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jay3
04-29-2017, 06:16 PM
I noticed on the C6500, mechanically the developer and toner both seem to feed to the same place (the rectangular hole on the top of the developer unit).

Does the machine stash away the developer somehow and mix it proportionally with the toner?

It's strange to me that a larger amount of toner would be consumed than developer when all the developer is actually filled and sitting in the developer unit first.

habik
04-29-2017, 06:50 PM
Developer unit is coming with developer (irone oxide filings)
Toner contains certain percentage of developer to "refresh" current stock/ level in developer unit.
There us a auger and paddle mechanism to mix toner&developer(toner carrier) to proportional ratio to create nice uniform creamy layer on developer magnetic roller which is then transfered on to drum. The developer is recycled for certain amount of rotations of the auger mechanism until it reaches the waste pipe and then it is drawn to waste box.


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blackcat4866
04-29-2017, 07:10 PM
OK, here goes:

Developer contains roughly 96% ferrite and 4% toner. First let's talk about the ferrite:

Ferrite is small particles of iron that are coated with a resin. When these ferrite particles are agitated and rub together they create the tribo-electric effect commonly know to most people as static electricity.

Toner is a fine ground plastic with pigment in it. When the developer is agitated, you have strong tribo-electric effect the toner particles cling statically to the outside of each ferrite particle. The proportion of toner to ferrite stays roughly the same until the developer starts to fail. We'll talk about that later.

So the developer is agitating, the toner is clinging, and the mag roller (magnetic roller) rotates to bring this mixture around to the front of an aluminum tube. There are stationary magnets inside the tube that make the ferrite particles stand up at the point when they are closest to the drum (aka developing brush, and mag brush height). So the ferrite particles are magnetically sticking to the mag roller close, with it's halo of statically charged toner particles away from the mag roller. Now a developer bias voltage is applied to make the toner particles break loose, and stick to the charged areas of the drum (or less charged if your thinking digital imaging, but I'll get to that later). Some of those toner particles stay clung to the drum and make up the latent developed image, and some are drawn back into the developing unit.

Now eventually enough toner will be depleted from this mixture that the toner sensor will identify low toner density and toner will be added from the hopper or bottle to maintain that 4% ratio.

Now some of the diversions/distractions:
When developer fails the resin coating wears off of the ferrite. Less tribo-electric effect is achieved, and the toner doesn't cling as well to the ferrite particles. Some of that toner will lay in the bottom of the developing unit, some will blow around decorating your machine. The toner density may increase above 4% or decrease below 4%, but in either case it's failed and needs replacing.

Many new models have self replenishing developer. They have a percentage of new developer mixed in with the toner in the cartridge. When the ferrite level increases above a certain level it dumps into the waste bottle. This vastly increases the life yield of the developer.

Differences between analog and digital:
Many of us were initially trained on analog equipment, so consequently we think of the voltages in analog terms, and the changes to digital as the opposite, for example:
Analog copiers use a direct light path from the optics to write the white areas of the drum to a lower charge. Digital copiers use a laser or LED array to write the black areas of the image to a lower charge.
Analog copiers attract positively charged toner to negatively charged areas of the drum (unexposed areas of text). Digital copiers attract negatively charged toner to less negatively charged areas of the drum (exposed areas of text).

Did I cover everything? =^..^=

habik
04-29-2017, 07:16 PM
Mono and dual component toner but that is not what this thread is about :D.
Nice broad explanation BlackCat! Think satisfactory level hit 100% .. for me at least.


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blackcat4866
04-29-2017, 07:40 PM
Ok, let's talk about monocomponent toner.

The previous description is based on the functionality of your bizhub 6501. Manufacturers like Canon, Kyocera, Kip, and Lexmark (probably others too) use or used monocomponent toner.

Here are the differences:
Instead of ferrite, monocomponent toner uses a similarly magnetic ... alright, I don't know what it is, but it's like ferrite. It's magnetic, it has the rosin coating. The difference is that it will melt and fuse. So during the development phase, both the toner and carrier are transferred to the drum, compose the latent image, and are fused to the paper.

Since the entire mixture is consumed at a constant rate the toner replenishing is much simpler. Many manufacturers use a piezoelectric sensor that just determines how much of whatever is in the developing unit. When it sings or buzzes there is not enough and toner is added. When it's quiet there is enough. Some manufacturers use an antenna system which is measuring how much of the developing bias voltage is being conducted to the antenna in the back of the developing unit. When the voltage level at the antenna is too low more toner is added.

Monocomponent toner has been either a curse or an advantage. Early monocomponent toner did not give very good fill (gray copies). No matter how much you tweaked the voltages, gray toner is still gray toner. Then in the mid 90's Canon came out with a much richer formulation of black toner. Now you could get a good quality image without having to deal with toner density, and developer yield issues. Remember, at the time a good developer yield was 20K to 30K copies. Today's machines can get 1M copy yield from a bag of developer, so it's less of an issue.

=^..^=

jay3
05-07-2017, 05:31 AM
Thorough answers! Very awesome of you guys.

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