Thursday, May 06, 2010

Further tests

I did a very careful, new series of speed tests using F960 (16 mm/sec) over a much longer diagonal baseline, viz, 1.7 meters, with the extruder running.

Here's what I found...

Step (mm)    Seconds (s)    Velocity (mm/sec)

    0.1                214                   5.77
    0.2                110                 15.40
    0.3                121                 14.14
    0.4                  80                  21.21
    0.5                  80                  21.21

Note that...

21.21 mm/sec ~ 16 mm/sec x 2^0.5

...which is about what you would expect for firmware that didn't correct for the angle of the print road.

As you can see, the break comes between gcode distances 0.3 and 0.4 mm and is quite abrupt. This means that the vectorization routine for Slice and Dice can be quite crude and work well with Rapman.


nophead said...

The speed reduction could be due to the firmware using acceleration. My firmware would give a similar effect, but the speed up on diagonals looks like a massive bug. How does anything print?

Forrest Higgs said...

As best as I can see Rapman doesn't do acceleration. I may be wrong, though.

Triffid Hunter said...

maybe your speed discontinuities are a result of aliasing between the steps/mm for your machine and your sub-millimeter commands?

as for getting 1.4x speed, what firmware are you using? I see code in the official FiveD to properly do diagonals, and my own firmware uses an integer approximation of the distance formula to do the same.