Kevin Guiney

Machine Design


This week the Harvard team set out to build a machine. We met on Wed night to decide exactly what it was going to do.

We devide the work into 3 groups : Milling, Assembly, and Programming

I was in the milling group and Thursday moring  we got started.  On difference from when I milled my .stl file into wax was the now we are working with vectors. Each level of the part we'd have to have a unique trace for and figure out the depth.We mesured our material and then figured the rest out in v-carve

We did run into a problem when we forgot we had to mill from the outside. When doing form the inside we lost a significant amount of the material and had to redo it.

The other problem we had to solve was accounting for the sharp corners in our material pattern (right angles). The drill bit would make them rounded, so we had to account for that. What we decided to do was draw ractangles on top of our vectors that were slightly larger and do traces of those. Because our lsat trace would be to cut out the shape completely, that would make a right angle where we wanted it.

Lastly, we had to decide if we wanted to add tabs to the piece so it wouldn't pop out when doin gthe final cut out trace. None of us really like tabs, and these pieces alread had holes that we drilled, so we paused right befor the final trace and put screws through our precut holes to hold down the board. Worked great.

As a final step, Rob taught me a new skill of tapping. This is to add screw threads down a hole. In our project we will have two pieces that need to be joined. In one, we have made a hole larger that the screw we are using. The screw will just pass through this hole. The second one is a little smaller than the screw. This is the one will will tap, so the screw can screw into it and hold the two pieces together tightly.

On the back of our bags of screws there will be 2 numbers. (we used the Line 7 bag of screws)

M5- means the screw is 5 millimeters wide

18- means how many threads are on a screw.

We got the tapping device, which sort of looked like a smaller manual drill-press. We located the M5 tap (since the info on the back of our bag told us these were M5) and put that in the device.  You just line up the hole right underneath the bit and slowly start winding the bit clockwise around. The bit is narrower at the bottom, so it starts to go in, then gets a little tougher as it gets wider, then gets easy again as the threads are cut. Go in reverse to get the bit out and you are set.

I cleared off a shelf that our group could use and labeld all our pieces and noted the ones that we had tapped.

While not quick, our part moved through pretty smoothly and most of the work was done by the end of Friday. We still have to build a frame, which may happen Sunday or Monday. We set up a GroupMe account and have been good about spliting off into pairs to work on this. I look forward to the other groups bringing this all together and seeing the final machine.



Additional Bonus:

On Thursday we went to the CBA shop for a recitation on cutting and folding sheet metal. Unfortunatley it doesn't seem like we'll be able to use the shop, but it was cool equipment and process to see.