Group 4 - Computer DVD Drive

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Hitachi-LG GCE-8400B

Executive Summary

The main focus of this product dissection was to fully disassemble a DVD-drive typical of optical drives used today for reading the data on the ubiquitous digital video disc. This particular device is intended to fit in the 5.25" drive bay of modern desktop computer towers. The procedure was to incorporate a complete product dissection including careful disassembly, component study, and reassembly. The initial phase consisted of a complete tear-down of the product and photo-documentation. Subassemblies were numbered and placed in separate containers for later identification and ease of reassembly. Each component and subassembly was studied in order to better understand its function within the unit, and how it interacted with other components in order to perform the same overall function. Once inside, the intricacies and capabilities of modern electronics can be fully realized. The product itself is able to load a DVD disc into the tray, read it through the use of a laser, convert the data into a signal readable by the computer in a package not much larger than the disc itself. After documenting a few crucial components in a 3-D CAD program the components were assembled back together. The process was straightforward and easy using only a small screwdriver and basic disassembly skills can completely remove almost all necessary components to study the product. As this was a base-model widely available device, and most certainly not intended for infinite life use, some of the components were not designed to withstand the forces necessary to disassemble it. These include many small plastic pieces and a small rubber belt that was missing upon delivery of the item.

Introduction

Product Description

Computer CD-R/RW, DVD Drive
Manufacturer: HL Data Storage, April 2002
Designed By: Hitachi-LG Data Storage
Model Number: GCE-8400B
Laser Class: 1
Buffer Size: 8 MB
Access Time: 110 ms
Read Speed: 40x
Write Speed: 40x
Rewrite Speed: 12x
Maximum Data Transfer Rate: 6,000 KB/s
Dimensions: 5.25in (length), .5in (height)

CD and DVD drives have become a crucial and effective way of storing, viewing, and saving data. Computer drives offer a simple exterior design that houses many well designed components. CD and DVD drives have been incorporated into society and have become essential to many situations.

Data is read from a disc using a laser and photosensor, the laser shines onto the disc reading the lands and pits. Pits are small bumps written to the disc; lands are the flat surfaces between the pits. The disc contains the lands and pits in a spiral track, when the spiral is stretched out it measures 3.5 miles in length. Upon a laser shining onto the disc it is either reflected into the photosensor or diverted away from the photosensor, this creates binary code. When the laser is reflected into the photosensor it is deemed a "1", when it is diverted away it is deemed a "0". The type and the contents of the file are determined by this code.

This drive also has the capability of writing or "burning" data to a CD-R(recordable). A more powerful laser is used to burn the pits and grooves into the blank CD. The CD-R has a data size limit; it cannot be exceeded. Also, once data is burned into the CD-R, it cannot be used again. There is another type writable CD the drive can utilize called a CD-RW(Rewritable), which can be used more than once, but also contains a data size limit. Data can be repeatedly burned onto the disc so long as it does not exceed its limit.

Group Members

All group members collaborated on the project and each had their own parts to work on.

Bryan Humes - Group leader, 3D CAD, wikipage, oral presentation
Brian Maisch - 3D CAD, oral presentation, references
Eric Klaben - Oral presentation, wikipage
Winnie Liu - Disassembly
Fahr-Deen Kadree - Reassembly

Before Disassembly

Purpose

The purpose of the CD-R\RW, DVD drive is to read and play CD's and DVD's. It can also burn data onto a CD-R or CD-RW.

Condition

The product was in fair condition, all moving parts functioned; However, the product was missing a pulley belt, therfore, it did not operate properly.

Parts and Materials

Our group estimated our product would contain approximately 20 different parts and 6 different types of materials before disassembly.

Disassembly Procedure

Step	Process	Difficulty(1-5) 5 being the hardest	Tools Required	Picture of Step
1	Remove 4 screws from bottom plate	1	Phillips Head Screwdriver
2	Unplug wires and remove main computer chip. This exposes all of the parts.	2	Hands
3	Remove the laser motor by unscrewing 2 screws. Then detach the drive interface by unscrewing 1 screw.	2	Phillips Head Screwdriver
4	Take the outer casing off of the internal frame	1	Hands
5	Remove the 2 plastic holders that are holding the laser by unscrewing 2 screws. This will free the red head assembly.	2	Phillips Head Screwdriver
6	Remove the red head assembly by lifting it out of the housing.	3	Hands
7	Remove the disc support from the internal frame by removing 2 screws. This houses the disc motor.	2	Phillips Head Screwdriver
8	Further disassemble the disc support by removing 5 screws and 3 hex screws. This frees the disc motor.	3	Phillips Head Screwdriver and Allen Key	[[Image: \|thumb]]
9	Remove the spindle motor, it should slip right out.	1	Hands
10	Take the CD/DVD holder out by removing the the front face plate	2	Hands
11	Remove the eject gear.	3	Hands
12	Remove the pulley.	3	Hands
13	Remove the lift actuator from the internal frame by squeezing the ends of it allowing it to become free.	2	Hands
14	Remove the height adjustor from the internal frame by applying force to it.	2	Hands
15	Remove the emergency eject mechanism from the internal frame by applying force, it should just pop out.	2	Hands
16	Remove the eject motor, headphone jack, and volume control from the top of the internal frame by opening clips that hold them in place. It is helpful to use a thin object such as a pen to help you in this step.	3	Hands and Pen

