Machining special pieces

[SeagullOne]

I'm considering giving NINA yet another refit--I feel this robot's getting closer to a design that is much more efficient. NINA will probably be on display at the local autism conference where she will demonstrate the idea of social machines (both robotic and animated computer characters for those cases on the autism spectrum with sensory issues such as with whirling servos).

Some of the pieces I'm considering machining for NINA will be nicer-looking. I'm through with rough-finished, pointed or misaligned edges and bends. I want NINA to look her best and have an efficient design.

Take the attached image of the bracket I need, for instance: I want it to be made of 1/8th inch of aluminum sheet metal with two bends and rounded corners. Now, I don't think a band saw will be efficient for a job like this, so I'm thinking of investing in another tool that can help me make cuts like these and others I have in mind for NINA's new refit. I'm just not sure what will do the job to cut out the shape. A dremel perhaps? Or maybe a lathe? I know nothing about lathes, but I'm willing to learn.

And now that I've downloaded eMachine shop, I can print out the pieces I need at actual size for better shape-accuracy on my part (I'd order these parts through eMachine shop, but its $18.50 a piece and I need 8 of them AND I have lots of other parts needed for this refit, plus I'm on a budget since I bought my new animation software. I'd rather just invest in new tools and do the job myself. That way I'll also be prepared for future machining savings and a new learning experience).

Anyone have any suggestions on what machine would suit this piece best? A dremel? A Lathe?

[waltr]

A lath turn the stock with a fixed tool to do the cutting. This is good for round pieces like bushings not for flat pieces.

You could use a bandsaw to rough out the shape then use a file or belt sander to get the finial sharp and smooth edges.

[SeagullOne]

Interesting. So I guess a lathe wouldn't work for this particular kind of piece.

I decided to take a look at Admin's tutorials and saw a very well made sensor bracket made of bronze with rounded edges and good bending. I wonder what tools he used and how he used them to make that bracket.

I'll consider using my band saw again, but it's been on the fritz lately. The blade keeps wanting to steer to the side and its quite tricky. I'm not sure why it's doing this. That, and the blade I'm using has gotten really dull. I can replace it, but for some reason Lowe's doesn't carry the blade in the store (they carry the wood blade though), and I have to special order it through them every time. Seems like the last one wore down quickly. Could it be because I'm cutting really thick metal? I tend to cut 1/8 inch thick sheet metal for NINA's parts.

Maybe I should also invest in a sand belt machine. That sounds like it would be good for finishing.

[waltr]

Could it be because I'm cutting really thick metal? I tend to cut 1/8 inch thick sheet metal for NINA's parts.

What is the blades tooth pitch?
The rule of thumb is that there should be 3-4 teeth in contact with the material being cut. So for 1/8 inch thick metal the the blade should have 24-32 teeth per inch.
Also, what speed are you running the blade at. Different materials like to have different cutting speeds.
There are many web sites with this information that can be found with Google. Here is one that has good info on using a band saw.
http://www.americanmachinetools.com/how_to_use_bandsaw.htm

[SeagullOne]

Again, interesting. Thank you, waltr for that information. I've bookmarked that page and it will be very useful for me in the future. Makes me what to look for better-suited blades.

And just so I understand correctly, a belt sander would be suitable for making those rounded corners, right? I'd file the corners down manually, but I think that might take too much time and would be very labor intensive--I might not get them all done in time for February. Plus, I think a machine like this would be an overall good investment.

[waltr]

Yes, rough the large curve with the band saw then smooth with the belt sander.
The small radiused corners can be easily done with a belt sander.

The type of belt sander I have in mind has the vertical belt and a small table that is horizontal.
Here is what one looks like:
http://www.google.com/products/catalog?q=belt+sander&oe=utf-8&rls=org.mozilla:en-US:official&client=firefox-a&um=1&ie=UTF-8&cid=7573470384363461512&ei=oLsOTdnmI4GClAeA8snMDA&sa=X&oi=product_catalog_result&ct=image&resnum=6&ved=0CGYQ8gIwBQ#
This one also has a vertical disk that also could do the radius you need. That is just an example I found, there are many others available and would be a great addition to your band saw.

[Gertlex]

Those bends look way too tight for 1/8" aluminum. (which I don't exactly consider to be sheet metal, but I'm no expert)

I'm assuming that piece is 3D anyways.

[waltr]

I see a 2D part, just a flat piece of metal since there isn't a second or third view.