Group 14 - Computer Hard Drive - 2
For this project, we were assigned with the dissection of a hard drive. For the dissection, we had to disassemble, analyze, and then reassemble all of the components of the hard drive, maintaining detailed records throughout the process. During the analysis process, we noted several design and manufacturing changes that could be made. We were completely successful in accomplishing all of these tasks.
The hard drive is a Seagate Medalist hard drive. It has an IDE interface, has 4303 MB of capacity, and spins at 5400 RPM. Our group consists of Daniel Simich, the group leader, Evangeline Rauch, Emmanuel Albert, Nathan Getze, and Lindsey Garay. Daniel modeled the hard drive in Autodesk Inventor, Lindsey did the presentation and compiled the parts list and disassembly procedure, Nathan analyzed how the product worked and all of the engineering models that could have been used, Emmanuel analyzed some design changes that could be achieved and also some manufacturing changes that could be made, and Evangeline helped with the disassembly and assembly process.
Before disassembly, Daniel took the hard drive home and installed it onto a computer. The hard drive spun up and data read/write was not tested. When the hard drive spun up, it emitted a high pitch squeal, probably due to its age/lack of use. We estimated that the hard drive had about 50 components. We believe the hard drive utilizes 5 different types of material.
How does the hard drive run
We believe that the hard drive uses an electric motor to spin the platters and a linear actuator to move the arm heads. The circuitry involved simply translates the data from the computer into information that the hard drive can use.
To simplify this page, we combined disassembly procedure, part table, and design changes into one table. Each part was taken off in the order that it is listed and any design change is listed next to the part.
|Part #||Part Name||Quantity||Purpose||Material and Reason for Choice of Material||Manufacturing Process||Tools Used for Removal||Ease of Removal (1-5, 1-easiest, 5-hardest)||Changes and/or Improvements||Reasons for the way it looks||CAD Model/Image|
|1||Screw||4||hold bracket in place||steel: durable, cheap||extrusion and machining||philips-head screwdriver||1|
|2||bracket/casing||1||cover, ventilation, easy attachment to computer||steel: durable, cheap||n/a||1||the overall shape of the hard drive conveniently fit into a computer|
|3||Screw||4||hold on first circuit board||steel: durable, cheap||extrusion and machining||torque wrench T8||2-difficult to find the right tool||Most likely this type of screw to prevent most people from taking it apart|
|4||circuit board||1||translate data from computer onto the hard drive||silicone||machining||n/a||1|
|5||anti-static material||1||prevent static from effecting the function of the hard drive||n/a||1||this was shaped to cover the entire inside of the hard drive|
|6||foil||1||hold cap on hard drive||aluminum||sheet metal forming||n/a||1||could be made reusable so that the hard drive could be reassembled without needing new material|
|7||hard drive cap||1||enclose hard drive||steel: durable, cheap||n/a||1|
|8||screw||1-in center||hold on mounting bracket||steel: durable, cheap||extrusion and machining||torque wrench||1|
|9||screw||1-on arm||hold on mounting bracket||steel: durable, cheap||extrusion and machining||torque wrench||1|
|10||Screw||2-on outside||hold on mounting bracket||steel: durable, cheap||extrusion and machining||torque wrench||1|
|11||mounting bracket||1||n/a||1||The cutouts in the plate are to minimize metal used and weight. They also are the exact depth needed to have proper clearance on all of the moving parts.|
|12||screw||1||hold on power and data provider||steel: durable, cheap||extrusion and machining||torque wrench||1|
|13||power and data provider||1||provide data (still attached by strip)||n/a||1|
|screw||1||arm base||steel: durable, cheap||extrusion and machining||torque wrench||1|
|14||bolts||2||hold on arm bracket||steel: durable, cheap||extrusion||1/4 wrench||1|
|15||arm bracket turn limiter||1||guide the movement of the arm||plastic||injection molding||n/a||1|
|16||screws||4||hold on palter||steel: durable, cheap||extrusion and machining||torque wrench||1|
|17||top of platter piece||1||hold on all of the platers and separators||steel: durable, cheap||metal casting||n/a||1|
|18||plater #1||1||hold the recorded data||aluminum||metal casting||n/a||1 to remove - 2 to reassemble|
|19||separator bracket||1||hold the platters separate to they can be accessed by the arms||steel: durable, cheap||metal casting||n/a||1||decreasing the space in between the platters could allow for more platters|
|20||plater #2||1||hold the recorded data||aluminum||metal casting||n/a||1 to remove - 2 to reassemble|
|21||separator bracket||1||hold the platters separate to they can be accessed by the arms||steel: durable, cheap||metal casting||n/a||1|
|22||arm bracket and arm||1||hold writing arm in place||steel: durable, cheap||metal casting||n/a||1|
|23||plater #3||1||hold the recorded data||aluminum||metal casting||n/a||1 to remove - 2 to reassemble|
|24||separator bracket||1||hold the platters separate to they can be accessed by the arms||steel: durable, cheap||metal casting||n/a||1|
|25||plater #4||1||hold the recorded data||aluminum||metal casting||n/a||1 to remove - 2 to reassemble||an increase in platters could be beneficial if it was compensated by a higher-speed spindle motor|
|26||motor screws||3||hold the motor in place||steel: durable, cheap||extrusion and machining||torque wrench||1|
|27||spindle motor||1||turns the platters||steel: durable, cheap||1||increased speed could allow for more platters but may also cause more heat and vibration|
|28||teeth screw||1||steel: durable, cheap||extrusion and machining||torque wrench||1|
Assembly was the exact opposite of the disassembly process. All the tools used were exactly the same. During assembly, we did not place parts 28 and 29 on initially so we needed to re-disassemble all that we had done, which luckily was minimal. Also during assembly, one of the arms' top reader was accidentally bent up to ~45° angle.
