Tag: mold design

STOP doing this to Cooling Circuits!

By Bozilla
May 2, 2023

STOP ignoring the importance of proper cooling circuit design for injection molding Cooling circuit design is typically not heavily weighted with regards to importance in the injection molding industry Cooling circuits need to be designed properly and the importance of the design must not be overlooked A common practice is to simply ‘place cooling in the mold’ and not much more Sometimes it is taken a step further where the practice is ‘to place as much cooling in the mold as possible’ This is a better practice but is it the best? We are going to discuss the importance of proper cooling circuit design and the implications of overlooking this important practice

Cooling Circuit Diameter

Is the diameter of the cooling circuit important? It certainly is In fact, the diameter of the cooling circuit must be a part of a larger consideration such as circuit spacing, pressure drop and flow rates A larger diameter may be thought to cool better since it is larger, which is somewhat true, however it will take up more space due to its larger diameter so it may be difficult to route in tighter locations

The spacing of larger cooling lines can be increased based on the diameter which can result in fewer cooling lines hence less gun—drilling, ie a cost savings but this is not always the better condition if the mold design is complex or small  Larger cooling lines will also have a lower pressure loss resulting in less power required to pump the water through the circuit This is a big plus but the difference in pumping efficiency may be negligible It is also important to understand that varying cooling circuit diameters within the same mold will only be as efficient as the smallest diameter of that circuit due to the higher pressure loss within the section containing the smaller diameter The flow may be turbulent in the portion with the smaller diameter yet may take flow away from the larger diameter portion resulting in a laminar flow condition in the section with that larger diameter

The Importance of Balanced Cooling Circuits

Optimal designed cooling circuits are the driving force behind productivity and cycle times

If your cooling circuits are not as working as efficiently as they can be, they will be costing you precious time and money Balancing cooling circuits plays a tremendous role in cooling efficiency

So why do the cooling circuits need to be balanced and what exactly does that mean?

In short, all circuits are not created equal If cooling circuits are not equally balanced, then the flow rate

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Lean Tool Validation for Injection Molding

By Bozilla
April 19, 2023

Lean tool validation video


Lean Tool validation for injection molding means developing a more efficient process that benefits the environment; Reduces CO2, and saves costs  Bozilla uses “cutting-edge” proprietary techniques developed over 21 years in the injection molding industry to determine if a tool can be optimized and brought back to life in its most efficient state

A typical scenario entails a company contacting Bozilla to make a tool more efficient or bring a tool back to life  We would ask them to send us everything about the tool, including CAD drawings, 3D part and tool drawings, machine process settings, current tool status, and other pertinent information about the tool

Analyze data for mold


Bozilla will investigate all areas of inefficiency, outline suggestions, and provide a proposal  During the beginning phase, there will be no up-front cost  The company then determines which recommendations can be practically implemented, and Bozilla provides a cost and time estimate  Should the customer accept the proposal, the work can begin immediately

Some examples of tools Bozilla has efficiently improved include those that have been cut wrong (tool dimensions did not match part specifications/dimensions), fouled cooling channels,  a poorly designed feed system(both hot and cold), cycle times that are excessive or are known to be inefficient and even tools that have been sidelined due to inefficiency

Once the project has started, the type of work performed is analytical where Bozilla models the current design and conditions in a virtual world using Autodesk Moldflow Insight

Optimize tool process


Initially, our team would identify areas of the process that can be optimized, make those changes and continue to further optimize the process  Once the process has been deemed efficient (based on the tool design, coolant flow rate, and other factors), the customer will have an opportunity to review and make as many changes as possible, which may or may not include tool modifications (such as adding cooling lines) It is not always apparent that a tool is underperforming unless a thorough investigation is performed   Each potential issue is identified accordingly, and proposed changes are provided to create a streamlined, lean running tool that will be lean and profitable

Some examples of proposed changes may include instrumenting the tool correctly,  determining pump efficiency, reducing cycle times, increasing temperature control, minimizing process variation, reducing energy consumption (creating less CO2),  recapturing costs from tools

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Part 2: Can Moldflow Validate the Quality of your Part?

