7. 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

Click here to group work.

For machine in our lab:

• Machine User Manual ResolvedIssues AdministatorGuide

From Group work, I learned that:

• The Big CNC machine in our lab is consists of three parts: control computer, machine tool, and air dust processor.

• We need to clean the machine tool before we use it. For fixturing - We need to fix the wooden board. As for how much the fixing clamp can clamp in, this will depend on the G-code file we cut and how big its working area is. The clamp should avoid the area processed by the file.
  

• We used an 8mm wood board milling cutter this time.Please check the cutter and lock it to avoid accidental injury during processing.
  

• For alignment, our technicians helped us set the processing origin in advance: the area where the entire wooden board is located is the first quadrant (x, y are both positive numbers); the origin (x=0, y=0) is at the lower left. Note that the cutter diameter is 8mm. During the calibration process, when the cutter is 4mm in the working area, and the line x=0, y=0 is found, we can have the workpiece coordinate origin.

• Because our machine does not support ‘automatic return to origin’, we need to delete the ‘automatic return to origin’ code in the G-code.

• For Speed modification:
  

For Machine in our lab:

• Press F8 to make the simulation CAM-path
• F9 - start cut
• F10 - pause
• F11 - stop

For working space:

• Plate size 2440 mm x 1220 mm;

• Workable area: 2400 mm x 1200 mm

Processing rules: We found that CNC machines can only process outer right angles, but not inner right angles. This is because the principle of processing cannot be avoided. Therefore, when designing, you should avoid designing internal right angles or drilling and cutting internal right angles.

Individual project - Make a Chair

I plan to make a stool/chair that will be convenient for people to pick and handle vegetables in daily life. I think the stool in the picture is still too high, so I decided to start designing my own furniture.

2D-Design via Fusion 360

Here I designed board 1 and board 2. Board 1 will be used as the backrest of the chair, and board 2 will be used as the base of the chair.

How to design the size and model a chair?

You can draw the unfolded picture first and estimate the appropriate size and angle.

Make a model of it and see if it needs to be modified.

Next, Start designing. (In my case, I am going to use decimals in my design, actually, you can choose any suitable proportions and bases for your design.)It’s easy to create Side view of a stool, to facilitate the definition of angles, auxiliary lines are used and constraints are added.

To facilitate future modifications, parametric design was used.

3D-Design

In order to make the structure symmetrical, I first extrude the board of one side.

Extrude - set Distance :

To extrude the left-leg:

Copy the left-leg and set the distance as 420mm far from the copied one. Now we got chair legs.

Next, select these 2 surfaces and extrude them to the same length.

Next, select these edges that you want to add fillet to:

My chair designed for trimming vegetables for cooking is finally finished!

To Export/Save the design file

I was told by the Instructor of Chaihuo that for Big CNC Machine and its’ corresponding software, .DXF file or .STEP file format are supported.

To Get .DXF file Format

Like Laser Cut, you can select the component and then click Create Sketch ,sketch file will be generated automaticlly under sketches directory.

You can rename the sketches file as you like.

Next, save the sketch file as .DXF file.

To Get .STEP File Format

Notice

After we finished Big CNC assigment later, we figured out that if you are using this software for milling, an .STEP File Format is strongly recommanded, as for these .DXF file Format , there will be a lot of break lines which you need to combine them one by one.

Preliminary experiment with laser cutting machine

To facilitate laser cutting, after I import the file into Xtool, I Zoom out the picture by lowering it 5.2 times.

This is the first trial (using initialize design file), it’s Ok if we look in this way.

but if we turn back, you can see the seat occupied most of the base.

The reason for this is that the grooves we see on the physical body are actually suspended and do not mesh together. Therefore, after the actual production, the position of the chair back will drop after meshing, forming the current effect.

And meanwhile, the base was at a rather slanted angle to the ground plane.

so I modified the dimensions and angles on the laser cutting machine software to get the second version, which I thought looked good and could be used for CNC cutting. So I measured the gap from the backrest to the base in this version and converted it to my Big CNC design drawing.

At the same time, I also adjusted the ratio of length1 to length2 to be close to 1:2

Here comes with my final version. Its proportions and load-bearing capacity look good.

Its proportions and load-bearing capacity look good.

Output the G-code

As we mentioned above, it’s suggested to use *.step file on Mastercam.

Our technician help us to generate G-code File.

G-code Generation and Tool path settings Summary:

1. It is best to make a dxf file, provided that there is no line break
2. After the file is input into the software, align the origin first
3. Set the tool, set the parameters, speed and number of layers, etc., as shown in the video
4. Click on your image to see if the direction of the tool is correct. If it is inward, it is inward cutting, and if it is outward, it is outward cutting. Here you can see if there is any line break
5. Then press the r key to generate the tool path

6. Confirm that there is no problem and click g1 to generate g-code

7. Generate the Toolpath Once all parameters are set, click OK to generate the toolpath. Mastercam will compute and display the toolpath on the screen.

8. Simulate the Toolpath To verify the toolpath, you can simulate the machining process. Go to the Verify tab. Click on Verify to open the simulation window. Run the simulation to check for any potential issues or collisions.
9. Post Process the Toolpath Once you are satisfied with the toolpath, generate the G-code for your CNC machine. Go to Machine Group. Click on Post Process. Select the appropriate post processor for your machine. Save the G-code file to your desired location.
10. Transfer the G-code to the CNC Machine Transfer the generated G-code to your CNC machine using the appropriate method (USB, network transfer, etc.). Load the G-code into your CNC machine’s controller and begin the machining process.

Milling via CNC machine

For Machine in our lab:

• Press F8 to make the simulation CAM-path
• F9 - start cut
• F10 - pause
• F11 - stop

The first board we made:

My project components:

Assembling the chair

Heroshot

Design File

Legs_x2 Base_x1 Backrest_x1