Difference between revisions of "Group 1 - Computer Hard Drive - 1"

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(Improvements at component level:)
(References)
 
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==References==
 
==References==
 
[http://www.apastyle.org/ APA Style]
 
[http://www.apastyle.org/ APA Style]
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Executive Summary and Introduction References:
 +
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1. Byard, F., Larry. A Brief History of the Hard Disk Drive. Retrieved on October 17, 2007
 +
        <http://www.duxcw.com/digest/guides/hd/hd2.htm...>
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2. Story from BBC NEWS. Factfile: Hard disk drive. Retrieved on October 18, 2007
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          <http://news.bbc.co.uk/2/hi/technology/6677545.stm
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3. Brain, Marshall. How hard disks work. Retrieved on November 14, 2007
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          <http://www.howstuffworks.com/hard-disk.htm>
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4. IDE/ATA Configuration and Cabling
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          http://www.storagereview.com/guide2000/ref/hdd/if/ide/conf.html
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5. IDE/ATA and SCSI Comparisons
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          http://www.storagereview.com/guide2000/ref/hdd/if/compSummary.html
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6. How hard drive works
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          http://www.duxcw.com/digest/guides/hd/hd4.htm
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7. Schroeder, B. and Gibson, G. A. 2007. Disk failures in the real world

Latest revision as of 01:55, 5 December 2008

Contents

Executive Summary

This report focuses on the study of an IDE hard drive done for a MAE 277 class project. The project involved the Disassembly/Assembly of an IDE hard drive in an effort to gain an understanding of the assembly and inner workings of a typical hard drive. This involved familiarizing ourselves with the different components of the product, their function and the materials used in their construction. The process also helped in the understanding of the electro-mechanical interface of the product. Each step of the disassembly was documented and each of the components was noted for its placement within the unit. This process also known as “reverse engineering” was done to gain a deeper understanding of the product at hand. The hard drive given to the group was a non-functional unit, and we did not test the hard drive after reassembly. Upon completion, CAD models of the hard drive were developed for the report. From the study of the hard drive, the group concluded that the product is a complicated piece of machinery requiring a great deal of precision in its manufacture and original assembly.

Introduction

The hard disk drive, more commonly referred to as a hard drive is the part of a computer where all the information is stored. As a cliché the hard drive can be labeled as the brain of the computer, a place where each and every bit of information lies. Having come into existence around half a century ago, the hard drive has become an integral part of the computer industry. The progress made in the field of hard drives in such a short period of time is really remarkable. The changes in the size of the hard drive serve as a good example to this as the first hard drive ever made was 24 inches long and was capable of storing only 5 megabytes of data at a cost of over $100 per megabyte.

The technology used in hard drives has been setting new standards periodically. Earlier, hard drives used electromagnets based on the principle of electro-magnetic induction to read the data. Later, drives began using MIG heads and thin film heads. Today, drives have the read and write elements close to each other but at the same time kept separate.

Today there are many types of hard drives present which function across different types of interfaces such as ATA, SATA, PATA, SCSI, SSD, IDE each one benefiting some area of the computing industry. These hard drives share more or less the same physical properties. The only difference between them is the interface across which they work. All the interfaces aim at providing higher random access speeds, longer MTBF (mean time between failures), higher read and write speeds, raw bandwidth and faster transfer speeds. The interface we are dealing with here is known as IDE - Integrated Drive Electronics.

IDE (Integrated Drive Electronics) were first introduced in the mid 1980’s. IDE was renamed to ATA, and then later to PATA ( Parallel ATA). IDE hard disk drives consist of a motor, spindle, platters, read/write heads, actuator, as well as many other components. IDE hard drives have been widely adopted as they proved to be easier to use and performed better than previous hard disks know as “hard cards”. Hard cards/hard disks were interfaced to a PC motherboard via an expansion board known as a hard disk controller. The use of IDE drives in servers and networks has given it a lot of impetus to create next generation transfer speeds. The main advantage of IDE drives is the speed which can be offered at a very low cost.

Data in an IDE hard disk is stored magnetically in a spiral pattern on a series of platters. The data is retrieved/stored by the read/write heads which are controlled by the actuator arm which in turn is controlled by the electrical impulse received from the logic board. The platters are mounted on the spindle which is turned by the drive motor. Most current IDE hard disk drives spin at 5,400, 7,200, or 10,000 RPM some at up to 15,000 RPM.


