Materials & Machining, etc.

I'm wondering what you more advanced builders do to construct your bases. I built one out of 3/4" plywood over the summer and while its
okay, I'd like to build one out of clear acrylic or Lexan, or even . What kind of materials do you guys use, where do you buy them, and what special tools do you use?
Also, how do you design? After sketching my first design by hand and then building it, I have a clear idea of what I want the next one to look like. I have a little experience with CAD programs, though, so I don't know what are the good ones, which are cheap/free, etc. Also, where I should go to learn how to use a CAD program better.
PS. If you live in the Atlanta area, please tell me of specific resources in the area.
Thanks, Mark
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Material depends on the task at hand. Personally, I prefer plywood over acrylic or Lexan for medium sized robots. Acrylic is fine for smaller ones, Plywood is even fine for larger ones, with some aluminum here and there.
I use laser cutting services like Filener.com and Pololu.com.
Can't help you with good/cheap CAD.
Mike

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I've not done much, but I've seen what a lot of others have done, they'll be glad to tell you their sources. See the botlanta link below...

I learned the basics of Autocad (it's the good one, any extra learning curve is absolutely worth it) many years ago, but the cost in the thousands, and even "Autocad Lite" is several hundred dollars. After some research I found this Autocad-compatible Intellicad at http://www.cadopia.com - after DL'ing and using the 30-day trial version, I was hooked, and these guys squeezed $149 out of me. I haven't done much robotics (with cad or otherwise), I bought this for other things as well.

If you're not here every month, you're missing out:
http://www.botlanta.org

----- http://mindspring.com/~benbradley
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Well it depends on what you are building and what materials you have on hand, scrounged or bought, etc Imagination, experience and or creativity helps a lot too. I have used plastics from www.budgetrobotics.com and www.lynxmotion.com use, I also have their robots too. I am particularly fond of carbonfibre panels for construction too. But it does get expensive. RC model airplane grade plywood is particularly good The extra fine grains and layers make for good machining capabilties. using cyanoacrylic adhesives (superglue) on a drilled hole makes it easy to tap using taps and dies. I also use aluminum in building chassis too. I have used stainless steel, but this gets extemely expensive. Your local RC model bobby shops are a good source. www.onlinemetals.com is another good source. This is a great way to get precut panels too, they cut really straight lines and the same size panels match up well too. www.ebay.com is a good source. You eventually wind up getting, borrowing, or using a small lathe, small milling machine, drill press, hand drill, dremel tool, bandsaw, scrollsaw, grinder, cut-off tool, hack saw, X-acto knives, X-acto micro saws, taps and dies, etc. You also need a oscilloscope (a used one from Ebay can be very inexpensive), DMM, logic probe. You can also make yourself a RC servo tester, a h-bridge motor controller tester, a AC-DC regulated powersupply (a heavy duty power supply for testing motors and motor controllers and such is invaluable). Basically, it seems you just can't get enough tools, always more are needed. The really serious guys get into brazing, and welding too. Books books books, magazines, etc., always another one to get. :)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Earl Bollinger wrote:

grains
easy to

Am I understanding this correctly? You drill a hole in plywood, and line it with superglue and you can tap this to hold a machine screw or bolt? Can you expand on that line of thought a bit more? If that's the case, that's one of the most useful hints I've heard in a long time!
Thanks,
Kevin
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@glenevin.com writes:

