CNC

• 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.

Material

We have milled in many different materials and learnt what works and what does not.

Plastics

Polycarbonate

===Acrylic plastic "plexiglas"

Security-rules

1. You must have taken the CNC-course by Chalmers Robotics to run the CNC-mill
2. 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