CNC-Fräse/Technical

This page descibes technical aspects of the CNC machine in more detail.

Stepper Torque

The torque of a stepper driver is not linear over the number of revolutions per second. It is nearly linear in the beginning but drops down at a specific point for each motor until it reaches zero. In our current setup we use Sanyo Denki 103h7126-0740 Motors, which are linear until about 1000 to 2000 pulses/second. We are using 8 Microsteps, so the normal 200 steps per revolution (1.8 Degree step size) must be multiplied by 8, which gives 1600 steps per revolution. Now we can calculate the maximum speed for a axis by taking the maximum pulses/second and divide it by the steps needed per mm (266,6 on our machine): ${\frac {2000{\frac {\text{pulses}}{\text{s}}}\cdot 8{\frac {\text{pulses}}{\text{step}}}}{266{\frac {\text{steps}}{\text{mm}}}}}=60{\frac {\text{mm}}{\text{s}}}=3600{\frac {\text{mm}}{\text{min}}}$ We need the factor 8 here because of the microstepping.

This aspect of a stepper motor means also: lower microstep setting allows higher speed and vice versa.

Calculate everything

Here are some hints to calculate even more stuff:

• https://www.htw-aalen.de/img/downloads/315_Gleichungen-Fertigungstechnik.pdf
• http://www.precifast.de/spannkraft-schnittkraefte-berechnen/

Debugging Checklist

• Damit die Limit Switches funktionieren, muss der Druckerport im BIOS auf ECC+EPP gestellt sein. Ansonsten sind die Relevanten Eingangs-Pins kommentarlos nicht einlesbar.
• Wenn man Limits in EMC ausgelöst hat, hilft ein "override limits häckchen", ein einschalten (F1/F2), und ein wegfahren in die entsprechende richtung (Cursortasten und Page up/down)
• Wenn man die Fräse einrichten muss, sind wichtige Hinweise hier gesammelt: Benutzer:Reox/CNC and Benutzer:Chrysn/Flausch-o-mat --Reox 18:10, 4. Jul. 2013 (CEST)

Hardware:

• Stepper Driver: 5x Leadshine M542 Manual
• Breakout Board: Benezan Mini Breakout6 Manual
• Spindle: Mechatron HFS-6508-AC Manual
• Frequency Inverter: Powtran PI8600 Manual
• Stepper: Sanyo Denki 103h7126-0740 Tech Specs (Page 36)