Tuesday, December 19, 2006
The vertical dimension is just at 20 mm and the spacing of the cross-hatch lines is a bit over 8 mm. It's pretty easy to see the slewing at the corners. I definitely need a more rigid pencil holder.
Here is a slightly different cross-hatching pattern where I locked the pencil down a bit more solidly. Much less pencil slewing, though the line quality leaves something to be desired.
You can access the firmware code here.
Is this line using your pseudo-stepper logic? Are the line 'pulses' caused by your feedback that tries to correct the motor placement, or something else? Any ideas?
I don't do PWM any more after I discovered that there is a bottom limit to how slow you can make a motor run using it. Instead I do what you'd call pseudo-stepping where I just turn the motor on and off for short intervals (between 5 and 100 msec which isn't high frequency) for each gearmotor and then adjust the pulse rate using the relevant shaft encoder feedback.
***Are the line 'pulses' caused by your feedback that tries to correct the motor placement, or something else?***
As best as I can see watching the lines being put down the "pulses" are caused by the pencil point chattering as it is pushed rather than pulled over the paper. That's why it only happens on the up stroke rather than the downstroke.
Looks to be a bit higher-priced then what RepRap is aimed at but there does seem to some overlap.
How difficult would it be to use an ultra fine tip ball point or felt tip pen, instead of a pencil? Or do you think such a tool would have as much chatter as the pencil?
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