Week7. 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

Group assignment can be viewed at this link. - week7 Group assignment

Group assignment

do your lab’s safety training test runout, alignment, fixturing, speeds, feeds, materials, and toolpaths for your machine

here is the CNC maching in our lab:

Runout, alignment, fixturing.

First we need to turn on the maching, then fix our lumber to the machine tool.

The working area of ​​the machine tool is 2400x1200mm.

then use the software on the maching, to set the Mechanical origin.

Move the tool head to the edge of the processing area, and then clear the coordinates to zero, When each axis is set, the small square on the left will show green.

Toolpaths for our machine

here is the CNC drill bit in our lab which is 0.8mm diameter.

Mouse right click on Gcode window, to upload the test file to the software, then press “F8” to Simulate tool path.

then press “F9” on keyboard to start milling,

speeds, feeds, materials

We can see that there are two speed displays at the top of the software, one is the feed speed and the other is the spindle speed.

The feeding speed can be adjusted. The teacher suggested that when we first start feeding, we can start at a low speed, and then slowly feed at a faster speed. To process wood, the speed should be between 5000 and 6000 mm/min.

The spindle speed needs to be fixed at 240000rpm.

Plate specifications: 2440 mm x1220 mm, thickness 18mm

The material we use is high-density wood. This is the actual measured thickness of our wood.

Then press “F9”, the machine starts processing according to the test file Because we only set the test file to cut to a depth of 5mm, the cut is as shown below

Individual assignment

make (design+mill+assemble) something big (~meter-scale) extra credit: don’t use fasteners or glue extra credit: include curved surfaces

Maker something big

I saw a coffee table that I like very much on the Internet. I want to make some modifications based on it to make it my own coffee table. Based on my measurements of many coffee tables, I decided to set the height of the coffee table to 600mm and the table top to a circle with a diameter of 600mm. This should look higher than the one in the picture, because I don’t want the coffee table to be too short, and I plan to make the lower part of the table without hollowing out, because I want the coffee table to look more solid.

Because the table legs are not hollowed out, I changed the installation method of the table legs and the tabletop to a mortise-and-tenon structure.

3D modeling

I use onshape to modeling Set the parameters that may be used on onshape:

MT (material thickness),

diameter (tabletop diameter),

height (table height),

gapeight (gap height of the mortise and tenon mechanism),

chamfer (chamfer radius)

and then start drawing the support components for the lower part of the table, which is

Using the Mirror Tool, make another copy, and then modify the latch structure to cut from the bottom up. The cropping tool is also used here to cut off the excess, and two sketches of the support structure are obtained.

Then I started to make the tabletop. The tabletop mainly needed to calculate the position of the cross mortise and tenon structure. Here I used 2/3 of the diameter of the tabletop as the length of the cross. I also used the cutting tool to cut off the excess lines.

Then export the step file as follows,

here is the “step” file I made:

table support01.step

table support02.step

table_desktop.step

Generate G code

We use Auto CAD to arrange the parts, In order to save more wood, we use Auto CAD to arranged the parts of everyone in the team on three complete wooden boards.

There was something wrong with the files made by some students, which resulted in disconnection of the line. Finally, we found that the disconnection problem occurred because the files exported by some people were in DXF, and the STEP file must be exported.

export the step file, and then open the step file in MasterCAM:

Select the tool in the top menu bar, then right-click in the left window that pops up and select appearance，then click on the 2D cutting method.

The teacher suggested that we should start milling from small parts

Edit the tool path direction to make sure all cuts are facing right direction. It should be:

outline _ cuts are facing outside

drilling _ cuts are facing inside

if there is wrong, we need to Change the tandem direction of the tool path.

Then we start choosing the tool here in our lab only have the basic 8mm tool

Set feed parameters feed rate is 5000, Cutting speed is 500 safety heigh is 50, Feed cutting position is 3，Workpiece surface is 1， depth is -18(because the wood thickness is 18mm)

Check the tool path again

z-axis layered milling then press “R” on keyboard Simulate layered milling paths

Confirm that there is no problem, click g1 to generate gcode

and here is our Gcode file:

01

02

03

Then we start the preparation work before cutting,

1/turn on the exhaust fan；

2/fix the board on the machine tool, making sure there are enough clamps on each side to fix the board.

then open the file

set the Workpiece origin

Then we need to know several shortcut keys on the keyboard:

“F8” - c;

“F9” - start milling;

“F10” - pause;

“F11” - force stop.

we press “F8” to simulate tool path, then press “F9” to start.

It looked like this after cutting. It looked very good,

but then I discovered something. Because the milling cutter is round, the inner corners cut out are all rounded. I need to use a filet to polish each rounded corner (solve)

Solve the problem that milling cannot produce right angles . When designing drawings, you should pay attention to setting the inner fillets like this:

the start to Assembling

Here we are, the final look.

and here is the hero shot