08. Computer-controlled machining

Computer-Controlled machining

Assignment: test runout, alignment, speeds, feeds, and toolpaths for your machine

Today we are working with a CNC. The first program we use is VCarve Pro

We fill first try to use styrofoam and cut a 3-centimeter layer from the top.

We enter the length and width of our block alt text

We choose a cut depth of 2 mm alt text

We should have the block that we created visible in 3D alt text

We can see the path the mill is going to take by clicking Reset Toolpath and Preview Toolpath alt text

When we are done, we have 2 files to save:

  • a .sbp file for the toolpath
  • a .crv file as a general save with all features

We are now ready to send the job to the milling program

Running the job

We will use Shopbot to do the milling

Stick base pane so it doesn’t fly off. alt text

Choose the good flute for the material we are going to mill and measure it alt text

We stick it inside the machine with 2 wrenches. We do not go too hard on then alt text

Choose rpm on the machine. It ranges 0-300, with 300 corresponding to 18,000 rpm. In our case we choose 167, which matches 10,000 rpm. alt text

We open the file with the program. alt text

We chose a z-zero at the top of the plane by clicking Move Tool. On our program, we have to click it twice.

alt text

We move the mill to the zero we want. alt text

When we are done, we click the Zero Axes alt text

When we are done, we click Start alt text

We heat up the machine by having it run for 10 minutes. This is done with Alt-C-5

The first run will be a dry run. We put the z axis higher than it should be. This way the machine is going to mill in the air so we can make sure the path looks ok.

When we are done, we set the z axis well again and click Cut Part.

We keep the index on the space bar to interrupt the process if anything goes wrong.

When we are done, we have a block of styrofoam where the top layer has been totally removed. alt text

Second assignment: make something big

Our machine is pretty small and we only had 2 days in the lab because of the confinement rules in France. So we made something small.

We made a small puzzle piece. We used a gap of 0.1 mm and couldn’t piece them together.

The first problem we had is that the milling went too far down. This dug too far down in the tabs, and as a result, the piece flew off.

alt text

We used 0.2 mm and it worked but it was way too tight. 0.3 mm was the perfect size. alt text

Hints for next time

The milling was very slow. Next time we mill into styrofoam, we can have a very small overlap, maybe 0.2. This way the milling can go faster