7.Computer-Controlled-Machining
Assignments
group assignment
- do your lab's safety training
- test runout, alignment, fixturing, speeds, feeds, materials, and toolpaths for your machine
individual assignment
- make (design+mill+assemble) something big (~meter-scale)
- extra credit: don't use fasteners or glue
- extra credit: include curved surfaces
Research
steel wire link
Dr.Taylors google site
Throughout The Week
Group Work
This week for the CNC machine I tested the Run-Out along with Dylan Ferro to see how the bit fit on the desktop CNC machine.
group site
Design
For my Work this week I wanted to design a Tensegrity Table but make it actually a chair to support me. I started off by ordering a 1/8" 100 ft strand of steel wire to hold my thing up. Once I ordered that I started off in fusion 360 for parametric design. After messing around trying to find a design I wanted I finally found it then remade it into a parametric one.
Here are the parameters for my file.
Once I was done I used the parameters to scale it down to cardboard thick and about 1/10 the size. Here is an image of that.
Aspire
After getting the full design ready I had to send it as a DXF file into aspire and setting all the settings for the size of the shopbot and the thickness of the plywood I'm cutting as seen here.
Next I had to use the scissor tool to get rid of all the extra construction lines that transferred over.
Then I just had to go into all the tool path settings and change the tool to a 1/4 inch bit. I chose this size because a 1/2-inch bit was too big, but I also did not want to choose a 1/8-inch bit because it would take much longer than I would need to for the cut. The next setting I changed was passes. It originally said I had 8 with around .1 inches per pass, but I changed that to 5 passes with .15 inches per pass. This way the bit would still not get hurt by going too far down, but the cut time was shortened by 15 minutes making it 37 minutes total.
Another setting I had to change was tabs. You can see them here in this 3d model of my file. They are what's connecting my cut to the outside. This happens so that when it cuts the piece it does not get flung out of its spot by the spinning bit. Also, as you can see here the cuts I did cut fully through the board. This is called a profile cut and this is because I needed to fully separate these pieces from their stock.
Shop-Bot
Learning
Before We could even think about using the Shop-bot we had to learn all about and differences in bits, speed, feed, chips, and many other components that will decide how good our cut is. Our teacher Tom Dubick taught us all about how to set up a cut on the machine and the computer for the cut. While our teacher and global evaluator David Taylor taught us all about bits and the different settings in a cut. He taught us through a slide presentation that I have linked above. Then I got into cutting.
Cutting
After I was taught how to use the CNC machine by our teachers I then started to cut my design. To start things off I imported my design into aspire on the computer connected to the shopbot. I sent my design into Shopbot software and set a 3d offset on the z value so that I could make sure it was cutting where I wanted it to with an air cut above the board. Once I made sure my cut was in the right spot I then redid all that with no z-axis offset and hit enter on the computer to start the design. Then I hit start on the Shopbot to make the bit spin then hit ok to allow the design to start cutting. Ryan Kim another FAB ACADEMY watched my cut with me so that we could turn it off real quick if anything happened. Here are videos of me cutting.
Once I was done cutting I had to put my table together. I had to go into post-processing and sand everything down using a router. And once I was done with sanding from 120 grit to 240 grit I then started to put things together. Luckily it all fit, so I just had to slide and pit it in.
Once I hammered it fully in with a wooden mallet to get it really in there and then did the same things with the wedges to get everything locked in there.
Then I just had to do the same thing with the other side in place so that they would both be interlocked.
Then I started to put it together by putting hooks into the wood and lining the steel wire to make it very taught
Here are some pictures of my original way of connecting all the pieces with the wire.
But doing it this way made it very hard to adjust so my teacher Tom Dubick told me about turnbuckles and how I could use those. This way I could just turn the turnbuckles to tighten and loosen the wire instead of manually having to do it.
It was also around this point that I learned it would not be able to be a chair because it could not support my body weight. Because my friend and also fab academy student Griffin Orsinger used my table to get up putting his body weight on it and making it collapse immediately. This was because of the wire and screw not being able to hold him up, but I did test the table up to around 50 pounds that it can carry.
Once I got the turnbuckles I just had to re-cut the wire to the new correct size and then just hook the turnbuckles to the screws for the table to be done.
But after doing this I realized that I still had to crimp the wire so that it could not move, and I had to cut the tips of the legs of the table because they got in the way. So I cut the legs and then Sanded it to make it a clean cut and here is the final result.
Summary
This week I learned how to design files to be safely cut using the CNC machine / Shop-Bot. I also learned all about how a CNC machine works along with how the difference in bits, feeds, and speeds can cause the cut to change. And for anyone wanting to make this table too, I have some suggestions. Start by thinking about how to connect the turnbuckles to the table from the beginning so that it is not a bad connection and can support more weight. And don't add extra height to the legs only what you need, so the effect is better.