Group 1 - Computer Hard Drive - 1

Executive Summary

This section is much like an abstract and summarizes the entire report

Introduction

This section should include an introduction of the product and a brief description of group members (i.e. who was responsible for which sections or tasks)

Before Disassembly Section

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

• 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

• 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

• 5. Remove logic board (P/N 5) from case. No tools are required.

 Figure 4 – Picture of logic board removed from assembly

• 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

• 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.

• 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

• 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/ (6) screws

• 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

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

 Figure 10 – Picture of ticker spacer removed

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

 Figure 11 – Picture of platter being removed

• 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

• 17. Remove P/N 20, “Lock arm”. No tools are required.

 Figure 13 – Picture of lock are removed

• 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

• 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.

• 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

Part No.	Name	Qty.	Material type	Mfgr process	Image
1	Philips Head Screw	5	Steel	Machining / Extruding	image here
2	Philips Head Screw	1	Steel	Machining / Extruding	image here
3	Philips Head Screw	2	Steel	Machining / Extruding	image here
4	Bracket	1	Steel	Stamped	image here
5	Logic board	1	Varied	Etching	image here
6	Torx Screw	3	Steel	Machining / Extruding	image here
7	Cover	1	Aluminum	Stamped	image here
8	Gasket	1	Foam	Injection molded	image here
9	Philips Head Screw	1	Brass	Machining / Extruding	image here
10	Philips Head Screw	1	Brass	Machining / Extruding	image here
11	Upper Magnet	1	Steel	Machined	image here
12	Philips Head Screw	1	Brass	Machining / Extruding	image here
13	Armature	1	Varied	Varied	image here
13a	?????????	1	Plastic / Copper	Varied	image here
13b	Data Ribbon	1	Plastic / Copper	Varied	image here
13c	Bearing	1	Aluminum	Machined	image here
14	Torx Screw	1	Brass	Machining / Extruding	image here
15	Torx Screw	5	Brass	Machining / Extruding	image here
16	Platter Flange	1	Aluminum	Machined	image here
17	Thick Spacer	1	Aluminum	Machined	image here
18	Platter	2	Aluminum w/ magnetic film	Machined	image here
19	Thin Spacer	1	Aluminum	Machined	image here
20	Locking Arm	1	Plastic	Molded	image here
21	Armature Guide	1	Plastic	Injection molded	image here
22	Philips Head Screw	1	Brass	Machining / Extruding	image here
23	Lower Magnet	1	Steel	Machined	image here
24	Housing	1	Aluminum	Cast / Machined	image here
24a	Motor	1	Aluminum / Copper	Varied	image here
24b	Lock Arm Post	1	Aluminum	Machined	image here
25	Air Filter	1	Synthetic fiber	???	image here

Assembly

• Document each step to reassemble the product
• How difficult was each assembly step?
• What types of tools were required to perform this step?

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 main circuit 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 circuit board. This information consists of requests for and returns of data which is stored on the hard drive.
• Power is transferred through the circuit board to two of the hard drive’s main components, the motor and the read head armature.

Main Components:

• Motor:
  • The motor receives power from the circuit board via a series of pins which protrude from the bottom of the housing and plug into the bottom of the circuit 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 a locking arm disengages and allows the armature and consequently the read heads to move freely.
  • The read heads are attached to the tips of the armature 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.

• Armature:
  • The purpose of the armature is to move the read heads across the platters from the inner to outer edges.
  • The armature 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 armature.
  • The armature rests on an axis and can rotate back and forth hundreds of times per second during read / write operations.
  • One end of the armature has a series of wires and rests 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 armature 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 armature. 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 locking arm and armature.

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 armature back in place before the locking arm.
• 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 armature 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 circuit 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

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