| Information |
| Category |
Optical |
Reference |
SVT039 |
| Description |
Crush & Egress Testing |
Issue
Level |
02 |
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| Definitions |
| 01 |
Crush |
The
destruction of a CD within a
drive, shattering through crack
propagation |
| 02 |
Crushable |
Describes
CD media that is brittle and that
will crush readily
Use low quality CD-Rs aged for
16hrs @ 90C as a benchmark
Slight flexing around a crack in
the CD should make it propagate
quickly |
| 03 |
Propagate |
A
crack growing under applied stress
Check propagation suitability by
applying slight pressure either
side of a crack
starting from the centre of the CD
- the crack should grow easily |
| 04 |
Egress |
The
ejection of CD fragments from the
drive following a CD crush |
| 05 |
Crack
propagation |
The
growth of the original crack
beyond the extent marked during CD
preparation |
| 06 |
Control
CD Drive |
A
CD drive identified by RM to be
particularly susceptible to crush
& egress |
| 07 |
Critical
Crack Length |
The
length of crack that will
propagate freely at a given CD
speed |
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| Procedure |
| 01 |
Crush
Resistance Testing |
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| 01.01 |
Purpose |
| 01.01.01 |
To
determine if the CD/DVD drive is
liable to crush CDs under normal
usage |
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| 01.02 |
Equipment |
| 01.02.01 |
6
CD/DVD drives |
| 01.02.02 |
40
Crushable CDs |
| 01.02.03 |
2
Control CD Drives |
| 01.02.04 |
CD
Speed Software |
| 01.02.05 |
CD
Marking Pen |
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| 01.03 |
Preparation |
| 01.03.01 |
Induce
an approximately 5mm long crack in
each CD, starting from the centre
hole
This is done by either tapping the
centre of the CD or by flexing it
slightly |
| 01.03.02 |
Ensure
the crack can propagate |
| 01.03.03 |
Mark
the extent of the crack on the CD
with a CD marking pen (ensure the
ink does not touch the crack) |
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| 01.04 |
Crush
Test |
| 01.04.01 |
Place
a prepared CD into the test drive |
| 01.04.02 |
Run
the CD Speed Software |
| 01.04.03 |
Record
in the Results Worksheet the
results of the test according to
the classification: |
| 01.04.03.01 |
Crack
propagation |
| 01.04.03.02 |
Crush |
| 01.04.03.03 |
Egress
-> ANY occurrence of egress
will immediately fail the drive |
| 01.04.04 |
Check
crack propagation: |
| 01.04.04.01 |
Ensure
the crack has propagated into the
data area of the CD |
| 01.04.04.02 |
If
the crack does not propagate into
the data area then the crack
length is less than the critical
crack length for the operating
speed of the drive |
| 01.04.04.03 |
If
the crack has not propagated check
that the CDs are crushable by
testing in the Control CD drive |
| 01.04.04.04 |
If
the crack has not propagated, but
the CD will crush in the Control
CD Drive, then inspect closely the
CD Speed Software drive
performance trace; it is possible
that the drive is not reaching its
claimed operating speed |
| 01.04.05 |
Check
the drive if a crush has occurred: |
| 01.04.05.01 |
Add
a pen mark on the drive casing to
indicate a crush event has
occurred |
| 01.04.05.02 |
Clean
out all debris within the drive |
| 01.04.05.03 |
Inspect
the drive for any sign of
mechanical damage, particularly to
the drawer locking mechanism |
| 01.04.05.04 |
Discontinue
use of the drive for testing if
the drive exhibits any sign of
mechanical damage |
| 01.04.05.05 |
If
the drive has experienced 5 crush
events, discontinue use;
substitute the next drive |
| 01.04.06 |
Repeat
the test for a total of 30 CDs |
| 01.04.07 |
Repeat
the test for a total of 10 CDs
using the Control CD drive |
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| 02 |
Egress
Resistance Testing |
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| 02.01 |
Purpose |
| 02.01.01 |
To
determine if the CD/DVD drive can
withstand a full speed CD crush
without egress |
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| 02.02 |
Equipment |
| 02.02.01 |
4
CD/DVD drives |
| 02.02.02 |
20
Crushable CDs |
| 02.02.03 |
Stopwatch |
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| 02.03 |
Preparation |
| 02.03.01 |
Induce
an approximately 5mm long crack in
each CD, starting from the centre
hole
This is done by either tapping the
centre of the CD or by flexing it
slightly |
| 02.03.02 |
Ensure
