The SD4DNCRouter firmware is designed to allow the SD4DX controller to operate four-axis stepper motor systems, wherein the intent is to control the four motors as one unit. It supports "perfect line" drawing, wherein the firmware controls the relative W, X, Y, Z stepping rates needed to cause straight (linear) motion between specified pairs of W, X, Y and Z addresses. Additionally, the code provides a simplified arc/circle (actually, a polygon) drawing tool, which permits easy drawing of near-circles and similar figures on any two of the four motors. It has support for both 'trapezoidal ramp profiling' and 'chained vector ramp processing', so that matching NC applications can optimize motor motion.
The firmware also supports automatic compensation for motor backlash. This means that if your gearing system has 'play', you can program the 'play' amount separately for each motor, and the firmware will automatically "wind up" the play at any time that any motor changes direction.
As an active warning to customers, this firmware is not always friendly to 1/2 step or full step step-and-direction driver boards. Due to the details of how the ramping is performed on the slower motors, it is possible to induce an unexpected resonance failure in a slower motor caused by step pulse timing variance. On 1/8th step and finer drivers, this effect should not be noticeable.
The SD4DNCRouter firmware shares many of the features of the SD4DPotRouter four-motor controller firmware. The outputs to the external step-and-direction boards are identical, as is the general method of sending numeric parameters for commands. Many of the commands which configure the system are also identical (such as setting the step rate); however, the fundamental control theory is different. The SD4DNCRouter firmware explicitly controls all motors at the same time, from a single command (such as Goto or Arc), with automatic step-rate ratioing in order to generate straight lines; while SD4DPotRouter explicitly controls the two motors independently, so that one motor may be performing a "slew" operation, while the other is executing a "goto".
The SD4DNCRouter key capabilities may be summarized as follows:
- Up to four stepper motor driver boards may be controlled at one time.
- Separate 'backlash' adjustments are available for each motor
- Limit switches may be used to automatically request motion stop of any motor in either direction.
- Rates of 1 to 49,152 steps per second are supported.
- Step rates are changed by linearly ramping the rates; the rate of change is independently programmed for each motor, and can be from 1 to over 100,000,000 steps per second per second.
- System can be operated in both "trapezoidal ramp" and "chained vector" modes of rate control
- Motor coordinates are maintained as 32 bit signed values, and thus have a range of –2,147,483,647 through +2,147,483,647.
- Both GoTo and step-wise Arc NC actions are fully supported.
- A TTL "busy" signal is available, which can be used to see if the motors are still moving. Note that this information is also available from the serial communications subsystem.
- Complete control of the motors, including total monitoring of current conditions, is available through the TTL-serial and the USB connections.
- Can run off of a single user-provided 6.5 to 15 volt or 5 volt DC power supply.
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