0
Design Innovation Paper

Gate Design in Injection Molding of Microfluidic Components Using Process Simulations

[+] Author and Article Information
David Maximilian Marhöfer

Department for Mechanical Engineering,
Technical University of Denmark,
Produktionstorvet, Building 427A,
2800 Kongens Lyngby, Denmark
e-mail: maxmar@mek.dtu.dk

Guido Tosello

Department for Mechanical Engineering,
Technical University of Denmark,
Produktionstorvet, Building 427 A,
2800 Kongens Lyngby, Denmark
e-mail: guto@mek.dtu.dk

Aminul Islam

Department for Mechanical Engineering,
Technical University of Denmark,
Produktionstorvet, Building 427 A,
2800 Kongens Lyngby, Denmark
e-mail: mais@mek.dtu.dk

Hans Nørgaard Hansen

Department for Mechanical Engineering,
Technical University of Denmark,
Produktionstorvet, Building 427 A,
2800 Kongens Lyngby, Denmark
e-mail: hnha@mek.dtu.dk

1Corresponding author.

Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF MICRO- AND NANO-MANUFACTURING. Manuscript received August 26, 2015; final manuscript received December 10, 2015; published online February 11, 2016. Assoc. Editor: Stefan Dimov.

J. Micro Nano-Manuf 4(2), 025001 (Feb 11, 2016) (12 pages) Paper No: JMNM-15-1060; doi: 10.1115/1.4032302 History: Received August 26, 2015; Revised December 10, 2015

Just as in conventional injection molding of plastics, process simulations are an effective and interesting tool in the area of micro-injection molding. They can be applied in order to optimize and assist the design of the microplastic part, the mold, and the actual process. Available simulation software is however actually made for macroscopic injection molding. By means of the correct implementation and careful modeling strategy though, it can also be applied to microplastic parts, as it is shown in the present work. Process simulations were applied to two microfluidic devices (a microfluidic distributor and a mixer). The paper describes how the two devices were meshed in the simulations software to obtain a proper simulation model and where the challenges arose. One of the main goals of the simulations was the investigation of the filling of the parts. Great emphasis was also on the optimization of selected gate designs for both plastic parts. Subsequently, the simulation results were used to answer the question which gate design was the most appropriate with regard to the process window, polymer flow, and part quality. This finally led to an optimization of the design and the realization of this design in practice as actual steel mold. Additionally, the simulation results were critically discussed and possible improvements and limitations of the gained results and the deployed software were described. Ultimately, the simulation results were validated by cross-checking the flow front behavior of the polymer flow predicted by the simulation with the actual flow front at different time steps. These were realized by molding short shots with the realized molds and were compared to the simulations at the global, i.e., part level and at the local, i.e. feature level.

Copyright © 2016 by ASME
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Fig. 1

CAD model of the first investigated microplastic part with highlighted treelike structure for the distribution of fluid

Grahic Jump Location
Fig. 2

CAD models of the microfluidic distributor with three different gate designs

Grahic Jump Location
Fig. 3

Viscosity versus shear rate at different temperatures (left) and pvT data at different pressure levels (right) of the PEI Ultem 1000 which was used for the microfluidic manifold [23]

Grahic Jump Location
Fig. 4

CAD model of the second investigated microplastic part which acts as microfluidic mixer

Grahic Jump Location
Fig. 5

CAD model of the second investigated microplastic part with feed system (film gate, runner, sprue)

Grahic Jump Location
Fig. 6

Viscosity versus shear rate at different temperatures (left) and pvT data at different pressure levels (right) of the COC Topas 5013-L10 which was used for the microfluidic mixer [23]

Grahic Jump Location
Fig. 7

Meshed microdistributor with closer view on some details (microwalls at outlets). Range of mesh edge length of the entire model: 40–800 μm.

Grahic Jump Location
Fig. 8

Meshed micromixer with closer view on some details (micropillars and rim). Range of mesh edge length of the entire model: 65–800 μm.

Grahic Jump Location
Fig. 9

Filling behavior for the three configurations of the fluidic distributor

Grahic Jump Location
Fig. 10

Top: Example of a rib acting as flow restrictors and causing the flow to lag behind compared to the bulk of the microfluidic distributor. Bottom: Thickness variation in the part which contributes to the disturbance of the flow front in the cavity during the filling phase of the microfluidic distributor.

Grahic Jump Location
Fig. 11

Warpage prediction of the simulation in x and y direction for the microfluidic distributor

Grahic Jump Location
Fig. 12

Warpage prediction of the simulation in z direction for the microfluidic distributor. Left: different gate designs. Right: Different sizes of gate design C (pin gate).

Grahic Jump Location
Fig. 13

Actual steel mold of the microfluidic manifold with stationary half (left) and the movable half (right). The cavity wasmachined according to the optimized design based on simulation results applying the insight from the simulations in practice.

Grahic Jump Location
Fig. 14

Comparison on part level by overlay of the actual flow front given by short shots molded in PP and the simulated flow front for the microfluidic manifold

Grahic Jump Location
Fig. 15

Comparison on feature level between scanning electron microscopy (SEM) picture of the actual flow front given by short shots in PP (left) and the simulated flow front (right) for the microfluidic manifold

Grahic Jump Location
Fig. 16

Left: film gate of the microfluidic mixer with quite even flow front when the plastic is entering the actual part cavity. Right: cross-sectional view of the flow in the microfluidic mixer with indication of the distinct hesitation effect at the micropillars: the filling in bulk direction is faster than in the direction of the micropillars, i.e., the flow length a in bulk direction is larger than the flow length b in direction of the micropillars.

Grahic Jump Location
Fig. 17

Average volumetric shrinkage for the three film gates of the microfluidic mixer

Grahic Jump Location
Fig. 18

Finished mold insert of the microfluidic mixer. The cavity design was machined accordingly to the findings about the design in the simulations.

Grahic Jump Location
Fig. 19

Comparison on part level by overlay of the actual flow front given by short shots molded in PP and the simulated flow front for the microfluidic mixer

Grahic Jump Location
Fig. 20

Comparison on feature level between SEM picture of the actual flow front given by short shots molded in PP (left) and the simulated flow front (right) for the microfluidic mixer

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In