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Importance of ink and solvent flush filtration in

CIJ printer systems

CIJ ink & solvent filters

Why and where?

• A major feature of a CIJ ink system is ink filtering.

• This is required because it is not possible to produce even dye based inks with zero suspended solids

• It is not possible to prevent all ink system internal wear over time either.

• Ink filtration should comprise a balance of depth and absolute filters split between ink manufacture and printer.

• Filtration of the fluid in the printer is best arranged so that: – A filter is incorporated with a disposable filter capsule on the supply side

– one on the printhead solvent flush supply line.

– An additional small last chance filter close to the printhead may also be required.

– Not forgetting a coarse mesh type filter on the ink return side.

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CIJ ink & solvent filters General requirement

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• Minimum main filter absolute size of approximately 1/10 the size of the nozzle diameter for dye based inks (for most CIJ the main filter pore size is around 5µm absolute. Larger for pigment based inks)

• Filter manufacturing method and welding construction must ensure strength, integrity and chemical compatibility. The filter must pass the burst pressure test

• Filter inlet and outlet connections are best being moulded as integral parts of the filter housing. This minimises the number of assembly parts, eliminates 2 extra interconnections and seal interfaces. Thus reducing risk of leaks.

• Moulding quality of a mesh filter is important as the mesh overmoulding must be complete and cover all around the edges of the mesh without unnecessarily reducing the filter effective area.

• For most filters manufacture methods, filter flushing after assembly and before packing to remove all manufacture and assembly particles (particularly on the ‘clean side’ of the filter) would prevent nozzle blocking, jet flicking and bad jet start/stop. These faults would otherwise occur, particularly when a new filter is installed.

• It is important that the flushing duration of filters before assembly into the machine be long enough to effectively flush filters of loose, shedding debris. Tests need to be undertaken to determine the flushing time necessary to clean the filters of shedding debris that would block nozzles and lead to random jet flicking and EHT trips.

Filtration issues

Possible root causes & solutions

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Issue Possible root cause Action to solve

Jet flicking , unstable and/or jet moving out of the gutter when new filter installed or new machine run for first time

Filter shedding or dirt introduced during filter change

Flush filters thoroughly for a minimum time before installing in the machine

Jet flicking , unstable and/or jet moving out of the gutter when printer running ok for days and there has not been a new filter installed

Ink jet gel formation, starting to block filter and filter rating not low enough to prevent ink gel passing through. Debris from ink wetted parts wear

Inspect ink system for gel in ink (white, silicon type matter). If found investigate quality of ink

Frequent nozzle blockages

Filter lost its integrity i.e filter element /cartridge fixing to body undone or split

Check quality of filter manufacturing and assembly. Change filter

Short filter life Ink gel blocking filter. Unstable ink forming agglomeration. Excess weld flow of filter housing material blocking significant part of the effective filter area

Check quality of filter manufacturing and assembly. Change filter

Unstable phasing, ink build up on gutter and EHT plates

Filter rating/size too high..start of ink gel formation… incorrect filter manufacture using mould release – debris from ink system wetted parts wear

Check quality of filter manufacturing and assembly. Change filter

Continuous Ink Jet ( CIJ) ink system filtration

Summary

At first glance, incorporating ink and solvent filters in a CIJ machine looks quite straight forward and, in general, it is; 4 filters in total in the ink system

However, inadequate, substandard filters and/or filtration scheme of the ink or solvent flush supplied to the printhead, could contribute to several printer faults leading to lengthy downtime and loss of productivity.

The filter design, manufacture, assembly and quality control (QC) are critical to effective filtration of ink and solvent in an CIJ machine. Effective filtration means extended uptime, increased productivity and reduced unscheduled maintenance

Sellenis engineers have the expertise and the know how in this field. Sellenis designs, manufactures, assembles and tests all its filters. This ensures that Sellenis filters incorporate the best design, the best materials and the highest quality of manufacture, assembly and Quality Control to ensure consistent effective ink and solvent filtration contributing to printer superior uptime.

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