Found a bug in the DSP controller. (Marco please help)
Posted: Fri Jul 10, 2015 8:30 am
Hi Everyone,
Hopefully Marco can verify this for me, this is going to be a long post so I apologize for that
I've been building laser cutters for a while now and all of them have this same problem, it's related to the "engrave reverse offset" compensation in laserCad, as you may know, this function is used to compensate for compliance, belt stretch, servo tuning, etc. for those who haven't used it's located under "Work parameters" in lasercad as I show in the following picture:
This option is used to correct engravings that come out like this:
Where the distance "d", is the value that must be compensated under "Reverse offset" settings, the stretch or compliance is different typically at different speeds so that's why you can specify a different compensation value for different speeds (I'm very grateful for that function by the way) when this function of LaserCad is used the problem is corrected and all engraved lines become perfectly aligned.
It's good so far, but what happens when you try to engrave something and cut on the same job?, let's say I engrave the following:
You would expect for the engraving to be perfectly centered inside the cut square but what you get looks like this:
You can see that the engraving doesn't come out centered as it was drawn in LaserCad, I did further experiments and found out that the shifted distance is always equal to half the "reverse offset" value entered in the system preferences, and the engraved image is always shifted to the left (if my memory doesn't betray me, sorry I don't have real engraved pictures with me right now to show, I could upload them later).
So, for the above settings, if I engraved this square at 400mm/s speed, which has a reverse offset compensation of 1mm, the engraving will come out shifted 0.5mm to the left, this is quite a big problem for small art, it's very noticeable and sadly, as I always use servomotors (which can't be easily tuned to perfection), I must always use "reverse offset" compensation, or else my engravings will come out blurry and unprecise, as you may be thinking the solution would be to move everything I´m going to engrave to the right, half the compensation value for the speed I´m going to use, It does work, If I do that I get perfect results but it's obviously a programming error in the DSP so hopefully it can be corrected by the programmer.
Marco, could you please ask Mr. Lee to take a look at this for me?
I would be very grateful if I don't have to move the artwork each time I have to engrave and then cut something
Thank you
Cheers
Fernando
Hopefully Marco can verify this for me, this is going to be a long post so I apologize for that
I've been building laser cutters for a while now and all of them have this same problem, it's related to the "engrave reverse offset" compensation in laserCad, as you may know, this function is used to compensate for compliance, belt stretch, servo tuning, etc. for those who haven't used it's located under "Work parameters" in lasercad as I show in the following picture:
- Reverse offset settings
- Reverse offset.PNG (32.72 KiB) Viewed 2124 times
- Bad engraving requires reverse offset
It's good so far, but what happens when you try to engrave something and cut on the same job?, let's say I engrave the following:
- Engraving example
- Cut after engraving.PNG (3.79 KiB) Viewed 2124 times
- Engrave and Cut problem
- Shifted engraving.PNG (2.52 KiB) Viewed 2124 times
So, for the above settings, if I engraved this square at 400mm/s speed, which has a reverse offset compensation of 1mm, the engraving will come out shifted 0.5mm to the left, this is quite a big problem for small art, it's very noticeable and sadly, as I always use servomotors (which can't be easily tuned to perfection), I must always use "reverse offset" compensation, or else my engravings will come out blurry and unprecise, as you may be thinking the solution would be to move everything I´m going to engrave to the right, half the compensation value for the speed I´m going to use, It does work, If I do that I get perfect results but it's obviously a programming error in the DSP so hopefully it can be corrected by the programmer.
Marco, could you please ask Mr. Lee to take a look at this for me?
I would be very grateful if I don't have to move the artwork each time I have to engrave and then cut something
Thank you
Cheers
Fernando