Tag: injection molding analyst

Medical Device Success-Faster to Market/Optimal results

By Bozilla
August 14, 2023

Let’s face facts 

Medical device failure can be a devastating event Encountering negative physical and financial consequences is not the path a #medical company wants to take

Alleviate device failure

Should cost be the primary determining factor when developing and manufacturing a medical device?

Could that upfront cost savings result in more significant money expenditure due to law suites, fines, and time lost? Let’s consider a new approach

You can avoid expensive law suites, FDA fines, and loss of time by considering additional factors during the initial stages of development

These factors include:

  •  Polymer choice
  • Consulting with an experienced #molding professional
  • Part design optimization utilizing experienced plastic engineers

You must have noticed that the word ‘experienced’ is used multiple times If you desire to manufacture a device successfully, it is vital to choose professionals who know what they are doing, from design creation to manufacturing Otherwise, you are at a greater risk of device failure

If cost is the only determining ingredient driving your decisions on any of the above considerations, you are putting your company and the patient at risk Gambling on any of the three factors above will reduce the chances of a successful medical device

Let’s get into itpolymer choice for medical devices

Polymer choice

What is significant about polymer choice?

Let’s recognize that an FDA-approved polymer is mandatory for most medical devices

From the polymer options the FDA endorses, which is best for your particular design? If you allow cost to drive this decision, it may come out poorly

At this stage, you should already be consulting a plastics engineer with extensive polymer knowledge The choice of polymer and its durability will depend on the device’s intended usage and exposure to environmental stresses

Injection Molding Consultant

It is critical to have an experienced injection molding professional guide you when developing a design for a device A consultant with a plastic engineering degree is a significant advantage

Hold up if you are cringing because the costs in your head are adding up Let’s get through this bit, and I will show you how it saves you money in the long run

An experienced injection molding professional should have these qualifications:

  • A minimum of 10 years in the injection molding industry
  • Exposure to multiple industries, eg, automotive, caps and closures, medical, housewares, etc
  • Fully understand how a polymer will respond during the injection molding process ( this will also affect your choice of polymer)
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Homopolymer vs. Copolymer

By Bozilla
May 24, 2022

Material selection for an injection molding application can sometimes prove to be very challenging What happens if you identify a material then find that it can be supplied as a homopolymer or a random copolymer Is there a difference? The answer is YES The choice made for your project can affect part quality  

The Homopolymer:

homopolymer chain

A homopolymer has the same base unit which causes the molecular chain to have a high degree of consistency and size However, length can vary depending on how long the polymerization process is allowed to occur

The high degree of consistency in a homopolymer creates a high degree of regularity When many of these changes flow and combine, they are able to create a very tight entanglement and when they cool and shrink, they also have a high degree of crystallinity which increases shrink

The Copolymer:

copolymer chain

A copolymer, as shown in the image above, has more than one base unit and each base unit is a different size There can be more than two base units Due to the variation in size of the base units, the copolymer chains will be spaced much further from each other and have a higher degree of irregularity And similar to the homopolymer, the length of the molecule will depend on how long the polymerization process is allowed to occur

The high degree of irregularity does not allow the polymer chains to form a tight structure, leaving a lot of space between the molecular chains Therefore, when the polymer flows, there can be alignment but there will be more irregularity and not as tight of a structure which prevents excessive shrinkage

When comparing the two types of polymers, assuming each is the same length (same molecular weight, per se) the homopolymer will be much more organized and structured therefore creating more mechanical strength and chemical resistance but have high shrinkage The copolymer will have more random orientation which will create space between the molecules allowing for easier chemical attack and less mechanical strength and also have lower shrinkage Of course, we could discuss these comparisons in much more detail but we will stick to the basics for now

As material selection relates to injection molding, the properties of the material is a crucial factor

The major properties when comparing homopolymers to copolymers are:

  • shrinkage
  • chemical resistance
  • mechanical strength

Each of these properties must be considered with regards to the outcome of part quality

