Wednesday, May 28, 2008

Soldering as an alternative to welding

I was just thinking about robot stuff to avoid doing my System Dynamics and Control assignment.

I've been doing a bit of soldering for an electronics assignment (which I nailed, by the way), and I realised that I am already quite handy with a soldering iron - so I decided to explore the advantages of using soldering as an alternative to welding.

  • Welding is generally stronger than soldering as a method of joining metals, however a large factor in determining the strength is the quality of the join. This means that a well done soldered joint might be stronger than a poorly done weld.
  • Soldering does not require bulky or expensive equipment - allowing us to quickly perform repairs at events and things.
  • Welding can sometimes warp a part or joint because of the extreme temperatures. This can also lead to stress concentration areas.
  • The solder used in electronics is a very soft and low strength type of solder. Other solders such as plumber's solder, aluminum solder and high tin solder are much stronger. This table contains a few types, and their strengths. A particularly attractive choice was a 90% tin solder with a tensile strength of 8000psi = 55MPa.
Anyway, I thought I'd just throw the idea out there. There is no point in using welding in places where extra strength is not required, so soldering might be a good option for certain parts.

Thursday, May 15, 2008

Workshop Initiation Reminder

Hey, for those of you still reading the blog, just a reminder that workshop initiation is next Friday 23 May.

Looks like we're going to be allowed to the student workshops after all.

Monday, May 12, 2008


After many setbacks and trips to the hardware store, I've finally managed to cut the stock steel tubing into pieces that we can use for our frame. One of the main purposes of this blog is to document our progress so that we don't make the same mistakes again. To that end, here is a quick summary of what I did do, didn't do and should have done.

With the exception of stone, metal is probably the most difficult common material to work with, and one of the hardest things that needed to be done was to cut the tube at a reasonable 45 degree angle. The tool I had to use was a small, hand-held 350mm circular saw.

The initial plan was to cut each piece from the next at alternating angles (diagram, top) to minimize the total number of cuts. I needed to figure out a way to clamp down the stock at a fixed angle with respect to the direction of cutting. I ended up using part of a phone book placed on the edge of a table to lift the saw up to the top of the tube. Then I taped the tube to the table at the correct angle with the part to be cut hanging over the edge. I could then run the saw along the edge of the table and cut a straight line through the overhanging part. Long lengths were hard to clamp in this way, so I ended up chopping the stock into sections first (diagram, bottom). A table saw would probably have been the best tool to use for this.

- Use the right type of blade: Initially, the only circular saw blades I had were designed for cutting wood. I made a test cut to see if I could use it, but it just skipped across the surface and shredded the walls - definitely not appropriate. To cut metal, use a fine toothed blade with suitably hard edges. For thick metal, you may even have to use an abrasive blade.

- Measure twice, etc: I used a pencil to mark the places I wanted to cut, but this was hard to see against the steel. I wrapped masking tape along the lines to make it more visible. I also did a quick double check just before I cut to avoid stupid mistakes (ie, cutting on the wrong side of the tape)

- Perform a test cut first: To see how the width of your blade will affect your finished product. I also tried to leave a little extra material on the ends since it would be easy to sand down the ends a bit instead of having to cut a whole new length if it was too short.

- Use a high rotation speed and a low cutting speed: This will minimize the wear on your tool, and result in a better finish. There is really no reason not to do this, unless you are in a huge hurry.

Sunday, May 4, 2008

Chassis Design

The frame for the chassis is going to be built from 16mm stainless steel tube. At present, it is simply a rectangle with inner dimensions of 300mmx400mm, but we will definitely extend it into a trapezoidal shape, and we can add reinforcing beams if necessary.

I stumbled upon this site while I was looking for metalworking circular saw blades. It has some good tips and info.

Check the comments for progress updates.