IDE drives were the first ones to popularize integrating the logic controller onto the hard disks. This helped in solving many issues that were related to the hard disk for example: poor signal integrity, and the capability of allowing any controller to work with any hard disk.

Member's and Contributions

The majority of the project was completed during meetings of the entire group with all members contributing. This includes product disassembly, assembly and all stages of the "after you assemble the product" section of the assignment. The section entitled "after you disassemble the product" was also completed as a group but with Taran absent due to illness. The wiki report and oral presentation were split up. Each member's individual responsibilities were as listed below.

  • Douglas Keddie: "Before disassembly" and "After assembly" sections of wiki report.
  • Stephen Briggs: "Disassembly procedure" and "Assembly procedure" sections of wiki report, 3D CAD Models.
  • Udeep Dhungel: Creation of powerpoint slides and oral presentation.
  • Joshua Poplawski: "After disassembly" section of wiki report.
  • Tarandeep Sodhi: "Executive summary" and "Introduction" sections of wiki report.

Before Disassembly

Purpose of product / How it works:

  • The purpose of a hard drive is to store and retrieve data. We believe that the data is stored magnetically on a series of discs which rotate either above or below read heads.
  • The read heads must be able to be moved from the inside to the outside of each disc in order to utilize the entire disc surface for reading and writing data.
  • We were unable to operate the product as it would require installation in a computer. We were also advised, upon receiving the hard drive, that it did not work.


Energy used / Transformed:

  • Electrical energy is received from the computer’s power supply and is transformed into the following:
    • Kinetic energy: Both in the rotation of the discs and the movement of the read heads.
    • Magnetic energy: Must be used to read / write data to the discs.
    • Thermal energy: Due to friction in any moving parts and the resistance of the electrical wiring.


Components / Materials:

  • We estimate that there are approximately 30 different components in the unit. This estimate counts all the components that are built into the circuit board (i.e. transistors, resistors, capacitors) as being part of the circuit board, not individual components.
  • We estimate that there are approximately 25 different materials in the unit. This estimate assumes distinctions between various types of plastics and / or metals.


Disassembly Procedure

  • 1. Remove P/N 1 & 2, (6) gold colored screws from the top panel using a screwdriver with a PZ-1 Phillips head screwdriver bit.

Figure 1 – Picture of assembled hard drive from top

MAE277 G01 IMG 1740.jpg
  • 2. Turn the hard drive over and remove P/N 3, (2) gold colored “Screws” from steel bracket (P/N 4) using a screwdriver with a PH0 Phillips head screwdriver bit.

Figure 2 – Picture of assembled hard drive from underneath showing bracket

MAE277 G01 IMG 1741.jpg
  • 3. Remove P/N 4, bracket. No tools are required.
  • 4. Pull open clip on data ribbon (P/N 13b) by releasing a small tab on each end of the clip. Then disconnect the data ribbon from the logic board (P/N 5). No tools are required.

Figure 3 – Picture of data ribbon attachment to logic board before removal

MAE277 G01 IMG 1752.jpg
  • 5. Remove logic board (P/N 5) from case. No tools are required.

Figure 4 – Picture of logic board removed from assembly

MAE277 G01 IMG 1755.jpg
  • 6. Remove all “warranty void” stickers from housing, exposing additional screws to be removed. Remove P/N 6, (3) additional screws using a screwdriver with a T9 Torx screwdriver bit.
  • 7. Remove P/N 7, Metal cover. No tools are required.
  • 8. Remove P/N 9 & 10, (2) screws holding down top bracket (P/N 11) using a screwdriver with a PH-0 screwdriver bit.

Figure 5 – Picture of bottom of hard drive showing (2) screws and bracket

MAE277 G01 IMG 1767.jpg
  • 9. Remove top bracket, P/N 11. The removal of the top bracket will require moderate force to break the magnetic attraction with the bottom bracket (P/N 23). No tools are required.