For example, when injection molding

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Key Factors in a Reliable Plastics Injection Molding Simulation Report

By Bozilla
November 30, 2021

I have written in a prior post about the key factors necessary in a plastics injection molding optimization analyst  Now, I would like to discuss the importance of a skillfully assembled simulation report  Jennifer Schmidt spoke of the key ingredients of a trustworthy injection molding simulation report in her talk at the Plastics Technology Molding 2021 conference In this brief, I will discuss the valuable information she provided and add additional feedback  If you want a successful outcome for your tool, these key components are essential to consider

 

Injection Molding simulation software

1Software

  • What version is being used and is the software up to date? Look for signs that the analyst is using an older version of software which will alter the results on the report, and ultimately the floor results

Typically, the output file(s) of the software contain the release version of the software  It might not be the absolute latest release of the software, but is should be a proven release which is typically a year old or less

Mesh quality for injection molding

2 Type of Mesh used: Consider the type of mesh that used for the part and the runner

  • Is the mesh type appropriate for the part geometry?
  • Is it precise enough in critical areas to capture important details?
  • Is the correct technology being used for the part geometry/runner combination, ie midplane, Dual-Domain, 3D or a specialty mesh used?
  • Will the report allow access to display the mesh?
  • Does the filling animation, weld lines and sink marks reveal insights into the mesh quality?

Consider: Simulations of the same part with the same material and same mesh density, but different mesh types for the part and runner, may produce different results for pressure at the fill-to-pack switchover point, which could make quite a difference in what occurs in an actual molding environment

There are many factors to consider and only a seasoned user with the proper education in the software will be able to make these determinations in order to provide the best analytical outcome

Material Data for injection molding

 

3 Material Data: An accurate molding prediction requires good material data

  • What was the material data in the simulation based on?
  • Was data on the actual material available?
  • Was the data a substitute?-a resin of the same generic family but has a
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Is this the correct Injection Molding Machine for your Tool?

By Bozilla
November 8, 2021

To start this discussion I’d have to first state that the size of the tool plays a large role when selecting an injection molding machine  More specifically, it is the projected area that is of concern and how the projected area, along with the pressure distribution over that projected area, creates clamp force

Selecting a machine based on clamp force (tonnage) is more common when you have a part with a large projected area; ie multi-cavity tools, bumper fascias, housewares and many other items

In today’s economic climate, it’s more important than ever to conserve energy  Many believe that using the smallest IMM is the best way to achieve this cost savings  However, there are reasons why a smaller machine isn’t always the most efficient machine

 Reason 1: If an optimum process is the objective, select a machine that does not allow the tool to exceed the clamp force and flash the tool (blowing open)  during an  ‘optimized’ process

We  have had many concerned customers consult with us about the process Their questions are directed at finding out why the part is warping or exhibiting cosmetic defects  Once I dig into the process, I typically find that the part is not packed sufficiently due to the tool blowing open  In order to keep the tool closed, they must pack with very little pressure for a very short time  Packing with too little pressure, too little time, or both can cause a loss of control with dimensional stability and/or cosmetic issues due to excessive shrinkage  These issues create problems that are caused because the tool is in an IMM that doesn’t have the proper clamp force requirement

In the image below the clamp force required to fill and make the part is 250 Tons  However, in order to pack the part out sufficiently and make a good part (meets tolerances, minimal cosmetic defects, minimal deflection, etc) the clamp force required during 2nd stage pack is 1,450 Tons  That’s a very big difference

clamp force plot

 

 Reason 2: You are able to make parts but the process window is so small that staying within the process window is difficult or impossible to maintain

The inability to stay within a process window could be caused by several issues, especially since there are so many variables in the molding process  However, if the machine does not have sufficient clamp force to stay closed during an optimum molding process, concessions will be made and

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How Experienced And Knowledgeable Is Your Analyst?

