Tag: injection molded part

Creating a Virtual Plastics Injection Molding Window

By Bozilla
April 27, 2022

Since the inception of plastic injection molding, creating a robust injection molding process has always been a challenge As time has progressed, the design of plastic parts has become more detailed and intricate, the tolerances have become tighter and the boundaries of injection molding standards are being pushed to their limits The combination of each one of these factors is making it more and more difficult to create and maintain a robust molding process

Initially, it wasn’t difficult to design a basic injection molding window that would result in a robust molding process However, with the advent of increasingly demanding factors it has become more difficult to design a process molding window that is large enough to be robust and create consistently good parts As a matter of fact, not only is it difficult to create a wide process molding window, it’s nearly impossible to create a suitable molding window- Period We will discuss how and why it is necessary to first create a virtual injection molding window and how that data can be translated to the floor in order to have the best injection molding window possible

Let’s begin with understanding what a molding window (or process window) is Typically, a molding window is comprised of three major factors: Fill time (or fill speed), Mold Temperature and Melt Temperature Each of these factors has the greatest impact on the injection molding process

Graphs below will illustrate the impact of each

The influence of each factor:

  • Fill Time (fill speed): As fill speed decreases, the material moves into and through the cavity slowly which allows the cooling effects of the tool steel to have more time to influence and cool the temperature of the plastic resulting in a higher viscosity response and a greater pressure to fill the cavity Conversely, as the fill speed increases, the material will shear thin (the viscosity will decrease) significantly, but ultimately the plastic will resist filling the cavity and require a greater pressure to fill the cavity Somewhere between filling extremely slow and filling extremely fast is a sweet spot that requires low pressure to fill the cavity If plotted out in a graph, it will be a u-shaped curve where the lowest point is typically a good fill speed

molding window pressure

  • Mold Temperature: The mold temperature is highly influential with regards to having the material fill the cavity The thickness of the part relative to the flow length is an important relationship with regards to the impact of the mold
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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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Finite Element Analysis(FEA) – On Every Tool?

By Bozilla
March 3, 2021

Finite Element Analysis (FEA) has been available to the injection molding industry since approximately 1978 when Moldflow pty Ltd produced the first simulation software to be used to optimize all phases of design and production processes for injection molded plastic parts

Over the years, FEA has proven to be a successful, cost-saving optimization method used for injection molded tool manufacturing

 

injection molding trouble shooting

Prior to FEA, a typical method used to refine product and process was to cut tool steel and design a feed system based on experience with older, comparable tools This method is also known as the trial and error method

This type of “guessing” process has cost manufacturers thousands of dollars in re-tooling and time delays that could have been prevented if they had first utilized FEA to troubleshoot the product and process

The question remains, “Should FEA be used for every tool?”  The answer is YES! Whether it is a new tool replacing an old tool running the same part, a New Tool being built for a new part, or a new mold for an existing part, FEA can positively refine both the quality of mold and the process

FEA is a gift to plastics manufacturers in that it provides an inside look at both the product and process before any steel is cut or altered  The refinement of product and process allows the manufacturer to perfect their part and save both time and money by limiting or preventing future rework

Contact Bozilla Corporation to assist you in achieving a successful part based on your budget and timing goals for your next project  We will provide you with detailed project data empowering you to make the most informed decisions to create a high quality mold

Do you remember the cost of your last mold?  If the answer is “yes”, do you really want to pay for it again because of rework/redesign?  

The plastic injection molding experts at Bozilla Corporation have over 20 years of experience with Autodesk Moldflow software, feed system design and field experience We provide the highest degree of professionalism, knowledge and quality to every project  Contact Bozilla Corporation Today and Let’s get started!

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