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New technologies of the inkjet textile printing system

New technologies of the inkjet textile printing system




Mitsuhashi, Taku* Takeuchi, Hiroshi* Fujii, Yozo*


Table 1 Characteristics of Nassenger-V


Ink Disperse dye ink, Reactive dye ink

Mode Resolution

Disperse dye


Reactive dye


Printing speed

High speed 540dpi x 360dpi 60 m2/h 48 m2/h

Normal 540dpi x 540dpi 40 m2/h 32 m2/h

High quality 540dpi x 720dpi 30 m2/h 24 m2/h

Maximum density 900dpi x 540dpi 27 m2/h 21 m2/h

Maximum printing width 1650 mm

Fabric size width: 330 mm to 1650 mm, thickness: 15 mm

Operating conditions temperature: 15°C to 30°C, humidity: 40% to 70%

Dimensions, weight W4200 mm x D1600 mm x H1545 mm, 440kg




A new inkjet textile printing system, Nassenger-V,

was developed. Reliability, productivity, and print

quality were highly improved in order to meet the

requirements as an actual production machine. A

newly designed inkjet print head, an ink drop

detection system, and a fabric belt feed system

developed specifically for this printer are discussed.


1. Introduction

The inkjet textile printing technology has been

rapidly getting accepted in the past few years.

The history of applying inkjet to textile printing is

rather long, as an alternative convenient method to

conventional printing technology. It was expected to

be suitable for quick delivery, short-run production

and photographic print with multi-level tone

reproduction, which is difficult to achieve with

existing analog technology. Some advanced users

have already used inkjet for years to manufacture a

wide variety of products, mainly for short-run

production or sample-making. Recently, however,

improved reliability of inkjet printers, along with the

introduction of digital technology in design process

has made this technology a realistic option to be

utilized for mass-production. Market expectation for

more productive inkjet textile printer has also

contributed to this new trend.


With the aim of meeting performance requirements

as a production machine, we have developed the


Fig. 1 Nassenger-V


inkjet textile printing system, Nassenger-V, reliability,

productivity and quality of which are remarkably

improved (Fig. 1).

The basic performance parameters of Nassenger-V

are summarized in Table 1. In order to achieve

these specifications, technologies such as, (1) a

newly designed print head customized for this

printer, (2) a fabric belt feed system and (3) an ink

drop detection system to detect miss-firing of

droplet have been introduced. These newly applied

technologies are explained in the following sections.


2. Newly developed inkjet head

Image quality requirements for inkjet textile printing

systems include graininess, sharpness, tone

reproduction, wide color gamut and high solid

density. We have reported that a resolution of 540

dpi is sufficient for obtaining practically acceptable


Konica Minolta Technology Center Inc.

Inkjet Technology R&D Center



image qualities in inkjet textile printing systems.*1

In Nassenger-V, the standard mode was decided to

be 540 dpi accordingly. In order for this mode to

achieve printing speed of 40m2/h, two 256 nozzles

heads were combined for each of 8 different color

inks, totaling 16 heads. Table 2 shows a summary

of characteristics of the print head used for this



Table 2. Characteristics of the inkjet


print head


Technology shear mode piezo,

drop on-demand

Number of nozzles 256 (128×2 lines)

Nozzle density 180 dpi (90 dpi×2lines)



18.2 kHz (disperse dye ink)

14.9 kHz (reactive dye ink)

Drop weight 18 ng (disperse dye ink)

20 ng (reactive dye ink)

Dimensions W59.5 x D18.3 x H67mm

Weight 50g


Though the ejection principle of this head is the

same shear mode piezo drop on-demand as the

previous model of Nassenger II, newly developed

high-precision process technology and actuator

lamination technology have made it possible to

provide180 dpi, 256 nozzle print head comprising

two 90 dpi, 128 nozzle actuators.

Ejection frequency was determined from print

speed, print resolution, number of nozzles, and

structurally caused non-printing time.

