To Do List

Here is the list of items to be completed in the next week:

• Fabricate hammer arm
• Fabricate hammer head
• Fabricate hammer release plate
• Fabricate hammer release pin
• Fabricate frame
• Fabricate motor mounts (#2, #3)
• Groove hex stock
• Groove 1/4" aluminum axle
• Assemble hammer/lever jammer
• Assemble frame
• Final assembly of scoring arm
• Assemble misc. components
• Final assembly of robot

Updated Schedule

MS8 and Last Shipment

This week we finished the MS8, including our MCM and our CAD Model for the final bot. One of the errors in our MCM was that the rpm's were too low. They need to be near 1000 for our MCM to work effectively. If needed, we can always make a new nut with fewer threads per inch and buy a new threaded rod to help ramp up the linear speed.

Peter will be buying the last of the needed parts for our bot over the weekend. Hopefully they should arrive by Monday or Tuesday. This week is going to be busy and require a lot of machining.

Quick Update

After two hours at the shop today.

We managed drill holes on the L bracket for mounting the motors
and the coupling device is one step away from being completed.

Meeting deadlines

Nov 24th is the due date of our MS8. Right now we still have a lot to do before we can meet that deadline.

Below are some tasks that are yet to be done for our MCM and MS8.

- device to mount motors on.
- milling the key way for our shaft
-machining the two coupling device for our MCM
- Bill of materials of our entire bot
- CADing the full assembly
- Manufacturing plans for the rest of the robot
- Drill holes on the threaded rod.

Hopefully we will have enough time to be able to finish all this before the deadline.

Desiging the Coupling device for the MCM

After our motor lab, we had to now design the coupling device and how we will mount our motor on to our MCM.
Our MCM needs two motors, one to drive the leadscrew, and one to rotate the arm. Instead of using a flexible coupling device that we used in the motor lab, we decided to use something that is more efficient because of the nature of the leadscrew (<50% efficiency)


WE decided to use the 1/2" square stock Aluminum as the raw material for our coupling device. I designed it so that it will tolerate misalignment of the motor shaft and the lead screw, since it will be really hard for them to be totally alligned.

We decided to use the same coupling device for the other motor that will coupled to our MCM too, because making two similar parts means simpler machining for us too.

Doing this made me appreciate the details that one has to pay attention to when engineering something. A simple component such as the coupling device requires much thought, and the difference between a bad and a good design may be quite big. It may certainly affect the performance of the whole machine.

Milling a Square Hole

Sometimes you have to put a piece of tube through a plate. When the tube is round, there isn't any problem. You just need to drill a hole large enough to fit the tube. When the tube is square, however, you run in to problems.

See, mill bits and drill bits are round. This means that no matter how small a bit you use to mill out a square hole, the corner of that hole will always be rounded. However, there is a workaround.

How to mill a square hole:

1. Drill a hole (I usually use a 1/4" bit) at each of the four corners of the square
2. Drill a hole somewhere inside the square large enough to allow the mill bit through
3. Switch to whatever size mill bit you think you need
4. Mill from the hole in the center of the square to one of the edges of the square you want.
5. Continue milling around the edges of the square

If done correctly, this method will create a hole with straight edges but no real corners. Congratulations, you can now fit your piece of square tube in the hole without having to worry about filing the corners square.

Manufacturing parts of the MCM

This week, we continued machining different parts for our Most Critical Module.
We planned to manufacture the cube inside the inner scoring arm, so that the arm can be attached to the thread and extend down as the motor turns the thread.

What we learned is to always expected some modifications to our original design. It took us four separate tries to successfully finish making this part. When the initial cut has been made from steel square stock, we found out another material that could be used as our inner scoring arm. Instead of using the Aluminum square stock with 1/8" thick walls, we decided to switch to a 1/16" wall because it will significantly reduce the weight of our arm. Thus to compromise to this change in design, we had to change the dimensions of the cube too.

We then made a few errors in filing down the cube to size, and also not aligning the drill bits of the mill correctly. On the thrid try, the hole was drilled 0.25" away from where it was supposed to be, and thus we had to re do the whole part.

In the end, We had to work extra hours in the shop just to make up for it. But we do realize that this kind of things happen during machining, so we did not dwell on it too much.

Choice of Suppliers

When it came to designing our scoring arm, we found that the materials in the kit just wouldn't cut it. Sure, the kit has the tubing for the inner arm. It has the stock to make a motor coupling and a custom nut. It even has the longest screw I've ever seen, a 24 inch piece of steel that's perfect for driving the inner arm. The kit was missing one thing though: The 1.25" square tube we would need to create the outer arm.

When it came time to order the part, I knew exactly where I could find it:
McMaster-Carr.
For those of you who don't know, McMaster is the go-to place for just about anything an engineer could want. It has everything from fasteners to fire extinguishers, calipers to 100 foot long pieces of steel bar stock. In this case, however, we needed a piece of aluminum tubing that was 1.25"x1.25" with 1/8" walls. It just so happens that McMaster has a piece with those exact specifications. 6063 Aluminum Tube, 36" long. The order was placed on a Friday afternoon, and the material came in the following Monday.

So if you ever need a piece of material, any material, fast, just go to McMaster-Carr's website and place an order. Just be sure not to get caught up browsing through their 480,000 item catalog.