Have you ever wondered why your scanner worked great when you bought it, but sometime later on you notice that it misfeeds or jams almost every time you try and scan your documents?
The reason for this is that the scanner contains consumable parts that are supposed to be replaced on a regular basis. These parts will wear out quicker if you are doing a high volume of daily scanning, and last longer if you are only scanning a few documents per day.
Here's a simple explanation of what these parts are called and what they do.
If you open the scanner lid, look inside and you will usually see several large grey rubber rollers and a metal/plastic springy plate. The grey rubber rollers are spongy. The lower grey roller assembly is usually called the pick roller. Its job is to pick the next sheet of paper from the input tray, moving it forward into the scanner. The upper grey roller assembly is usually called the brake roller. Its job is to hold the other sheets back in the ADF so that only 1 sheet is scanned through. The little metal/plastic finger is called the brake or return spring. Its job is to help stop multiple sheets from being pulled into the scanner.
When you scan tens of thousands of pages, these parts wear and then they don't do their jobs properly. This results in multi-page jams, misfeeds and skewed documents.
How can you tell when these parts need replacing? Most scanner drivers keep a count of how many pages have been scanned and provide another counter that measures roller usage. During scanning, they also provide on-screen warnings to indicate that these parts need to be replaced.
Many scanner vendors design the pick and brake rollers like car tyres, they have tread patterns on them. Take a close look at the rollers. Is the tread wear uneven, lopsided or is the tread completely bald? Do the rollers have flat spots, or bulges? Are bits of the rubber torn or missing? These are all visible signs that indicate the rollers should be replaced. The scanner vendors sell consumable kits for individual replacement parts or all replacement parts. It's considered best practice to replace all the consumable parts at one time, thereby returning the scanner to excellent scanning condition.
Please note there are also other smaller orange/black/white rollers that are made of hard plastic/nylon. These simply assist with helping the paper to exit through the scanner. They are fixed in place and are not a user-serviceable part. Those rollers should be cleaned on a regular basis. Over time they do get a build of black ink residue from the scanner pages. You can normally clean that off with an alcohol pad, or by softly dislodging it carefully with your fingernail.
Scanner vendors recommend that scanners are cleaned on a daily basis. They provide detailed instructions on how to do this on their websites and in the documentation that was supplied with your scanner. They sell cleaning consumables as after-market kits, but rarely include them with the scanner. There are usually specific cleaning cloths for cleaning spongy rollers, hard rollers and the scanner throat area.
If you buy or rent a scanner, you should also purchase the cleaning kits and roller consumable kits necessary to ensure the ongoing trouble-free operation of the scanner.