The volume of ejected ink droplet was

experimentally determined to optimize image quality

and performance. More specifically, the droplet

volume has to be determined according to the print

resolution. If the volume is larger than the optimum

amount, not only are graininess and sharpness

deteriorated but also is image quality degraded due

to blur. On the other hand, if it is smaller, it becomes

difficult to obtain required color gamut and/or solid

density. In the worse case, white lines appear

where sufficient ink amount was not delivered,

resulting in considerable deterioration of image

quality. In 540 dpi print mode, the optimum ink

droplet volume of disperse ink for polyester was 18

ng, while that of reactive ink for cotton and silk was

20 ng.

The structure of a head that meets above

performance specifications was designed by highly

advanced computer simulation. Basic head

performance can be calculated from dimensions of

channel, actuator and nozzle shape, physical

characteristics of piezo element, structure material,

adhesive chemicals, and driving waveform to drive

the actuator. All these parameters and ink

characteristics determine the total inkjet head

performance*2. The head dimension parameters

such as channel length and nozzle shape were

optimized to meet required printer specifications,


taking into account easiness of exhausting air

bubbles in the channel to ensure stable ink ejection.

The driving waveform was also improved to achieve

stable ejection at a higher operating frequency.

The head housing was re-designed to cope with

increased heat generation associated with the

increased number of nozzles and raised frequency

so that quick heat release is assured. The head

mount mechanism was also improved to ensure

easy head replacement by the user, which leads to

easy maintenance. Because of the compact design

of the print head, the carriage size where heads are

mounted was greatly reduced from the previous

printer, despite the fact that the total number of

nozzles used is four times that of the previous

printer. Fig. 2 shows appearance of the newly

developed inkjet print head.


Fig. 2 Inkjet print head



3. Fabric belt feed system

Feed length of the previous printer, which adopted

a feed roller system, varied by fabrics according to

their thickness and friction behavior. It was

necessary therefore to adjust the feed length for

each fabric to be used, costing laborious work.

This feed system also had difficulty in handling thin

or elastic fabric accurately due to stretch or bent of

the fabric. Moreover, in the case of thin fabric

printing, ink having passed through the fabric on to

the feed roll caused image stain of the successive

print area.

In order to cope with these problems, a fabric belt

feed system with electrostatic adsorption

mechanism was introduced (Fig. 3). This system

enabled feeding fabrics at a predetermined length

regardless of the fabric characteristics such as

thickness, since the feed length is determined only

by combination of drive roller and feed belt.

In order to achieve higher image quality, print

resolution of feed direction should be raised from

300 dpi to 540 or 720 dpi. Feed length accuracy of

the previous printer, comprising worm gears and a

timing belt, was found to be insufficient in

preventing overlaps or jumps of each main-scan

print swath.

To improve this accuracy, a new driving system



Driving roller Belt Weight roller

Driven roller


chuck system


Driving roller Belt Weight roller

Driven roller


chuck system


Fig.3 Schematic diagram of the belt feed


comprising a DC servomotor and a harmonic drive

was introduced. PID control of it was also optimized.

Results are shown in Fig. 4. Feed length for each

scan is plotted on Y axis. The graph shows that

fluctuation of feed length was reduced to

approximately 25% of that of previous system.


Fig.4 Fluctuation of belt motion

1 6 11 16 21 26 31 36 41 46 51 56 61

Number of carrige scan

Amount of feed

Nassenger-V(belt feed) Nassenger-II (roller feed)


Cleaning roller

Squeeze roller

Permeate print


Weight roller

Remaining ink

Fig.5 Schematic diagram of the belt cleaning


With this belt feed system, when the fabric being

printed is thin enough for the ink to get through to

the backside and to reach the surface of the belt, or

when the user intentionally deliver too much ink

onto the fabric to let the ink reach the back side, the

belt becomes wet with this ink. Therefore the belt

should be cleaned to prevent it from staining

successive print area at the next belt turn. A belt

cleaning roller made of porous medium was

therefore installed to touch the belt surface in the

lower part of the machine to remove residual inks

on the belt surface (Fig. 5).

