How do discs spin in drives?

I was thinking about this the other day. When I place a blu-ray disc into my PS3, about halfway through it “sucks/draws” it in automatically (like when you put a CD into the disc changer in your car). What exactly is the “force” that pulls it in? Is it some sort of mechanical tool, and can it damage your discs?

Also, I have always been confused as to exactly HOW discs spin inside the drives. I know some drives, you “lock” the disc in (the small, round thing in the middle that locks the disc in also spins it). However, in others, a tray ejects and you place the disc onto the tray. Well, the disc goes in, and you cannot see what happens to it from that point on …

How do discs spin in those kinds of drives? And how are they “locked in?” I mean, don’t they have to be “locked” in order to spin without wobbling? But if you simply place it onto a tray, how can the drive “lock” the disc in and spin it automatically? I just wish I could see it happening inside the drive for myself …

I’m always afraid my blu-ray discs will get damaged somehow (not scratches, but CRACKS) inside the PS3, because I always leave them inside the console after I finish playing (I usually spend 2-3 weeks on a game, so it would not be practical to eject the game every day), and once you “send” the disc into the PS3, there’s no telling what is happening to it on the inside.

Thanks!

Found something here. Basically two “arms” grab or push out the disc.

Thanks, that link helps a lot. However, I still wonder how the disc gets “locked.” It says the “spindle” moves on its own, but without some kind of force, how could it “lock” the disc in?

Typically, the spindle moves up to lift the disc off of the tray. At the sam time a weighted clamp comes down to the top of the disc to hold it firmly to the spindle.

You should find an old CD/DVD ROM drive and take the cover off. It’s interesting to watch it all at work. You can also close the tray with no disc and see the laser servo move back and forth looking for a disc.

Thank you for that answer.

But when you say that the spindle and clamp LOCK the disc into place, is that only true for when the device is powered ON?

What happens when the device is OFF, but the disc is left inside? Does it rest on a tray or something? Or is it suspended/locked in place?

Caution: wordy ramble following. :bigsmile:

There is no special power off sequence for optical drives. The drive is not reset, no precautionary measures are put in motion (none need to be in place, really), and things remain just as if the drive was powered on.

When the tray is closed, for as long as it is closed (on or off), the disc is locked in place. The spindle motor has the disc suspended slightly above the tray, the magnetic clamp is in place, and the drive does not exit this state until the tray is next ejected.

With no disc in the tray upon closing, the spindle motor still rises as if there was a disc there, the magnetic clamp still clamps down as if a disc was there.

Ejecting the tray pulls the clamp apart from the spindle motor (and the disc, if one had been inserted), leaving the clamp suspended in the lid.

For some desktop drives, before the tray is ejected, the optics return to a “home” position & the servo controlling the optics will “beep” or “click” at this time. For other desktop drives, after the tray is ejected & reinserted, the optics will return to their home position as part of the disc check; the “beep” or “click” of the servo pushing/pulling the optics back & forth will occur then.

For slot loading drives, the disc remains suspended in the same manner & all the above still applies. Upon power up, with no disc fully inserted, the drive may do a sweep to ensure there is no disc partially inserted using the eject mechanism; if a disc is inserted far enough, the drive may suck the disc in as normal. Upon power up with a disc, the drive will just pretend as if the disc was just inserted & begin trying to ready itself for use.

Wow thanks, that’s a really thorough explanation.

So if the drive “holds” the disc in the same manner when the device is OFF as when it is ON, then does that mean the disc is as “safe” inside the drive as if it were in its case?

Because I tend to leave blu-ray discs inside my PS3 until I finish the game. Otherwise I’d be putting the same disc in and taking it out every day for weeks. It seems like there’d be a greater chance of “damage” being done to the disc by this constant ejecting/re-inserting and taking it out and putting it back in its case.

If the console (powered off) were to be “bumped” (just slightly), would there be any physical way for the disc to be damaged if it were inside? I’m trying to imagine it in my head, and if it is locked in place by a spindle and clamp, then it should be immune to damage, right?

I mean, a game in its case is also “locked” in place, and hypothetically even if you were to throw the case all over the room, the disc would still be suspended inside the case and would be fine. I would hope the same would be true inside the drive.

Can’t always stop kids from bumping into stuff.

With the drive powered off, the disc should be suspended completely & safely above anything that can cause damage to the disc, and the clamp system is more than enough to keep the disc secure.

For an example: Xbox 360 consoles have drives that are blamed for scratching discs. However, the drives have to be powered on and rotating the disc, and the fall has to be fairly significant. Powered off, there are significantly fewer issues.

I have still seen someone complain about moving a console when the whole console has been powered down, but I have transported a number of external drives & consoles with a disc still inserted while powered down, and none have sustained damage. (I have flipped a drive from its side to its belly while spinning at full speed, and there WAS a scratch; I highly recommend you avoid this).

Thanks a bunch, that’s a real relief to hear. :clap:

But I was curious about the spindle/clamp that lock the disc into place … do they make contact with the disc only at the [B]plastic ring[/B] in the center (where no data is stored)?

Because it would seem like if it were to exert pressure on the disc at any other place (even the edges), there would be a risk of scratching/cracking, especially when the disc is spinning?

[QUOTE=princekrillo;2586845]Thanks a bunch, that’s a real relief to hear. :clap:

But I was curious about the spindle/clamp that lock the disc into place … do they make contact with the disc only at the [B]plastic ring[/B] in the center (where no data is stored)?

Because it would seem like if it were to exert pressure on the disc at any other place (even the edges), there would be a risk of scratching/cracking, especially when the disc is spinning?[/QUOTE]
It depends on the drive, most of them just use the center plastic ring, others I’ve seen take up a large portion of the disc top!

These posts describe some differences in DVD Drive design in Panasonic and Funai-manufactured stand-alone recorders:

http://www.avsforum.com/avs-vb/showthread.php?p=19651878#post19651878

http://www.avsforum.com/avs-vb/showthread.php?p=19647592#post19647592