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I am working through the book Learning Robotics using Python, which is for Python programmers who want to learn some robotics. Chapter 2 shows you how to use LibreCAD to design the plates and poles that form the chassis of the turtlebot-like robot. For instance, the base plate looks like this:

enter image description here

Then, there is nothing more about it but suddenly in a later chapter there is a picture of the fully manufactured plates assembled into a chassis, and the author acts as if this should just be something we know how to do:

enter image description here

How did he do that? We have these CAD drawings, and suddenly there are these plates that were manufactured via some magical process the book never discusses, he never gives things like tolerances, the material that they are supposed to be made out of, etc., the kinds of things discussed here:

http://www.omwcorp.com/how-to-design-machined-parts.html

I know nothing about this stuff, in terms of how to go from CAD design specs to getting an actual part manufactured. What kinds of companies should I use, what is a reasonable price to expect, what is the process?

In general, how do I go from CAD design to manufactured item? Do I find a local machine shop that specializes in robotics, bring my CAD drawings, and work with them to try to build the parts?

I am totally a noob, I hope this isn't a question like this:

http://blog.stackoverflow.com/2010/11/qa-is-hard-lets-go-shopping/

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    $\begingroup$ There are an awfull lot of ways to do this. Wood or plastic (acrylic?) would be OK. You can re-draw the outline on a piece of wood, and saw it out? Or you could buy a robot chassis of eBay. Or let it print by a "3D printer hub". Maybe the book doesn't elaborate it, since it's not really the most important part of robotics, and it's highly based on ones preferences, materials, requirements and skills. $\endgroup$ – Paul May 31 '16 at 22:05
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    $\begingroup$ What are the dimensions anyway? $\endgroup$ – Paul May 31 '16 at 22:08
  • $\begingroup$ Paul that is a good point, and for beginning robotics something that could have been put in a single paragraph or two in the book. It spends a page giving url's of LibreCAD, for instance. More nuts 'n' bolts details about the part and how to make it would be worth their weight in gold (at least for a noob like me, coming as a software person) .. Incidentally, the part is 15 cm diameter. The book is literally building everything from scratch, so it would be nice to see more detail on these kinds of things, IMO. $\endgroup$ – neuronet Jun 1 '16 at 1:23
  • $\begingroup$ @Paul it is 15 cm in diameter. $\endgroup$ – neuronet Jun 27 '16 at 18:19
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I think this is a great question.

The two basic options are make it yourself or have someone else make it. EDIT: check the bottom for a third option...

Make it yourself

To make it yourself you need to choose a material and manufacturing process for the part, then acquire the material and skills needed. (Usually people select a process they know how to do already.)

For a hobby robot, often the exact material is not too important. For instance, for the part you show, you could make it from wood, plastic, or metal and it would work ok. Cardboard or corrugated plastic (for making posters) would work too and you could cut it with a hobby/xacto knife.

The way to go is to find a friend that likes to make things and then get their help to learn some making skills. You can also try learning from a website or book. (another website)

Have someone else make it

There are some companies that focus on the hobby market and you may find their services the easiest to use. Pololu and eMachineShop are two of many. I have never used them so you should read reviews online to determine if they will work for you.

There are lots of companies that specialize in fabricating parts using one process or another. You would have to learn a little bit about each process to choose whether it will work for any given part. If you are only making a few parts it is usually too expensive for a hobby project. eMachineShop is an easy way to get a general idea of what the cost of different processes because you can create your shape and then ask for quotes for different processes to make that shape. Laser cutting vs machining for the circular plate for instance.

If you can afford to use eMachineShop, it's definately worth checking out your local shops. The two factors that determine the cost are the quantity of parts and how "hungry" the shop is, meaning, how much business do they have going on right now. It's harder work to contact a lot of local shops, but if you do, you will probably be able to find one that will be cheaper than eMachineShop.

For simple shapes there are companies that have a catalog of basic designs for which you can change some dimensions or details when you order. Misumi is a good example. For basic shapes like shafts, brackets, bearing blocks and spacers, there is a good chance that you can get a semi-custom part cheaper than if you had a shop make it.

Option 3 - Adapt something that is close

There is no rule that you have to start from raw, unprocessed, material when making something. You can use something you find in a junk yard or at a store that is close to what you want and make small changes to it. Also, very few robots are made entirely from scratch. They all use components like bearings, motors, couplings, gears, and other things. There are many sources for these components. In the US, McMaster Carr is a good place to start, RS is an international company worth checking.

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  • $\begingroup$ Thanks for bringing up option of doing it myself. There is actually a makers' space near me where I could likely get help from a cadre of hobbyists. In terms of machine shops, people might want to balance the ease of access of national chain services like emachineshop with their downsides: they have fairly slow turnaround time, high cost, and impersonal customer service. The local shop you can just drop in and develop a personal relationship. this assumes you are lucky enough to have a local shop. When I finish, I'll edit this answer, or add a new one with details about what I did. $\endgroup$ – neuronet May 30 '16 at 13:36
  • $\begingroup$ Please do come back when you are done and edit this answer or add your own. I did not add much about shops (local or otherwise) because it's usually out of the price range of hobbiests; but I guess that depends on the shop and the location. $\endgroup$ – hauptmech May 31 '16 at 8:23
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    $\begingroup$ Probably closer to $200, cheaper if you get the right shop at the right time. $\endgroup$ – hauptmech May 31 '16 at 21:44
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    $\begingroup$ Why pay that much to print a part that polulu is already selling (pololu.com/product/250). $\endgroup$ – Paul May 31 '16 at 22:15
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    $\begingroup$ @Paul nobody in his right mind would print a part like that anyway. $\endgroup$ – Bending Unit 22 May 31 '16 at 23:04

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