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Reducing Injection Molding Risks

Even the simplest injection molded part can be a risky undertaking for those without the experience.   Tooling can be expensive and a bad tool design can lead to a huge unforeseen failure months down the road.   The most important thing you can do is to mitigate the risks at the beginning of the project in order to ensure the best possible outcome.  We mitigate the risks by identifying as many of the possible pitfalls that we can.   PPT has developed a framework for identifying risks during the quote stage so that we can ensure the over all success of the project.   This framework evaluates several areas of risk that are common to new injection molding projects.   Risk Assessment occurs during nearly all phases of the project, but what i will talk about today is risk assessment during the pre-production or quote phase. 

When a customer gives us drawings and a solid model to quote, we evaluate the drawings closely.     Our risk process is lengthy so i will only touch on a few portions from within each category but you will get an idea on how we identify risks before a project kicks off.   The output of our risk analysis is an overall risk score which will be used for quoting.  If a project is too risky, we may not bid on the project or will request that the customer implement certain changes to lower the risk level. Currently our risk analysis consists of  nine different Risk Categories.

Part Design

The first risk category we look at is part design.   We evaluate the drawings at a very detailed level and try to identify “difficult to mold” geometry or part geometry that may cause molding issues in the future.   Improperly designed parts can lead to voids, sink, dimensional issues and extra cost for the customer due to excessive cycle time.  Lets say we run into a part that has a very thin wall that may not fill properly because the plastic cannot flow.  We may recommend that the customer thicken that section or conduct a mold flow analysis to ensure the part will fill.  Mold flow is an excellent resource to evaluate injection molded part design.


Material selection is important and can add to risk if you do not have a good grasp on material science. if you choose the wrong material for a particular application it may fail in the field.  If you have a low volume part that uses 500 lbs of material a year but you select a special material that  has a minimum order requirement of 6600 lbs your costs will increase.  We try to evaluate if the material selected is the right material for the job and is capable of meeting the dimensional requirements on the drawing.   We also look at any risk associated with the supply of the material.   These are all important risks that must be evaluated prior to production.  Our material suppliers are great resources and offer design guides for most of their materials.   We will review the design guide and spec sheet for important information such as tool design or processing parameters.   Some times, we may get our material suppliers involved in the material selection process.


Example of Mold flow Cooling analysis

Tooling risk incorporates Information from many other risk areas.  Material selection, part design and labor all determine how the tooling is designed.   The goal with this risk assessment is to make sure the tooling is going to work as expected and deliver the proper amount of parts for the expected life of the program.  If we are going to run a million parts, we would never build tooling out of aluminum because it is soft and will wear out prematurely.  PPT manufactures all of its tools to SPI specifications and since all tooling built and retained by PPT will be maintained at no cost to the customer, it is in our best interest to conduct a full risk analysis and mitigate any risks up front.  This Risk category is deep and we look at all of the mechanical aspects of the tool design.  For instance, tool steel, ejection, gating, sprue design, molding machine selection etc.    We often utilize mold flow to mitigate tooling risk.  PPT can take our tool design and run simulations with different processing parameters to give us a good idea on how the tooling will perform in real life.   The image on the right is an example of a cooling analysis used to predict the performance of different core materials. Keep an eye out for more articles in the future on mold flow analysis.


We look at this section to mitigate risk associated with labor.  Ideally when injection molding a part, we try to design the tooling so that the part will de-gate automatically which reduces the amount of labor required for the job and lowers cost.   Sometimes, reducing the labor is not an option, for instance, when an operator has to hand load an insert for over molding.  When it comes to labor risk, we have to look at the requirements of the job and ensure that we have the type of labor that is qualified to run the job. Does this job require skilled labor with specific technical expertise?   Can the job be performed with unskilled labor?  What happens when an operator fails to follow procedure?  Take the hand-loaded insert example that I provided, what happens when the operator loads the insert wrong.  Does it crash a multi-thousand dollar tool?  If that is the case, we mitigate the risk by Pokeyoke’ing the tool to ensure the operator cannot fail.


This section looks at all of the equipment required to produce the job, not just the molding machine but all equipment associated with the job.   chillers, oil heaters, Hot Runner controllers, robots, driers and inspection equipment.   We need to be able to prove that we have the required equipment to complete the job.  If we don’t have the required equipment, would we be willing to purchase a piece of equipment?  Probably, but it is important that we know what will be required of the job.  It is obviously a good idea to review the tool design and insure that the size of the mold will fit into the machine that it will be quoted on right?    What if the tool will physically fit in the machine, but the machine does not have enough capacity to fill the cavity with plastic?   We have to look at all aspects when it comes to how the job will run in our factory.


As you are probably well aware, PPT is a full service injection molder.   We not only produce plastic parts, but we can produce finished goods.  This means we can assemble, pouch, package, seal, label and ship finished products to the end user.  When evaluating packaging we need to make sure that our methods can keep up with the cycle of the machine.  We look at sourcing for pouches, any special labeling requirements and how to protect the assemblies during shipment.  We don’t want the parts to be damaged during transit.   Packaging requirements are different for every customer.  Some customers specify a particular box size or weight, so we have to ensure that gets incorporated into the final product.


In many cases we don’t know the end use of the product, but this is information that we always try to gather.  We need to know if this is a critical safety item.  PPT will try to look at how the part is going to function in the environment it is to be used in.   Our customers know their products far better than we do but we will look for any red flags or risks that we can find.   For instance, if we know this is an outdoor application but the customer has chosen a material that does not have any UV protection.   PPT would identify that as a material risk and notify the customer.

Regulatory Concerns

Sometimes parts have a specific set of  requirements that we have to plan for.  Some medical parts may have more stringent FDA requirements than others and PPT will need to plan accordingly to ensure that we can meet the customers and the regulating body’s expectations.   This category can encompass, regulatory or statutory concerns.

Special Quality Requirements

What inspection equipment will be used?

This is a very important section.  We need to know the critical dimensions on the part and ensure that we have the capability to effectively measure the parts.   What frequency will the parts need to be measured.   Does the part have any special PPAP requirements, if so what level?  Does it require OQ, PQ, IQ Validations.   The goal is to identify the requirements before hand.   This type of work can be bandwidth heavy and we need to plan accordingly.   PPT will generally request a conversation with the customers Supplier Quality Engineer in order to get a better understanding on specific quality requirements related to the part.   At the very least, we will review the customers Supplier quality manual, which generally provides incite into the customers quality requirements.

In Closing

Every project is different.  We have large projects and  small projects but  the most important thing to remember is that they all begin with a thorough risk analysis aimed at ensuring the overall success of the program.

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