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Flashcards in Lec18 Deck (19)
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1

Inkjet printing if surface energy too low

print beads up

2

inkjet printing if surface energy too high

coffee staining occurs

3

Subtractive manufacturing

parts made by removing material in the form of chips from a bulk

4

Additive manufacture

parts made from small building blocks

5

adv of additive manufacture

zero waste
more design freedom
tailoring is much easier

6

disadv of additive manufacture

production rate is slow
expensive
strength in Z axis and overall strength of objects sometimes an issue

7

inkjet printing is

an additive technology

8

Injet printing adv

does not need masks or stamps to form a pattern
can switch rapidly between patterns automatically
does not generate wase
reduce costs
can be scaled up

9

How we build bring with injet

row of overlapping drops results in a line
an array of drops results in a film

10

Dot spacing inket printing

space between centre of two droplets - larger the dot spacing the less overlap
larger dot spacing can give narrower lines but also result in line breaks

11

Droplet evaporation leads to

coffee ring effect

12

conditions needed for coffee staining

a volatile and partially wetting solvent
a pinned contact line
evaporation occurring at the contact line

13

wetting meaning

perfect non wetability droplet will bead up and roll off
a wetting surface droplet will spread out and soak in

14

How to stop coffee staining

reduce edge evaporation; two solvent system

15

Two solvent system

combination of two solvent one high boiling point and low boiling point

16

if surfacen energy is high

line will be broad and may coffee stain

17

if surface energy of the substrate is low

lines will break up into beads

18

control remove coffee staining

by controlling evaporation at the edge

19

two solvent system

experiment to optimise ratio
take into account drying time and amount of liquid per unit area
playing with ink chemistry can help in some situations