Updated 25/04/2022
Do you wonder how laser printers work? Far from it being some kind of magical spell, there are complicated processes involving lasers, mirrors, carbon, static and heat. Read on to find out how laser printers work and what they do.
How does a laser printer work?
- The printers laser beams your print onto a metal drum.
- The drum uses static electricity to attract powdered toner to the drums cylinder.
- The drum rolls the toner onto the paper in the form of your print.
- The toner is melted & pressed onto the paper by heat from a fuser as it passes through its rollers.
- Your print comes out of the printer.
Find the full technical explanation here.
What does a laser printer do?
There are many different types of printer available on the market today, and each uses various technologies to achieve a similar result of the printed page. The laser printer was the first to be invented and was done so in 1969 by Gary Starkweather while working in the Xerox product development team. His idea was to use lasers to imprint an image onto a copier drum which would then be transferred onto paper. Hence, the name ‘Laser printer’.
Do laser printers need ink?
No, laser printers use coloured powder called toner which is very different from the liquid ink used in inkjet printers.
Are laser printers better than inkjet printers?
Why choose a laser printer over any other type of printer like an inkjet? Laser printers are very efficient and cost-effective to use when you need to print in large quantities over short periods. The toner cartridges hold enough to print thousands, sometimes tens of thousands of pages, which is beyond the capabilities of most inkjet printers. This also makes them more cost-effective than inkjet printers.
However, as inkjet technology is advancing, there are now many business inkjet machines that are exceptions to the rule.
How Laser Printers Work – Full Technical Explanation
For those who love a good technical explanation including all the ins and outs, and science behind how a laser printer works, read on. There are many moving parts and components inside a laser printer that work together to produce your final document or image, each have an important part to play. The key parts of the printer include, toner cartridges, image drum (also known as drum unit or photo-conductor), transfer roller or belt, fuser unit, laser, and mirrors.
Step-by-step
- The moment you press print on your computer, tablet or mobile device, the information is sent to the printer memory, where the data is stored temporarily.
- The printer begins to warm up. This is the point where you usually need to wait, and it’s because the corona wire is heating up and getting ready to pass its positive static charge to the drum.
- As the drum (coated metal cylinder) begins to roll, it received a positive charge across its whole surface. Some printers contain four drums, one for each colour – Cyan, Magenta, Yellow & Black.
- The laser activates, and beams against a series of mirrors to reflect across the surface of the drum(s) imprinting the shape of your print using an opposite negative electrical charge.
- The toner cartridge and hopper sat next to the drum(s) slowly releases positively charged carbon toner particles on to the drum as it turns. The toner is attracted to any areas of negative charge leaving positively charged areas of the drum untouched.
- The transfer belt rolls the paper through the printer giving it a positive charge. As it passes the drum, the negatively charged toner is attracted to the page in the shape of your print.
- The toner is then melted to the paper by hot rollers called the fuser unit, and voila, your page is printed.
Here’s a fantastic video created by Static Control showing the whole process to help explain things a little better:
Printer Components Explained
Toner Cartridge
A toner cartridge contains coloured or carbon / iron oxide powder (toner) that is positively charged, and then melted onto the paper. Toner Cartridges are a consumable item that needs to be replaced in a laser printer once the cartridge is empty and is available in 4 different colours black, cyan, magenta and yellow (CMYK).
Drum unit
A drum unit is a metal cylinder that has a special coating (green colour) That can receive a static positive and negative electrical charge from the laser within a laser printer. The drum can be seen in the printer as a green cylinder and can sometimes be built into the toner cartridge rather than a standalone unit.
The drum receives its initial static charge from the corona wire which is heated during the printer warm up process.
Laser
The laser part of the printer transmits light from the diode across a series of mirrors. They reflect the laser onto the drum unit to imprint the shape of the intended print.
Transfer belt
The transfer belt moves the paper through your printer and passes it across the drum so that the toner can be transferred. Some smaller printers do not have a transfer belt but instead have rollers that act in the same way as a belt.
Fuser unit
The fuser unit is a heated roller that melts the toner particles onto the page as it passes through. This seals the toner to the page so it’s no longer in powder form and makes sure that the toner doesn’t smudge of fall off the paper when it comes out of the printer.
About Stuart DeavallI have been working in the printing industry with TonerGiant for over 16 years, and I'm the resident technical printer expert, helping people fix their printer problems for over 14 years. I have taken part in many training courses with HP, Samsung, Brother, Canon and Xerox to further my knowledge, and I'm also the Digital Marketing Manager at TonerGiant.co.uk (degree qualified).
I never really thought about why a laser printer is called that, so I didn’t consider how lasers are involved in the printing process. It is so interesting that the laser “charges” the spinning drum which allows it to pick up toner before transferring that to the paper. I need to buy new toner cartridges for my new printer for the first time, so I’m glad I ended up learning more about how they work!
today you learned something new ,laser is light amplification by stimulating emission of radiation
Thanks, Stuart. This was a very detailed tutorial, much appreciated.
Well fascinated by the explanation… I really understood how this thing works cause I have been wondering what magic I there…. I wana be a laser technician in the future now
if i print in black only does other clours come out also or only the black
A small amount of colour is also used when printing black.
