Scrubbing though the .MOV video in QuickTime player, I see 4 frames at the same ‘left’ position. Scrubbing forward to the ‘right’ position, I see another 4 duplicate frames…
This video is 29.99fps
So:
At 1000 speed the full pause is ~4 frames: ~133.3ms (4 frames * 1/29.99ms), and at least >100ms (3 frames * 1/29.99ms)
At 600 speed the full pause is ~2 frames: ~66.7ms (2 frames * 1/29.99ms)
Maybe more pause is needed for inertia (let the elastic material of the laser head settle?).
Also, I wonder if the deceleration could be a lot more aggressive to get this thing moving faster…
At 450LPI, engraving a 3in fret slot (0.023" wide) at 1000 speed, there’ll be at least 100ms * 450lpi * 3in of pausing == 135seconds == (135/60)min == 2.25 extra minutes of pause on top of the actual work being done, and that doesn’t include the time needed for accel/deceleration…
(3 minutes, if you’re using the 133.3ms measure)
would be interesting to see a video from a pro at 1000… wondering if it has less pause.
The first column is the delay in waveforms tick, which are 100us. So it is only actually stationary for about 20ms I think. Not really a pause, just the first step of the acceleration ramp.
The second column is the byte in the file in hex, the next three columns are X,Y,Z motor positions in stepper units. I have skipped over the bytes where nothing happens. I.e. when the lines starts with 199 there have been 199 bytes of do nothing. Not the most efficient coding scheme!
I think the ruler engraves at 700 but if it uses the same acceleration the last steps of the turnaround should be the same.
Each step is less than 1 thousandth of an inch so you probably perceive it stationary for several steps. The last four steps take 82ms to go both ways.
See the two videos I posted. In one video the pause was 2 frames (at 600 speed) and in the other video the pause was for 4 frames (at 1000 speed). equating to 60ms and 133ms pauses each if we are to trust the sampling rate of a 29.99fps video… crude measure i know. but… should be as accurate as the sampling rate.
nah, it’s microscopic. In line with what I’d except for backlash. And I see this on other people’s machines too. note, the offsets are only seen in tiny sub 0.5mm text (or thin vertical lines). What the GF needs is a backlash calibration, it would seem (for the offset error… for the pause, idk what it needs).
It looks like turn arounds at each end are not symmetrical, which is odd. Also they vary a little from line to line. Perhaps that is due to the quantisation at 10kHz. It makes all the stepper pulses jittery. An engraving section looks like this:
Here is a graph of speed against time during a turnaround. There are only a few discrete speeds you can do at 10kHz so it dithers between the nearest two to get intermediate ones.
Looking further it does seem that most lines have a 60ms pause as each end. The first line seemed different for some reason.
Here is graph that goes right up to full speed where it starts engraving. To get an idea of the real speed I used a one tap IIR filter to average the dithered speed. That is the red line.
