Maximizing production efficiency: The importance of preventive maintenance

In today’s plastics injection molding manufacturing world, experiencing unscheduled downtime due to a machine breakdown can be an expensive and painful experience. In addition, it often occurs at the most inconvenient times, such as when you have tight deadlines or are just about to ship parts to a customer. Therefore, machine reliability and repeatability are critical for maintaining a successful business. Adopting a preventive maintenance strategy and following maintenance routines are essential to avoid disruptions in production and remain profitable.

Injection molding machines and automation are complex and need continuous monitoring and care to maintain a high level of performance. Both well-established and cutting-edge preventive maintenance techniques can be used to ensure the injection molding machine can produce on time, all the time. Here is a comprehensive plan that you can implement to establish regular preventive maintenance routines for your entire team, maximizing your uptime and productivity.

Unscheduled downtime in injection molding

Unwanted production stoppage is a crucial topic in injection molding as it negatively affects the ability to produce parts that meet customer needs. ENGEL machines are designed to run well, and customer demands are not being met when they are not running. One way to prevent unscheduled downtime is to listen to the machine. And this has not changed over the past two decades - ENGEL machines give telltale signs when they are not functioning correctly, which can lead to a disruption of the production process and have severe consequences.

Reasons for unwanted stoppage

There are some key reasons why a machine goes down unexpectedly if you don’t follow regular maintenance routines:

1. One is a machine or operator safety error. If a machine fails and there’s a safety error, we must stop the press immediately, make the needed repairs, and then get it back into production. There is nothing more important than a safe-running machine.
    
2. The next reason an injection molding machine can go down is when a production or process parameter is outside the limit. For example, the temperature is too high (or low), the oil is too hot, or the clamping force is not reached.
    
3. Another reason for unwanted stoppage is an alarm caused by a machine malfunction. We can encounter a whole host of alarms that will lead to unscheduled downtime. Some examples include when a primary safety device or a locking plate is not in the position, or a nozzle guard is open.

TIP: Creating checklists for routine preventative maintenance

A checklist can be a valuable asset for routine inspections. The list does not have to be anything elaborate. It can be as simple as the top ten things you want to look at without getting overly technical. Logical yes or no questions are sufficient to help identify possible issues that can result in a production stoppage. If any questions are answered with a “yes”, then the maintenance group can be notified and address the issue if detected early on. This can save on downtime and repair costs.

Preventive maintenance routine: Walk-around inspections for the machine operator

So now it’s time to get to the how-tos your team can employ to reduce unscheduled downtime. These should be routine maintenance procedures for every machine operator. At the start of each shift, they need to do a basic walk-around:

1. The operator should first make sure that the guards are in place and closed and that the Plexiglas isn’t broken. This will guarantee that the airflow can adequately cool the hydraulic cabinet.
    
2. The next step is to ensure that the emergency stops are mounted to the machine and in good working order. They should be in a fixed position and not hanging loosely off the machine. Preferably, they should be mounted to the machine controller or robot or mounted on or near the clamping area of the injection molding machine.
    
3. Another vital check for the operator is ensuring the main disconnect is intact and can perform a lockout/tagout. Additionally, all electrical cabinet doors have to be closed and secured.
    
4. Next, the fluid levels must be checked to secure that they are within the required parameters. This includes hydraulic oil, the lifeblood of the machine, lubrication oil for the ways and the slides, and the gear oil to keep the plasticizing unit lubricated and cool.
    
5. As part of the maintenance routine, the operator must perform a clear site inspection to check for oil leak points, which should take about three minutes. The inspection should look for leaking or wet areas in the tubes, pipe plugs, and other piping in the injection manifold, PQ manifold for the clamping cylinder and pistons, and the hydraulic lines on the automatic tie-bar retractor. All of these are potential risks for oil leaks and should be carefully observed during the walk-around.

Reasons for & actual impact of an oil leak

One of the most common reasons for an oil leak is the heat exchanger is plugged up, creating an inadequate exchange of cold water versus hot oil. Another cause is a choppy cycle or erratic movement of the clamp, with rapid acceleration and rapid deceleration. With this, you get constant heating of the hydraulic hoses. This heating, over time, will lead to oil leaks. It’s necessary to check the heat exchanger filter to make sure the incoming tower water is clean or else the filter can get clogged leading to overheating. If the oil temperature is over 125 degrees for a significant amount of time, it will lead to oil leakage. Keeping the oil temperature around 110 to 115 degrees is ideal to prevent overstressing the hydraulic system. After the walk-around inspection, the operator must note and tag the location of any oil leaks detected.

But what is the true impact of an oil leak? Firstly, it’s a definite safety hazard. Oil on the floor can lead to slipping or tripping. The next is the cost, this number can add up quickly as you must consider the cost to clean up the leak, the cost to dispose of the waste oil, the cost to replace the oil and the cost of the machine downtime itself. The leakage could start with as little as one drop every 10 seconds. Over time, this can lead to a stream of oil leaking. A small stream could be as high as 24 gallons a day, translating into hundreds of dollars per day in wasted oil, labor, and disposal fees. If you multiply that by the number of machines running in a plant, the costs could add up to several thousand dollars a day, beyond the waste in lost production time.

