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Reverse Purging Canon or Epson Print Heads - TSG02 | Back to Notes Index |

Theory

This process is recommended for removing semi-solid obstructions from inside Canon print heads by reversing the flow of fluid in the print head.

Overview

Like any print head used in most inkjet printers, Canon print heads can suffer reduced or negated ink flow for many reasons. The most common form of obstruction is either solidified dye or precipitated pigment which obstructions the ink channels in the head or the firing area of the nozzles. This can be a result of improperly filling of cartridges, re-use of cartridges which are beyond recommended use life, the use of improper or aged inks, use inks with bio-contaminants in them, or storing printer for long periods of disuse. Once the external cause has been fixed, a user is still left with the process of restoring the print head to usable condition.

There are several ways to attempt to un-clog a print head. The most common method is to soak the firing plate in a solution of distilled water or better a dedicated print head cleaning solution. Cleaning cartridges can also be used, in place of regular cartridges, For more extreme situations, another method is to attempt to force fluid through the print head using a syringe.

While soaking works well for distal clogs located in the firing chamber, it has absolutely no effect on proximal blockages which may occur closer to the print head intake filters, nor can it remove blockages on the filter.

Cleaning cartridges depend on the ability of each nozzle to fire liquid. A solid clog near a firing thermal resistor prevents the cleaning cartridge from working effectively. Cleaning cartridges work best with partial blockages, where the fluid can pass around the obstruction material and work from both sides.

Pressure purging, forcing a cleaning through the nozzles in the normal flow direction, suffers from the same limitation as Cleaning Cartridges with the additional problem that the obstruction may be forced deeper into the pathways and that the obstruction may be too large to pass through the nozzles.

When dealing with a clogged Canon print head in which standard soaking seems to have no effect, it may be better to try to remove the obstruction by pulling it back towards the way it came in the first place. Closer to the filter, the pathways are larger and can aid cleaning fluids in more effective removal of a dye, pigment, or bio-contaminant based clog.

The Reverse Purge Process is a meld of both soaking and standard forced purge, the primary difference being that instead of forcing fluids from the filter through the print head pathways and out the nozzles, we instead using a soaking solution and syringe to draw fluid from the nozzles through the print head pathways and out of the filter into a syringe. This has the benefit of forcing obstructing particles backwards into large spaces where the cleaning fluid can break the particles down or where foreign matter can pass back through the filter (where it most likely passed through in the first place).

This process can be used to restore any Canon or Epson print head that has not had its circuitry permanently damaged. Epson print heads should only be cleaned with this method if you can safely remove the head from the printer.

Performing the Reverse Purge Process
This process may be used with any Canon removable print head, including BC-21e and BCI-24 print heads.
You can also use this with Epson print heads if you can remove them from the printer.
Items needed:
bulletYour Print Head
bullet5 cc Luer Lock Syringe with the tip modified as shown figure 1. Use a 3/16" drill bit to drill out the center tip of the syringe.
bulletSoaking station - such as one shown in figure 2.
bulletUltra-FLO™ Purge & Clean Solution for Dye based Ink heads or Chromium™ Purge & Clean for Pigment Color Ink Heads
bulletSeveral lint free paper towels or cloths
bulletCup to collect waste solution

Initial Soaking

  1. Set-Up the soaking station similar to figure 2. Fill the dish with between 2 millimeters and 3 millimeters of cleaning fluid.
  2. Place the print head on the station a let sit for at least 30 minutes to allow the solution to work on any soluble clogs in the print head firing nozzle area.
Figure 1
Figure 2

Reverse Purge

  1. Take you syringe and, holding the barrel with one hand as shown in figure 3, press the modified tip over the filter of the color you wish to purge.
  2. Holding the barrel firmly, use your free hand to lift the syringe plunger up to the 3/4 cc mark and hold for about 30 seconds or until the syringe fills with ink.
  3. Remove the syringe and dispose of the waste fluid. Repeat steps 1 & 2 until clear fluid is being drawn into the syringe. Refill the soaking dish as needed.
  4. Repeat this process for every color you wish to purge.
  5. Once you have completed this procedure, inspect the cartridge and pat dry gently with a lint free towel to remove any excess moisture from the outside of the print head. We recommend that the head sit on a dry paper towel for about 30 minutes to allow it to thoroughly drain any hidden fluids and to air dry.
  6. Re-Install the print head. We recommend that a KNOWN fresh set of cartridges or refills be used to perform cleaning and test prints.
  7. Use alternating deep cleanings and test prints (space the deep cleanings at least 1 minute apart to prevent overheating the print head), to check the nozzle patterns.
  8. Run a print head re-alignment and then one last nozzle check.
Figure 3
Figure 4

 
 

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