As I'm not so strong on math so I go with hard way.
As Linuxcnc output is restricted to change with base_period the timing
for the laser is in same range. So I just convert the laser position on
arc (actulay polar coordinate) for each position when can change (for
each 15us) to cartesian and check image what is in that position. If
there is a trace (black) then laser is off else the laser is on.
So the preprocesor is like this
for yboard=0 to boardHeight step 0.01
for angle = 0 to PI step arclenPer15us (scan only half of arc)
convert polar (angle/arm length) to cartesian (x/y)
if image at x,y+yboard = black
laser off
else
laser on
next
next
It's not perfect but works.
As pixels on the edges get more laser energy I expect some overexposure
and wider laser track but in practice I doesn't see any problem with
that. But maybe I just didn't hit the limit yet. As for now I do boarda
only 10cm wide I don't use the most distorted area.
Slavko.
On 13. 12. 2014 06:27, 'Jeff Heiss'
jeff.heiss@... [Homebrew_PCBs] wrote:
> At certain locations in the rotation angle, the laser does not fall directly
> in the center of the pixels. How are the pixels in the bitmap mapped to
> their position in the arc? Is the Bresenham algorithm or a similar
> algorithm used?
>
> -----Original Message-----
> From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
> Sent: Thursday, December 11, 2014 2:30 AM
> To: Homebrew_PCBs@yahoogroups.com
> Subject: Re: [Homebrew_PCBs] Re: laser ablation of paint on copper clad
>
> Hello..
> It's written in video description. The data is provided by python script.
> Well the workflow is like that:
>
> -Draw board.
> -export board to 800 or 1000DPI BW image -pass that image to python script
> to get bitfile -load bitfile into LinuxCNC -Push start
>
> Slavko.
>
> p.s.
> It's possible to pass just BW image to Linuxcnc but the power of my computer
> is just little to low to provide data in realtime. So I do preproces data.
> Maybe just better algorithm can solve that...
>
>
> On 11. 12. 2014 00:43, 'Boman33' boman33@... [Homebrew_PCBs] wrote:
>> Very nicely done!!
>>
>> What software are you using to do the bitmap or vector to rotary
>> control/firing?
>> Bertho
>>
>> -----Original Message-----
>> From: Homebrew_PCBs@yahoogroups.com
>> [mailto:Homebrew_PCBs@yahoogroups.com]
>> Sent: Wednesday, December 10, 2014 09:06
>> To: Homebrew_PCBs@yahoogroups.com
>> Subject: Re: [Homebrew_PCBs] Re: laser ablation of paint on copper
>> clad
>>
>> Just make a crapy video to show how I do that.
>> Instead to use CNC XY table and get 1200mm/min I add A rotational axis
>> and got 30159mm/min scan rate and use only Y axis to advance board
>> every revolution of arm by 0.01mm.
>>
>> The laser is mounted in aluminum arm to the stepper motor. Powering
>> stepper motor with 16 or 32x microstep was total disaster. Now I drive
>> motor in full step but picked speed where inertia of arm just coencide
>> with resonance so motion is wery smoth.
>>
>>
>> http://youtu.be/8ekioGZOkb4
>>
>>
>>
>>
>>
>> ------------------------------------
>> Posted by: "Boman33" <Boman33@...>
>> ------------------------------------
>>
>> Be sure to visit the group home and check for new Links, Files, and
> Photos:
>> http://groups.yahoo.com/group/Homebrew_PCBs
>> ------------------------------------
>>
>> Yahoo Groups Links
>>
>>
>>
>>
>
>
>
> ------------------------------------
>
> ------------------------------------
>
> Be sure to visit the group home and check for new Links, Files, and Photos:
> http://groups.yahoo.com/group/Homebrew_PCBs
> ------------------------------------
>
> Yahoo Groups Links
>
>
>
>
>
>
> ------------------------------------
> Posted by: "Jeff Heiss" <jeff.heiss@...>
> ------------------------------------
>
> Be sure to visit the group home and check for new Links, Files, and Photos:
> http://groups.yahoo.com/group/Homebrew_PCBs
> ------------------------------------
>
> Yahoo Groups Links
>
>
>
> .
>