technoform for rapid repeatable thermoformability analyses
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Technoform – For Rapid, Repeatable Thermoformability Analyses . Dr. Amit Dharia Transmit Technology Group, LLC, TX www.transmit-technology.com. Outline. Properties –Thermoforming Process relationship Current test methods Description of Technoform Application and data interpretation

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technoform for rapid repeatable thermoformability analyses

Technoform – For Rapid, Repeatable Thermoformability Analyses

Dr. Amit Dharia

Transmit Technology Group, LLC, TX

www.transmit-technology.com

outline
Outline
  • Properties –Thermoforming Process relationship
  • Current test methods
  • Description of Technoform
  • Application and data interpretation
  • Products – Basic, Standard, Advanced
  • Conclusion
thermoforming process
Thermoforming Process
  • Extruding sheet stock
  • Heating sheet above Tg
  • Stretching heated sheet in rubbery state
  • Cooling
  • Trimming
  • Finishing
structure properties thermoformability
Structure - Properties -Thermoformability
  • Rate of change of strength with the change in strain rate at forming temperature
  • % Crystallinity – Breadth of rubbery Plateau
  • Molecular weight, Molecular weight distribution, molecular architecture (branching, crosslinking) – MFR, Melt Elasticity
other parameters
Other parameters
  • Density - % filler, type of fillers, degassing
  • Geometry – Thickness, area, multi-layered structures, adhesion between layers
  • Residual stresses between and within in extruded layer sheet stock
  • Thermal diffusivity (Cp, K. Rho)
  • Extrusion quality ( gels, unmelts, thickness variation, grain patterns)
  • Color (IR absorption)
current tests
Current tests
  • Low shear melt viscosity (MFR, RMS)
  • Melt Tension (Draw Force –Melt tension, Break Velocity -extension)
  • Sag Test (sag distance, sag time)
  • Hot Creep Test
  • DMA (Relaxation time)
major disadvantages of current methods
Major disadvantages of current methods
  • Most tests are conducted in melt or near melt phase
  • Test Specimens does not reflect actual test geometry (shape, size, clamping mode)
  • Tests does not account for orientation, thermal stresses, thickness variations
  • Isothermal environment, does not account for transient nature of heating/ cooling
  • Effects of secondary process parameters can not be evaluated
  • Results cannot be directly used.
what processors want to know
What processors want to know?
  • Will this material thermoform?
  • Will this new material process the same?
  • Will this lot process the same as the last one?
  • Why this lot does not process the same?
  • How much time is needed to heat the sheet?
  • How fast material will heat?
  • What is the right forming temperature range?
  • Will melt adhesion between layers survive heating and stretching step?
  • Will material discolor, fed or degrade during heating?
what processors want to know ii
What processors want to know? -II
  • What is the maximum draw down?
  • How fast part can be made?
  • What is the MD and TD shrinkage?
  • Will material tear at the corners and ribs?
  • How much regrind can I use?
  • Will grains retain shape and depth?
  • Does extruded sheet have gels or unmelts?
what industry needs
What Industry Needs?
  • A standard test method which reflects all unit steps – heating, 3D stretching, forming, and cooling
  • A test equipment which can be precisely controlled, is rapid, easy to use, provides repeatable and quantitative information, using the lease amount of material.
  • Easy to use “Thermoformability Index” standard for comparing, contrasting effects of selected process/ material variables
technoform tm
TECHNOFORM TM

TTG

PatentPending

TECHNOFORM

typical data input
Typical Data input
  • Mode of operation – Plug Assisted, Vacuum
  • The heating element distance from the sheet surface
  • The heating element temperature
  • The sheet temperature
  • Heat Soak time at given temperature
  • Plug velocity (2 to 200 mm/second)
  • Plug Delay Time
  • Plug Temperature
  • Part Cooling time
typical user input screen
Typical user Input Screen

Strain

hardening

Thinning

Thermoformability Index=

slope

SagDistance

Forming Depth mm

typical data output
Typical Data Output
  • Heating rate (Delta C/ time) = f (thickness)
  • Sag distance
  • Forming force (Stress) vs. forming distance (strain)
  • Forming Force vs. time
  • Yield force
  • Forming force vs. actual temperature
  • Shrinkage (manual measurements)
plug material and shapes
Plug Material and Shapes
  • Truncated cone with flat end (2.5” Top D, 0.75 “ Bottom D, 4” Height)
  • Truncated cone with Rounded End (2.5” Top D, 1” D bottom, 4” Height)
  • Hemisphere of 3.5” Diameter
  • All tools made of Foam Epoxy
force 100 f t v material
Force100 = f (T, V, material)
  • F(ABS) =9.2348 -0.0547 T (R2 =99%)
  • F(PMMA)=7.1587 -0.0341 T(R2=98%)
  • F(PETG)=10.096 -0.0601 T (R2=92%)
  • F(HIPS)=9.6782 - 0.0503T(R2=93%)
  • F(HDPE)=5.2771 -0.0266 T (R2=86%)
conclusions
Conclusions
  • Technoform is a simple to operate test equipment is which closely reflects all unit steps of the typical thermoforming process and generates quantitative and repeatable information in short time.
  • The test data can be used in raw form to compare or contrast various materials, process parameters or can be further modeled as a design or predictive tool.
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