Disc Wizards

Computer optical drive loading mechanisms

Exploring the different types of drive loading mechanisms and how to decide on the best option for you

When searching for a CD or DVD drive, there are several factors to consider, and the disc loading mechanism is an important consideration.

The loading mechanism is the mechanical component that is responsible for loading the optical disc into the reading / writing drive.

There are three loading mechanisms available in the market, they are; tray, slot and the caddy.

Because you come into contact with the loading system every time, during the loading and unloading of a disc, it is important to choose the most suitable one for you.

Let’s have a closer look at each of the three.

Fig 1: Tray loading mechanism

Tray loading mechanism

The most common of the three, the tray loading mechanism, is made of a plastic tray driven by rubber belts and gears.

The tray moves in and out when the eject button is pushed. When open, a gentle push of the tray can also retract the tray.

Unlike the caddy, which we will look at briefly, the tray is overall less expensive. However, it has several disadvantages, one of them being that it is prone to breakage, which can happen from mis-usage.

The tray loading mechanism is made of plastic that can crack or split if pressure is applied to it when it is open. The tray mechanism doesn’t hold the disc securely, so if the disc is not placed properly, either the disc or the tray may be damaged.

Another major disadvantage is that it cannot work well when in a vertical position because gravity disallows proper loading. However, this can be overcome by opting for a version that has clips that will grab the CD.

Slot loading optical disc drive

The slot loading is identical to the system used in the CD player of most modern vehicles or the drives of Apple laptops and iMacs.

It is the simplest of the three to use because all you need to do is just slip the disc into the slot and a mechanical arm grabs the disc, drawing it inside the drive.

Most of the time, the drives that use this mechanism tend to have the capability of holding more than one disc inside.

The main drawback of the slot is that if the CD jams, it can be difficult to repair.

Another disadvantage is that if you are using flexible eco discs, then these have a tendency to have readability issues in a slot loading drive.

Fig 2: Slot loading optical disc drive
Fig 3: Caddy-style disc dive

Caddy-style disc drive

Though the caddy-style disc drive is less popular due to the convenience offered by the tray, it is still widely used in many high-end drives.

This mechanism requires that the CD be placed in a caddy, which is a casing with a shutter that is made of metal. The container has a lid that opens to insert a CD, and thereafter the lid is closed. The caddy is then inserted to the main drive. The metal shutter at the bottom of the caddy gives access to the laser that reads the CD. If you have ever seen a minidisc, then it is a similar concept.

The caddy is most advantageous if all of your CDs are in their own caddies, so you can handle the caddy without touching or contaminating the disc. This system also ensures that the disc is properly positioned when inside the drive.

The caddy has a faster access time and it works well whether it is in a vertical or horizontal position.

The disadvantage of a caddy is that it is expensive and you can only get one caddy per drive.

Caddies are suitable for rugged computers that are used in harsh environments and where a person with gloves or dirty hands will have to change the disc.


The tray based drives are the most common types found in computers and other devices using drives. The caddy-based system is expensive, but very useful if the contents of the disc are very valuable and/or are being used in an environment where an exposed disc is at risk of damage.

Do bear in mind the caddy-based system is probably the most expensive of the three options especially if you need separate caddies for all your discs. The slot mechanism is very neat and tidy to use, but you may have issues with playing certain types of discs.

Hopefully the above details will provide you with enough information to choose the right type of drive for your requirement.

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