By Bozilla
August 4, 2021

In this economic climate, it is critical to create higher quality processes and parts while keeping costs as low as possible This typically means getting analysts involved in the beginning phases of a project Because a mold typically costs in the range of $12,000 to above $200,000, spending less money up front with analytical work will save you from costly tool re-work at the end of a project

More businesses are turning to mold flow analysts to provide in-depth, technical knowledge before, during, and after the course of their project Whether the analyst is internal or is a hired consultant, it is extremely important to know what type of experience and knowledge they have in order to take full advantage of their expertise

What basic requirements should an Injection mold flow analyst (example: Autodesk Moldflow) have when analyzing the injection molding process

Qualities of an injection molding analyst

  1. Injection molding knowledge: What type of focus does your analyst have in the injection molding sector? For instance, are they knowledgeable about mold design, polymers, and flow, etc?

Having an analyst that fully understands the scope of their position is an absolute necessity In order to have a comprehensive understanding of their job, analysts must be knowledgeable in all aspects of the injection molding process This includes injection molding processing, mold design, part design, and polymer chemistry and properties(eg a plastics engineer)

Plastics engineer

Plastics Knowledge: Is the analyst a Plastics Engineer or will a Plastics Engineer be involved?

Without a full understanding of polymers, it is extremely difficult to understand polymer behavior during processing This understanding begins at a molecular level and extends far beyond standard processing knowledge  A Plastics Engineer is able to identify the differences between polymers and each polymer’s flow characteristics This information can be used in conjunction with the simulation software to optimize the analyzation process Therefore, it is crucial to have a Plastics Engineer involved with plastics processing

injection molding worker

Injection Molding Experience: Has the analyst ever run an injection molding machine or been formally trained on one?  Does he/she understand ancillary equipment such as thermolators/chillers?

Without injection molding experience, it is difficult to properly analyze such a process

A mold flow analyst is typically required to identify and understand polymer flow behaviors within the injection mold Frequently, this can involve analyzing the 1st stage, 2nd stage, and cooling stages of the injection molding process If your analyst must survey these phases of the

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Actual Injection Molded Part differs from Analytical Prediction

By Bozilla
July 28, 2021

In this discussion, we will explore a part that was injection molded and scanned for deflection Interestingly, the actual deflection did not match that of the analyzed part Unfortunately, this can sometimes happen and when it does, it is the responsibility of the software expert to investigate why the predicted analysis results are not matching the floor results This can be a challenging task

In the engineering world, it is common to hear the phrase ‘garbage in equals garbage out’ In other words that phrase means that all inputs plugged into any set of calculations will directly influence the outcome of those calculations When it comes to FEA, having correct input data is especially critical since technical software can only be as good as what is entered into each specific section But what steps should be taken if you have ensured that the analysis is set up correctly yet, the analytical results do not match the results on the floor? In the sample study below, we will take a closer look
For this study, we will look at a part that we will call the ‘console’:

Console Fill Console DeflectionConsole

 

We will compare the analytical inputs to the inputs used on the floor Then, we will explore how the analytical results compare to those on the floor

In preparation for any analysis, the user must take the necessary precautions to ensure that the inputs in the mold filling software are as accurate as possible

Part model

1) Is the part model prepared so that it meets or exceeds the standards that the software supplier recommends?

Yes, the part was modeled as a 3D model and exceeds the recommended criteria

Feed system design

2) Does the feed system match the final design of the finished product?

Yes, it was designed per the specifications provided by the tool shop

Material data

3) Is the material data in the analysis the same as what is being used on the floor?

Yes

   Is the material card comprehensive ie, is it fully characterized?

Yes

Process inputs

4) Do the process inputs in the software match the floor inputs?

Yes, see the Table 1 Below

analytical process setting vs floor process setting

 

Once the inputs have been confirmed as optimal and correct, we inspect the results and compare them

First, we examine the filling pattern to see if it is predicted correctly
To determine the correlation of flow patterns between Moldflow and

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