Jan

How Does a Copy Machine Work?

Sarah

copier drum, copy machine, Copy Machines, science

Office workers use photocopiers every day, but not many of us understand how they actually work. Essentially, copiers function through the use of light, static electricity, and the attraction of oppositely charged particles.

The process begins when a positive charge is applied to the copier drum, an internal metal roller (pictured above).

Just like a balloon that’s been rubbed on the carpet and charged with static electricity, a charged copier drum will attract nearby objects – except instead of hair and paper, a drum attracts toner particles.

Of course, if the drum were uniformly charged, it would attract toner all across its surface and you’d wind up with a completely black piece of paper. Not ideal.

Instead, your copier drum is selectively charged, so that only the black areas of the paper receive a charge.

This selectivity is achieved with light – that’s where the “photo” part of “photocopier” comes in. Here’s how it works:

The toner begins with a uniform positive charge.
Photons of light hit the drum only through the white areas of the original piece of paper – the dark spots block the light.
Electrons on the drum are attracted to the photons, thus neutralizing the positive charge on certain areas of the drum.
The toner is negatively charged, so it only sticks to the non-neutralized, positively charged regions.

Once the toner is on the drum, it has to get on the new sheet of paper. To accomplish this, the copier gives that paper a charge, empowering it to pull the toner particles from the drum.

Finally, heat is applied to seal the paper to the toner, which is heat sensitive. And presto chango – you’ve got your copy in hand!