By Bozilla
September 30, 2022

Part 2: Can Moldflow Validate the Quality of your Part?

In Part 2 we will continue our discussion of utilizing the Moldflow software to ensure the part does not fail in the field (Part 1: Can MoldFlow Validate the Quality of Your Part?)

Is the gate in the best location?

In many cases, the customer provides a part with a suggested gating location The gating location is sometimes determined during the part design process and is designed based on the assumed gate location However, the pre-determined gate location may not always be the best location for several reasons:

  • The gate location may not provide a balanced filling pattern which can cause severe velocity changes to the flow front or an undercut scenario where the flow direction changes after the frozen layer on the wall has been established which causes tremendous shear within the part laminae Both of which can cause part deformation or even failure
  • If the gate location creates an imbalanced filling pattern it can create a pressure spike which will also create a clamp tonnage spike Both of which lead to issues mentioned in aforementioned bullet
  • The gate location may not be in the best location with regards to the material freezing back to the gate which is essential for proper part packing Some regions of the part may not be able to be packed due to a poorly selected gate location This can cause excessive volumetric shrinkage in isolated regions of the part which can lead to sink marks or even voids In the images below there is a wheel for a drawer carrier which is failing due to internal voids There is a cut-away showing the voids which are revealed in the analysis where the high volumetric shrinkage shows the regions where the voids can potentially occur:injection molding voids

    Has the tool design been verified?

    This may seem like a redundant question but there are times when the tool may undergo some design changes which may affect the outcome of the part design such as:

    • Cooling inserts added
    • Rerouting of cooling lines
    • Cavity orientation changes
    • Feed system changes (perhaps due to cavity orientation changes)
    • d possibly other tool design changes

    Many businesses integrate a final tool review before or at the initial trial run, so if this is not standard procedure it is highly recommended If anything HAS changed, the mold filling analyst will need to re-optimize the process based on those changes

    Has the material been qualified/verified? (Keep the material

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Can Moldflow Predict Part Quality? (Part 1)

By Bozilla
September 2, 2022

This subject contains a significant amount of important information so it will be broken into two parts

Part 1: Can Moldflow Validate the Quality of Your Part?

The short answer is YES Validating your plastic injection molded part before it enters the field is the purpose for which the Moldflow software was created

A well trained and seasoned user of the Moldflow software should be able to take a part through the entire injection molding optimization process and validate each of the factors that will ensure the part meets the design criteria ie quality of the part

Injection molding design validation

For most parts, the criteria is very similar:

  • The part must meet design tolerances and must have minimal deflection/warpage
  • Weld lines must form in acceptable places or perhaps weld lines are not allowed on specified surfaces
  • Air traps must be kept to a minimum and/or be vented properly
  •  The process must have a large molding window so that any minor variations will not cause the part to fall out of specification
  •  The design of the part must meet injection molding standards (correct draft, not have any regions that are die-locked, must have correct thickness ratios, etc)
  • The design of the mold must allow for adequate filling and cooling along with many other criteria such as proper ejection (that will not deform the part) and so-on

Why is injection molded part failing


What happens if you believe your part design and process is optimized properly only to find out that it fails in the field?  This is a very common situation

The purpose of the Moldflow software is to mitigate such a situation I’ll explain

In order to understand if a part is going to be molded correctly, the analyst must utilize the software to correctly optimize, at a minimum, each one of the following points

1 Is the part filling at the right speed? 

It is critical to fill the part with the proper flow front velocity (screw velocity profile) As the cavity is filling, the flow front of the polymer can cool off or heat up; both of which are critical with regards to how much stress is imparted in the polymer as it fills Too much stress during the molding of the part can cause excessive post-molding stress relaxation and deflection

2 Is the feed system designed correctly? 

An improper feed system design can control cycle time or cause the pressure requirement to fill the cavity

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