Importance of using a good PCR and maintaining PCR well for good print quality

January 2020 - Week 3

A- Is the outer carbon impregnated polyurethane and rubber roller that makes up the main part of the PCR. The outer coating, the hardness/softness and texture of the roller, then the electrical resistance to be as close to 6Ohms possible, are all factors that will affect the output contact voltage that the PCR delivers to the OPC Drum. If the PCR roller is too hard it will damage the OPC  Drum, and if too soft the contact area becomes too large and roller gets contaminated. As the outer of the PCR makes contact with the OPC Drum, it will always get residual toner and other compounds from the toner that will build up on the outer PCR, so keeping the outside of the PCR clean is critical. The (A) rubber roller fo the PCR also forms a shield between the metal roller that carries the main electrical charge and the OPC Drum, so if the outer rubber layer of the PCR becomes damaged at any time there is a good chance that there will be an electric arc or spark from the metal roller to the OPC drum, damaging the drum, and if the drum makes use of an Amorphous Silicon Drum then this can be very costly when it could have been prevented. So choosing a good PCR is always a wise choice.

B- Is the metal inner shaft or the PCR, and it is not only the inner shaft, but it also carries the main electrical charge from machine, that then is carried to the drum through the outer rubber roller. This electrical charge is generally delivered to the shaft via a small copper strip, and it is important that the contact area of the copper strip is clean where it contacts the metal inner shaft, so the maximum voltage is always transferred to the PCR, as if the copper strip contact point is dirty, or if it is damaged, it will not be able to provide the correct voltage to the PCR, resulting in bad copies. One can also apply a conductive grease to the contact point of the copper strip where it contacts the PCR. One must also make sure the PCR shaft is clean in the bushes it runs in so it rotates freely, otherwise one gets an irregular rotation, and jitter marks on the images.

C-  The contact between the PCR and the drum needs to be equal across the PCR and drum, and also the PCR must run straight along the length of the drum, otherwise one will get uneven copies due to irregular application of electrical charge from the PCR to the drum.

D-                       The copper metal strip the carries the electrical charge to the PCR is often neglected and bent or broken during installation of the PCR. The constant pressure, and clean contact points on this strip are critical to good crisp copies at all times.

E-  Applying of equal and constant pressure of the PCR to the drum is also crucial to having the PCR not only function properly, but if too little pressure, the PCR will not deliver enough electrical charge, and if too much pressure there is a good chance the PCR and/or the drum become damaged. Preferably do not change the pressure on the springs that apply this pressure.

F-   Drum, be it an OPC Drum or an Amorphous Silicon Drum, the condition of the drum is critical to making good prints and should be clean at all times, and outer coating should not be damaged in anyway.

G-                      Application of a Bias voltage and/or Earthing/Grounding of the drum is also critical to maintaining good print quality. Many drums have a copper strip inside the drum that makes contact with the drum shaft, and it is also important that the contact strip stays clean and in good condition to allow it to let the drum maintain an electrical voltage and then release the voltage in the areas that the laser bean strikes the drum, and this voltage then needs to be released to through the Ground/Earth of the drum. If the drum is not earthed one will get irregular print quality.

Colour copiers and printers have different ways of regulating the toner density and ratio in the developer. Some use an ATR, Automatic Toner Replenishment sensor, to measure the toner in the carrier/developer

On other colour copiers/laser printers, there is a colour patch processed on the drum and then onto the transfer belt and this patch is then read by the machine to determine the correct ratio of toner in the developer in the imaging unit, and with anything wrong in the PCR and charge area of the copier/printer, a machine may be over toning or under toning and one will look for the problem been caused by the toner or the imaging unit, when it can be caused by a simple dirty contact, dirty PCR, or any of the above.