Preventive maintenance routine: Walk-around inspections for the maintenance team

Since every injection molder is different, it is up to the individual company to decide on the frequency of a maintenance routine, whether daily, weekly or another schedule, whatever works for your production needs. This second-level inspection goes beyond and works in tandem with the machine operator’s operational and functional injection molding machine inspection.

1. First, pay attention to the current state of equipment. Are there oil leaks? Is the machine overheating? These and other questions must be answered and recorded. If there are any issues, they should be addressed when they are minor and easily correctable.
    
2. As a part of the maintenance team’s walk-around inspection, they should physically inspect the pump group, the electrical connections and the plugs for any damage or wear. Additionally, they need to make sure all the conduits are effective, connectors are engaged, and have proper strain relief.
    
3. Be wary of loud or abnormal noises when performing maintenance routines. For example, when the machine reaches full clamping force or is dropping clamping force, and you hear a loud bang, this can indicate a decompression issue. Also, pay close attention to the pump case temperature. The smart pumps on the machines can get hot quickly when running an accelerated cycle time. And if they get too hot, particularly in the 130 to 145-degree range, the case pumps will fail. The key for pumps is to catch serious issues with them early, during the first stage of failure. This is critical to avoiding expensive repairs and prolonged downtime. The benefits to detecting this in its infancy are that the pump does not implode and does not shower debris down into the system, the tank, and the valves. Failure to catch this can lead to debris problems that can go on for several months after the initial failure.
    
4. Next on the list for the maintenance team to check are the hydraulic manifolds. Most injection molding machines today have catch basins for oil collection, so it is necessary to be even more vigilant for oil leaks. The inspection should include looking for standing oil in each area of the collection system, including the clamping manifold, injection manifold, and pump cavities. This can be done with the machine running and at a safe distance. If there is standing oil, the next step is to stop the machine and investigate further, so proper repairs can be made before it becomes a major issue. The goal is to have a dry machine and eliminate safety hazards.

Preventive maintenance routine: ENGEL service support

The day-to-day activity can be overwhelming in a fast-paced manufacturing environment. ENGEL provides goods and services to ease and support our customers’ operations and maintenance routines. Not only can we help get your ENGEL machine running at its optimal level, but we can also offer services to help lengthen the life cycle of the machine:

1. The benefit of bringing in an ENGEL field service technician is that we will get the job done right because we know everything about ENGEL injection molding machines. We bring calibrated test equipment, a validated process, and documentation of the complete maintenance visit. ENGEL technicians can also fine-tune your machines to optimum performance to fit your specific processes.
    
2. The next significant benefit of ENGEL service support is that we are here for your convenience. We have service teams dedicated to each geographic area across the United States and Canada. Also, we can guarantee that one of our approximately 70 service technicians is quickly available for on-site assistance at your production facility and serve as an extra on-site resource when performing maintenance routines, as needed.
    
3. With special preventive maintenance packages, ENGEL service support technicians can also save you time and money. Our offerings include complimenting your existing preventative maintenance measures with a review of your machinery and a checklist of concerns that need to be addressed. This can help you to schedule downtime ahead of time to take care of the issues in the priority you assign them with a best practice preventative maintenance approach. With ENGEL care, you can ease your maintenance workload to focus on production.
    

Read more about ENGEL care & other service packages.

TIP: The most overlooked preventive maintenance methods

When performing preventive maintenance to avoid unwanted downtime, it is essential not to overlook certain maintenance routine checks. A reliable method is to use our sense of smell. In many cases, a possible failure can start out with a minor smell, like the smell of burning plastic could indicate a nozzle leak. The odor of burning rubber could mean an electrical issue. And the smell of hydraulic fluid most certainly reveals a hydraulic leak. Early detection of these odors can prevent more significant problems and save time and money. The next sense we can use is hearing. Listening to your injection molding machine is crucial to your maintenance routine. A sound that is not normal could indicate an issue, for example, the squeal of a bearing, the whine of a hydraulic pump, the chatter of a hydraulic valve, the slamming of the mold, or the ejector plate bouncing. It is worth listening to what the machine is telling you.

Greatly reduced downtime

In conclusion, reliability and repeatability are key factors in injection molding machine performance. A carefully constructed predictive and preventative maintenance plan is therefore essential. Machine operators and in-house maintenance staff should perform consistent, routine walk-arounds to identify potential machine issues. Once issues are discovered, the correct team must be notified immediately to ensure the problem is resolved promptly. Identifying and tagging the concerns is a helpful way to visualize and track the repair progress for your injection molding machines. Outside assistance from your ENGEL service support technicians compliments your existing preventative maintenance protocols and sheds some of the burden from your internal teams.

ENGEL is your service partner with a comprehensive portfolio of maintenance packages for your needs. Call us at (717) 714-3235 or contact us at [email protected], and we can work on maximizing your machine availability together.

For more information, visit engelglobal.com.