CNC
From Chalmers Robotförening
- The CNC can cut in many different materials, and create different shapes.
- the CNC either runs a program which reads instructions from g-code, or takes user input through the keyboard. controlling the CNC from the keyboard is called jogging, and this is rarely used to cut trough material.
- jogging is mostly used to verify that the g-code will run withouth problems and to calibrate the CNC before execution of the g-code.
- as the progam runs the g-code, each line contains a command (or comment, which will be ignored by the program)
- the program may need user interactions for events such as tool-change.
Security-rules
- You must have taken the CNC-course by Chalmers Robotics to run the CNC-mill
- Always follow the Checklist
Specification
| Brand | Optimum |
| Modell | |
| Max-X-travel | ca 480 mm |
| Max-Y-travel | ca 128 mm |
| Max-Z-travel | ? |
| Max-RPM | ca 3000 ( vid hög växel) |
| Max-Jog-speed | 1500[mm/minute] |
some hints:
- Max travel does not determine the maximum dimension of the piece you can manufacture, you have to take into acount that the tool has a diameter which you need to subtract from max "work-area".
- It's recomended to not attempt to manufacture a piece bigger than 110x400mm in one run.
- If you need to manufacture a piece bigger than 110 in both x and y direction, you may manufacture it in two runs ( but this is difficult and time-consuming).
CNC Milling calculating-rules
RPM [Revolutions per Minute]
- RPM = M / Tooldiameter
| Material | M |
|---|---|
| Polycarbonate | 20000 |
| Aluminium | 10000 |
| Nylon | 7000 |
| Steel | 5000 |
- A typical RPM could be 3000
Cut Feed-rate [mm/minute]
Cut feed-rate is the speed which the tool will travel in the XY plane while cutting through material
- Feedrate = K * ToolNumberOfTeeth * RPM
- K is the width of each teeth-stroke in the material in mm.
- K is usally 0.05
- K is maximum of 0.2 for rough finish in soft materials
- K is maximum of 0.1 for aluminium
- K is maximum of 0.05 for steel
- K should be 0.025 for high finish (almost glossy) DON'T use a lower K!
- K defines how fine the cut should be
- A typical Feed-rate could be 300 mm/min
Plunge Feed-rate [mm/minute]
Plunge feed-rate is the speed which the tool will travel in the Z-axis while cutting through material
| Små frässtål (3 - 5 mm) | Plunge feed-rate = 20% av cut feed-rate |
| Medelstora frässtål (5 - 8 mm) | Plunge feed-rate = 10% av cut feed-rate |
| Stora frässtål (8 - 14 mm) | Plunge feed-rate = 5% av cut feed-rate |
- No more than 100 mm/min
