8. Computer controlled machining¶
Assignments for the Week:¶
Group Assignment:
- Complete your lab’s safety training
- Test runout, alignmnet, speeds, feeds and toolpaths for your machine
- Document your work to the group work page and reflect on your individual page what you learned
To view our group work for this week, please click here
Individual Assignment:
Make (design, mill, assemble) something big
Design Something Big¶
What a fun week to experiment and explore. I know we have the freedom to try new things each week to let our personalities shine, but this week of design work definintely made it a little easier. The part that was not easy was all of the prep to actually mill out the design.
I had some very brief experience with the Alpha Shopbot during Spring of 2021 when I stepped in to cover an engineering class. During this time, we had the students create some beautiful custom cutting boards for their final projects. I was able to use the Shopbot to help them cut profiles and pockets for their boards. Although we worked on the project boards for a few weeks, the time spent on the Shopbot was still limited.
One thing I did have working for me is that when it came time to start with the Shopbot again, I wasn’t as nervous because I remember seeing the stuff from last year. We also have an extensive workflow for this machine, since there is so much to remember.
To start working this week, our instructors gave us tutorials on how to use the machine. I think it is important to walk through what I learned in this tutorial first, as it helped us with our group work and finally cutting my final design. So, for my first personal walk-through, I followed the workflow in the same manner.
Designing¶
I found mannequin images in a Google search I like the design and shape of. I saved these to trace in Fusion360 so I would have proper proportions for sides for my design. I opened the svg in Fusion and began laying points in sketch mode. Once my points were all laid out, I used the spline tool to connect them and after selecting my last point, the interior turned blue indicating it was a closed loop! YAY!
However, no matter what I tried to do, I coudld not dimension or move or resize any part of my sketches. I had my instructors try, as well as a Charlie Horvath, and nothing shifted. (UPDATE: After bringing this issue up in a Saturday session a few weeks later, Rico from Kamakura told me to try projecting the sketch onto a parallel plane in order to get it to work. Charlie being our resident Fusion expert tried to help me with this as well, and we still were not able to get it to shift.)
Since I didn’t want to lose more time trying to figure out what was wrong with my Fusion design, I decided to move over to Cuttle to draw out my designs. The process was a little slow, as I am still trying to learn this software after hearing about it for the first time in a previous week.
I traced my image again, and was able to easily manipulate and adjust the size and dimensions. I added tabs and for the sake of getting it done quickly, I used the same profile for the side and the front views. In this manner, the dress form looks like she has a “uni-body” (so termed by Rico).
My original design for the base did not work very well. The two “legs” were not stable enough to hold up the top portion of the design. I sat with one of our lab instructors, Dr. Taylor, and looked for a new idea. One of our senior students had actually designed a side table that I liked the form of. So, I modified it so my dress form could sit on top and then re-created her base for my use.
Laser Test Cuts¶
Almost all projects in our lab are test cut on the laser first. And with good reason. We are able to check to make sure things fit, the designs are what we expect them to be and just the fact that after you print something you might just change your mind and can make adjustments without ruining expensive material.
Thank goodness I test cut! I hadn’t realized that when I changed my parameters in my design to cut on cardboard I accidentally changed a dimension I didn’t mean to. It showed up in the cardboard cut when my base pieces would not fit together. I had mistakingly reduced the size of the top of one of the cross-sections by half the size!
I was able to quickly catch it and I reprinted the base to make sure everything fit well and was working correctly.
Safety¶
I began with the setup for safety, the Shopbot machine and the software. The first step was to make sure we followed all safety procedures and protocols for the lab. Anyone using the Shopbot should start with the following:
- Put on eye and ear protection (goggles and over-the-ear headphones).
- Close to door to the workroom with the Shopbot. It is also important for everyone in the lab to know that when they view someone working on the machine through the window, they do not interrupt.
- Remove the key from the Shopbot machine (this is what starts the spindle).
ADD PICTURE OF SAFETY MATERIALS AND KEY REMOVED FROM MACHINE
Shopbot Setup¶
Once these safety procedures were complete, I moved to setting up the machine correctly. I used the workflow to perform the following tasks:
- Measure the thickness of the material that you plan to cut.
- Raise the Z-axis so the bit won’t drag on the table (no higher than 4 inches, so set Z height to 4)
- Use the proximity switch to set calibrate the X and Y origin (this will move the spindle to default (0,0))
- Calibrate Z AXIS on the table using the Z plate (the final number should be 1 if it correctly recognizes and measures the height)
- Raise Z AXIS 4 inches using the JZ, 4 command
- Attach material to the table using screws or other applicable fixturing (see here for our group work on fixturing)
- Using keyboard jog to the appropriate X and Y location to change the origin point. (J2 X,Y)
- Using keyboard to zero the appropriate X and Y Location.
Aspire Setup¶
Aspire File and Toolpath Setup¶
Setting up the file in Aspire took some time as well. It’s not a program that is fairly intuitive to me. I believe that’s mostly because I don’t have a lot of experience using it or other types of the same software.
One good point our instructors made is to remember that the 2D design work is done in the menu on the left and the toolpaths and 3D work is done on the right. Remembering these variations prevented some headaches when I was trying to search for items to fix. At least I knew where to start looking.
One of the things I liked best about Aspire is that I was able to use the software to add my t-bones to the press-fit corners in my design. It’s really nice to have this done directly in the software! Becuase I was able to complete this step in Aspire, it saved me a lot of time during the set up.