Figure 6 – Picture of lower case with top bracket removed

MAE277 G01 IMG 1768.jpg
  • 10. Remove P/N 12, (1) screw using screwdriver with PH0 Phillips screwdriver bit. The following (4) parts are removed as a sub assembly; P/N 13 actuator, 13a actuator coil, 13b data ribbon, and 13c bearing.

Figure 7 – Picture of actuator sub-assembly being removed

MAE277 G01 IMG 1771.jpg
  • 11. No action required, skip this step.
  • 12. Remove P/N 14 (5) silver colored “Screws” and P/N 15 (1) black colored “Screw” from top of platter flange (P/N 16) using a screwdriver with a T6 Torx screw-driver bit. There was no indication of any significance of the (1) black colored screw versus the (5) that were silver in color, a match mark was made anyway to identify the location of the black screw.

Figure 8 – Picture of platter flange w/o (6) screws

MAE277 G01 IMG 1777.jpg
  • 13. Remove P/N 16, “Platter flange” by raising it off of the motor. No tools are required.

Figure 9 – Picture of Platter flange removed

MAE277 G01 IMG 1780.jpg
  • 14. Remove P/N 17, “Spacer ring, thicker”, by raising it off of the motor. No tools are required.

Figure 10 – Picture of thicker spacer removed

MAE277 G01 IMG 1781.jpg
  • 15. Remove P/N 18,”Platter” by raising it off of the motor, No tools are required.

Figure 11 – Picture of platter being removed

MAE277 G01 IMG 1782.jpg
  • 16. Remove P/N 19, “Spacer ring, thinner”, and then P/N 18, “Platter”. Both of these parts will be removed by raising them off of the motor. No tools are required.

Figure 12 – Picture of bottom case with thinner spacer and second platter removed

MAE277 G01 IMG 1785.jpg
  • 17. Remove P/N 20, “Lock arm”. No tools are required.

Figure 13 – Picture of lock are removed

MAE277 G01 IMG 1786.jpg
  • 18. No action required, skip this step.
  • 19. Remove P/N 21, “Actuator guide” by raising it from the bottom case (P/N 24). No tools are required.

Figure 14 – Picture of actuator guide before removal

MAE277 G01 IMG 1787.jpg
  • 20. Remove P/N 22, (2) “Screws” holding the bottom bracket (P/N 23) to the bottom case (P/N 24) using a screwdriver with a PH-0 Phillips screwdriver bit.

Figure 15 – Picture of bottom bracket before removal

MAE277 G01 IMG 1788.jpg
  • 21. Remove P/N 23, “Bottom bracket” from the lower case. No tools are required.

This completes the disassembly of the hard drive. The following items were identified as separate parts. However these parts were not removed from the bottom case; P/N 24a, “Motor” P/N 24b, “Lock arm post” P/N 24c, “Filter”

After Disassembly



Parts List:

Part No. Name Qty. Material Type Manufacturing Process Image
1 Philips Head Screw (a) 5 Steel Machining/Extruding
MAE277 G01 IMG 1746.jpg
2 Philips Head Screw (b) 1 Steel Machining/Extruding
MAE277 G01 IMG 1746.jpg
3 Philips Head Screw (c) 2 Steel Machining/Extruding
MAE277 G01 IMG 1746.jpg
4 Data Ribbon Cover 1 Steel Shaping
MAR277 G01 IMG 1747.jpg
5 Logic Board 1 Plastic, Copper, Tin, Lead Varied
MAE277 G01 IMG 1744.jpg
6 Torx Screw (a) 3 Steel Machining/Extruding
MAE277 G01 IMG 1758.jpg
7 Housing Cover 1 Aluminum Shaping
MAE277 G01 IMG 1760.jpg
8 Housing Cover Gasket 1 Foam Injection molded
MAE277 G01 IMG 1764.jpg
9 Philips Head Screw (d) 1 Brass Machining/Extruding
MAE277 G01 IMG 1763.jpg
10 Philips Head Screw (e) 1 Brass Machining/Extruding
MAE277 G01 IMG 1763.jpg
11 Top Magnetic Bracket 1 Steel Machined
MAE277 G01 IMG 1769.jpg
12 Philips Head Screw (f) 1 Brass Machining/Extruding
MAE277 G01 IMG 1763.jpg
13 Actuator Arm 1 Aluminum Machined
MAE277 G01 IMG 1772.jpg
13a Actuator Coil 1 Plastic, Copper Injection Molded
MAE277 G01 IMG 1772.jpg
13b Data Ribbon 1 Plastic, Copper Varied
MAE277 G01 IMG 1772.jpg
13c Actuator Bearing 1 Aluminum Machined
MAE277 G01 IMG 1772.jpg
14 Torx Screw (b) 5 Brass Machining/Extruding
MAE277 G01 IMG 1763.jpg
15 Torx Screw (c) 5 Brass Machining/Extruding
MAE277 G01 IMG 1763.jpg
16 Platter Flange 1 Aluminum Machined
MAE277 G01 IMG 1779.jpg
17 Thick Spacer Ring 1 Aluminum Machined
MAE277 G01 IMG 1779.jpg
18 Platter 2 Aluminum with magnetic film Machined
MAE277 G01 IMG 1778.jpg
19 Thin Spacer Ring 1 Aluminum Machined
MAE277 G01 IMG 1779.jpg
20 Actuator Lock 1 Plastic, Steel Injection Molded
MAE277 G01 IMG 1786.jpg
21 Actuator Guide 1 Plastic Injection molded
MAE277 G01 IMG 1789.jpg
22 Philips Head Screw (g) 1 Brass Machining/Extruding
MAE277 G01 IMG 1763.jpg
23 Bottom Magnetic Bracket 1 Steel Machined
MAE277 G01 IMG 1791.jpg
24 Housing 1 Aluminum Cast/Machined
MAE277 G01 IMG 1792.jpg
24a Motor 1 Aluminum/Copper Varied
MAE277 G01 IMG 1792.jpg
24b Actuator Lock Post 1 Aluminum Machined
MAE277 G01 IMG 1792.jpg
25 Air Filter 1 Synthetic fiber Injection Molded
MAE277 G01 IMG 1778.jpg
26 Read/Write Head 3 Copper, Steel Shaping
MAE277 G01 IMG 1773.jpg


Additional Part Information:

  • Philips Head Screw (a):
    • Reason this material was chosen: Inexpensive
    • Additional Description: This is a standard round head Phillips screw.
    • Function: To fasten the housing cover to the housing.


  • Philips Head Screw (b):
    • Reason this material was chosen: Inexpensive
    • Additional Description: This is a standard round head Phillips screw with a built in washer. It has the same length and thread size as Philips Head Screw (a).
    • Reason for its appearance: There does not seem to be a reason this screw looks different than the other five screws. It is likely that this screw was an extra that was mixed in with the normal screws.
    • Function: To fasten the housing cover to the housing.


  • Philips Head Screw (c):
    • Reason this material was chosen: Inexpensive
    • Additional Description: This is a standard Phillips-head screw. It is copper in color.
    • Function: To fasten the data ribbon cover to the housing.


  • Data Ribbon Cover:
    • Reason this material was chosen: Inexpensive. Easy to shape. Strong enough to protect the data ribbon.
    • Additional Description: This is a sheet of steel bent to fit over the data ribbon.
    • Reason for its appearance: It must be wide enough to cover the data ribbon.
    • Function: To protect the data ribbon.


  • Logic Board:
    • Reason this material was chosen: These are the standard materials for a circuit board.
    • Function: To provide power to the electrical components. To control the electrical components. To process data.


  • Torx Screw (a):
    • Reason this material was chosen: Inexpensive
    • Function: To fasten the circuit board to the housing.


  • Housing Cover:
    • Reason this material was chosen: Lightweight, inexpensive, sturdy
    • Function: To protect the moving parts inside the housing.


  • Housing Cover Gasket:
    • Reason this material was chosen: It is able to create an air-tight seal
    • Additional Description: This is a gasket around the outer edge of the housing cover.
    • Reason for its appearance: To conform to the shape of the housing.
    • Function: To create an air-tight seal between the housing and the housing cover to regulate air pressure inside the hard drive during operation.


  • Philips Head Screw (d):
    • Reason this material was chosen: Inexpensive, non-magnetic
    • Additional Description: This is a standard flat head Phillips screw. It must be non-magnetic for ease of installation near a strong magnet.
    • Function: To fasten the top magnetic bracket and the actuator guide to the housing.


  • Philips Head Screw (e):
    • Reason this material was chosen: Inexpensive, non-magnetic
    • Additional Description: This is a standard flat head Phillips screw. It must be non-magnetic for ease of installation near a strong magnet. This is the same as Philips Head Screw (e) except shorter.
    • Function: To fasten the top magnetic bracket and the actuator guide to the housing.


  • Top Magnetic Bracket:
    • Reason this material was chosen: It can be used to make a permanent magnet
    • Additional Description: This is a steel bracket with a permanent magnet mounted on the bottom.
    • Reason for its appearance: It is arc-shaped to create a path for the actuator to move.
    • Function: To create a magnetic field to allow the actuator to move.


  • Philips Head Screw (f):
    • Reason this material was chosen: Inexpensive, non-magnetic
    • Additional Description: This is a standard round head Phillips screw. It must be non-magnetic for ease of installation near a strong magnet.
    • Function: To fasten the data ribbon to the housing.


  • Actuator Arm:
    • Reason this material was chosen: Lightweight
    • Additional Description: This is a four-pronged arm.
    • Reason for its appearance: It must be able to move the read heads between the platters.
    • Function: To move the read heads over the platter.


  • Actuator Coil:
    • Reason this material was chosen: Conductive
    • Additional Description: This is a coil of copper wire mounted in a plastic holder..
    • Reason for its appearance: It must be coiled in order to create a magnetic field when a current is applied.
    • Function: To move the actuator arm.


  • Data Ribbon:
    • Reason this material was chosen: Flexible, conductive
    • Additional Description: This is a ribbon containing small wires.
    • Reason for its appearance: It must be thin enough to bend with the motion of the actuator arm.
    • Function: To provide power to the actuator coil. To transfer data between the read heads and the logic board.


  • Actuator Bearing:
    • Reason this material was chosen: Lightweight
    • Function: To create a pivot point for the actuator arm.


  • Torx Screw (b):
    • Reason this material was chosen: Non-magnetic
    • Additional Description: This is a standard flat head torx screw.
    • Reason for its appearance: It is non-magnetic so it doesn’t interfere with the read and write operations.
    • Function: To fasten the platter flange to the motor.


  • Torx Screw (c):
    • Reason this material was chosen: Non-magnetic
    • Additional Description: This is a standard flat head torx screw. It must be non-magnetic for ease of installation near a strong magnet. This is exactly the same as screw (h) except it is black.
    • Reason for its appearance: There does not seem to be any reason this screw is black.
    • Function: To fasten the platter flange to the motor.


  • Platter Flange:
    • Reason this material was chosen: Lightweight
    • Reason for its appearance: It must fit on top of the motor.
    • Function: To hold the spacers and platters on the motor.


  • Thick Spacer Ring:
    • Reason this material was chosen: Lightweight
    • Reason for its appearance: Must fit around the motor.
    • Function: To maintain the height of the platters.


  • Thin Spacer Ring:
    • Reason this material was chosen: Lightweight
    • Additional Description: This is exactly the same as spacer (a) except thinner.
    • Reason for its appearance: Must fit around the motor.
    • Function: To maintain the height of the platters.


  • Platter:
    • Reason this material was chosen: Lightweight
    • Reason for its appearance: Must be very flat so the read heads can maintain the same distance.
    • Function: To store data.


  • Actuator Lock:
    • Reason this material was chosen: Lightweight, magnetic (steel ball)
    • Additional Description: This is a small arm with a pivot point in the center. On side has two prongs while the other has a wide surface with a metal ball implanted in it.
    • Reason for its appearance: The side with two prongs must fit between the platters. The other side must be wide enough to block the motion of the actuator arm when in the locked position. The metal ball is needed to be pulled by the magnetic field back into the locked position.
    • Function: To stop the actuator arm from moving until the platters are spinning at the correct speed to read and write data.


  • Actuator Guide:
    • Reason this material was chosen: Inexpensive, quiet
    • Additional Description: It is curved with a hook on both ends.
    • Reason for its appearance: The hooks must block the path of the actuator arm.
    • Function: To prevent the actuator arm from moving too far.


