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Injection Molding: Put Out the Production Fire Once and for All

A deliberate approach to failure assessment, root-cause analysis, solution development, and continued monitoring is the only way to get off the treadmill of chasing the latest production problem.


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Without the proper approach, a production system can quickly fall into one of two categories: tribulation or turmoil. Quite often you will hear “old-school” injection molders describing their battle to achieve a robust processing system as “firefighting.”

In real terms, “fighting fires” on the production floor is a sign of system failure. True molding standards don’t require constant coddling, adjusting, sorting, etc. It is really easy to fall into the trap of applying Band-Aids to molding situations when the proper approach should have been:

  1. Analyze the root cause;
  2. Develop a long-term solution;
  3. Monitor the correction to verify that further action isn’t needed.

Ignorance of mold, press, material, and manpower failures can become embedded in a company’s overall ideology and approach. I couldn’t tell you how many times have I heard, “It always runs that way,” or “It can’t be fixed,” and felt a mental cringe that I compare to fingernails being dragged heavily across a chalk-board.

Bad production systems exist because problems are ignored, or “quick fixes” become long-term remedies. No thought is being put into root causes and solution development, because poor performance is accepted as normalcy. Worst-case scenario:

The production run is implemented without proper process-engineering protocols being followed and enforced.

Ignorance of mold, press, material, and manpower failures can become embedded in a company’s overall ideology and approach.

The industry’s shared quest for continuous improvement is readily preached, but commitment to the concept can often fall short. Production needs can sometimes make rushed systems seem logical; but most often rushing through the engineering phase into production leads to broken molds, poorly maintained presses, and scrap parts reaching the customer.


Perhaps “firefighting” is a slang molding term you are unfamiliar with. It frequently describes a molding scenario where processors are running from press to press, “putting out fires” (addressing immediate problems). In many cases, a thorough assessment of what are the recurring problems, and making a commitment to eliminate those issues, would remove the virus from the system, creating a healthy production operation. This article will outline many common situations that occur and offer suggestions on how to identify problems, develop solutions, and enforce the ideology of continuous improvement.

Continuous improvement is not bound by time constraints. With hard work, commitment, and a true analysis of facility failures, any company can plow through even the worst complications and succeed.

All of this may sound complex, but it is easier to address than you may believe. The most important thing to remember: Approach each problem one at a time. Develop a team to evaluate and resolve the issues based on their exposure, skill sets, and knowledge of the situation you are focusing on.

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Once the team has developed an approach that the vast majority of people involved will support, stick to your guns and enforce the correction. Once the change has been firmly implemented, utilize the same team to develop a method of monitoring whether the new approach/equipment/procedure has given your operation the boost you desired, and leave it to them to make the determination to accept, improve, or replace the change implemented.

Here are some of the most common failure areas on the plastic injection floor. Many are easy to correct; others require more concentration:

• Molds that repeatedly show poor production characteristics: poor ejection, repeating mechanical breakdowns, defects that consistently plague a molder from one press to the next. Evaluate tooling for ways to eliminate problematic runs through mold modification.

• Material issues that continually rear their ugly head: contamination, color swirls, burns, etc. Make a list of your own that you have noted as being recurring problems. Perhaps the list is press- or mold-specific, or it could be observed from one press to another consistently. Utilize the tools of historical data to pinpoint specific causes and correct these conditions. The importance of meticulously tracking scrap cannot be stressed enough. In some cases, making changes to the material itself might provide improved results, such as adding a lubricant to the material to improve part extraction.

• Presses, robots, and auxiliary equipment can be an additional source of production failures. Screw assemblies fail; press components fall short of production requirements; machine/equipment inconsistencies can prevent processors from controlling scrap, efficiencies, and downtime. Note what issues you see in your production schematic that continually frustrate you.

• Manpower can be another source of failure: Operators fail to meet production demands and miss quality problems; technical-support crews fall short of production needs or miss crucial data and defects, leading in the end to unwanted scrap, downtime, and equipment, tooling, and/or communication breakdowns. Make yet another list of the failures you note in regard to this area of concern.

Successful molders do the following:

  • Recognize their weaknesses;
  • Plan and implement a corrective strategy;
  • Enforce, improve, and monitor the repairs they implement;
  • Review the completed change to ensure that the desired effect is achieved;
  • Reevaluate poorly performing corrections for improvement or replacement.

TRAINING: When it comes to your facility, training should never be deemed unnecessary, or the potential victim of a budget cut! Your team is only as strong as its weakest link, and training is a crucial buffer when it comes to production. Utilize not only those in your facility that can offer their own expertise and input, but some of the other outside entities that have been exposed to multiple facilities.

Withdrawing from the industry to pursue your own perception of “the right way to do things” is not only limiting but dangerous. The best way for you to keep in tune with industry growth and exposure is participation. Research and implement training sources that best fit the scope of your operation.

ENGINEERING: There is an old saying that “success or failure is an engineered path.” Avoid shortcuts in the pre-production stage, and thoroughly plan your production through research and team thought. Problems are easiest to remove during the planning stage.

DESIGN: Tooling, equipment, material, and layout are either your best friends or your worst enemies. Take the time to evaluate the overall picture of what you intend to achieve and don’t be afraid to be critical of the successes you plan. What are your potential limitations? Has your tooling been validated, allowing for material fluctuation? How do you expect to be limited in your processing? Are work instructions in place that clearly define each team member’s responsibility and what procedures they must follow to properly perform their job duties?

TOOLING: The best time to address tooling failures is during the development/design stage. Are there potential failures that should be tackled prior to the production stage? What preventive-maintenance procedures need to be implemented and enforced to ensure that the tool life is as expected, or extended? What tool functions are most likely to lead to production break- downs and limitations, and what are the ways and means to reduce or eliminate these risks?

These are just a few considerations you need to evaluate in the pre-production phase. Success is more likely when planned, rather than the depending on Lady Luck to look over and bless your company. After all, team engineering efforts can eliminate “firefighting” in your plant, but ultimately it is your plant that makes the choice.

ABOUT THE AUTHOR: Garrett MacKenzie is the owner/editor of, as well as a consultant/ trainer to the plastic injection industry. He has spent more than 31 years in plastics processing, engineering and development, including scientific molding experience with U.S./Japanese automotive OEMs and in handgun manufacturing. He offers in-house processor training customized to customer needs. Contact: