7. Computer Controlled Machining¶

This week I worked on making a big furniture and getting to know how to use CNC Machine.

Weekly Objectives¶

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

Code Example¶

Group Assignment¶

In this week group assignment, I did the thickness gauge with Kathryn Wu using the small ShopBot. I also did the alignment for the CNC Machine. You can find our full group documentation here.

Aspire Features¶

Notes: This is specifically for Charlotte Latin Fab Lab CNC Machine Setup.

For Job Setup¶

Z-zero Position should be Machine Bed
Measure the Actual Material Size (IMPORTANT)
Remember which one is x-axis and which one is y-axis so you won’t cut it wrong!

Dogbones¶

We need to add dogbone fillets to the corners of the design because the bit isround and it cannot cut a perfect sharpe 90 degree angle.

Remember: The Radius of the Dogone should ALWAYS be half of the diameter of the bit.

If the dogbone feature does not work, first select the whole design and use Joint feature to make the whole design a closed shape and then dogbones would successfully be added.

For Toolpath Setup¶

Profile Toolpath VS Pocket Toolpath¶

Profile cuts along the line
Pocket shaded out the area of the shape
The outline you are cutting has to be closed shape

Tool Base¶

Only use the tools in the “Charlotte Latin ATC ShopBot-Current”.
Choose the right material (Since I was cutting plywood, I chose the “Hardwood”)

Setting Up Profile Toolpath¶

When setting the toolchain, be sure you see the pink outline!
There’s three options for Machine Vectors: Outside, Inside, and On. Choose the appropriate ones.

Just for reference: When I was cutting my ieces, I used Inside for the holes on my pieces; I used Outside for the outline.

Tabs: Never put tabs on the corners and be sure to put at least three tabs on each pieces.

Tabs is to hold the pieces so it won’t fly in the air and hit you after fully cut.

Ramps: Adding ramping let bits cut at an angle to gradually cut to the depth needed to lengthen the life span of the bit.

After Calculating the Toolpath, Aspire would automatically give you a preview for the toolpath.

Use Toolpath Summary to check the estimated time
Remember to Save the Toolpath once you are done. Since we are using Shopbot, the saved toolpath file type should be .sbp in inches

Setting up Pocket Toolpath¶

Cutting Depth

Cut Direction

Notes: Raster before Vector (don’t wanna a piece to move when rastering )

Cat House Designing¶

When I saw the individual assignment, I spent a long time trying to figure what I should do to meet the requirement of BIG (Miserable, especially when Mr.Dubick kept asking what you are making and keep telling you to settle down your ideas). I asked my mom, my classmates and even my friend in China for inspirations. At last, my mom suggested me to make a cat house for my lovely Cocoa Puff since she saw this cat house online.

Measuring my Cat¶

After decided to make a cat house, I first chose a place at home for me to put my cat house.

Then I started to measure the size of my cat since cats like a space that can barely fit them in.

Then I wrote down the dimensions of the cat house.

Next, I started my design in Fusion 360.

Design in Fusion 360¶

I had no idea how to design the tabs, so I went over Adam Stone’s documentation and took his design as a reference.

I useed the Parametric design in Fusion 360 since I needed to adjust the thickness and the tab width according to the thickness of my wood.

I first designed one of the floor pieces of my cat house using parameters.

Then I used Move/Copy feature to make all 4 floor pieces.

Then I exturded all them and started to design the side pieces.

I used Project feature to make sure all the tabs and holes are the same size on the side pieces.

Then I extruded the side pieces and put them all together using Move feature.

Before I wasn’t sure about the wood thickness, so I set the tab width as 1 inch. Then I realized my wood thickness was only 0.5 inches. So I changed the parameter. Unfortunately, the projected points did not change with the parameters. So I had to redo the sides of the cat house and after 2 hours struggling, I got this.

Then I added the circles and squares as the entrances on the cat house and I got my final design!

Importing the design into Aspire¶

Since Aspire is a 2D design software, I needed to lay all pieces on the same plane.

I referenced Mr.Budzichowski‘s documentation. I first converted all the parts from bodies to parts. Then I used the Arrange feature to lay the parts flat.

However, when I exported the file as .dwg file and imported the file into Aspire, it did not work.

I asked Dr.Taylor for help. After 30 minutes, we figured out that it has to be only 2D planes not 3D parts.

Then I folowed this video and figured out how to import parts with only 2D sketches. Then I exported it as .dwg file and imported it into Aspire.

Laser Cutting¶

In order to make sure my design can fit together, I did a model using cardboard by laser cutting. I scaled the pieces down so that the tab width is the thickness of the cardboard.

Toolpath¶

After doing laser cutting, I started to set up the toolpath for CNC machining.

I followed previous instructions of setting up toolpath and dogbones and saved the toolpath as .sbp in inches and I was ready to cut！

Notes: this is only part of my design. Since I am using another separate half sheet, I need to make two separate toolpaths.

Preparation for CNC¶

Adding Brads¶

After moving the whole wood sheet, with the help of Andrew Puky and Amalia Bordoloi, to the machine bed, I needed to use brads to secure the sheet. Cooper Cumbus helped me with this process.

Secure your material to the machine spoilboard using the composite nail gun.