After Disassembly

Component Table

Part Number	Part Name	Quantity of Type	Part Material	Manufacturing Process	Image of Part
1	Bottom Plate	1	aluminum	stamped
2	Main Circuit Board	1	FR-4, steel, copper, various	printed circuit board (PCB)
3	Sled Motor	1	aluminum, steel, copper wire	stamped, welded
4	Red Head Drive Interface	1	plastic	cast
5	Metal Case	1	aluminum	stamped
6	Red Head Brackets	1	plastic	cast
7	Red Head Assembly	1	various; metal, glass lens	mass produced	blank
8	Disc Tray	1	plastic	cast
9	Eject Gear	1	plastic	cast
10	Eject Pulley	1	plastic	cast
11	Disc Support	1	aluminum, rubber damping	Stamped
12	Support Springs	1	Metal	blank
13	Spindle Motor	1	steel, aluminum	mass produced
14	Lift Actuator	1	plastic	cast
15	Height Adjustor	1	plastic	cast
16	Emergency Eject Mechanism	1	plastic	cast
17	Eject Motor, Volume Control, Headphone Jack	1	FR-4, steel, plastic	printed circuit board, cast
18	Internal Frame	1	blank	Injection Molding

Fasteners

Type	Size (inches)	Quantity	Purpose
Phillips Head	3/16 x 5/16	4	Holds the bottom plate in place
Phillips Head	2/16 x 3/16	4	2 screws hold the laser motor in place 2 screws hold the laser brackets in place.
Phillips Head	1.5/16 x 1.5/16	1	Connects the laser drive interface with the laser.
Phillips Head	3/16 x 8/16 washer 4/16 diameter	2	Connects the disc support to the internal frame
Phillips Head	6/16 x 5/16	3	Holds the disc support and disc motor together
Allen Screw	.0591 x 6/16 washer 4/16 diameter	3	Holds the disc support and disc motor together

Part Description

Bottom Plate: Provides protection to the delicate interior components.

Main Circuit Board: Relays signals through the system.

Sled Motor: This motor provides motion to the red head assembly, moving it at a constant rate as the disc spins.

Red Head Drive Interface: This interface connects to the red head assembly and fits into grooves located on the sled motor. There are 2 notches on the interface that fit into the grooves, as the sled motor rotates it now moves the red head assembly through this interface.

Metal Case: The metal case is the rest of the exterior that provides protection for the interior components.

Red Head Brackets: The brackets hold the red head tracks in place. The red head assembly can now move on its tracks.

Red Head Assembly: The red head assembly houses the laser, photosensor, and various lenses. The laser is focused through lenses and onto the disc. The laser is responsible for reading the data from the disc and the photosensor it responsible for recieving the data.

Disc Tray: The disc tray holds the disc as it is placed into the drive and ejected from the drive. It is made to fit the standard disc diameter of 120mm or 4.28in.

Eject Gear:

Eject Pulley:

Spindle Motor Support: This support houses the disc motor when assembled. It contains rubber dampers to provide cushioning for the motor when it moves up and down as a disc is inserted or ejected. It also houses 2 springs that provide support and cushioning.

Support Springs: These are located inbetween the spindle motor support. They provide support and cushioning for the spindle motor.

Spindle Motor: The spindle motor provides motion to the disc. The motor lowers when the disc is ejected and rises as a disc is inserted, landing in the center of the disc. The motor has grooves carved into the top which grab the disc as it rotates. The motor rotates with speeds from 200-500rpm.

Lift Actuator:

Height Adjustor: The height adjustor provides a track for the spindle motor support to travel when lowered or raised. It has grooves on top to provide a way to lock it in place, when the eject button is pressed the....

Emergency Eject Mechanism: This mechanism is a way to retrieve your disc if complete failure or a power outage occurs. There is a small hole in the front of the drive, where a small rod or paper clip can be inserted. When inserted far enough it triggers the mechanism to eject the disc tray. The tray is now free and can be pulled out with little effort.

