Computer-Controlled Machining


  • I -- group assignment:
  • - test the runout, alignment, speeds, feeds, and toolpaths for our machine
  • II -- individual assignment:
  • - make (design+mill+assemble) something big (~meter-scale)

I -- group assignment:

For this weekly task I used an Gauss CNC Router that has a working area of 2500x1300 mm. Material that we used was a plywood 2500x1250mm and 15mm thick.

Below the plywood is a MDF board so as not to damage the surface of the machine.

To prevent the plywood from moving during the milling process, it needs to be fastened with either clamps or screws. I tightened the plywood with screws.

We decided to mill out two 70x70mm squares with corner fillets. We cut one square with the inside toolpath and the other with the outside toolpath. We did this so that we could compare the accuracy of the two toolpaths and also see if the cut out square would fit in the square hole.

After the grooved and toothed parts were made, their dimensions were measured using a moving scale to calculate the accuracy of the machine.

After measuring the parts I assembled them with a little help of sandpaper and a hammer and the parts fit into each other.

For work on the milling machine I used two types of milling cutters, plywood milling cutter -Ø 12 mm and engraving milling cutter - Ø2 mm

II -- individual assignment:

As my "something big" I chose a table - a bar table. I imagined a table that doesn’t need screws but holds itself. The table has three legs that hold two rings and has two plates on the top. The top plate has an engraved TSSB on it as an abbreviation of the school where I work.

The table has three legs that hold the rings. I made three incisions in each ring. The idea was three rings however .... Each joint is 15 mm wide due to the thickness of the plywood.
At the ends of each joint, I placed a rounding to make it easier to cut and move the cutter.
Because the cutter is circular in shape it cannot reach the corners of the joint.
There are several solutions to this problem.
Since I was working with my colleague Ivan on a group assignment and he chose the T-bon principle of joining parts, I decided to join the parts of my desk in this way and see what would happen.

When joining the table, the joints fit perfectly into each other.

After I made a 3D drawing in AutoCad I exported it to dxf format so that it could be loaded into the milling machine software and make a G-code.

After loading the dxf file into the program, the processing parameters are set.
Spindle speed is 22,000 rpm.
The dimensions of the plywood are 1250 mm x 2400 mm. One-sided milling is done in two passes 8 mm deep. I used a 12mm end mill.

The machine speed of 50% is selected, which is 8000 mm / min. The reason for setting the speed of 50% is that it is done with plywood because otherwise the material would tear. Excessive speed would not result in a nice cut. The figure on the right is an example of the results of the wrong speed selection.

Tool path


A wireless remote control can also be used to make the milling machine easier to operate.

When milling plywood, a lot of dust appears - sawdust that needs to be vacuumed.
For this purpose, there is a vacuum cleaner in the milling machine which uses a brush located above the milling cutter - which surrounds the milling head - to clean the workpiece from excess waste particles generated in the process.

Sawdust and dust are sucked directly into the bags.

After all the parts have been cut out, it remains to engrave the inscription in the upper plate.
For engraving purposes, I used a 2 mm diameter cutter.

The final result of engraving ...

And now came the compilation. I needed help because I couldn’t really hold three legs and two rings on my own at the same time. Two? Where did the third one go?
The third couldn't stop, not at all. Simply however I would try to place the third ring - the middle one - it was not possible to put the others. The idea of ​​a good realization 0.
So from the three-ring table came the two-ring table and it’s just great.
It's as if that's exactly how it's imagined.

AND .......

And finally my table is over. :) And used. :)