the crack can propagate |
| 02.03.03 |
Hardwire
the CD drive to operate
continuously at its maximum speed |
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| 02.04 |
Egress
Test |
| 02.04.01 |
Place
a prepared CD into the test drive |
| 02.04.02 |
Turn
on the system & start the
stopwatch |
| 02.04.03 |
Wait
for a crush to occur & stop
the stopwatch |
| 02.04.04 |
Record
in the Results Worksheet the
results of the test according to
the classification: |
| 02.04.04.01 |
Crack
propagation |
| 02.04.04.02 |
Crush |
| 02.04.04.03 |
Egress
-> ANY occurrence of egress
will immediately fail the drive |
| 02.04.05 |
Check
crack propagation: |
| 02.04.05.01 |
If
the crack has not propagated,
check that the crack can propagate
& re-test |
| 02.04.06 |
Check
the drive if a crush has occurred |
| 02.04.06.01 |
Add
a pen mark on the drive casing to
indicate a crush event has
occurred |
| 02.04.06.02 |
Clean
out all debris within the drive |
| 02.04.06.03 |
Inspect
the drive for any sign of
mechanical damage, particularly to
the drawer locking mechanism |
| 02.04.06.04 |
Discontinue
use of the drive for testing if
the drive exhibits any sign of
mechanical damage |
| 02.04.06.05 |
If
the drive has experienced 5 crush
events, discontinue use;
substitute the next drive |
| 02.04.07 |
Repeat
the test for a total of 20 CDs |
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| 03 |
Egress
Risk Assessment |
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| 03.01 |
Egress
risk assessment will be undertaken
in all instances that Crush /
Egress test data is supplied by
the vendor |
| 03.02 |
The
drive will be inspected and the
likelihood of egress assessed
according to the following: |
| 03.02.01 |
Loading
mechanism - does the CD have an
easy egress path from its
operating position? e.g. slot
loading drives |
| 03.02.02 |
Mechanical
robustness of the drawer door -
does it appear strong &
adequately attached to the drawer? |
| 03.02.03 |
Mechanical
robustness of the drawer locking
lugs - do they appear strong and
supported? |
| 03.02.04 |
Mechanical
robustness of the fascia - does it
flex easily or detach easily from
the casing? |
| 03.02.05 |
Evidence
of design features clearly
incorporated to reduce the
likelihood of egress from the
drive e.g. metal reinforcement or
shielding, crush features,
redirection features etc. |
| 03.03 |
The
Egress Risk Assessment will be
used as a check to the validity of
the vendor supplied Crush / Egress
test data |
| 03.04 |
If
the Egress Risk Assessment
suggests anything other than a low
risk, RM will perform an
independent Crush / Egress test |
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| Procedure
Notes |
| 01 |
All
crush/egress testing must be
performed in a safe environment,
utilising appropriate safety
equipment and working practice at
all times e.g. the wearing of
safety goggles, pointing test
drives away from people etc. |
| 02 |
Drives
must not be tested when loosely
placed upon a bench etc. Reliable
data will only be achieved if the
drive is secured during testing,
either by being clamped firmly to
a bench or by being installed in a
system case. Loose drives will
allow CD crush energy to be
dissipated into movement of the
drive. |
| 03 |
An
acceptable result for the crush
resistance test is that the crack
will just propagate into the data
area of the CD, at which point the
CD will become unreadable. The
drive will then be unable to spin
the CD further and hence the crack
will be unable to propagate
towards crush. This result
suggests that the drive firmware
or servo control hardware is
"catching" the presence
of the crack, backing off the
speed before critical crack length
is reached. It is demonstrated by
the CD Speed Software drive
performance trace, which shows the
firmware back-off as a slow down
of the drive. |
| 04 |
An
unacceptable result for the crush
resistance test is that the crack
will propagate continuously within
the data area of the CD, leading
to a CD crush. This result
suggests that the drive firmware
or servo control hardware is not
"catching" the presence
of the crack and hence is not
reducing the speed of the drive.
It is demonstrated by the CD Speed
Software drive performance trace
and audibly by the sound of the
drive. Egress is then a
possibility. |
| 05 |
An
acceptable result for the egress
resistance test is that no egress
occurs |
| 06 |
An
unacceptable result for the egress
resistance test is ANY occurrence
of egress |
