7. Computer-Controlled Machining

Also called Computer Numerical Control (CNC) is a manufacturing method that use preprogrammed software to control the movement and speeds of the tools. There are a lot of different types of CNC like routers, drills, water jets, etc.
This works thanks of a G-code or M-code this two contains the instructions and parameters of the tools. First you have to create a drawing CAD for then, thanks to a post processor generate the code.

Goup Site

If you want to read the Group Page, Click Here.
Safety

Whenever you use a machine there is always a risk, so a way of preventing them is using the appropiate equipment. Also knowing where are the fire extinguisher, fire alarm and school nursing.

    Safety Equipment (hover on each one):
  • Safety Goggles
  • Noise Headset
  • Lab Coat
  • Safety Boots
  • Face Mask

Design

For this week assignments I will be making a desk that can adjust it height in 3 different levels (chair, workshop bench and standing). After investigating different designs on Pinteres I found something to recreate and modify. We will use MDF of 15mm, this is important to consider the dimencions of the slots and the stress of the parts they will take.
First I made a sketch of the parts to give me an idea of the dimensions of the mdf and with a flexometer meassure other Desks to find the different heights.


This is the final design and how it is done:

Each Part Designing

Leg

CMA1200

Support Bar

CMA1200

Low Support

CMA1080

Heigh Stabilizer

CMA1390

Desk

CMA1390

Under Desk

CMA1390

Joint

CMA1390
     
After assembling everything to verify everything fit perfectly it looks like this. I added some transparency and a woodish material to a better understanding of the parts and how it will look.

Software

For the procces I used the software VCarve to generate the code and modify all the needed parameters.

Board dimension


CMA1200

Is the first thing it appears when creating a new file. Here you can change the dimensions of the material you are cutting in mm or in.

Import files


CMA1200

For adding the files you have to import them as Vectors (they will be open).

After adding all my parts I order them to fit in the material.

Join Vectors


CMA1080

It is important to join the vector to be a continuous contour. For this, select all the parts and click on join vector. There you can see how many are open and close.

Fillets


CMA1390

Like we want to be all pressed fit and the tool is circular, we can't make 90° turns in the holes, so adding a fillet help our parts to fit right in. There are diferent types of fillet, Dog-bone and T-bone, select one and add it to all the inside corners.

Change the tool


CMA1390

Depending on the material you got, it is important to change all the tool parametrs. Acording to the table on the group site, change the spindle speed, feed rate, number of passes, etc.

Simulate


CMA1390

After adding everything using the simulation can give a great reference of what the machine will performs in case you don't lika a movement you can change it before it is too late.

     

Machine

I will be using the Mach router. After having my code in a USB.

    Steps:
  • Turn on: red switch on the front
  • Open Mach3 app and load the file
  • Secure the MDF board to the table

    Calibrate Axis:
  • Calibrate XY: move with the keyboard arrows to a corner.
  • Calibrate Y: go to the center of the machine and start lowing the tool (Re Pag and Av Pag).
    • *Note: press shift for quicker moves.

For setting the coordinates click on the buttons next the XYZ.



Now that wa have all set, load the file into the computer and start cutting. Don't forget to turn on the filter to collect the shavings.

Thanks to the tabs the parts won't be loose so this is how it should look.

Assembly

After getting all our parts it is important to remove the tabs that the machine left.



Now that the part are completly clean we can start to assemble the desk.



Final Shots

In the pictures above we can see the final assembly at different heights.

Other CNC


Milling Machine

Another machine we have is the HAAS VF1. For making parts in this milling machine fist you have to make the part design on CAD, after in the same program you select all the milling operations and generate the code. Last semester I made a F1 steering wheel which I decorated using 3D printing parts.

 Tools configuration
One of the amazing uses of the machine is the option for changing between tools that are mounted up on a carousel. You can change by giving it diferent CNC codes. Such as:

  • N = Block number
  • S = spindle speed
  • F = cutting speed

    • The speed of the spinde and of cutting depends on the same rules as wood, just for aluminum material, in this case for a:

  • End Mill 3/4, S = 3600 (facing).
  • For a End Mill D 12, S = 2133 (We did almost all the part with this).
  • For End Mill D 8, S = 3200 (Inside pockets).
  • For End Mill D 5, S = 4000 (First holes).
  • And End Mill D 4, S = 4000 (Complete pockets).

    • As we can see all the tool parameters depends on the Mill, its size and the material you are cutting.


    Universal Robot (UR)

    Also adapting a UR robot for engraving and cutting is possible, in this case using RoboDK simulator. After selecting the tobot, creating a working plane and adding the tool and dxf file, we can create a code using its post processor.
    For making the mill we use a dremel and connect it to the engraver.
    After calibrating the UR and the mdf material we can start the procces.


    Files