(I'm not the person who made the original suggestion, but -- ) Not much expansion to be done -- the CA soaks into the wood a little ways, and sets. Then you can tap it. I've never measured the strength, but I'm sure it's as strong as threads in plastic. For that matter, lining the hole with CA makes a big difference to the strength of something held together with wood screws, too.
I don't know exactly how far in it soaks, so I wouldn't use it for something being held together with 1/4" screws or something, but for small hardware (certainly up to #6, probably bigger) it works great. Also adds a lot of strength to something held together with wood screws.
--
Joseph J. Pfeiffer, Jr., Ph.D. Phone -- (505) 646-1605
Department of Computer Science FAX -- (505) 646-1002
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Another hady tip for working with wood is to use sheet metal screws. Sounds silly, but the thread is deep, giving you nice bite.
I like "T nuts" for working with wood.
Remember, they used to build airplanes out of the stuff. There were even a WWII fighter called the Mosquito built out of wood.
Mike
writes:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Yup that is exactly what you do. The superglue sort of plasticizes the hole, making it harder than just the wood itself. After it has set, you can tap it with a tap. It is a old RC model airplane trick, it has been around since when they first came out with superglue. Some plywoods have a bit of a waxy relase agent on them from the manufacturing process, you may have to lightly sand the plywood to remove it before trying to superglue it. Another trick is to use baking soda with superglue to make fillets in the joints that are too big, or that has gaps. Baking soda makes superglue fire off instantly (watch your fingers it does get real hot too). Which is great as superglue doesn't fire off fast with some woods or plastics, but the baking soda serves as a catalyst and a filler. The baking soda also plastisizes up real nice and hard and can be sanded or even machined to some extent. But it is harder than the wood so be careful sanding it. A hole that has stripped out in wood can be filled with a little baking soda and superglue, then redrilled and tapped as well. Don't fill the hole up all the way, a bit of baking soda a bit of superglue, and bit of baking soda, and more superglue, and so on. Important, lightly oil the tap so that any uncured superglue doesn't glue itself to the tap in the hole your tapping. :) Of course some plastics don't glue well, like delrin, nylon, teflon, polyethelyne, there is too much oil in them (plastic actually comes from oil you know).
A long time ago when I was racing RC model airplanes, we used to build up three to five models in a week before the weekend race. I would quickly build the whole plane out of superglue, balsa and plywood, with maybe a little 5 minute epoxy around the firewall to fuelproof it. In racing crashes were fairly common, so having spares was important.
Another of my favorite glues is "GOOP", it works on all sorts of stuff, but it does take a while to cure. It has replaced the old RTV or silicon adhesives I used to use all the time. Of course it goes without saying the 5 minute epoxy is tops too.
Important buy "GOOP" at The Home Depot or Lowes, superglue and 5 minute epoxy at your local RC model hobby shop. Cyanoacylic or Superglue has a shelf life and the stuff you get in the stores is old and stale. The RC hobby shops sell fresher glues, in bigger bottles too for a much better price.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
[snip...snip...]

WRT CAD programs, a good choice today would be one of the IntelliCAD family. http://www.intellicad.org/default-net6.asp The core program is available from a lot of different vendors, each of whom has a greater or lesser amount of "value added" on top of the core app. I've been using CMS Intellicad http://www.intellicadms.com/ for several years and, overall, have been pretty happy with it.
In a nutshell, Intellicad gives you Autocad compatibility at a fraction of the cost.
--
Rich Webb Norfolk, VA

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Mark H wrote:
[snip]

How 'bout QCad (http://www.ribbonsoft.com ). It's $29 (if I remember right) and free if you run it under Linux and compile from source (!).
The demo version is available for download and runs for 10 minutes (so you can check it out before you buy).
I have no association -- just really happy that I purchased it.
They are also very generous with their licensing. The purchased license is good for both Linux and Windows.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
You may try to find an old copy of CADkey version 97 and up for your CAD work if you are going to model your bot in 3D solids. It is the most intuitive and easy to use and runs circles around even the very latest version of Autocad for 3D solids capability, features and editing. I use both. If you are only going to do 2D then Autocad is the way to go.
Dave

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I've bought a copy of Turbo Cad of ebay and I'm very happy with it. The version I've got is a bit older that the current one, I've got 8 and the newest is 10.5 or something. It's got 2D and 3D capabilities with decent rendering. If you want to buy the latest/greatest it'll set you back a couple of hundred but if you buy an older version of ebay you could get away under $50.
I was new to the hole designing bit and I was able to get my first design on screen after doing the tut that came with the package. Certainly worth it for me. Fick
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I've bought a copy of Turbo Cad of ebay and I'm very happy with it. The version I've got is a bit older that the current one, I've got 8 and the newest is 10.5 or something. It's got 2D and 3D capabilities with decent rendering. If you want to buy the latest/greatest it'll set you back a couple of hundred but if you buy an older version of ebay you could get away under $50.
I was new to the hole designing bit and I was able to get my first design on screen after doing the tut that came with the package. Certainly worth it for me. Fick
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.