Some Tips For Operating and Maintaining Plastic Injection Molds

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The molds represent a very crucial part of injection molding. The quality and suitability of a mold are important in injection molding. So is the suitability of the plastic for the product type.  A well-made mold contributes a large chunk to the total cost of injection molding. Molds can cost hundreds of thousands of dollars. And when you spend that much on something it is worth paying attention to how to make it last and work well. To plastic engineers and manufacturers, the molds are an investment. One which generates a return. This is in the form of a cost and time-efficient injection molding process. Yes, a well-designed and well-fabricated mold tends to cost a pretty penny. But the cost of a mold does not end with mold machining cost or the cost to get the mold. To get the best return from the investment, follow proper operational procedures. and routine maintenance is a priority. This means investing in well-trained operators, maintenance, tools, and consumables. This can even include investing in software that aids automated operations and maintenance. 

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Proper Operation and Maintenance Slows Down Depreciation 

Like most machinery and tools, your mold depreciates from the first use. But the rate at which it depreciates depends on the manner of use and maintenance. Routine maintenance goes a long way to ensure you get enough use out of your mold. If the mold is getting regular maintenance.  This will not be as effective if the operation puts unnecessary strain on the mold. It is thus important to have a set of rules to guide the operation and maintenance of the mold. The operation of the injection molding process varies for different types of plastics. covers a range of topics on plastics in the blogs. 

We are all aware of how two people can own the same model and type of vehicle. Yet one still drives and looks better after 5 years than the other. This is down to how the vehicle gets used and maintained. One driver might slow down and navigate bumps with caution to reduce the impact on the car. The other driver might tend to speed through bumps and may not change the oils and filters as often. So leaving a well-made mold with an untrained operator is another sad story in the making.

There’s the maintenance you carry out on a daily basis and the maintenance that is less regular. Say every few months or once a year. The daily maintenance takes from seconds to a few minutes. The monthly or annual maintenance might need dismantling the mold. You should have spare molds ready to take the place of the mold during such maintenance. This is to avoid downtime in production. 

Tips for Optimal Operation of Injection Mold

  • Set the required standard for part quality
  • Training of personnel to the required standard
  • Have guides or checklists for mold operation procedures to reduce human error. This includes loading and unloading as well as maintenance
  • Set and track daily production targets. Falling short of targets serves as a performance indicator. This is for the injection molding process and workforce
  • Track raw materials consumption. This can show, for example where the shot size is too large. 
  • Track scrap rate. Generating a lot of scraps indicates operational inefficiencies that must get addressed.
  • Ensure adequate resin selection 
  • Put in place sampling procedures for raw materials and products.   

Types of Injection mold maintenance

Routine Preventive Maintenance

These are daily, weekly, monthly or annual maintenance carried out. This to ensure smooth running. This includes; mold inspection, cleaning, lubrication of moving parts amongst other daily maintenance. Less regular routine maintenance may include more intensive cleaning of the ejector units.

Non-Routine/ diagnostics Maintenance

This is not a desirable approach. It would mean a fault has developed before the maintenance gets carried out. This is often done after a fault occurs. The engineer then carries out maintenance checks. This is to see what fixes the problem and then diagnose.

Some Tips For Maintaining your Mold 

It is important to ensure that the product is well designed in the first place. Bad design can result in problems like difficult ejection and poor mold filling. Ensure the right draft angle gets used, ejector pins are well located and the right gates get used. Faults from other parts of the injection molding machine can end up in the mold. While you can have a good mold operation and maintenance. If the other processes in the injection molding machines are not running well. The problems that result may get transferred to the mold. For example, if injection pressure is too high this can put unnecessary strain on the mold. Or if the melt is not well mixed and melted and contains particles that might damage mold surfaces. It is important that the other parts are also well operated and maintained. This is where it is important to work with a reliable mold manufacturer. This to ensure that these factors get considered in the first place. At we provide the optimal mold design that best suits your process. Below are a collection of tips from different experts in the field.

  • A maintenance plan that gets adhered to
  • There should be a documented maintenance schedule. This contains a procedure for maintenance work.
  • A process to confirm maintenance work carried out and when the next maintenance is due
  • Every mold should come with a operational and maintenance instruction manual and checklist. This guides operators and cut the chances of human errors.
  • A feedback system that allows the detection of errors before they occur
  • Proper training and continued training of operators
  • Regular inspection of cavities, gates, and runners for wear, blockages, and damage
  • Lubrication or surfaces
  • Regular cleaning and removal of debris from cavities and all parts
  • Ensure cleaning agents are nontoxic and use recommended solvents and cleaning agents
  • Use corrosion or rust prevention agents and coatings
  • Avoid moisture problems by proper flushing and draining of water lines
  • Check plates are well aligned 
  • Ensure ejection system is  not obstructed and n proper operation
  • Clean and lubricate ejector pins and parts
  • Check and replace all parts that need replacement such as pins, screws, bolts, and bushings
  • Have a routine for replacement of parts after a certain level of use. Even where there are no detectable damages. This promotes a maintenance culture that minimizes the chances of mold damage
  • Follow the mold manufacturer’s operation and maintenance guidelines if provided. The mold maker is likely to have some recommendations on how best to operate and maintain the mold. Take these recommendations serious.
  • Have a system to track the number of cycles a mold runs. Since many molds get rated according to the number of cycles.  Depending on your scale and capabilities, this can be a digital or analog system for tracking. The cycle track can then serve as an indicator for maintenance. For example, maintenance after 100 cycles may be different from that after 1000.
  • Ensure that the other parts and processes are running well. 
  • Check that the cooling line is well sealed and no leakages. This might cause corrosion or inefficient cooling
  • Have a dedicated budget for maintenance

