Comparison of switchover methods for injection molding
Download
1 / 42

Comparison of Switchover Methods for Injection Molding - PowerPoint PPT Presentation


  • 324 Views
  • Uploaded on

Comparison of Switchover Methods for Injection Molding. David O. Kazmer, Sugany Velusamy, Sarah Westerdale, and Stephen Johnston Plastics Engineering Department University of Massachusetts, Lowell Priamus Users Group Meeting September 30 th , 2008. Agenda. Motivation

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Comparison of Switchover Methods for Injection Molding' - eve


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Comparison of switchover methods for injection molding l.jpg

Comparison of Switchover Methods for Injection Molding

David O. Kazmer, Sugany Velusamy, Sarah Westerdale, and Stephen Johnston

Plastics Engineering Department

University of Massachusetts, Lowell

Priamus Users Group Meeting

September 30th, 2008


Agenda l.jpg
Agenda

  • Motivation

    • Manufacturing competitiveness

    • Characteristics of highly productive molders

  • Switchover Methods

    • Overview

    • Experimental Setup

    • Results

    • Conclusions





U s manufacturing productivity6 l.jpg
U.S. Manufacturing Productivity

Where is it going tocome from?

  • Manufacturers need 1.5% annual productivity gains to remain competitive


Characteristics of highly competitive molders l.jpg
Characteristics of Highly Competitive Molders

  • Highly systematized

    • Excellent layout

    • Consistent and often uni-directional flow of materials

    • Uniform internal planning processes

    • Uniform quality control processes.

  • Many highly productive facilities use only one primary supplier of plastics machinery.


Characteristics of highly competitive molders8 l.jpg
Characteristics of Highly Competitive Molders

  • Highly utilized

    • 24 x 7 operation

    • 90% plus machine utilization

  • Steady state strategy

    • Use fewer and better machines running continuously rather than more machines running fewer shifts


Characteristics of highly competitive molders9 l.jpg
Characteristics of Highly Competitive Molders

  • High yields

    • 95% typical

    • 99.8% not necessary

  • High quality assurance

    • Automatic: in-mold systems, vision, poka-yoke

    • Conservative rules to contain defects

      • Better to automatically reject 10 good parts than accept one bad part


Characteristics of highly competitive molders10 l.jpg
Characteristics of Highly Competitive Molders

  • Industry sector andapplication focus

    • Connectors

    • Gears

    • Syringes

  • Focus provides

    • Advanced application-specific knowledge

    • Market commitment and technology investment


Obsolete vs competitive l.jpg
Obsolete vs. Competitive

  • Number of machines

Obsolete Competitive


Obsolete vs competitive12 l.jpg
Obsolete vs. Competitive

  • Number of workers

Obsolete Competitive


Obsolete vs competitive13 l.jpg
Obsolete vs. Competitive

  • Number of supervisors

Obsolete Competitive


Obsolete vs competitive14 l.jpg
Obsolete vs. Competitive

  • Plant size

Obsolete Competitive


Obsolete vs competitive15 l.jpg
Obsolete vs. Competitive

  • Energy usage

Obsolete Competitive


U s manufacturing productivity16 l.jpg
U.S. Manufacturing Productivity

  • Manufacturers need 1.5% annual productivity gains to remain competitive


Agenda17 l.jpg
Agenda

Motivation

Manufacturing competitiveness

Attributes of highly productive molders

Switchover Methods

Overview

Experimental Setup

Results

Conclusions


Overview switchover concept l.jpg
Overview: Switchover Concept

Switchover is the point at which the filling phase ends and packing phase starts

From a controls perspective, there is a switch in the system’s boundary conditions and stiffness

Variances cause:

Dimensional errors

Part weightvariations

Back flow

Pressure

Velocity

Switchover

time

time


Overview switchover methods l.jpg
Overview:Switchover Methods

Various methods for switchover:

Screw Position*

Injection Time

Injection Pressure

Cavity Pressure

Cavity Temperature

Nozzle Pressure

Tie Bar Deflection

Other studies have been conducted.

This study is more comprehensive with respect to number of methods and also long term variation.