After assembly, the hard drive was not tested for functionality. This was due to the fact that the arm piece was bent up. For fear that the arm might start to break apart during spin up, the hard drive was not tested.
Clearly explain how your product works now that you have seen its component structure. Does your product run the same as it did before you disassembled it?
One of the first pieces that comes off while dissecting a hard drive is the logic board. This holds the electronics of the hard drive. This is what basically runs the hard drive by controlling the read/write arms and the motor that spins the platters. Once the electronics board is removed, the whole hard drive can be seen. The part that actually stores the data and information in a hard drive is called the platter. There can be multiple platters in a hard drive allowing it to store more data. For every platter, two read/write heads are needed for maximum memory because each platter is double sided. The read/write heads are usually controlled by a high speed linear motor which allows for fast and precise movement along the platters. That actual storage of data on a platter is done on a circular system. Each platter is broken up into multiple sectors and tracks. One track is made up of two concentric circles and this pattern is continued from the outer ring to the inner ring of the platter. These tracks are than broken up into wedge shaped sectors. This system allows for a quick and precise way for the CPU to store data and also find stored data. The downside to dissecting a hard drive is that it will now run properly once it is taken apart. This is due to the magnetic parts that are used for the reading and writing of data.
Explain how analyses could be used to design and test your product (or some of its components). What type of basic engineering models could be used? Could you use estimates or would you need very precise models?
The use of mathematical models while designing a hard drive would help the process a little more than the other type of models. There are no real restrictions that need to be taken into account while designing a product like a hard drive and this allows the designers to be able to use rough estimates. The only two constraints that an engineer must follow during the design stage are to attempt to make the product so that it conserves desk space and the casing of the hard drive must be big enough to hold all of the parts. This is why most external hard drives typically are in the shape of a rectangle because it can have a smaller width while still being able to hold the electronics. A graphical model should also be used because the scaled drawings and CAD drawings for a hard drive allow engineers to effectively manufacture a product that has a smaller casing that does not waste space. Estimates could not be used due to the highly precise nature of the hard drive.
What could the manufacturer do to optimize the design, manufacturing process, maintenance, and disposal?
Changes in design were covered in the part list.
Additions to the design could be:
- An encrypting chip to provide on-board data encryption.
- Use of flash memory for the cache instead of a designated zone on the platters.
Design simplifications could be:
- Use flash memory instead of platters and an arm. This also speeds up the read/write/seek time, while escalating the cost.
- Use Phillips screws instead of Torx screws.
- The platters should be made of non-corrosive material so that they do not get damaged when touched. Some other material can be used to manufacture these platters so that they do not get damaged by humidity thus increasing the re-usability of these platters. And it also removes the cost of manufacturing dehumidifier bags that are made specifically for these platters.
- The hard drive uses a contact start-stop system for the read-write head which basically parks the head onto a specific spot on the platter when the power is turned off. Instead of that a Load-Unload system can be used where the head is kept on a special ramp outside of the platter when the power is turned off, thereby reducing the risk of the head touching the platter and damaging it.
- The manufacturer used screws that used non-standard screw heads to help minimize the risk of people opening the hard drive and damaging the innards.
- This makes maintenance difficult. To alleviate this difficulty, the manufacturer should use standardized heads such as Phillips head screws.
Disposal of the hard drive is difficult. If sensitive information is on the hard drive, the user wants to make sure that the data can not be accessed. This is typically done by:
- Drilling a hole in the platter (Note: This permanently damages the hard drive.)
- Passing a very high-powered magnet over the hard drive's surface.
- Using a professional program that wipes data off of the hard drive permanently.
Once data removal is accomplished, the hard drive can not be simply thrown into the garbage. It should be taken to a recycling center or electronic parts drive.
To help alleviate some of the issues involved, the manufacturer could:
- Provide a service that allows consumers to send the hard drive in for proper disposal.
- Use components that can be thrown away.
In conclusion, the disassembly and assembly of the hard drive was successful. Even though the product was not tested after assembly, if the arm was not bent up, the team is confident that the hard drive would still work.
Brian, M (2000). HowStuffWorks "How Hard Disks Work". Retrieved December 4, 2008, from http://computer.howstuffworks.com/hard-disk.htm