Research Papers

Microcrystal Particles Behaviour in Inkjet Printing of Reactive Nylon Materials

[+] Author and Article Information
Saeed Fathi

e-mail: Saeed.Fathi@gmail.com

Phill Dickens

Wolfson School of Mechanical and Manufacturing Engineering,
Loughborough University,
Leicestershire LE11 3TU, UK

Marianne Gilbert

Department of Materials,
Loughborough University,
Leicestershire LE11 3TU, UK

1Corresponding author.

Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING. Manuscript received March 18, 2012; final manuscript received November 28, 2012; published online January 22, 2013. Assoc. Editor: Yong Huang.

J. Manuf. Sci. Eng 135(1), 011009 (Jan 22, 2013) (12 pages) Paper No: MANU-12-1087; doi: 10.1115/1.4023272 History: Received March 18, 2012; Revised November 28, 2012

A novel process using inkjet printing of molten materials to produce nylon 6 for additive layer manufacturing applications was investigated. Different reactive mixtures of molten caprolactam with activator and catalyst were characterized for physical properties to understand their jettability in an inkjet system. Although it was found that the surface tension and viscosity of all materials were within the range suitable for inkjet technology according to the literature, microcrystals of undissolved salt of the catalyst complex (caprolactam magnesium bromide) were found to influence melt supply behavior. The influence of the process on the catalyst microcrystal consistency and agglomeration beyond the jetting system was investigated for purged, deposited multiple droplets and also individual droplet samples using hot-stage polarized light microscopy. Quantitative image analysis showed that although microcrystal agglomeration occurred within the accumulated droplets due to kinetics of droplet impact, this however was much less than with the purged samples. A generally consistent content and dispersion of the microcrystals existed within the consecutively deposited droplets.

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Fig. 1

Melt supply unit with Luer connection joined to the printhead

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Fig. 2

Jetting assemblies

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Fig. 3

Arrangement for optical microscopy of the catalyst mixture for characterizing microcrystals

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Fig. 4

Polarized light microscopy revealing an agglomerated particle area of the molten synthesized catalyst mixture, CLMgBr-CL, at 80 °C

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Fig. 5

The effect of increasing temperature on the agglomerated area of microcrystals in the synthesized catalyst mixture during the hot stage polarized light microscopy

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Fig. 6

Dissolution of CLMgBr microcrystals with increasing temperature in the synthesized catalyst mixture during the hot stage polarized light microscopy (heating rate: 10 °C/min)

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Fig. 7

Processing of polarized light microscopic images (a) caprolactam original image, (b) processed image, (c) the activator mixture (2 ml melt level) original image, (d) processed image, (e) the catalyst mixture (2 ml melt level) original image, (f) processed image

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Fig. 8

Polarized light microscopy images of the catalyst mixture (C10-CL, 20% concentration) from the 4 ml melt level at 80 °C. Images in (a)–(h) correspond to the labels as shown in Fig. 3.

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Fig. 9

Microcrystal content as white pixel area at different imaging locations as shown in Fig. 3 for different melt levels of the first set of samples

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Fig. 10

Microcrystal content for different melt levels of the second set of samples

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Fig. 11

Mean values for microcrystal content area versus melt level for the two sets of trials

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Fig. 12

Microcrystals within samples of coalesced droplets of the catalyst mixture on the glass slide. Three samples at the 4 ml melt supply level are shown, (a) 10×, (b) selected areas with 50×.

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Fig. 17

Total white pixel area as a proportion of the image size representing the agglomerated microcrystal content of the catalyst mixture at different melt supply levels

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Fig. 16

Analysis of the microcrystal content of a deposited droplet (4 ml melt supply level), (a) original image, (b) processed image with threshold grey levels of 32, (c) 64, and (d) 128

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Fig. 15

Microcrystal content within individual droplets in two arrays at different melt supply levels

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Fig. 14

Microscopy of the microcrystals in two individual droplets (4 ml melt supply level) at different focal lengths (10×), (a) droplet 1 original image, (b) droplet 1 processed image (threshold grey level: 128), (c) droplet 2 original image, (d) droplet 2 processed image

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Fig. 13

Schematic of controlling the focal length for microscopy of microcrystals in a spread droplet



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