WILLETT 430, Service Manual

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Technical Description: Ink System
Issue 2
83
Part No. 306-0430-102
Owing to the type of filter media used in the main system filter, which provides a large surface area to catch
particulates, it also offers a long service life.
The filter has two filtration ratings, which are selected dependant upon the type of ink used for the printing
application.
Pigmented inks utilise the lower filtration rating, typically 20 microns due to the pigment used to colour the ink
having a relatively large particulate size.
Machines using non-pigmented inks generally have a smaller filtration rating, typically 5 microns.
The filter housing also provides an important means of damping the small pressure oscillations caused by the
gear pump during normal operation.
Pre Pump Filter (located inside the filter compartment)
The Pre pump filter filters all the ink prior to entering the main system pump.
The filter medium is stainless steel with a filtration rating of 30 microns.
Pre Head Filter (located below the FMS printhead connection manifold)
The pre head filter is a secondary filter to the main system filter.
When the main system filter is exchanged for a new item during routine servicing, contaminants may
accidentally be introduced into the system pipe work. The pre head filter is fitted to trap these particulates.
The filter medium is stainless steel with a filtration rating of 8 microns.
Nozzle Filter (located behind the nozzle in the printhead)
The nozzle filter which is fitted to the ‘clean’ nozzle assembly during manufacture is a ‘last chance’ filter,
designed to prevent ingress of particulates into the nozzle whilst being assembled at the factory or fitted as a
spare part during servicing.
The filter medium is stainless steel with a filtration rating of 18 microns.
Flush Filter (located near flush pump)
The flush filter is designed to remove any particulates from the flushing solvent prior to being delivered to the
nozzle during ‘clean jet start’ and ‘stop’ routines.
The filter is fitted in the pipeline after the flush pump rather than in-line before the flush pump eliminating the
possibility of introducing contaminants into the flush line in the event of the flush pump being exchanged for a
new item.
The filter medium is stainless steel with a filtration rating of 8 microns.
VMS Filter (located inside FMS top box)
The VMS filter is a ‘last chance’ filter designed to catch contaminants, which may be introduced during the
replacement of the main system filter and thereby obstruct the inlet restrictor orifice (R1) of the VMS system.
The filter medium is stainless steel with a filtration rating of 75 microns.