An issue that came up was the software kept telling me I had open vectors in my design. I didn’t understand this at first, but after talking to Dr. Taylor about it, he said that since I designed my structure in Cuttle, I must not have grouped or joined or merged my vectors together correctly. Or they weren’t actually touching and closed. In Aspire, you can select to close all open vectors that are touching, and this brought mine down to only 2 left open. But I could not get the 2 to close. I opened the file in Cuttle again and we found that the connector for one of my slots just missed the edge of the other end, so it was in fact open. I closed the joint, resaved the file and brought it back into Aspire. It still told me I had an open vector, but this time I was able to close it in Aspire.
I then adjusted any sizing issues I had and saved my Aspire file in order to set up the toolpath next.
One of the biggest issues this week was time management. Since there is only one Shopbot in the lab, we needed to be aware of not only how much time we would need to cut, but also setting up files and tying up the computer unnessarily. With 13 students in our lab doing Fab Academy right now, it was an interesting few days!
We have computers in the lab classroom connected to the rooms where our machines are. We use the computers to design and work on files, and once ready, they are transferred (via Google Drive) to the computers attached to the various machines. We teach the students that the computers on the machines are to be used to run the files, not for file work or modification. If your file is incorrect, you are to return to the classroom computers to adjust as needed. This way, another person can use the machine if ready!
So, we all used the computers in the classroom to set up our toolpaths. Unfortunately, it wasn’t until the end of a really long day that we realized our cut time on the machines was incorrect. Estimated cuts were taking several hours even for simple straight cut designs. We learned that Aspire uses very conservative numbers for their speeds/feeds and the computers in the classroom didn’t have the correct bits/speeds/feeds optimized the same way the machine computer did.
We were able to test our toolpaths on the classroom machines to see if everythign was placed correctly, but didn’t set them up to run or save toolpath files until we were on the machine computer.
In my test run, I laid out all of my pieces. I ran a profile cut from the toolpath selection. I made sure the depth of my cut was the same as the measurement of the piece of plywood I was using. Anything too big, and it would cut into the spoilboard of the machine; too small, and it wouldn’t have properly cut all the way through.
I added tabs as needed so the pieces that would be eventually cut out wouldn’t go flying and would stay in place. An important thing we learned during our group work, was selecting where the toolpath should run during a specific cut - inside, outside or on the line. For my tabs, I selected inside the line so that my tabs wouldn’t be bigger than I needed them to be, resulting in a press fit that would be too large. For everything else, I selected on the line.
Once that part was done, I ran a preview toolpath test to see how the 3D viewer would show my project. I was happy with the results and saved my final file.
Aircuts¶
After adding my name to the list to use the Shopbot, I realized I could separate my pieces into two files and use the desktop version to cut my parts. Overall, my design qualifies for the build big, but my individual parts are small enough to mill in the given space restrictions for the desktop version.
I checked with Mr. Dubick to make sure I didn’t have to use the Shopbot Alpha a second time (I used it with a group member while cutting the test cuts and setting up for our group work earlier in the week). He told me I was fine to use the desktop version to maximize lab time.
So, I reworked my files and separated out my pieces onto 2 boards I planned on using. Everything else for the setup of the files was the same as above.
I adhered my first board to the spoilboard using screws and set up my file and toolpaths on the new machine.
There were a few small nuances in setting up the machine or starting/stopping I needed to be aware of. For example, on the Alpha, you need to manually start the spindle before the machine will begin cutting. On the desktop, it’s all in one step after you load the file. I also had to set the frequency on the desktop version before I could begin. Once I knew where the emergency button was location, I began my first aircut.
The aircut looked good, so I thought I was ready to start. Right before I hit go, I just happened to glance at my screen and noticed I picked a 1/4” bit. I realized I never verified that was the bit in the machine! I removed the spindle key for safety, and lowered the dust brush to gain access to the collet. The bit that was in there was actually a 1/8”. I grabbed the tools needed to change it out, but the collet would not budge. Afraid it was overtightened and not wanting to ruin the collet, I reach out to Mr. Budikowski for help. He helped loosen the collect and I added the new bit. I tightened everything up, had him look at it and upon his approval I was good to go!
Final ShopBot Milling¶
I was really exicted to get to this point of figuring it all out. My board was set, so I inserted the key, turned on the vacuum and ventilation and started everything up. In the video below, you can see it all starting correctly and then all of a sudden the bit drags across the middle of my board. I stopped the machine and called Mr. B over for advice. He removed the collet and tightened up the bit a little more. He said it was slightly loose and that might have been what caused the issue. I was really lucky it didn’t go flying out of there!
I hit the resume button and the file finished cutting. Upon removal of the board, I noticed I had mistakingly cut my tabs into the spoilboard. I couldn’t understand why and then it hit me. Staring at me from the screen I realized I didn’t select the correct postion for the Z axis when zeroing it out. I had the default “from top of material” instead of “machine bed” selected. This was also the reason my bit ran into my material and not because of a loose collet like we originally thought.
Luckily, the part where the bit travelled did not affect the actual milled part of my design and the small portion it did hit, I was able to remove in post processing.
Post Processing¶
Post processing of my pieces was quick and easy because they were cut on 1/8” wood. I cleaned up the edges and did a quick sanding session on the flat sides to smooth them out. Once all of my pieces were sanded, I inserted the correct sides into each of the slots I created.
Next, I cleaned and set up the base in the same way. Once my base was set, I inserted the top mannequin into the base.
ADD POST PROCESSING AND COMPLETED PICS