Turn on the red air compressor and wait til the red tank is fully filled. (The sound will stop once it is full)
Attach the neon yellow air compressor hose to the nailer’s air inlet.

Load the brad nailer by opening the magazine by locating the magazine latch, release it, and slide the magazine open.
Place the appropriate length brad nails into the magazine with the pointed ends facing outwards.
Position the nailer by placing the safety tip flat against the work surface where you want the nail.
Fire the nail by squeezing the trigger while keeping the safety tip pressed against the surface.

We placed a few brads in the middle of the sheet to make it more secure. Then the wood is ready to be cut!

CNC Machining¶

Aircut¶

In order to reduce the risk of wasting a whole wood sheet, we are required to do an aircut first before the actual cutting.

Bring the spindle to the origin (JH) and set the Z-Height to 1 inch above the material. (Ex. JZ1.5 for 0.5”plywood).
Use the Zero-Z-Axis (Zz) command to zero the Z-axis for a new temporary origin above the material.
Run the file with no offset and it will run as an aircut. Be sure you engaged the spindle and pressed “Start” button when it asks you to.
Once the routine is complete, run the C3 command to rehome the machine and reset the Z-zero height to the machine bed.

Actual Cut¶

Workflow for the CNC Machine¶

Put on eye and ear protection.
Close the doors.
Run the C3 command to rehome the machine and set the Z-zero height to the machine bed.
Turn on the dust collector. Make sure the gate is open to allow air flow to reach the CNC spindle. Select FILE-LOAD
Load the appropriate file
Select no offset
Press enter
Engage the spindle using the key. Turn on the spindle by pressing the GREEN Button You should hear a “SOUND”
Press enter again to start cut
When the Cut is done, Turn off vacuum (which is so loud you shouldn’t forget)
Clean up after yourself

Video of CNC Machining¶

Me and my pieces!!!¶

Removing Tabs¶

I used the oscillator to remove all the tabs on my pieces.

Then I have all of my pieces ready to assemble (not quite).

Assembling Parts¶

Miserable After-cut Process – Sanding¶

Right after I got all of my pieces, I started to assemble it. However, the tabs did not want to fit together. The tabs are little too wide to fit in. So I started the sanding process the next day.

After seeing how many pieces I have, my teacher Mr. Dubick told me to recut. At first, I thought sanding is not a big deal and I did not want to waste meterials as my design cost one and a half wood sheets to recut. I started to use the oscillator as a sander to sand the tab as the tabs are too sall for the round sanders to fit in.

But when I finished sanding the first piece for 6 hours, my mind had shaken. I even cut out a test piece for the preparation of recutting. However, there were not enough sheets for me to cut because there are other people who had not cut yet. I had to got up early in the morning almost every day in the week to sand.

(Me and my homie Kathryn sanding in the morning)

After sanding for more than 10 hours, I finally finshed every sanding I needed and started to assemble my parts together.

Assembling the refined pieces¶

During the assembling process, I had to use the wooden hammer to let the piece get together.

Notes: Do NOT use metal hammer (would break the wood)

Sometimes, the tab are still too wide, but part of the tabs are already in the right places, so I had to use chipper to chip the excess away. Sometimes, the floor pieces are slanted. Then I had to force the piece to fit into the holes, wishing the wood won’t break. Luckily, fate felt like it had give me enough jokes and let the floor pieces fit perfectly well.

Picture of the half assembled cat house

When I finally finished assembling pieces all together, Mr.Budzichowski found out that I made one piece upside down so that there is a part sticking out.

I was frustrated that I almost said I don’t wanna redo thatpiece, However, my perfectionism forced me to redo the piece. Mr.Budzichowski helped me take off the piece. The tabs are so tight that the piece had some chips at last. We did not found out until we saw that the tabs could not fit tight enough. Mr.Budzichowski used the chipper to chip the piece away.

Then Mr.Bdzichowski taught me how to use the clamps to make the tabs fit tigher instead of just using hammers.

Then my cat house is finally done!!!! YAYYYYYY:)

Test pieces for recutting¶

When I decided to recut, Garret, the great mechanical engineer, suggested me to cut out a test piece. He also taught me how to modify my file without redesigning everything. He told me that there is a thing called Allowance Offset in the toolpath setup in Aspire.

Allowance Offset¶

If I put in positive number in the allowance offset, the tabs would be wider and the gap between the tabs are gonna be smaller.
If I put in negative number in the allowance offset, the tabs would be narrower and the gap between the tabs are gonna be bigger.

I designed a test cut and reduced the holes holding the tabs by 0.01 inches and made the tabs the same size.

When it came out, the tabs and the holes fit together perfectly!

Reflection of the Week¶

This week is very intnse and miserable. Most of the people fell behind because it was very time-consuming to use CNC machine to cut such a huge design. The after-cutting process was very very long and tedious because you need to stay in the wood working room and keep sanding until your piece finally fit into the holes on your other pieces. The design process was also frustrating since you had to adjust your deisgn several times before cutting. But when you finished everything, it was worth it. When I looked at the cat house at my house, I am still proud of myself for making such a cute and delicated thing for my cat.

File Download¶

You can download my files here.

Last update: March 25, 2025