Month: August 2021

Valve Gates and Sequencing-for injection molding

By Bozilla
August 24, 2021

Valve Gates are invaluable as they relate to their primary design purpose and have many important functions

 They can:

✔ Eliminate waste that cold runners create

✔ Eliminate vestige

✔ Be sequenced

✔ Eliminate weld lines

✔ Control filling patterns

However, users should be aware that there are a few potential issues that could come with using valve gates and sequencing

valve gates for injection molding

 Vestige v Witness Marks

Valve gates can minimize or completely remove vestige by direct gating on the part  They do leave witness marks on the part where the valve gate tip seats into the cavity but with proper grinding or surface finish, it can be minimized or completely hidden

 Controlling the Fill Pattern v Machine Stroke Programming

When multiple valve gates are used to fill a part, it may be necessary to time the sequencing in order to create a more uniform filling pattern  It is extremely important to understand that if the valve gates are sequenced, then the flow rate input must also match the demand of the feed system

For example: If your tool has four valve gates and you initially open two valve gates, then open the next two valve gates, the IM machine must deliver twice the flow rate when the two additional valve gates are opened in order to maintain equal flow rates through all nozzles in the feed system

If the machine stroke is not profiled to compensate for the flow rate demand, the properties of the polymer will change in the cavity due to different filling rates  This could translate into non-uniform shrinkage and stress which directly translates into warpage  It can also cause surface finish variations as shown in the picture below

Nozzle and machine pressure for injection molding

Cascade Sequencing (eliminate weld lines) v Machine Stroke Programming

If the intention is to sequence the valve gates as the flow front passes by in order to remove weld lines, then the same concerns arise if the machine stroke is not programmed to compensate for the additional flow rate demand as additional nozzles are opened

Cascade sequencing can also create back-flow and uneven packing along with uneven stress even if the machine stroke is profiled to compensate for flow rate

Cascade sequencing removes weld lines, therefore the potential problems that accompany it must be weighed  Cascade sequencing should be used as a last resort when trying to eliminate weld lines

Valve Pin Control

Hot runner manufacturers have now developed controllers to

Read More

Can Gate Location Really affect Part Warpage?

By Bozilla
August 17, 2021

Based on part geometry, gate location(s) will determine how the polymer fills the cavity  If the cavity doesn’t fill in a balanced/uniform fashion, the internal stresses will be anisotropic- meaning non-uniform properties  So it is important to place a gate in a location such that the polymer flowfront fills the cavity at a uniform rate and reaches the end of the cavity at all locations, including weld line locations, simultaneously

With simple part geometry, identifying an ideal gate location may be possible by using experience and examining the part  However, with more complex geometry and gating limitations (cooling line interference, ejector pin interference, slides, etc), it is nearly impossible to determine the appropriate gate location(s) without using FEA(flow simulation)  Not only can FEA(flow simulation) produce actual deflection results(warpage), it can also provide data that is a precursor to warpage-such as volumetric shrinkage and frozen-in stress which is typically due to a response from forcing the material into the cavity while the material is trying to freeze

gate location and part warpage courtesy of sciencedirectcom

Gate location(s) will determine polymer orientation  Based on that location, it will ultimately determine polymer shrinkage  Also, different regions of the part will cool at different rates(regions of the cavity near the gate that were first to fill will cool before regions furthest from the gate)

 

Why is this important?  Because there are 3 major components that contribute to warpage:

 ✔ Polymer Orientation

✔ Polymer Shrinkage

✔ Cooling Effects

 

Shrinkage and orientation are both directly correlated to injection location(s) on a part as it relates to processing conditions  Warpage due to cooling effects is  based on the rate of how the polymer cools on one side of the cavity relative to the other side Non-uniform cooling through the thickness will create warpage

Because gate location(s) directly correlates to the contributors of warpage, gate location is therefore extremely important in the tool creation process and ultimately the quality of the part

The injection molding professionals at Bozilla Corporation have over 20 years of experience assisting OEM’s, Tier 1 & Tier 2 suppliers, and Tool Shops to create quality parts that meet timing and goals

wwwBozillaCorpcom

 

About the author

Chris Czeczuga President Bozilla Corporation

Chris Czeczuga is a Plastics Engineer, Injection molding expert, Military Veteran and the President of Bozilla Corporation He has proven success with many OEM’s Tier

Read More

Failure Diagnosis-Product & Process

By Bozilla
August 12, 2021

Bozilla Corporation’s core business is performing CAE analyses, specifically mold flow analyses, on products to optimize both design and process Our procedures and standards set a benchmark to create the highest degree of part quality with the least amount of difficulty and waste

Because many companies have not used FEA, they are turning to the injection molding specialists at Bozilla Corp with issues relating to part failure or processing problems Fortunately, we are solving many of them with Failure Diagnosis

What exactly is Failure Diagnosis?

Failure Diagnosis is the process of identifying why a product or process isn’t performing properly

The injection molding professionals at Bozilla Corporation have cultivated and executed proven techniques to execute this vital task and resolve our customers’ concerns on all levels

This type of diagnosis requires calculated procedures and thorough knowledge in:

✔ CAE Analysis

✔ Root Cause Analysis

✔ Experience with similar products/issues

✔ Indepth knowledge of polymers

If you are experiencing problems with a product in the field or with its process, we will implement our procedures to assist in solving these issues

 Some examples may include:

➤ Start up times for a tool are taking longer than expected, the process is difficult to stabilize, or the start up time on the same tool varies from machine to machine

➤ The process has variation and too many bad parts are being produced

➤ The parts seem to be fine but are failing in the field which causes customer dissatisfaction and more work/costs for you

As an added bonus, the Failure Diagnosis procedures can further lean your process and potentially save you money

Bozilla Corporation has worked extensively with companies to resolve their injection molding performance issues Contact us today and find out how we can help diagnosis any issues you may be having with your injection molding product and/or process and get you back on track!

 

wwwBozillaCorpcom

We Know Injection Molding! Plastics Engineering, Consulting, Optimization, Failure Diagnosis, Training

About the author

Chris Czeczuga is a Plastics Engineer, Injection molding expert, Military Veteran and the President of Bozilla Corporation He has proven success with many OEM’s Tier 1’s, Tier 2’s, Tool Shops, Molding shops, Part Designers, Processors and Fortune 500 companies throughout the injection molding industry A graduate from UMass Lowell, he is Expert Certified with Autodesk, has 20 years of field experience, intimate knowledge of injection molding part, tool and feed system design Bozilla Corporation’s success is built on providing the highest level of injection

Read More

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

Read More