Filling Stage

Packing Stage


Experimental setup l.jpg
Experimental Setup

  • Molding Machine

    • 50 metric ton All Electric Machine

    • Make: Ferromatik Milacron

    • Model: Electra 50 Evolution

  • Plastic Material:

    • AMOCO Polypropylene

    • Grade 10-3434


Process monitoring control l.jpg
Process Monitoring & Control

  • Extremely well instrumented machine & mold

    • Screw position transducer

    • Nozzle pressure transducer

    • Ram load transducer

    • 3 barrel thermocouples

    • 4 in-mold pressure transducers

    • 2 in-mold temperature sensors

    • Nozzle infrared pyrometer

    • In-mold infrared pyrometer

    • PRIAMUS DAQ8102 acquisition

  • Custom machine override circuit

    • Internal or external voltage signal triggers the machine for switchover


Switchover methods measured attributes l.jpg

Seven Switchover Methods

Machine Controlled

Screw Position

Injection Pressure

Injection Time

Externally Controlled

Nozzle pressure

Runner Pressure

Tensile Cavity Pressure

Cavity Temperature

Six Measured Attributes

Impact Thickness (mm)

Impact Weight (g)

Impact Width (mm)

Tensile Thickness (mm)

Tensile Weight (g)

Tensile Width (mm)

Switchover Methods & Measured Attributes




Molding machine statistical characterization l.jpg

100 consecutive molding cycles were monitored & data acquired

The average & standard deviation was calculated to measure of short term variation

Molding Machine Statistical Characterization



Design of experiments doe l.jpg

DOE performed to impose long term variation same part weight

Design of Experiments (DOE)


Analysis l.jpg
Analysis same part weight

  • The 90 cycle DOE was repeated for each of the seven switchover conditions

  • Parts weighed & dimensions measured

  • The data was analyzed in Matlab to provide:

    • Individual traces for each of 630 cycles

    • Overlaid traces for all cycles in a DOE run

    • Overlaid traces for all cycles in a switchover method

    • Regression coefficients & main effects plots



Main effects on impact thickness for ram position switchover l.jpg
Main Effects on Impact Thickness Switchoverfor Ram Position Switchover

Good process robustness


90 cycles across the doe for filling time switchover l.jpg
90 Cycles across the DOE for SwitchoverFilling Time Switchover

Time Switchover


Main effects on impact thickness for filling time switchover l.jpg
Main Effects on Impact Thickness Switchoverfor Filling Time Switchover

Very poor process robustness



Main effects on impact thickness for cavity pressure switchover l.jpg
Main Effects on Impact Thickness Switchoverfor Cavity Pressure Switchover

Good process robustness



Main effects on impact thickness cavity temperature switchover l.jpg
Main Effects on Impact Thickness SwitchoverCavity Temperature Switchover

Best process robustness


Coefficient of variation cov l.jpg
Coefficient of Variation Switchover COV = σ / µ

Different switchovers are best for different attributes


Switchover performance short vs long run variation l.jpg
Switchover Performance: SwitchoverShort vs. Long Run Variation

Short Run Variation (%)

More robust

Long Run Variation (%)


Switchover performance long run variation l.jpg
Switchover Performance: SwitchoverLong-Run Variation

Screw position

Injection time

Machine pressure

Nozzle pressure

Runner pressure

Cavity pressure

Cavity temperature


Conclusions l.jpg
Conclusions Switchover

Cavity temperature provided the most robustness against changes the process settings.

Place the sensor near but not at the very end of flow due to small control system delays (speed matters)

Cavity pressure provided reasonable switchover control but had susceptibility to changes in melt temperature and velocity.

Position control provided reasonable control but roughly twice the variation of cavity temperature.

Injection time is the least reproducible method for the transfer from fill to pack, with literally 10 times the variation of temperature control.


Conclusions41 l.jpg
Conclusions Switchover

  • Measured consistency is much better than SPI guidelines of 0.2%

    • Response time of the molding machine, controller and ram velocity are important to process repeatability.

  • Weight and thickness show higher COV than length and should be used for QC

In-mold instrumentation is vital to achieving process robustness, automatic quality control, and competitiveness.


Acknowledgements l.jpg
Acknowledgements Switchover

National Science Foundation grant numberDMI-0428366/0428669

Priamus System Technologies


ad