A the photocopy machineThe cylindrical drum turns to

A photocopy machine, also named photocopier, is an apparatus that duplicates documents and on paper. Photocopiers mostly use a copying process called xerography. This image-forming process was invented by Chester F. Carlson in 1938 and started to be developed and commercialised by the company Xerox. In order to function, photocopy machines use xerography, also called electrophotography, which is a printing technique that works on the basis of electrostatic charges. The key pieces of photocopiers serve different functions and all play a major role in the process of xerography. The photoreceptor drum is a metal cylinder entirely covered by a photoconductive silicon and is the most important piece of the system. The corona wires are thin cables that let through electrostatic energy in order to charge the drum. Lamp and lenses are essential to the photocopying process. The lamp moves inside of the photocopy machineThe cylindrical drum turns to the speed of the paper performance. After this, the document to copy is positioned on a screen and scanned by a strong lamp which illuminates and reflects the blanc zones of the original copy on the drum. The black areas of the documents are not reflecting light so that area on the drum stays charged negatively. “The white part reflects most light and look bright. However, the black letters absorb nearly all the light striking them.” (Pople, 2007) This means the image is projected on a drum through a lens and mirrors. For the image to become visible, ink under the form of a powder or a liquid, also called toner, is dropped on the heater cylinder, which is negatively charged. The paper is pressed against the drum and the toner transferred on the electrically-charged printing medium that is heated and pressed to set the toner. The image is set on the paper by the exposition to heat. This process can be summarised in 6 key points : charging, exposing, developing, transferring and fusing. Even if very different prototypes of photocopy machines exist, they usually are a very durable apparatus in consideration of the quantity of copies they can furnish. The expected durability of a photocopier is around 6 years, going from 1000 copies per month maximum for low-end machines and up to 50000 copies for high-end machines. The printing is also very fast, and is estimated to be in average 40 copies per minute. The environmental aspect, however, can be argued. There is evidence that shows that photocopiers don’t only cause an economic problem but can also lead to health complications due to a high exposure. According to the International Agency for Research on Cancer, the apparatus releases ozone in air, which can, to high exposure, irritate the respiratory system and eyes if the filter is not changed regularly. The toner used in the dry-copying process, under the form of powder if gotten into air, can be harmful to the respiratory system again, coughing or sneezing and cancerogenic composants have been found in the same toners. Visible and ultraviolet light are emitted in the copying process of photocopy machines, which can cause eye strain if exposure of the sight for a certain time to the ultraviolet light rays. To conclude, photocopiers’ dry-copying process consists in 6 key points : charging, exposing, developing, transferring and fusing.

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