Прототипирование по Гураву Агарвал, MIT.

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Мы продолжаем знакомить вас с менторами проекта. Гурав Агарвал – исследователь в Массачусетском институте технологий, его статья посвящена раннему прототипированию. Участникам проекта она поможет сориентроваться в сфере компетенции ментора, а заодно и освежить свой английский. Вы также можете воспользоваться translate.google.com

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Development of a successful product involves various stages. The complete life cycle of product design and development broadly involves the following

  1. Planning
  2. Concept Development and System design
  3. Detailed Design
  4. Product Testing and Evaluation
  5. Production planning

The activity for the concept development can be further divided into doing (1) research, (2) making concept sketches, (3) product renderings, followed by (4) engineering drawings/layouts and (5) making models.

During the research phase, one generally considers about the potential market, existing products, its intended end user requirements, ergo dynamic features. It is at this this stage that some should be put some thought regarding the mechanical design, materials and the manufacturing process.

The next stage involves making concept sketches. This is relatively quick and iterative process that allows visualizing the earlier phase results and conceptualizing the functions of the product. This phase is generally requires pen and paper or 2D rendering software like AutoCad. For three 3-D product renderings, either clay or CAD software like Google Sketches or Solid Works can be used.

Till this stage, the engineering component is very limited in the product design and is mainly an artist’s visualization of the product. It is very necessary that before detailed engineering drawings be made (either for the mechanical components or for designing printed circuit boards for electronics), one should have the knowledge of the following:

Firstly, one should have the knowledge about the manufacturing processes. The manufacturing process can be divided into two brad categories (a) Conventional machining: It is a form of subtractive manufacturing process where tools like lathes, milling machines, drill presses are used along with sharp tools to physically remove the material to achieve the desired shape/ geometry or (b) Additive manufacturing is opposed to the subtractive manufacturing as the model is manufactured by adding material, usually layer upon layer.

Any functional prototype is made by combination of the above-mentioned two processes. It is necessary to evaluate all the options available as it impacts both the time and cost estimates. The first option requires a fully functional workshop, which is well equipped (e.g. http://hobbyshop.mit.edu/tools/) and a skilled machinist who can give you best time and cost estimates for finishing the job. For the additive machining, one can use online services offered by many vendors including:

1)   3D systems http://www.3dsystems.com/on-demand-3d-parts

2)   Redeye http://eu.redeyeondemand.com/Default.aspx

The benefit of additive machining process is that one can control the material type, color and finish of the final products. One of the best examples of the RP product is this clock at MIT media labs http://www.hyperexperience.com/?p=1842. While this is a very limited view of the manufacturing processes, a book on Materials and Processes in Manufacturing is recommended reading http://www.amazon.com/Materials-Processes-Manufacturing-Paul-DeGarmo/dp/0471033065

For the designing of the printed circuit boards, one can try the SDK kits offered by many vendors like http://www.expresspcb.com/expresspcbhtm/Costs.htm. A nice resource to know learn more about circuits and in general electronics is Electronics for you http://www.electronicsforu.com/electronicsforu/default.asp

Second most important aspect for designing the prototype is to know what components are actually available in the market. The process is similar to assembling a desktop, where one needs to know which parts are compatible, available, easily serviceable and within the desired budget. The mechanical component industry is a standardized and follows ASTM standards for material grades and sizes. While in each country there are many local hardware shops and markets. One of the most comprehensive resource to buy (or even compare) raw material stock, screws and fasteners, tools, industrial equipment workshop supplies are

1)   MSC Industrial Supply: www.mscdirect.com/

2)   McMaster Carr: http://www.mcmaster.com/

3)   Fischer Scientific: http://www.fishersci.com/ecomm/servlet/home?storeId=10652

 

At times one might need very small precision parts and one of the best sources for the same are the following:

 

1)   For gears and transmission belts: SDP Si www.sdp-si.com/

2)   For other precision parts: www.smallparts.com/

3)   Berg: http://www.wmberg.com/

 

For electronic components, the following have the best coverage in terms of part collection:

 

1)   Digi-Key Corp: www.digikey.com

2)   Mouser Electronics: www.mouser.com

 

For the pre assemble kits and other electronic devices:

1)   E-bay: www.ebay.com

2)   Sparkfun: www.sparkfun.com/

 

While selecting components one should take care for the units and dimensions (try to use either Metric or Imperial units) based on consultation with the machinist as well as the availability of the correct tools.

Once the components are almost selected and basic design and renderings in mind, it is time to do detailed design. While there are many softwares available in the market, my personal choice is Soildworks as it is intuitive to learn and use. It is important one should use correct projections http://en.wikipedia.org/wiki/Orthographic_projection for making the drawing and it is clearly mentioned on the paper drawings before giving to the machinist. It might sound stupid but engineers at times may make mistake or a machinist may over look this fact, thus leading to a costly mistake. A thought should also be given to repair/fix and service the product once it is assembled. It is also very important to embed some options into the design such that the design itself becomes flexible. This design flexibility will help in future testing and expansion of the product design itself. More about this subject of “Engineering Systems Analysis for Design“ can be found at http://ocw.mit.edu/courses/engineering-systems-division/esd-71-engineering-systems-analysis-for-design-fall-2008/

Once drawings are ready, and before ordering the raw materials, it is always nice to get them approved by the machinist if all the shapes/features can be machined. Once approved, order material in bulk and for small components, its advisable to order few pieces extra. In case of urgent need, overnight shipping is costly!!!

As you get the finished parts, it is sometimes nice idea to photograph them before assembling, as it will help in the documentation process that generally starts at the end. Before final assembly, it is always a good idea to fit them loosely as to see if all parts fit well.

In assembling parts, adhesives and adhesives tapes play an important role. One commonly used adhesive are fast-acting adhesives (commonly known as crazy glue) that dry in seconds. Caution should be exercised while using such adhesives as they irritate sensitive membranes in the eyes, nose, and throat. Further, they react with cotton and cotton based materials as they produce a lot of heat, which might cause burns. For deboning cured cyanoacrylate, Acetone, commonly found in nail polish removers might be used.

Coming back to adhesives, one of the best sources of adhesive tapes and similar products is 3M®. One should explore their automotive, manufacturing product lines. http://solutions.3m.com/wps/portal/3M/en_US/Products/ProdServ/Dir/Mfg-Ind/. One can even try their dentistry product range to mold and bond precision ceramics products.

Another important aspect of any prototyping place is to have a clean well-lit place to work upon. It is advisable not wear any loose clothes while working on any machining tools like lathes, wear proper shoes and try to protective gears including safety glasses, gloves and ear protection. While working with sharp blades care should be taken to properly handle them. In overall one should main 5S at the workplace. 5S is a workplace organization methodology based on seiri, seiton, seiso, seiketsu and shitsuke. These 5 Japanese words translate sorting, straightening, systematic cleaning, standardizing, and sustaining of the work place.

I hope these tips will help you in finding the right tools, technologies, raw stock and finished components to make your prototype quickly and efficiently within a reasonable cost.

Gaurav Agarwal, MIT researcher