Eject Motor, Volume Control, Headphone Jack: The eject motor is responsible for ejecting and inserting the disc tray. The volume control is in the form of a wheel, it can be turned either way producing a louder or quieter sound. The headphone jack is a small opening in the front of the drive. A set of headphones can be plugged into the drive to isolate the sound to the headphones.

Internal Frame: The internal frame is essentially the chassis of the entire drive. Everything is connected to the internal frame as it provides structure for the drive.

3D CAD Models

Major Components

Side View	Angled View	Top View

Spindle Motor: The spindle motor is essential to the DVD drive. The spindle motor support which houses the spindle motor lowers with the help of the hieght adjustor and the lift actuator. The lift actuator slides down through the groove in the height adjustor, which in turn lowers the spindle motor. The disc is now able to be inserted into the drive with no obstructions. The spindle motor support is now raised with the help of the same mechanisms. The spindle motor is now in the center of the disc and will spin it when the energy is provided. The spindle motor runs between 200 and 500 rpm depending on the location of the laser.

Side View	Angled View	Top View

Sled Motor: The sled motor provides a constant rate of motion for the laser. The laser motor has a series of spiral grooves in which the drive interface is connected. The drive interface is connected to the laser. As the motor turns the spiral grooves, it provides motion to the drive interface which moves the laser.

Side View	Angled View	Top View

Red Head Assembly: The red head assembly contains the laser, lenses, and photo sensors. The laser beam is focused through the lenses to read the lands and pits on the DVD or CD. The red head is installed on a set of rods(tracks) and is provided motion from the sled motor.

Assembled in Sequence

Assembly

Step	Process	Difficulty(1-5) 5 being the hardest	Tools Required	Picture of Step
blank	blank	blank	blank	blank
blank	blank	blank	blank	blank
blank	blank	blank	blank	blank
blank	blank	blank	blank	blank
blank	blank	blank	blank	blank

Assembly Video

After Assembly

Does it still work? Our product still does not work after assembly. The product did not operate properly before disassembly nor were we able to connect it to a computer interface to test it.

Reflection

Was assembly a mirror process of dissasembly?
Reflect on the assembly process.

How it Works

The CD-R\RW, DVD drive works in a general sense by converting electrical energy into mechanical energy. This mechanical energy is used first to load the disc tray into the chassis, then to spin the disc at a variable angular velocity so as to obtain a constant bit rate. This is due to the angular velocity being greater at the outer edge of the disc than at the inner edge. The device must also simultaneously transfer the rotational motion of the laser motor into a linear path from the innermost edge of the disc to the outer edge while the laser is scanning the disc. This is an interesting mechanism and can be seen below. It utilizes a spiral engraved shaft to transmit motion to a plastic interface component that carries the laser the needed distance, at a predetermined rate. The device then uses several feedback mechanisms and circuitry to convert the laser information which is a measured voltage difference into binary coded data and exports it through the use of a parallel ATA-type communication link. The data can then be processed by software programs intended for the purpose of multi-media type data interpreting.

This animation shows how the disc is read and how the data is interpreted <embed src="http://static.howstuffworks.com/flash/cd-read.swf" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="440" height="150"></embed>

This animation shows how the laser tracks across the disc and how the motor changes rpm <embed src="http://static.howstuffworks.com/flash/cd-drive.swf" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="400" height="300"></embed>

Energy Transfered

Electrical Energy: Electrical energy is transfered to the drive from an ordinary household eletric supply.
Rotational Energy: Rotational enery is transfered when power is supplied to the spindle motor, thus creating rotation.
Thermal Energy: Created by friction due to moving parts, such as the red head and the spindle motor.

Types of Materials

Plastic
Silicone
Metal
Copper
Rubber
Aluminum
Steel

Recommended Design Changes/Improvements

Overall this product was very well designed. The only improvement we could suggest at the time of production is removing the pulley system and replacing it with a set of gears. We suggest this because upon recieving the DVD drive the pulley belt was missing, which would cause the product to malfunction. If this belt was replaced with a set of gears this problem could be averted all together. The DVD drive was very well put together and designed.

Conclusion Remarks

Conclusion Remarks.

References

Elton, M. (2006). How DVD and CD Drives Work. Scribd. Retrieved October 10th, 2008, from http://www.scribd.com/doc/596/How-DVD-and-CD-Drives-Work

Byte, U. (2008). Compact Disk. USByte. Retrieved October 15th, 2008 from http://www.usbyte.com/common/compact_disk_4.htm

Sweet, M. (n.d.). How DVD Drives Work. Smart Computing. Retrieved October 20th, from http://www.smartcomputing.com/articles/archive/r0403/08r03/08r03.pdf