Now that I’ve spent about 7 hours using the CNC machine I’m getting pretty comfortable with it. I’ve learned that the machine definitely is a little crooked because of the flooring, and that the wood I used was bent toward the center resulting in pieces that didn’t breakthrough. Although Mastercad is an ugly interface, I’m used to the work flow now, and I barely have to go back to my Vectorworks file to edit before milling. I definitely didn’t expect each piece to take about an hour to mill. And if I didn’t get sick over break, I would have had enough time to finish this before class. I drastically underestimated the time I would need on the CNC machine, and having everyone using it around the same time didn’t help.
First, I sketched out each piece on paper to visualize how much wood I’ll need.
Then I created 3 Vectorworks files, one for the back, one for the two sides, and one for the top and bottom. As you can see below, I didn’t add any pockets on the top and bottom of the side parts, which I realized was a mistake later.
In order to get the dimensions right, I made a tiny model out of paper with the measurements to see how the parts connected.
Once I got all my measurements in order I went to Mastercad and started with the pockets for each file and then added contouring. Because I used a single rabbit joint, I set the pockets to be half of the width of the plywood which was .725, so my pockets were set to .363 (that’s with .5 added tolerance). I also double checked that the settings were on Absolute.
My plywood was cut to about the size of the bed (4 x 4) and screwed into place with 5 screws.
I realized there was a slight bend in the middle of the wood. Unfortunately, no screws could fix this issue.
I loaded the “back” piece and after pressing start I realized that I didn’t zero the mill far enough to the left on the X axis. The mill went off the side of the wood, so I loaded the side pieces and re-purposed that piece of plywood for those two parts.
Once the side pieces finished I started milling the top and bottom parts. Something strange happened during this process. The piece of plywood was also bent in the middle and this caused the mill to miss the middle of the pocket during the first couple of runs.
This surprised me because half way through the process, it started milling the middle in what seemed like an even line all the way from one side to the other!
The finished top piece didn’t go all the way through on the other side, but looked pretty good from the front.
The bottom piece milled the same way the top did, leaving out the middle until creating a heavy line midway through the process.
The last piece I milled was the back. I made sure to zero the machine all almost all the way to the left on the X axis. To my dismay, and because of the wood being bent in the middle, the CNC started milling the tab in the middle upper portion of the wood and scraped the middle of it on it’s way over there. I stopped the process and started again, zeroing the Z axis a little higher, but that wasn’t enough either and I ended up with two marks in the middle of my nice piece of wood.
Eventually, I had to bring the Z axis much farther up so the bit could pass the middle bent section without hitting it. That resulted in my entire piece not breaking through to the other side.
I had to do something about the fact that most of my pieces didn’t breakthrough so I grabbed a hand tool to take off the edges of some of my pieces.
That left me with quite a bit of sanding to do. I made sure to not sand down the pockets like I did when I practiced making my joints.
The sanded pieces looked pretty good after a while, aside from the back piece which had the two track marks in it.
Then it was time to glue the pieces together. I started with the top and bottom and glued it to the back with 4 90 degree clamps.
Once I had both sides clamped there wasn’t much more I could do because the CNC was booked until the next day when I had 3 more hours in the evening to finish the shelves and two doors. That was around the time I got a text from NYU saying they would be closed the next day due to a snowstorm. I left the top, bottom, and back pieces for the snowday clamped together for a strong hold.