Alfonso (amazing TA) trained us on how to use the ShopBot! We also learned that for our cut bit, the type (upcut or downcut) can be determined by rotating it clockwise and observing if it appears to spiral upward or downward.
As a group, we first tested the runout and found that the path width was smaller than expected, possibly due to wood expansion. We also cut a square block to test alignment.
There was a bit of difference for vertical and horizontal cut: our design was 3 in x 3 in, but we got 3.024 in x 3.015 in.
For our plywood material, we discovered that the thickness varies depending on the wood sheet.
We assumed our wood thickness will be 0.5 in, but the wood sheet we were using was around 0.463 in, which means that if we use 0.5 in in for our joint hole, it could be a bit loose.
For a perfect fit, we will need to take this into account when creating our joints.
We determined for our spindle to be 10,000 rpm and feed rate to be 150 in/min.
Individual Assignment
For my individual assignment, I decided to create a bedside table! I wanted to create a table that is exactly at the level of my bed so that I can put my laptop when watching a movie, or put my phone for charging.
Additionally, I wanted to have a stand on the bottom where I can put my books. I prefer minimal design with high functionallity, so I tried to use few components as possible for my bedside table design.
For the joints (to not any fasteners or glue), I explored various joints that could be used, such as dovetail and mortise & tendon.
I soon realized that the dovetail joint can't be cut with the machine but need to be cut with hand, and for mortise & tendon, it might be better to use when have thicker wood.
Therefore, I decided to continue with the dogbone joint we explored with during our group work.
Computer-Aided Design on Fusion360
As a lot of the process might be repeating so I didn't added here, but my initial cut was a failure (my joints weren't aligning well).
I realized it is very important to use constraints and have a more parametric design where I can adjust different joint hole sizes.
After the iteration, I first created a sketch where each of the holes will go, and then added the dogbone joint using coincident and center constraints.
Also, I initially used 0.90 as my joint, but it turned out to be too tight, so I increased the gap to 0.94 in (offset 0.02 on ech side) for my 0.65-0.8 in thickness wood.
I was thinking of increasing even more, but I wanted a tight fit, so I decided to sand a little bit afterwards instead.
My second iteration plan worked out perfectly!
Milling my pieces on ShopBot
Although my design was relatively simple and small, I encountered many challenges while milling my pieces on the ShopBot.
Some of the mistakes I made could have been dangerous, so it's helpful to be mindful of these to avoid wasting wood resources and save our expensive machine.
Special thanks to *Dan, Alfonso, Geoffrey, and Marcello*, who helped me troubleshoot and overcome these challenges!!
Here’s a list of reminders and tips to prevent any mistake:
Path planning: * For upcut 2D contour, make sure that you are selecting bottom closed chain.
* Also for path planning, start from inside (holes) to outside (block) when selecting them and select preserve order on Preserve Order tab. If not do this, the wood can fly away when creating the holes and potentially cause machine to break.
* For the tabs, I recommend 0.5 in instead of default 0.25 in for a more stable cut, and when manual selecting the place of the tabs, at least do 4 tabs per 10 inch.
* Lastly, just in case, take photo of all the x,y,z coordinates for each cut. Also, don't forget to zero z axis after changing to upcut bit! Also, when doing this, increase z axis high enough before the setting. Sometimes, when it's too low, it will give error and the program will stop.
* When ShopBot3 program is not responding, press option+command+esc for task manager and force quit.
Drilling: * Make sure to hold the drill vertically and push it in with both hands; otherwise, the drill may spin out of control or risk injuring your wrist.
Milling: * I had a very high pitch sound (machine crying), for one of the iteration, and it was due to upcut router bit being too low. I usually have hard time unfastening the bit so made it slightly loose, and this made bit to slide down a bit.
This will not only make your cut not clean but also break the machine. Check the height and fasten it strong!
* After pressing cut parts on ShopBot, read each pop-up message carefully! I forgot to press start button on spindle, and end up just pushing in the spindle like the third photo above.
Assembling: Sanding & Chiseling
I only knew about sanding, so I initially used sand paper and was going to sand the extruded part of the joint to fit in better, but Geoffrey saved me by suggesting to use chisel and hammer to take away some chips of wood and also use hammer for a tight fit.
Marcello also suggested to use a hand machine with sand paper for better edge finish.
Finished Woodwork
Below is the finished bedside table where I can put my laptop, phone, lamp, and books!
