troubleshooting for injection molding by ides

Scientific Troubleshootingof Common Injection

Molding Defects

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Intelligent Molder

in·tel· li·gentAccording to Encarta:

1 : the ability to learn facts and skills andapply them, especially when this abilityis highly developed


Intelligent Molder

According to the New YorkTimes… Intelligence is defined

as problem solving ability

This is the basis of this presentation


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Intelligent Molder Series: Process Evaluation• In-Mold Rheology Test• Gate Seal Worksheet• Decoupled II Process Worksheet• More Details at the End of the Presentation


Scientific Troubleshootingof Common Defects

• Real-Life Troubleshooting Scenarios• Who is a Scientific Troubleshooter?• Process Documentation• Causes for Common Defects• Troubleshooting Methods• FREE Training Offer• Q & A Session


Real-Life Troubleshooting Scenarios

Case #1 – Material Issue - Problem• Scenario:

– Connector Mold– New Material Supplier with “Identical Material”– Could Not Maintain Desired Cycle Times– 13.9 seconds vs. 11.2 seconds



Case #1 – Material Issue – Solution• Process, machine, & mold – identical• What changed… Material

– Internal lubricant was not the same– Internal lubricant not at the same percentages

• Established:– Correct internal lubricant– Correct percentages of lubricant

• Resulting in a cycle time under 9 seconds!



Case #2 – Part Design Issue - Problem• Scenario:

– Kitchen shelving support– Operating at 17.2 second cycle time– Needed to maintain critical dimensions– Wanted to optimize process



Case #2 – Part Design Issue – Solution• Design Change

– Added 0.25º draft angle

• Resulting in a cycle time under 12 seconds!



Case #3 – Machine Issue - Problem• Scenario:

– 3 plate mold replaced with hot runner mold– 6 second capable automation added– New machine could not plasticize fast enough– New machine could not move all machine

functions at simultaneously



Case #3 – Machine Issue – Solution• Specified new machine with:

– Better screw design– Independent machine functions

• Resulting in cycle time under 4 seconds!• Machine could outrun the automation!



Case #4 – Mold Issue - Problem• Scenario:

– Theft protection tag– 3 plate mold has slow process– Cycle time above 23 seconds– High scrap rate ~35%



Case #4 – Mold Issue – Solution• Specified mold with hot runner system• Significantly reduced scrap• Resulting in cycle time under 10 seconds!



Case #5 – Technology Issue - Problem• Scenario:

– Tubular coat hanger– Intermittent short shots– Due to viscosity variations in off-spec materials



Case #5 – Technology Issue – Solution• Specified process monitoring system with:

– Cavity pressure transducer– Integration to boost cutoff

• Resulting in elimination of short shots• Variations in material viscosity had little to

no change in process


Who is a Scientific Troubleshooter?

trou·ble·shoot·erAccording to Merriam-Webster:

1 : a skilled worker employed to locatetrouble and make repairs in machineryand technical equipment



A Typical Troubleshooter:• acts upon learned behavior• makes multiple changes at one time• rarely documents anything• often blames the tool or material• avoids speaking in specifics



sci·enceAccording to Merriam-Webster:

1 : the state of knowing : knowledge asdistinguished from ignorance ormisunderstanding



sci·ence + trou·ble·shoot·er =

'a skilled worker who acts from astate of knowing'



A Scientific Troubleshooter:• knows the history of the process, mold,

machine, material, technology• determines what has changed• acts on knowledge• verifies the results of any change


Process Documentation

Machine Inputsvs.

Process Outputs



Setup Technicians Typically Document:• machine-dependent inputs• speed settings• time settings• temperature settings• pressure settings• tonnage settings



Scientific Troubleshooters Document:• machine-independent process outputs

– temperatures– times– plastic pressures– weights– additional data



Process Outputs - Temperatures:• plastic melt temperature• coolant temperature in• coolant temperature out



Process Outputs - Times:• fill time• pack time• hold time• gate seal time• cycle time• recovery time



Process Outputs - Plastic Pressures:• back pressure• pressure at transfer

– and/or peak pressure

• pack pressure• hold pressure



Process Outputs - Weights:• fill weight• pack weight• final weight



Process Outputs - Additional Data:• cavity measurements• quality measurements• clamp tonnage• photographs• observations• cavity balance



The Scientific Troubleshooter UsesDocumentation To:• know how the process ran• determine what changed• act on knowledge• verify the results


Causes/Symptoms for Common Defects

The Typical Troubleshooter Asks:

'what buttons do I pushto correct the defect?’

they often rely on learned behavior & troubleshooting guides



The Scientific Troubleshooter Asks:

‘what change occurredto cause this defect?’

process documentation is crucial for these people


Flash


Flash

What Changed:– high melt temperature or degradation

Causes:– reduced melt viscosity– more material enters cavity during fill

Symptom:– flash anywhere on part– decreased plastic pressure at transfer

• or peak pressure during fill

– increased fill weight– change in screw recovery time


Flash

What Changed:– low melt temperature

Causes:– high melt viscosity– more pressure is required to fill mold

Symptom:– flash near gate or center of mold– increased plastic pressure at transfer


– decreased fill weight


Flash

What Changed:– decreased fill time due to high flow rate

Causes:– lower viscosity due to shear thinning– excessive material enters mold during fill