  • Philips Head Screw (g):
    • Reason this material was chosen: Non-magnetic
    • Additional Description: This is a standard flat head Phillips screw. It must be non-magnetic for ease of installation near a strong magnet. It is exactly the same as screw (f) except shorter.
    • Function: To fasten the bottom magnetic bracket to the housing.


  • Bottom Magnetic Bracket:
    • Reason this material was chosen: It can be used to make a permanent magnet
    • Additional Description: This is a steel bracket with a permanent magnet mounted on the top.
    • Reason for its appearance: It is arc-shaped to create a path for the actuator to move.
    • Function: To create a magnetic field to allow the actuator to move.


  • Air Filter:
    • Reason this material was chosen: Inexpensive
    • Function: To catch debris inside the hard drive.


  • Motor:
    • Reason this material was chosen: Lightweight
    • Additional Description: This is a brushless motor.
    • Function: To spin the platters.


  • Lock Arm Post:
    • Reason this material was chosen: Inexpensive
    • Additional Description: This is a small shaft attached to the housing.
    • Function: To create a pivot point for the lock arm.


  • Housing:
    • Reason this material was chosen: Lightweight, sturdy
    • Additional Description: This is the main housing for all the parts.
    • Reason for its appearance: Must provide room for each part.
    • Function: To mount each part.


  • Read/Write Head:
    • Reason this material was chosen: Lightweight, conductive
    • Additional Description: This a thin piece of metal at the end of the actuator arm.
    • Reason for its appearance: Must be thin enough to flex under the force of the air pressure from the spinning platters.
    • Function: To read and write data to and from the platters.

Improvements at component level:

  • Use a uniform type of screw head and diameter for all screws to reduce inventory and tooling requirements during assembly, with the exception of the very tiny screws used to fasten the platter flange onto the motor.
  • Remove the empty corner of the housing to save on materials and reduce cost.
  • Create a mechanism to manually unlock the actuator in case the actuator lock becomes stuck or there is not sufficient air pressure to release it.
  • Replace motor lead pins with more durable and easier to assemble plug and socket (see #4 on re-assembly).

CAD model:

  • 6 Components were selected that are assembled in sequence and a 3-D CAD model was developed. Below is a table listing these components with images rendered from the CAD model.

Part No. Name Qty. Image
24 Housing 1
MAE277 G01 CAD lowercase.jpg
24a Motor 1
MAE277 G01 CAD motor.jpg
19 Thin Spacer 1
MAE277 G01 CAD thinner spacer.jpg
18 Platter 2
MAE277 G01 CAD platter.jpg
17 Thick spacer 1
MAE277 G01 CAD thicker spacer.jpg
16 Platter Flange 1
MAE277 G01 CAD platter flange.jpg
  • For assembly of these components please refer to "Assembly Procedure" steps 6 through 11.

Assembly Procedure

  • For assembly of the hard-drive, the following steps were followed (P/N = part number);
  • 1. Starting with the bottom case, turned upside down as shown below.

Figure 1 – Picture of bottom case with all parts removed (except for 24a, 24b, & 24c)

MAE277 G01 IMG 1792.jpg
  • 2. Install P/N 23, bottom bracket onto bottom case (P/N 24) using (1) screw (P/N 23) and a screwdriver with a PH-0 screwdriver bit. Difficulty level is easy.

Figure 2 – Picture of bottom bracket installed

MAE277 G01 IMG 1788.jpg
  • 3. Install P/N 21, “Actuator guide” into bottom case (P/N 24). Two small pins at the bottom of the actuator guide insert into holes in the bottom case. No tools are required. Difficulty level is easy.

