Computer Controlled Machining¶

Group assignment

Complete your lab’s safety training
Test runout, alignment, fixturing, speeds, feeds, materials and toolpaths for your machine
Document your work to the group work page and reflect on your individual page what you learned

Individual project

Make (design+mill+assemble) something big

Learning outcomes

Demonstrate 2D design development for CNC milling production
Describe workflows for CNC milling production

Have you answered these questions?

Linked to the group assignment page
Documented how you designed your object (something big)
Documented how you made your CAM-toolpath
Documented how you made something BIG (setting up the machine, using fixings, testing joints, adjusting feeds and speeds, depth of cut etc.)
Described problems and how you fixed them
Included your design files and ‘hero shot’ of your final product

Time Management¶

You can access my timetable here.

Group Assignment¶

You can access the link to our group assignment here.

ShopBot PRS Standard CNC Specifications¶

The CNC machine at our lab is the ShopBot PRS.

Workspace: 2400mm x 1220mm
Speed: We used the speed of 10000 RPM to cut our design
Software: ShopBot Control Software for operation
Fixture: Cutting material is attached using clamps.
Setting origins: We use shopbot3 software to set the origins. Proximity sensors are used. For the z axis you have to manually set the origins through the use of zeroing.

Safety Measures¶

“look,listen and smell” during operations for smoke or strange smells!
Wear (PPE)personal protective equipments: protective goggles and ear defenders.
Never leave the equipment running unattended.
Keep hands, hair, and attire away from moving components.
Use suitable feed rates and spindle speeds for different materials.
Tie up long hair neatly.
Collet and tool bit for tightness.
Keep the emergency stop button within reach at all times.
Clean the work area and store the tools and bits safely.

Reflection¶

This week’s group assignment was very fun. We were able to learn so much about CNC machine and the fact that all of us got to make our own individual huge project was really cool! We also learned about the safety measurements needed while handling a CNC machine! Overall, it was a very fun week.

Individual Assignment¶

3D designing¶

For this week’s assignment, I wanted to make a study table for myself. I am using Fusion 360 to make it.

You can follow along with me here:

Let us set the parameters first.

Reasons behind the parameters

thickness(18mm): this is the thickness of the material which I will use to cut my table.

leg length(50mm) and leg width(50mm): these are the dimensions for the legs I will be designing for my table. The height will be the thickness of the material. The reason the 2 parameters are of the same value is because the height of the table I want happens to be the same as the width of the table top. Since I am creating a hole in the leg as you will use below, it doesn’t look like a square though.

length(100mm): this is the length of the table top.

width(leg_width): this is the width of the table top.

shelf_height(leg_length/4): the shelf height is how much I want the height of the shelf underneath my table top to be. I used that parameter because I wanted it to only 1/4 of the height of the whole table.

shelf_length(length + 2thickness): This is the length of the shelf underneath the table top which should be the length of the table top + 2 thickness because we also have to consider the thickness of the wood which will be present on both its side.

Designing in Fusion360

In a new design file, I started by making the legs of the table. I did so by creating a sketch of 2 rectangles(since I will only be making 2 legs for my table) with the help of my parameters that I defined earlier and extruding it. To make it fancier, I made holes in the rectangles extruded, with ‘spline’.

Create a sketch for the table top.

Extrude it by the parameter you defined for the thickness of your material.

Now, let’s create the joints(very IMPORTANT). I made a sketch of a rectangle using the dimensions ‘thickness x 80’. Then to multipy that, I chose ‘rectangular pattern’ under ‘create’.

NOTE: the width of the slot in the above picture is 15mm, when it should actually be 18mm(the thickness of the material I am using). I made sure to change it later on.

Now, select all the small rectangles you created, andx extrude it. Make sure to set the ‘operation’ to ‘cut’. Drag it so that it will be able to cut both legs at once.

Extend the table top using the sketch you drew earlier to fit the slots inside.

To make a small shelf inside the table, I created another sketch for another set of joints.

Here is how the top views looks like alone.

Continue making the joints for the shelf.

This is how it looks like now.

Dog bones¶

Image source

In Fusion 360, dog bones are fillets or relief cuts added to internal corners of a design to compensate for the round cutting path of a CNC machine.

I went through this tutorial. To download the zipped folder containing the files for Dog bone, tap this link and download it. Next, navigate to the downloaded folder and rename it ‘Dogbone’.

Inside Fusion 360, go to ‘Tools’ and click on ‘Add-Ins’, under that, select ‘Dogbone’, and enable ‘Run on Startup’.

Next, you can select the edges where you have to add the dogbones to. After selecting, tap on ‘dogbone’ under ‘Create’.

Set the Tool Diameter, which refers to the CNC end mill (cutting tool) you are using, to 6 mm. This should change according to the end mill you are using.

Press ‘OK’ and do the same with all the other 90 degrees edges facing inwards and you are done!

Next, create a sketch plane with the dimensions 1200mm X 2400mm because that is the dimensions of our CNC machine where the boards will be cut. Arrange all your compartments there.

Mistake!!

Wait!! It is actually not necesarry for the compartments to be arranged in that manner. It makes things even more confusing because if you are like me, you will end up being unable to select the compartment because you will be clicking on the sketch instead😔💔 Thank you to Mr. Anith for helping me out with that.

You can simply project each compartment by one. Press the keyboard shortcut ‘P’ for ‘project’ and select your component. Press ‘Ok’ once you are done.

A new sketch will be created. Export it.

Here is the final model of my table in Fusion 360.

Milling and Assembling¶

Generating toolpath¶

I am using the software VCarve. You can follow along with me here.

Open VCarve and set up the width and height.
Go to file> import> import vectors and select your dxf file.
To move your design, select your design and tap on the icon highlighted below.
Now, go to toolpath> profile toolpath.
Keep the start depth at 0 and the cut depth to the depth of your workpiece.
Go to ‘add taps to toolpath’> ‘Edit Tabs’ which will take you to ‘Toolpath tabs’. Increase the number of tabs according to your design. I made mine 4. Press ‘Add tabs’ and ‘Close’ once done. If the lines of each compartment are not recognized as one, select all the lines from one body go to edit> join vectors.
This is how it looks like after adding the tabs.
Press close.
Save toolpath.
Open Shopbot and import your toolpath file.

Setting origins¶

You can start cutting only after setting your x, y, and z origins.

Setting x and y origin

Bring the drill to the corner from where you want to start cutting using the arrow keys to move the spindle tip. Find and press the “Zero Axes” button. Check the boxes for X and Y to confirm you’re zeroing those axes, and then press Enter to confirm.

NOTE: we are setting the origin on top of the material.