Symptom:– flash anywhere on part– increased fill weight– decreased fill time– increased pressure at transfer



Flash

What Changed:– increased fill time due to a low transfer setpoint

Causes:– excessive material enters mold during fill

Symptom:– flash anywhere on part– increased fill weight– increased fill time– increased pressure at transfer



Flash

What Changed:– increased pack and hold pressure

Causes:– excessive pressure within mold

Symptom:– flash anywhere on part– increased pack weight– increased final weight


Flash

What Changed:– low clamp tonnage

Causes:– insufficient tonnage to hold mold closed

Symptom:– little change in outputs– increased pack weight– flash anywhere on part


Flash

What Changed:– high cavity imbalance

Causes:– excessive material enters during fill

Symptom:– not all cavities may flash– intermittent shorts– intermittent flash– incorrect fill time– flash anywhere on part


Flash

What Changed:– inconsistent check ring

Causes:– inconsistent material during fill

Symptom:– intermittent shorts– intermittent flash– inconsistent fill time– flash anywhere on part


Flash

What Changed:– excessive mold and platen deflection

Causes:– inconsistent tonnage across parting line

Symptom:– little change in outputs– flash near center of the mold


Flash

What Changed:– mold damage or wear

Causes:– wear or damage occurs

Symptom:– little change in outputs– flash in a unique area– flash near a moving component


Sinks and Voids


Sinks and Voids

What Changed:– high melt temperature

Causes:– excessive shrinkage occurs

Symptom:– shrinkage anywhere on the part– decreased pressure at transfer


– increased fill weight


Sinks and Voids


Causes:– excessive pressure loss occurs

Symptom:– shrinkage near the end of fill– increased pressure at transfer




Sinks and Voids

What Changed:– increased fill time due to low flow rate


Symptom:– shrinkage near the end of fill– decrease pressure at transfer


– change in fill weight


Sinks and Voids

What Changed:– decreased fill time due to a high transfer

setpoint

Causes:– insufficient material enters mold during fill

Symptom:– shrinkage near the end of fill– decrease pressure at transfer


– decrease in fill weight


Sinks and Voids

What Changed:– decreased pack and hold pressure

Causes:– inadequate pressure within mold

Symptom:– shrinkage anywhere on part– decreased pack weight– decreased final weight


Sinks and Voids

What Changed:– poor gate seal due to a low hold time

Causes:– material exits the cavity through the gate

Symptom:– shrinkage near the gate– decreased final weight


Sinks and Voids

What Changed:– high mold temperature

Causes:– excessive shrinkage occurs

Symptom:– shrinkage anywhere on the part– decreased pressure at transfer



Voids

What Changed:– low mold temperature

Causes:– polymer freezes to mold surface as part shrinks

Symptom:– voids anywhere on the part– increased pressure at transfer



Short Shots


Short Shots



Symptom:– increased pressure at transfer


– decreased fill weight– decreased pack weight– decreased final weight


Short Shots

What Changed:– increased fill time due to low flow rate


Symptom:– decrease pressure at transfer


– change in fill weight– decreased pack weight– decreased final weight


Short Shots

What Changed:– decreased fill time due to a high transfer

setpoint

Causes:– insufficient material enters mold during fill

Symptom:– decrease pressure at transfer


– decrease in fill weight– decreased pack weight– decreased final weight


Short Shots

What Changed:– decreased pack pressure

Causes:– inadequate pressure to complete mold filling

after transfer

Symptom:– decreased pack weight– decreased final weight


Jetting


Jetting


Causes:– high viscosity prevents fountain flow

Symptom:– increase pressure at transfer




Jetting

What Changed:– decreased fill time due to high flow rate

Causes:– high flow rate prevents fountain flow

Symptom:– increase pressure at transfer


– increased fill weight– decreased fill time


Jetting

What Changed:– low mold temperature

Causes:– poor adhesion to mold surface prevents

fountain flow

Symptom:– increased pressure at transfer




as you can see…

if the process is documented,the scientific troubleshooter canquickly identify what changed


Troubleshooting Methods

Again… A Scientific Troubleshooter:• knows the history of the process, mold,

machine, material, and technology• determines what has changed• acts on knowledge (intelligence)• verifies the results of any change



Step 1: Examine the Part to Ensure:• proper diagnosis• no other defects are present



Step 2: Rule Out Obvious Causes:• check the simple causes

– where applicable



Step 3: Compare with DocumentedProcess Outputs• focus on related outputs• process of elimination



Step 4: Return Process to DocumentedStandard• change one parameter at a time• allow each change time to affect the

process



Step 5: Verify Other Process Outputs• verify any relevant parameters• a full verification may be necessary• if cause not found, check the mold,

machine, & material



Step 6: Document Any Changes Made• record actions and causes• ensures others can follow


Scientific Troubleshooting

In conclusion: it is not only abouttroubleshooting a process…

All factors such as material, mold,machine, part design and

technology must be documented.



Intelligent Molder Series: Process Evaluation• In-Mold Rheology Test• Gate Seal Worksheet• Decoupled II Process Worksheet



Follow-Up Email Will Contain:• Instructions to Download Worksheets• Instructions to Receive Free Trial• Webinar Notes & Special Offer


Scientific Troubleshootingof Common Defects

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troubleshooting for injection molding by ides

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