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© Copyright 2012 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Ink Delivery System (IDS) issues overview
Gengrinovich Semion
IDS group
© Copyright 2012 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Content
2
• What it is IDS?
• Pressure
• Temperature
• Maintenance
• Numerical Simulation
© Copyright 2012 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
IDS – what is this?
3
IDS – system that responsible supply ink whenever PH’s need
ink ink inkink
Load Cell
Ink
Atmosphere
10L Supply Tank
Ink ID
Air Purge valve
Pressure 0.9bar
T2 (Optional)
Pum
p
Radiator
Filter 1m
ic
3Way Valve
ffl
ffl fflffl
Recycling Bath
fflffl
ST1 ST2
Filte
r 1m
ic
Feeding main Tank /
Recycling pump
3Way Valve
Ink Ink Rec Ink
Ink
Ink
Ink
Ink Rec
Air valve 2Air valve 1
Ink Circ
Air for ST’s valves
Air relief for Valves
Pressure/Atmosphere
Atm
Heater
Water IN
T1
fflCritical
fflFeelingffl
OverflowPressure Transducer
3Way
Val
ve
Feeding Secondary tanks Pump
Ink Ink
OverflowFeeding
LowCritical INK line
INK RecyclingINK CirculatedWater lineAir Valve reliefAtmosphere/Purge
Manual Valve
Waste Tank
Ink ID
Manual Valve
Separator
Waste pump
Vacuum knife
Waste lineSimplified IDS
Actually IDS
© Copyright 2012 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
IDS – what is this?
4
Pressure issues in PH’sMachine serge
-140
-120
-100
-80
-60
-40
-20
0
20
40
1550 1600 1650 1700 1750 1800
Time (50samples per sec)
Pres
sure
(mm
H2O
)
Machine serge
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-120
-100
-80
-60
-40
-20
0
20
-3 -2 -1 0 1 2 3 4
Time(sec)
Pres
sure
(bar
)
theoretical calculation Machine phenomena
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-120
-100
-80
-60
-40
-20
0
20
-3 -2 -1 0 1 2 3 4
Time(sec)
Pres
sure
(mm
H2O
)
Theoretical calculation Surge with flexible tubes
1!]
© Copyright 2012 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Pressure issues in PH’s
5
HP Confidential
-100-90-80-70-60-50-40-30-20-10
0
0 5 10 15 20 25 30 35 40
Pres
sure
(mmH
2O)
Time (sec)
Valves 400 in nominal condition (pressure in Inlet of PH 16)
Valve 400 – opens dH=40mm
H=50mm
-150
-100
-50
0
107 112 117 122 127 132 137
Valves 400 - closed during the printing)
After 4 copies in print mode 480 BB 100% 3.2 meter - Failure appear
H=80mm
-110
-60
-10
110 115 120 125 130 135 140 145
Siphon installed - valves 400 in nominal conditions
H=30mm
Valve 400 – opens
• After 20 copies in print mode 480 BB 100% 3.2 meter –Stable (Failure not appear) butnot repeatable in all colors
• After 20 copies in print mode 480 BB 100% 3.2 meter –Stable for all colors
© Copyright 2012 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Pressure issues in PH’sSolved the “starvation” – tested on one machine – 6 colors
6
• After 4 copies in print mode 480 BB 100% 3.2 meter - Failure appear in all colors
• After 20 copies in print mode 480 BB 100% 3.2 meter – Stable for all colors
© Copyright 2012 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.7
18 October
Particles with a size of 20 m or larger should be prevented from reaching thenozzle. Inside the printhead, this can be achieved through filters. But dustparticles from outside also form a threat. Printing in a clean environment shouldprevent particles from reaching the nozzle. Unfortunately, for printers in anindustrial environment it is often impossible to control the cleanness of theambient air.
Air entrapment triggered by particles in the ink, disrupting the droplet formation
J. Acoust. Soc. Am., Vol. 120, No. 3, September 2006 de Jong et al.: Air entrapment in piezo-driven inkjet printheads
© Copyright 2012 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.8
Air entrapment caused by an ink layer on top of the nozzle plate
The ink layer on the nozzle plate should stay below a thickness of 30 m. This
may be accomplished by a special design of the nozzle plates.
J. Acoust. Soc. Am., Vol. 120, No. 3, September 2006 de Jong et al.: Air entrapment in piezo-driven inkjet printheads
© Copyright 2012 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
White ink sedimentation
After Week End of 60Hr (2.5 days) and post weekend maintenance of purge 2sec * 3times @ 2bar in machine #40, was discovered a lot of missing nozzles in the middle of the beam. After additional full cycle maintenance, problem disappear.
© Copyright 2012 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
White phenomena solution – through RCD
10
Missing Nozzles in the middle of the beam requires twice the “Purge”
process to “wake up”
During circulation More fresh ink is available at the mid ink bushing for
sediments
Sedimentation rate of pigment at the middle of the beam is higher
Stagnation point of bushing creates more sediments in the
mid beam area
High ink waste – 66% at xx usage
Sedimentation rate of pigment at the middle of the beam during
circulation is higher
And/Or
And/Or
Change in flow direction separates the pigments from the carrier
during the flow
First DOE iteration point us to that
Root Cause
Well, Why the middle is dramatically different from
others? Lets work on circulation sequence.
Ok, This one can be easy to check, by removing
the insert from the middle
This one not easy to implement for proving, and can affect on
whole white system
© Copyright 2012 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Decap/Open time No First drops jetting due to changing of ink
properties
Ink polymer separation in nozzles
Under investigation
Proven false hypothesis. This is not a cause of the problem
Proven true hypothesis
NOT Under investigation
Last Update: 22/03/2012Updated by: Semion Gengrinovich
Locally in nozzles Ink properties changed to
viscoelasty
Cross talk pressure wave during the
printing
Temperature gradient between nozzles and
plenum
Cheek depth geometry differences
Temperature gradient between PH’s in the
beam
Ink Volume above the PH’s
Short decap / open time
Spontaneous curing of ink at nozzle level
Sedimentation of ink at nozzle level
Ambient temperature
Higher ink Evaporation at nozzles level
Stray lights
And/Or
Nozzle plate protruding
No circulation/mixing/vibrations during the
idle time
Degassing level of ink
Ambient Air flow above nozzle plate
And/Or
Initial Conditions After 10min with air flow
After 20min with air flow
After 40min with air flow
RCD:
60 min idle, “micro purge” 0.01bar, 10 sec, no dripping observed
© Copyright 2012 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Thermal issues
© Copyright 2012 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Solution to dissipate the heat
Temperature during the printing @30kHz with Heat Sink
37394143454749515355
1400 1450 1500 1550 1600 1650 1700 1750Time (sec)
Tem
pera
ture
(C)
Ink temperature inside the PH chamber Electronic part of PH
Condition with water cooler. The effect of water cooler is clearly observed (The temperature almost identical on the all area of PH – around 41.5C).Temperature at PHs ink chamber– 37C
•Max hot spot temp(Initial to max)=44-40.5 = 3.5 [°C]•Reservoir printing max Ink temp (Initial to max) = 38.5-40.5 = 2 [°C]
© Copyright 2012 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Thank you