Friday, April 23, 2010

Foundry "Robot" - part 1

I built a furnace/ foundry for casting in Aluminium, Brass, and Bronze. (more details on that later) - to manipulate the crucible, I looked at a number of options, but this.. is what I ended up building and using.
It's all home construction - tools used was welder (arc), grinder (grind, and cutoff discs), and miscellaneous hand tools.

The "robot" is not a real robot (powered with a form of control), but rather more a mechanical machine which I control. (yes I won't split hairs over semantics - compared to the robots at work, THIS doesn't count)

The distance between the operator, and the gripper is 3.0m (10'), and there is no lifting required, except to assemble and relocate. All "lifting" is done on a counterweight system, and my own body weight is used to my advantage.
Following over the remainder of this page, and the next pages will be photos of the robot, and text explanations of the mechanisms. All steel sizes are as much a reflection of my stockpile, rather than calculated engineering recommendations - in fact everything I write should be taken with the usual legal indemnities/ waivers applied. - in other words, if you don't know what you're doing, and aren't prepared to wear the consequences, don't use anything I've done help you qualify for a Darwin award.

Overview of the "robot" - open gripper facing camera.
The crucible is on the ground in the shot above - the pipe is 2 1/2" OD for the main beam.
Now some detail - working from the bottom up...
The spigot joint (Slew)...

The spigot joint is made of three lengths of pipe, two the same diameter, and the third a slip fit inside the first two. The bottom pipe, and the central (internal) pipe are welded together, with a washer across the top of the internal pipe. A steel mouse ball is placed on top of the washer, and the third pipe is dropped over the top of the whole lot. Inside the third pipe is another ppe with a wisher, so the bearing surfaces are the two washers, with the mouse ball between them. The three bits of pipe form a spigot joint for rigidity, and the ball/ washer bearing for friction reduction. The legs on my robot fold up, but that's a personal choice.

The top joint is complex - please bear with me.
On the top is a "sleeve" joint, complete with bearing shells (made from pipe halves), to provide a rotational, and sliding joint. The photo below show the bearing opened on the LHS and the upper bearing shell moved to the left. Obviously the whole bearing assembly is greased up in use.

The shells are tightened via the wingnuts at the lower edge of the photo, and normally there is a dust cover over the entire sleeve joint.

The other major axis of movement is the tilt joint located under the sleeve joint. It's hard to photograph, but it's simply a short length of pipe mounted across the top of the spigot joint pipe, and a slip fit bar running inside the pipe, welded between two "cheek" pieces (shown as yellow in the photo below.

Part 2 will show more of the joint, and focus on the gripper

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