Figure 3 – Picture of bottom case with actuator guide installed

MAE277 G01 IMG 1787.jpg
  • 4. Install P/N 13, 13a, 13b, & 13c Actuator sub-assembly onto bottom case (P/N 24).
  • 5. Install P/N 20, “Lock arm” onto bottom case (P/N 24). The lock arm is slid onto the “Lock arm post”. No tools are required.
  • 6. Install P/N 18, “Platter” by lowering it onto the motor. The spacer ring will fit snugly onto the motor. No tools are required.
  • 7. Install P/N 19 “Spacer ring, thinner” by lowering it onto the motor. This will rest on top of P/N 18 from previous step. No tools are required.
  • 8. Install P/N 18 “Platter” by lowering it onto the motor. This will rest on top of part no. 19 from previous step. No tools are required.
  • 9. Install P/N 17 “Spacer ring, thicker” by lowering it onto the motor. This will rest on top of P/N 18 from previous step. No tools are required.
  • 10. Install P/N 16 “Platter flange” by lowering it onto the motor. Align screw holes in platter flange with screw holes in outboard face of motor.
  • Note: steps 4 through 10 have a difficulty level of easy.
  • 11. Install P/N’s. 14 and 15 (6) Screws through the platter flange (P/N 16) into threaded holes in outboard face of motor. Use a T6 “Torx” screw-driver bit. Tighten hand-tight (torque specification is not available). There was no indication of any significance of the (1) black colored screw versus the (5) that were silver in color. Difficulty level is easy.

Figure 4 – Picture of bottom case with actuator sub-assembly and platters installed

MAE277 G01 IMG 1784.jpg
  • 12. Install P/N 12, “Screw” through hole in data ribbon (P/N 13b) into bottom case (P/N 24) using a screwdriver with PH-0 screwdriver bit. This step can be difficult due to tight spacing constraints while trying to hold the data ribbon, aligning screw, and driving the screw.
  • 13. Install P/N 11, “Top bracket” onto assembly with P/N 9 & 10 using a screwdriver with a PH-0 screwdriver bit. Difficulty level is easy.

Figure 5 – Picture of top bracket installed

MAE277 G01 IMG 1777.jpg
  • 14. Install P/N 7, “Metal cover” onto assembly with P/N 1 & 2 “Screws” using a screwdriver with a PZ-1 Phillips screwdriver bit.
  • 15. Install P/N 5, “Logic board” onto underside of bottom case (P/N 24). Carefully align holes on the logic board to mating leads from the motor which protrude from the bottom case. No tools are required. Difficulty level is moderate; the motor leads will bend easily and must be re-aligned if not perfectly straight.
  • 16. Insert loose end of data ribbon (P/N 13b) into clip on logic board. Push in (2) tabs at either side of port on logic board to secure the data ribbon.

Figure 6 – Data ribbon attachment to logic board

MAE277 G01 IMG 1752.jpg
  • 17. Install P/N 4, “Bracket” to bottom case (P/N 24) with (2) screws (P/N 3) using a screwdriver with a PH-0 Phillips head screwdriver bit. Difficulty level is easy.

Figure 7 – Bracket (P/N 4) installed

  • This is the end of the assembly instructions.

After Assembly

Power / Data transfer:

  • The unit receives electrical power from the computer’s power supply via a cable which is attached to a series of pins. These pins are soldered to the hard drive’s logic board.
  • Information is transmitted to and from the rest of the computer through the data cable which also connects to a series of pins soldered onto the logic board. This information consists of requests for and returns of data which is stored on the hard drive.
  • Power is transferred through the logic board to two of the hard drive’s main components, the motor and the actuator arm.


Main Components:

  • Motor:
    • The motor receives power from the logic board via a series of pins which protrude from the bottom of the housing and plug into the bottom of the logic board.
    • The motor causes the platters to rotate at a constant speed, measured in rotations per minute. This speed varies for different hard drives and is increasing in newer models. A faster RPM rating leads to faster data retrieval.


  • Platters:
    • The platters are thin discs covered on both sides with an extremely thin coating of a magnetic film.
    • A read head is positioned on both sides of each platter and is used to read and write data to the platters. Both sides of each platter are used to store data thus maximizing the possible storage capacity.


  • Read heads:
    • The read heads are tiny components which can create a magnetic field due to electric current. The direction of this magnetic field can be changed constantly by altering the current flowing through it.
    • This magnetic field is used to arrange the tiny particles of the magnetic film on the platters into sections of positive or negative charge. This is how data is stored and later retrieved.
    • The read heads must not touch the surface of the platter while it is in motion or irreparable damage to the magnetic film will occur. For this reason, when the platters are not in motion the read heads rest on a portion of the platter near the center, where no data is stored.
    • When there is enough air circulating the actuator lock disengages and allows the actuator arm and consequently the read heads to move freely.
    • The read heads are attached to the tips of the actuator arm and hover very slightly above the surface of the platters on a cushion of air.
    • This cushion of air is created by the rotation of the platters themselves.


