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Hardware -- Drives

Page history last edited by PBworks 15 years, 11 months ago

Media-type Related Considerations:

 

Discussion of choosing the makes/models of drives appropriate for the reading/writing jobs you plan to perform.

 

Special Capabilities (todo):

 

Discussion of these CD topics:

  Lead-in / Lead-out reading

  HTOA audio extraction capabilities

  Accurate Stream

  C2 Error capabilities and trustworthiness

  Caching

  Cache-clearing

 

Discussion of these DVD topics:

  Bitsetting

  Scanning

  Media support

  Off-speed burning support

 

Pointers to additional resources (e.g. some already cover which drives handle the above items the best).

 

 

Physical and Behavioral Considerations regarding drives for robotic use:

 

1. Almost all optical drives ship with retension clips, usually spaced at 1/4 intervals around the disc holding location, that allow the drives to be mounted vertically.  You need to remove these for proper usage with robotic loaders.  Unless the clips pop out (rare), a dremel is the tool to use to take care of this easily.

 

2. Older optical drives almost all extended the disc-holding circle of the tray much farther out than contemporary drives, primarily due to the move to drives with smaller dimensions of "depth" (for compatibility with the SFF market).  Robotic duplicators were all designed to vertically load and unload the tray and therefore need room to do so without the edges of the disc impacting drive parts of the target drive or the drives above it.

 

It is often the case that with a contemporary consumer optical drive packaged, it is not possible to pick a centered disc out of the tray (or drop one into the tray) without interference with the front faceplace of the drive or the drives above it.  For this reason, if replacing a robotic duplicator drive with a different model, it may be necessary to remove the plastic faceplace of the drive as well as the end-of-tray trim piece that often has the customized drive info printed on it (as many drives are OEM'd to more than one "branding" seller).  In extreme cases, the aluminum casing of the drive may need to be dremeled back a bit in the center area as well, esp. if the lip (used to help keep the plastic front bezel in place) is larger than normal.  Don't forget to look at the clearance of the casing both above and below the tray, as you may be stacking this drive on top of another.

 

The above is true for most robots, but especially true for vacuum-based pickers where there is often more variance on pick and place centering issues:  they tend to require the most modifications to the drives as the original drives that sold with these either had custom tray-extension firmware modifications or custom placement (or removal) of the end-of-tray-extension sensor inside the drive.

 

4. A special notice for Microboards hopper-based loaders: the above is true for them, but the microboards-specific two-flap lifter narrows down the potential drives further due to the requirement of cutting parts of the tray off.

 

The track(s) on the bottom side of the tray, used by the sprocket(s) that move the tray, must not be to the extreme left or right of the tray, due to the need to physically modify the drive to allow the lifters to reach under the disc.  Most contemporary drives have trays with this track located near the left/right edges, though some have it far enough offset that the dremeling, if done carefully, will not damage the track.

 

I will try to come up with a list of known drives that conform to this more constrained requirement.

 

5. Tray "heartiness".  Similar to #2, robotics were often designed before the move to lighter-weight tray and tray transport compontents.  e.g. some of the older vacuum-based pickers will, in their normal operations, significant bend a tray when they pick up or place a disc from or into the tray, potentially damaging the drive.  Even newer pickers can damage trays if they impact them from below instead of from above (if, say, the application does not properly ensure the other trays are closed during inserts or grabs).

 

There are two potential ways to address this - adjustments to the loader and use of more heavy duty drives.

 

6. Drive behavior with unrecognized discs:  some drives, especially older CD-* only drives, will, when a disc type is not recognized, automatically eject the tray after a minute or two of trying to recognize the disc.  These drives are *not* suitable for use with multi-drive robots.  I repeat:  if the drive auto-ejects, on its own, discs that are not recognized then the drive is unsuitable for use with robotic loaders.  Test your drives, really.

 

7. Special alignment issues.  General alignment should be straightforward, but if you are using a unit that has seen better days, you may find that the unit has a slightly bent picker arm or that the drive mount location is not properly aligned.    Before addressing these by fixing them directly, there might be lower risk workarounds, such as using shims in the drive cage's bottom mount points to slightly angle the drive cage itself to match the robotic arm's slight misalignment. 

 

Modification Instructions:

 

 

 

Diagrams:

 

Link to removal of disc-retension clips on tray.

Link to removal of additional plastic on tray that can interfere with placement and removal.

Link to removal of faceplate.

Link to removal of small amount of case material for extreme cases.

Link to pictures or diagrams of tray bottoms showing the differing track locations.

Link to pictures of heavy duty and lightweight trays and mechanisms

Link to pictures of shimmed drive cages.

etc.

 

 

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