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laser printer ambiguity 1
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Where the drum hasnt been touched by the laser light a lower negative charge is still there, so the particles are not attracted to this section of the photosensitive drum.Yeah, this part pretty much settles it, but it's so round-about that it makes me a little skeptical. If seems like there would be a doc somewhere that says "the laser hits the drum where you want the toner to stick" or "the toner is attracted to the drum where the laser made contact, or something fairly affirmative like that.
Is that the way you read it too?
I read it as "where the laser has hit the drum, that is where the toner is". I understand where you are coming from, as it's always pretty "sticky" wording. I found some very techy explanations, that really got me more confused than it was worth, but I think the wording from
was probably the best explanation I could find that wasn't too confusing....
was probably the best explanation I could find that wasn't too confusing....
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Another problem is that it seems that the positive and negative charges can be reversed depending on how the manufacturer chooses to build the machine. But most of the docs I've read specify the charge polarities, leading to contradiction between documents. I finally found one that just came out and said the positive and negative can be reversed. I also found one reference that claimed that the laser hits where you DON'T want the toner to stick, but I think that one is just flatly incorrect.
CiscoGuy33
Instructor
jmille34,
Here is a very straight forward explaination from How Stuff Works - the laser draws on the drum, changes the charge on the drum area, so the toner will stick there in that area -
From -
The Basics: Drum
Initially, the drum is given a total positive charge by the charge corona wire, a wire with an electrical current running through it. (Some printers use a charged roller instead of a corona wire, but the principle is the same.) As the drum revolves, the printer shines a tiny laser beam across the surface to discharge certain points. In this way, the laser "draws" the letters and images to be printed as a pattern of electrical charges -- an electrostatic image.
The system can also work with the charges reversed -- that is, a positive electrostatic image on a negative background.
The laser "writes" on a photoconductive revolving drum.
After the pattern is set, the printer coats the drum with positively charged toner -- a fine, black powder. Since it has a positive charge, the toner clings to the negative discharged areas of the drum, but not to the positively charged "background."
This is something like writing on a soda can with glue and then rolling it over some flour: The flour only sticks to the glue-coated part of the can, so you end up with a message written in powder.
With the powder pattern affixed, the drum rolls over a sheet of paper, which is moving along a belt below. Before the paper rolls under the drum, it is given a negative charge by the transfer corona wire (charged roller).
This charge is stronger than the negative charge of the electrostatic image, so the paper can pull the toner powder away. Since it is moving at the same speed as the drum, the paper picks up the image pattern exactly. To keep the paper from clinging to the drum, it is discharged by the detac corona wire immediately after picking up the toner.
Hope this helps!
E.A. Broda
CCNA, CCDA, CCAI, Network +
Here is a very straight forward explaination from How Stuff Works - the laser draws on the drum, changes the charge on the drum area, so the toner will stick there in that area -
From -
The Basics: Drum
Initially, the drum is given a total positive charge by the charge corona wire, a wire with an electrical current running through it. (Some printers use a charged roller instead of a corona wire, but the principle is the same.) As the drum revolves, the printer shines a tiny laser beam across the surface to discharge certain points. In this way, the laser "draws" the letters and images to be printed as a pattern of electrical charges -- an electrostatic image.
The system can also work with the charges reversed -- that is, a positive electrostatic image on a negative background.
The laser "writes" on a photoconductive revolving drum.
After the pattern is set, the printer coats the drum with positively charged toner -- a fine, black powder. Since it has a positive charge, the toner clings to the negative discharged areas of the drum, but not to the positively charged "background."
This is something like writing on a soda can with glue and then rolling it over some flour: The flour only sticks to the glue-coated part of the can, so you end up with a message written in powder.
With the powder pattern affixed, the drum rolls over a sheet of paper, which is moving along a belt below. Before the paper rolls under the drum, it is given a negative charge by the transfer corona wire (charged roller).
This charge is stronger than the negative charge of the electrostatic image, so the paper can pull the toner powder away. Since it is moving at the same speed as the drum, the paper picks up the image pattern exactly. To keep the paper from clinging to the drum, it is discharged by the detac corona wire immediately after picking up the toner.
Hope this helps!
E.A. Broda
CCNA, CCDA, CCAI, Network +
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