etc. should be inspected for proper working conditions.
By Garrett MacKenzie The weekend comes to an end and the time comes to bring the molding floor back online for the beginning of a new work week. A molder can sometimes dread the tasks associated with a full plant restart. There are many potential failures that can occur as a plant is returned to a production state. Despite these risks, much of the headache can be avoided simply through proper shutdown and start up procedures. The following article addresses many key components that often lead to poor restarts. It also provides insight into some of the methods that can be implemented to not only reduce system breakdowns, but also can offer smoother start-ups with fewer problems. Anyone who has experienced a full plant restart can tell you it can either be a smooth or a tragic event. As much as we wish that machines, tools and equipment would just cooperate, this simply is not always the case. It is important to understand the key components of start-up to be able to counter with fail-safe procedures on restart. Rushing through start-up often leads to failures within the facility. Here are some of the key components that lead to poor starts, as well as what you can do to prevent these factors from negatively affecting your shop: Shutdown: One of the first key considerations to plant restart is shut down. Shutting your shop down is best viewed as preparation for plant start-up. Your facility’s shutdown procedures are one of the biggest contributing factors in how effectively your team brings the plant back into a new production workweek. Here are some of the primary focuses in plant shutdown: 1. Material Handling: There are many material-related failures that can cause poor starts. At shutdown, make sure your gaylords and material containers have been covered to prevent contamination and excessive exposure to moisture. Dried material in hoppers or one-shots above the press should be removed in anticipation of the restart, and to prevent wet material from being a start-up concern. As the press is shut down, run the barrel dry. This prevents material from bridging in the feedthroat of the press and causing unneeded downtime. If dryers are to be left on over the weekend, their temperatures should be banked (lowered) to help prevent overdrying. 2. Tooling: Molds are a key focus. Improper shutdowns can be a primary reason for poor start-ups. Mold chillers are prone to sweating and should be cycled 5-10 minutes with the chiller off prior to full shutdown. This helps to reduce sweating, a primary cause of rust. Tooling should be cleaned and sprayed with rust preventative, and moving components should be inspected for wear and proper grease. When working with clear polycarbonate or light colored materials and a hot runner mold, it is good practice to shut the hot runner off and allow the machine to cycle until the mold no longer produces parts. This keeps material from baking in the manifold, and reduces contamination at start up. Mold should be left with mold halves touching (not under pressure) to protect the mold faces. Look for signs of water leaks on top of the mold. If they exist, fix the leak and soak up water to prevent it from getting inside the mold. Main water should be shut off and relieve the pressure from all water circuits. 3. Press Side: The barrel should be left empty, and the screw sucked back to about 1.00 to prevent drooling and to leave the screw in a neutral state. As mentioned above, mold halves should be left touching to prevent exposure to environmental exposure to moisture while in stasis. Check the bushing, purge tray and press bed for material to prevent unneeded downtime during start-up. The production area should be left clean, and ready for the team responsible for beginning the production week. Heats should either be banked at 300F, or you can perform a complete press power down, depending on your facility’s start-up approach. Materials prone to degradation (such as nylon, acetal, ABS, etc.) should be purged out using a purging compound and/ or an inert material such as polypropylene. Verify that drying sources have either been set to banked (reduced) temperatures or have been powered down. Thermolators should be turned off, and the pressures on them released. Need in-plant process training? Fill in the form below and we will be happy to assist you!