Fig. 6 shows a relationship of the cleaning roller

pressure to the belt and cleaning performance.


When the pressure is high enough, the residual ink

is completely removed from the feed belt.


Fig.6 Relation between pressure of the

cleaning roller and remaining ink

amount on belt








Amount of contact of belt and belt cleaning roller

Remaining ink amount on conveyerbelt(mg/. )

To feed the fabric accurately with this belt system, it

is necessary to assure the fabric adhered firmly to

the belt. Without enough adhesive force, feed

length of the fabric will be affected by its self weight

and friction force. Hence ensuring stable feed

performance regardless of the kind of fabrics

becomes difficult. The electrostatic adhesion

system was adopted to fix the fabric onto the belt.

The system is illustrated in Fig. 7. High DC voltage

is applied to electrodes embedded in an insulation

layer, alternately charged positive and negative,

thus generating positive and negative charge

between the belt and fabric. Table 3 shows the

adhesion force of typical fabrics to the belt.

Adhesion force here refers to tensile force

necessary to start moving a 100 mm x 100 mm

piece of fabric adhered on the feed belt. Fig. 8

shows fluctuation of feed length for polyester. The

use of the electrostatic adhesion system clearly

increased the adhesive force between them.


Fig.7 Cross section of adhesion system+-+-

Adsorption layer

Insulation layer




Table.3 Adhesion force for fabric


Type of fabric Adhesion





Polyester 775 39

Cotton 470 29

Polyester knit 794 29

Satin 775 29



Table.3 Adhesion force for fabric


Type of fabric Adhesion





Polyester 775 39

Cotton 470 29

Polyester knit 794 29

Satin 775 29


(x 10-3N)


Fig.8 Deviation of fabric motion










1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31Fabric feed(m)

Deviation of feeding amount(%)

4. Detection of ink drops

The number of nozzles in one print head has been

gradually increased in line with market demands for

higher image quality at higher print speed, resulting

in development of printers having more than 4,000

nozzles with 16 colors. Ideally all these nozzles

should be kept in good condition, but in reality,

some of them may fail in ejecting ink. If printing is

continued with these faulty nozzles, image quality

deteriorates considerably with bandings. If ink drops

can be detected, it becomes possible to clean the

nozzles only when miss-firing occurred, instead of

regularly cleaning all the nozzles even when they

function properly. This leads to reduced ink

consumption, shorter print loss time and remarkably

improved reliability of the system by substituting

faulty nozzles with other good nozzles.

Fig. 9 illustrates a schematic diagram of the layout

for an ink droplet detector, inkjet heads and a

spittoon. A light detector and a detection circuit

are placed in a shielded case, placed opposite to a

light source. Fig. 10 shows the mechanism of this

system. A row of nozzles are arranged in parallel to

an optical path consisting of the light source and the

detector. Ink drops are ejected one by one from a

nozzle at one end to the nozzle at the other end of

the optical path. Shadow of ink drops thus ejected

is checked by the light detector to identify the flying

of the ink drops for every nozzle. Nozzles which do

not eject ink drops are judged to be faulty.


Fig.9 Schematic diagram of ink drop detection system


source Light


light beam











Ink drop



Light source


Light detector



Signal corresponding to


Signal corresponding


normal nozzle.


to clogged nozzle.


Light is not blocked.


Light is blocked by ink drop


Fig.10 Mechanism of drop detection system


5. Conclusions

In the development of Nassenger-V, intensive

improvement in the printer, including the newly

designed head, belt feed system and ink drop

detection system, has successfully contributed to

greatly enhanced productivity, along with user

friendly operation by sophisticated software and

offering of post processing options. Nassenger-V is

expected to be used as a very efficient inkjet textile

printing system.


• References

1) MITSUHASHI, Taku, and KATO, Takayuki:


Journal of Society of Photography Science and


Technology of Japan, 41, 67 (2002).


2) TAKEUCHI, Yoshio: Konica Technical Report, 15,

31 (2020).