Hi Stuart.
I have a problem with my Dell C2660dn laser printer, the black is very light, there are no codes showing, I have cleaned it out so many times to no avail, as per manual, reset the printer settings on printer but when I print out printer settings directly from printer it still comes out far to light.
Also when I try to print photos they come out ghostly as if the black is not working.
Hi Philip, how does the faint print look? for example is it completely faint / evenly faint on the whole page or in lines? If its in lines, its likely to be the drums at fault. If its even across the page then it could also be the fuser unit. It’s trial and error unfortunately so best to try a new toner or drum first and if that doesn’t fix the issue then a new fuser.
Hi! I am doing a project on how printers work for my physics class.
I am just wondering if the special coating (the green color) on the drum unit is photoconductive, where when light hits it becomes a conductor?
Thanks!
Hi there, another name for the drum unit is a photo-conductor unit so I would imagine you are correct. It definitely holds a charge because it uses a static charge to hold the toner and the paper has an opposite charge so that it’s transferred across.
Hi, my university project is about how laser cartridges and copiers work and are made.
And also if calculations are made on the manufacture of the cartridges.
I’m looking for books and articles on the internet to help me with this, but I could not find them.
I am an electronics student. If you know a source, please help me.
Hi there, good luck on your project. I don’t beleive the information is readily available as the technology is patented. The only thing you could do is contact manufacturers directly and see if they can help.
Hi Stuart,
I have a HP LaserJet printer, and I just replaced the toner cartridge with a new one, although it is a couple of years old, but was stored in our cupboard still in original packaging. Now when it prints the text is so faint you can hardly read it, I have shaken the cartridge and still the same result. I assume it was the cartridge so replace with the second spare (another new one) I had, and again I get the same result.
I have also played with the setting to see if we change it to the darkest setting if that resolves the issues, again the exact same result.
My understanding of the toner, it will last a lifetime, so I was wondering if the issue could be caused by the fuser or drum, not keen on buying new toner cartridge if that is not the issue.
Any ideas on what could cause this issue, when it worked fine the day before, your help would be greatly appreciated.
Regards
Hi Jason, have a look at the tips on the faint print article which should help identify the problem https://www.tonergiant.co.uk/blog/2014/10/faint-print-5-things-that-could-be-causing-your-printer-problem/
Hi, Stuart,
Thank you for the fantastic information. Very helpful~
I have a question about how positive toner be released when next to the drum(s), is it by line? how the difference of the positive toner be released when 3 lines of words, half a line of the words, and half a page of words? which one produces more waste toner powder?
Thanks
Hi Jessica, if I understand your question correctly, basically the larger amount of text printed would create more waste toner but a printer with multiple drums would print each colour one layer at a time as the paper passes by (black can use multiple colours as well). A drum collects the toner in a completed image so in your examples whether that be 1 line of text or 3 they are all distributed by the drum in one revolution of the drum.
Hi! Thank you for the article. Hp m255dw user (colour laser). I have a problem with random white patches in my print, a couple of cms wide and seemingly spanning all colours but definitely black. General print quality is fine, except for these occasional ‘voids’. Can’t find solution anywhere online! Any clue what could be causing them please?
Have a look at this page to see if it helps: https://www.tonergiant.co.uk/blog/2017/05/black-lines-down-the-page-4-causes-and-how-to-fix/
Hi Stuart,
If I design and print letterhead shells on a laser printer….then later print the content of a letter onto that same letterhead, through another laser printer….will the heat of the second pass of the shell cause the toner of the first pass break down causing it to discolor the rollers and possibly transfering that image onto clean sheets of another printing?
That shouldn’t cause an issue but I think it depends on which printer brand / model and the paper type. There are some manual duplex printers that print one side and then the second side later by taking the paper back into the printer so I would imagine this won’t cause a problem. Also toner particles are tiny spheres that melt so once they’re already broken down shouldn’t break down further, however, I have to say I’ve never tried it so I can’t be 100% sure.
Nice article, still after all these years. One thing I hate about inkjet printers is that they go through a cleaning process which uses a lot of ink. I have a home office and I don’t print very much. I can go a few weeks with out printing, but when I do, the printer goes through the cleaning process sometimes for several minutes. And then, this ink goes into a holding tank with absorbent cotton batting and when the tank becomes full, the printer is useless.
I know laser printers don’t have a print head that needs to be cleaned, however does the toner ever suffer quality issues from not being used?
Hi Trevor, I’ve typically had more problems leaving inkjet machines idle because as you mentioned they need to be regularly cleaned to keep active and stop the ink from drying out. I’ve even had a new inkjet machine break because it was left idle during lock down. Our Laser machines were absolutely fine because the toner is dry powder and you don’t need to keep cleaning them.
Dear Mr. Stuart, can I use plastic sheet which is used for binding documents, in place of paper? I want to know whether it has negative effect on the printer.
Thank you
Mengesha Kebede
No I wouldn’t do that! It may be melted by the fuser and damage the printer. The toner wouldn’t stick to the sheet anyway.