What different kinds of PCR do we get.

Week 2 January 2020

All digital copiers are designed differently, they have different OPC drums, different toners, different laser units and print at different speeds, so the charging of the OPC drum in each machine is different and therefore different brands of machine use different types of PCR (Primary Charge Roller). Also then comes down to the cost of the units, and low cost toner cartridges that have the OPC drum and PCR in the toner cartridge such as in many monochrome machines, the PCR will be of the lowest cost, so simplest and easiest manufacturing methods.

One finds 3 basic types of PCR,

1. Dense Carbon Impregnated Rubber - most commonly used

As you can see from the picture, this is a hard rubber, that has a certain percentage of carbon in it, allowing it to have certain conductive properties, and most commonly used in smaller laser printer engines, or laser printer cartridges. It is the easiest and cheapest version of PCR to manufacture. This PCR runs on the surface of the OPC drum, at slow speed, and low pressure.

2.  Solid PCR with Nylon Bushes at each end of the PCR

The PCR with Nylon Bushes at each end is difficult to produce for aftermarket manufacturers to the same level or performance of the OEM due to the extremely accurate tolerances in production. The Nylon Bushes run on the edge of the OPC drum where there is no OPC coating, and are generally about 0.1mm larger than the charge portion of the roller, and imagine, just 0.1mm off the surface of the OPC drum, so manufacture needs to be extremely accurate. These PCRs also have a cleaning system to keep the roller surface from becoming contaminated with toner or developer. Most commonly used in Ricoh machines.

3. Foam Core with Solid Rubber Sleeve PCR 

As with the Nylon Bush PCR, this PCR requires a few steps in production to manufacture these PCRs. One needs to mold the foam core first, and this core needs to be a certain sponge property to it, and is able to compress a bit. Then only once the core is cured, can one mold the outer solid rubber sleeve. This PCR runs on the OPC Drum, and being softer than the solid rubber core PCR, this PCR is used more in the larger Canon copiers.

So important factors in designing and manufacturing PCRs needs to be the accuracy of the machining of the  PCR shaft. Then the resistance or conductivity of the rubber needs to be good and consistent, and maintain the same conductivity through the life of the PCR. The rubber also needs to be of a high quality in larger machines as a PCR is subjected to high voltages causing a deterioration in the rubber, and once the PCR rubber wears down or cracks, arcing of the high charge occurs between the PCR shaft and the OPC drum, severely damaging the OPC drum. Then the accuracy and hardness of the rubber portion of the PCR is critical, as they run either on the OPC drum or 0.1mm off the OPC drum, so if the PCR does not run smoothly or even along the surface of the OPC drum, it will cause irregular or bad printing.

Next week - How and why to maintain the PCR well, and the benefits.