Tangential knife

Setup for a tangential knife, driven by an own axis

A tangential knife is connected to a vertical axis and points towards the direction of the XY moves.
The initial direction (= angle 0°) is towards positive X-direction.

The main settings are [Setup - Graphics import - Path import - Path modification]:

• Select the axis name to be used as G-Code command.
• 'Swivel angle' defines, when to lift the knife, adjust the angle and lower the knife - if the change in angle is too big.
• 'Correct start angle' - a single tangential axis command will be set before a straight line, if the change in angle is greater than this value.
• 'Units per turn' - when using 'Z' as axis name, the feedrate for the tangential axis is limited by the X and Y axis, when together in motion. Using e.g. 3.6 units for a full turn, speeds up the tangential motion dramatically.
• 'Limit tool angle >=0°, < 360°' prevents the tool to exceed this angle-range (e.g. because the angle of rotation is limited by cables).

During the import of a vector graphic, the G-Code for the tangential axis will be generated - if enabled.
Example 1: Using a four axis controller, axis 'A' as tangential axis.
Example 2: Using a three axis controller, axis 'Z' as tangential axis and spindle PWM to drive a RC-Servo to lift the knife.

Calculating $102 (instead step/mm I assume step/1°), If the knife is directly connected to the Z stepper-motor: One turn = usually 200 step - times microstepping (m = 2, 4, 8, 16 or 32)
$102 = 200 * m / 360° =  0.555 * m. As "Units per turn" also use "360". This may cause bad performance because of low accelarting rates. To get around that:
$102 = 200 * m / 3.6° =  55.5 * m. As "Units per turn" also use "3.6".

Example 1

Just enable the tangential axis. The default values should work: Setup for A

I never tried this setup.

Example 2

Select the Z axis: Setup for Z

In [Setup - Graphics import - Path import - G-Code generation] disable Z-axis and enable Servo Control for Pen up/down motion.

Unfortunatly my mechanical setup is not strong enough for real paper-cut.