Week7. Computer Controlled Machining

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

1. Group Assignment My Part

• Safety training is extremely important this week because the CNC machine used for cutting furniture is highly dangerous.This week, we'll do the lab's safety training and test runout, alignment, fixturing, speeds, feeds, materials, and toolpaths for the machine.

Safety Training

Emergency Procedures:

• Train operators on emergency stop locations and usage. • Know first aid for burns, cuts, and other injuries. • Review fire evacuation routes and procedures regularly.

Machine Safety:

• Understand machine controls and their functions. • Don't bypass safety devices or guards. • Ensure the machine is grounded for welding.

Machine Setup

Test Runout and Alignment:

• Check for runout or misalignment of the spindle or cutting head with a dial indicator. • Make sure all axes move smoothly with no obstructions or strange noises. • Confirm the tool is perpendicular to the work surface for precise cutting.

Fixturing and Workholding:

• Use proper clamps or fixtures to hold the aluminum plate securely. • Support the workpiece well to reduce vibrations and movement during cutting or welding.

Material Preparation:

• Clean the aluminum plates to remove oils, dirt, and debris. • Check and remove burrs or sharp edges before processing.

Operational Procedures

Speeds and Feeds:

• Based on the aluminum type and thickness, determine the best cutting speeds and feeds. Aluminum needs higher speeds and lighter feeds. • Use manufacturer's guidelines or CNC software to set parameters.

Toolpaths:

• Design toolpaths to reduce tool wear and heat buildup. • Use climb milling for a better finish and tool life when cutting aluminum. • Check all paths in simulation software to avoid collisions and ensure efficient material removal.

Coolant and Lubrication:

• Use the right coolant or lubricant to reduce tool wear and prevent overheating. • Check and maintain coolant levels and system functionality regularly.

Machine Maintenance:

• Clean and lubricate moving parts regularly. • Inspect and replace tools before they wear out or get damaged. • Follow the manufacturer's recommendations for regular maintenance checks to ensure the machine's longevity and performance.

2. Individual Assigment

The assignment for this week is to make a piece of furniture using a large CNC machine. So, I want to make a small bookshelf for storing books.

Inspirtion and Preparation

01 I was inspired by the bookshelf online and decided to make one for myself

02 I carefully studied this picture, figured out how these wooden pieces were joined together, then conducted a simulation with waste cardboard and determined the dimensions.

The most difficult part are the bottom and finally it turns out it was slided into all the vertical borads.

Even it is a totally parper-board sheep, but it stands up!

3D Design using Fusion 360

Step 1 Decide Components Division

It will always be the most important step to make a 3D design with multiple parts: Decide how to divide your design into components.

The second most important thing is to design the parameters well.

Step 2 Start from the Vertial Body Part

    - The vertial body part will be on the YZ plane to define the base for the whole design, so it is the first component to start.

The second most important thing is to design the parameters well.

     - I drew a rectangle first and drew all the outlines with spine -> Control Point Spline, then deleted the rectangle lines.

Step 3 Second is the Font Body Part

     - Decide the offset plane first

     - Define the distance of the offset plane to original plane using parameter

     - Start to design the sketch

     - Important steps creating this sketch:

     - 1 Project is the vertical body.
       Because this part will be intesect with the veritcal body, so it needs to project the vertical body part to find the center position to start.

     - 2 Draw Circle and use spine-> Control Point Spline to draw the surrounding petal shapes.

     - 3 Make sure the interlocking parts are parallel

     - You can use the dot projected to decide the parallel starting point

     - For the rest of the legs, mostly I used the spine -> Control Point Spline again

     - The other two calves that need to be interlocked with the legs on the body. Just pay attention to the setting of the parameters.

Step 3 The Back Body Part

     - This part needs to set up the offset plane correctly and then just simple copy the body of the font part.

Step 4 The Bottom Part

     - The bottom needs to intersect with the all the other parts, so the offset plane setting is very important.

     - Calculate the offset value of the plane, it needs to be exactly the gap position of the vertical body part.

     - Construct the offset plane.

     - Sketch.

       The sketch of this part is very easy，needs to project the two body part, because It is necessary to determine that the bottom plate and the two vertical body parts exactly avoid creating sufficient notches for interlocking.

Change the parameter

Firstly, I set the gap for the parts of the board that need to be inserted and assembled to 15mm. Later, after measuring the thickness of the board at 18.60mm and consulting the master about the approximate kerf, I set this value to 18mm.

Laser Cut

1. For the laser cut parameters setting: 1.1 Firstly, I decided to use a board with a thickness of 5mm. Then, according to my previous kerf tool, it was more appropriate to set the actual thickness value for the insertion at 4.8mm. So, I calculated the ratio of 18mm to 4.8mm as 0.267. Then, when I opened the dxf file with a thickness value of 18mm, I performed a manual scale of 0.267 times to generate a new dxf and carried out laser cutting. 1.2 Before scale, the patten is huge. 1.3 Scale to 0.267 1.4 After Scale

Laser cut the pieces and assemble the sample

BIG CNC CUT

    1. Our big CNC machine

2. Export the step file and the master who taught us CNC combined all the furniture designs of everyone using software.

3 Generate the toolPath.

3.1 The toolpath could start at the default position. It's better to start from the smaller board. There's not much difference between forward and reverse rotation. 3.2 Then create the tool, an 8mm diameter tool. Set the tool parameters as follows: rotational speed 15000, feed rate 5000, plunge rate 500. Keep the cutting depth as default. Set the safety height to 50mm, the feed plunge position to 3.0, and the depth to -18. 3.3 Press "R" to view the tool path. If there's an incorrect tool direction, change its series direction. 3.4 Set the toolpath to cut multiple layers 3.5 Press "R" to check whether the tool path is correct and whether all lines are in the correct direction. Copy all the same configuration parameters and check whether the tool path for all three layers is correct. Then generate the G-code.

4. The Gcode is ready，now we are going to cut.

4.1 Fix the board on the machine tightly, it needs to be fixed very tight otherwise the board may shift positions.

4.2 Adjust the X and Y orgin

4.3 XYZ origins all set

4.4 Set the feed rate to be 5000 mm/min and the spindle speed to 24000 rpm

We are using synthetic wood boards with a thickness of 18mm. For this type of material, setting the feed rate to 5000 mm/min and spindle speed to 24000 rpm is based on several considerations. The 18mm thick synthetic wood board requires a suitable cutting speed to ensure a smooth and clean cut.This speed setting provides the necessary force and cutting action to efficiently process the material without causing excessive chipping or splintering. Additionally, this speed helps to maintain the quality and accuracy of the cut, ensuring that the final furniture components meet the design specifications. At the same time, it allows for a reasonable production rate, balancing the efficiency and cost-effectiveness of the manufacturing process.

5. Load the Gcode file

6. Press F8 to make the simulation path

7. Press F9 to cut!

8. Our First board!

. My part is cutting

Assemble

Part 1 Legs

When I tried to install the legs, the original size was supposed to fit perfectly.

So after piecing it together, the legs were not flat.

The reason is that the machine cannot cut right angles during the cutting process but can only cut at angled arcs.

So I decided to use a file to file the angled arcs into right angles

After few minutes，got the right angles

Now the legs can be perfectly fit.

Splice the bottom plate and the front and rear plates

Finally, splice the middle board.

Here is a group photo of all our furniture!