  • Actuator / Actuator Arm:
    • The purpose of the actuator is to move the read heads across the platters from the inner to outer edges.
    • The actuator arm receives both power and instructions for reading / writing from a ribbon which attaches to a clip on one end of the circuit board. This ribbon also provides power to the read heads on the tips of the arme.
    • The actuator arm rests on an axis and can rotate back and forth hundreds of times per second during read / write operations.
    • One end of the arm has a series of wires which rest in a magnetic field created by two permanent magnets. When current passes through these wires a force is created. By adjusting this current, the rotation of the arm about its axis and the movement of the read heads across the platters can be controlled very precisely.


Does the item operate the same as before?

  • After disassembly the item still does not operate. Even if it had worked originally, the disassembly process would certainly have destroyed the data on the drive if not the mechanical operation of the drive itself. A hard drive is a highly precise device and is not meant to be opened or disassembled.


Engineering models / analyses:

In the design process of a hard drive of this type, certain types of models could be used:

  • Physics / mathematical models: could be used in determining the amount of air flow that would be necessary to allow the read heads to hover over the platters. Also would be useful in determining how to properly control the movement of the actuator arm. Specifically, how much current should be passed through the wire and how strong the magnetic field should be.
  • CAD models: would be useful in determining the size, shape and positioning of all of the components as well as of the housing. CAD could also prove useful in determining physical interactions between some of the internal parts of the hard drive such as the actuator lock and arm.


Both the physics and CAD models would need to be quite precise and detailed. The hard drive is a precision instrument and rough estimates would likely lead to failures. The read heads grazing the platters and destroying data, would be one example of a failure that could be caused by inaccuracies in either the physics or CAD models.

Reflection:

  • The steps for reassembly of the hard drive were very nearly the reverse of the disassembly steps with one exception. During reassembly we had to put the arm back in place before the actuator lock.
  • The same sets of tools were used during reassembly, and we were able to reassemble the entire product.
  • During the disassembly process we made the decision not to attempt to remove the motor assembly from the housing as it is permanently built in and would require breaking the housing. Also, we decided not to separate the actuator arm into its individual components, namely the ribbon and a plastic clip. The ribbon was soldered onto the armature in a few spots and the plastic clip was glued on. Both cases would have caused permanent damage and wouldn’t have given any greater insight into the workings of the unit. Also, the logic board was not disassembled as it has hundreds of tiny components. Removal of these components would not have been reasonable and would not have provided any additional insight.



Improvements / Changes at product level:

If simply looking for a way to accomplish the same goal of data storage / retrieval in a more efficient fashion, we would suggest scrapping the hard disk drive system entirely in favor of solid state (flash) memory. Solid state memory has no moving parts, which enables it to be far more durable, consume less power and manipulate data much faster than any hard disk drive currently available. The downside of solid state memory is it's large cost compared to typical hard drives but this cost is dropping quickly.

We are unable to recommend any improvements or changes to the hard drive at the product level aside from those that are already taking place. Namely, faster read / write times and greater capacity. Changes to the shape, configuration and layout would not be reasonable for a hard drive manufacturer due to the fact that the drive must fit properly into a standard computer case. Also, the interfaces for the power and data cables must be a standard size and shape.


References

APA Style

Executive Summary and Introduction References:

1. Byard, F., Larry. A Brief History of the Hard Disk Drive. Retrieved on October 17, 2007

        <http://www.duxcw.com/digest/guides/hd/hd2.htm...>

2. Story from BBC NEWS. Factfile: Hard disk drive. Retrieved on October 18, 2007

         <http://news.bbc.co.uk/2/hi/technology/6677545.stm

3. Brain, Marshall. How hard disks work. Retrieved on November 14, 2007

         <http://www.howstuffworks.com/hard-disk.htm>

4. IDE/ATA Configuration and Cabling

          http://www.storagereview.com/guide2000/ref/hdd/if/ide/conf.html

5. IDE/ATA and SCSI Comparisons

          http://www.storagereview.com/guide2000/ref/hdd/if/compSummary.html

6. How hard drive works

          http://www.duxcw.com/digest/guides/hd/hd4.htm

7. Schroeder, B. and Gibson, G. A. 2007. Disk failures in the real world