Have a Maintenance log

It is important to keep a record of the maintenance carried out on each mold. Each mold should have an identification code and a log of the following information:

  • Number of cycles
  • Maintenance works carried out
  • Date of each maintenance work
  • Personnel who carried out the maintenance work
  • Parts that got replaced or repaired
  • Detail of repairs done

What Happens To Your Mold Under Poor Operation And Maintenance?

Manufacturers may have different reasons for skipping maintenance. Some may be to avoid downtime or to cut costs required for maintenance tools or skilled labor. Either they are usually not a good decision. This leads to even longer downtime and higher costs when the whole thing breaks down. Where the mold gets mishandled, this leads to not only deterioration of the mold itself. This problem can get passed on to the product resulting in part defects and rejects. In a system where the operator waits for a fault to arise before mold maintenance, the damage is already done. Below is a list of some of the problems that can result from improper mold handling and maintenance.

  • The build up of materials on surfaces result in problems such as burns, and part defects.
  • Increased scrap rate and material wastage
  • Loss of production time in troubleshooting, fixing, and waiting
  • Extral cost to repair and replace parts and tools which would otherwise not have damaged.
  • Damage to the Injection molding machine
  • Potential loss of warranty. This is as a result of mold not operated and maintained according to the manufacturer guide. 

What should be in a maintenance guideline

Some of these maintenance checklists apply to whether the mold is in storage or in use. Improper maintenance during storage can also result in mold damage and deterioration. You can have mold sitting in storage and getting damaged even while not in use. For example, storing a mold that is not completely dried can result in rusting. Storing your mold in poor or extreme conditions also affects the mold. For example, a wet mold stored in freezing conditions can get cracks. A maintenance guideline should contain the following:

  • List of parts and items to inspect. This includes the sprue, runners, mold cavities, and ejector components 
  • Criteria for functionality; Indicators of fault or functioning. This lets the operator decide, by inspection if a mold is ok or needs to get replaced. 
  • Frequency of inspection for each part. There can be a list of a daily maintenance checks, weekly, monthly, or annual.
  • List of recommended cleaning agents, solvents, and lubricants for each type of mold

Detailed procedure for either re-installing the mold back unto the injection molding machine. Or for sending it to maintenance. This should include how to label and store and the location for maintenance. For example, a mold that is not getting returned to the machine needs to get dried and coated. This is to prevent corrosion over the storage period.

Example Maintenance Checklist

Maintenance ChecklistFrequency of MaintenanceMaintenance procedureCriteria for functional or faulty
Visual Inspection of moldEvery cycleClean all debris and stains from the inside and outside of the moldNo fluid leaks from any fittings
No surface damage
Mold surface cleaningEvery cycleClean off the thin film of melt that gets to the surface of the mold.
Select the right solvent for the plastic-type that will not corrode the mold.
Clean mold surface free of thin film
Blow out with compressed airSpecified intervals as recommended by mold manufacturer/ engineerBlowing out of debris from tight corners and channels such as runners and sprues. This builds up over time in use or storage. Regular blowouts prevent this from causing problems.Small spaces and crevices free of debris and allowing easy airflow when tested
Full dismantling and detailed inspection After thousands of cycles as recommended by the mold manufacturer or engineerDismantle mold fully. This includes sliders, ejector systems, cooling channels, ejector pins, and fittings. Clean out all parts to remove all debris and inspect for rusts, leaks, and damages.All parts and fittings free of debris, damages, and rusts
Lubrication During the full dismantling All moving parts should get lubricated to reduce friction and prevent wear.All moving parts are well lubricated and glide with ease.
Mold cavity surface treatmentEvery number of specified cycles as recommended by manufacturer or mold and/or resinFor some resins tend to be more corrosive to the mold. The mold cavity gets treated with either anti-corrosion agents. Other molds might need a mold release agent. This is to prevent part sticking and difficult ejection.The surface is uniform and parts get formed and released without defects.
Mold Drying Every cycleRemove all traces of water that can lead to mold rust and cause product defects. This is done by passing compressed air. Systems can also get put in place to automate the detection and removal of water from the mold.No leaks from the cooling channel. No traces of water in the mold cavity or on the mold surface.


At Cavity Mold, we build molds to last. Companies that are in it for the long run know that maintenance is not negotiable. Neither is proper mold operation. To get the most use out of your investment the watchword is preventive maintenance. Rather than having to carry out repairs. So what you want is preventive maintenance. This gets achieved through maintaining optimal operational standards and maintenance schedules. The article provides tips on how to operate and maintain plastic injection molds. The maintenance and operation of specific mold vary. It depends on the types of mold, plastic, and part design that is getting molded. A good starting point is to have an experienced mold specialist. This aids you in operation and maintenance planning. 

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