Yanxin,

I'm the one that developed/invented this process by varying the power to laser engrave 8bit shades and I do have to say, very good job!

Why don't you jump over to the Hobby CNC Art laser diode thread and post your results? This is a CO2 laser build thread that Tweakie started. Just a suggestion.

Jeff

Thanks Jeff, I read your threads before, lots of my ideas are coming from you, have not got a chance to say hi! I tried to register the forum you and John mentioned but I do not understand the language(hungarian?), will try again, I'll move to that thread once registered.

Yanxin

Yanxin

Too early to say that, it shows up as it burns more, sounds like the lead screw problem.
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Yanxin,
You might try to chase the threads of the lead screw with a sharp (new) thread die if you have one.  It might help. 

John Champlain
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I do not have the tools, I actually swapped the X and Y axis by swapping X and Y within the gcode and run it again, the lines is still the same direction, so my Y axis does have problems, it does not produce even lines, sometimes the spacing is larger. X is fine, no lines.

Yanxin

In preparation for the arrival of Mach version 4 (which does not support parallel port operation) I have been experimenting with the Smooth Stepper (external motion controller) and how it performs when controlling my laser.
Greg at Warp9 has done a great job with this product and the USS software plugin already supports the use of the M10 / M11 command set so it should have been a straight forward ‘plug and play’ exercise but unfortunately this was not to be the case.
I was getting occasional ‘wrong direction’ axis movements and after making many changes to the various USS settings nothing could cure the problem.
It transpires that my rather ‘old technology’ Alegro based stepper motor’s driver was experiencing signal related issues. After a bit of experimentation I fitted additional Schmitt trigger outputs (including a 150nS delay) to the direction signal lines from the USS and hey-presto there are no longer any axis ‘wrong direction’ moves.
Ahh - the mysteries and the wonders of electronics. 
Still some more investigation to do but I am hoping to determine just why this rather crude fix has cured my problem.

Tweakie.

Tweakie, I'm glad you have it sorted but interested in your on going investigation.  Can you elaborate any more on how you pinned the problem down and what components you used for the fix? 

Brett

Hi Brett,

I have sent you a PM but some more information for those that follow;

Initially (and as Jeff at the Warp9 forum suggested) I investigated electrical noise / incorrect earthing etc. (USB cables seldom have a screen to carry the PC earth via the USS to the Parallel Port cable screen) - once electrical noise / earthing had been ruled out my next thoughts was one of timing where the direction pulse was not being seen soon enough. Delaying the step pulses (to give the direction line transition more time) made the situation a whole lot worse so it definitely was not that.
In my mind there was always the possibility that if tri-state logic had been used in the SS design my stepper's driver could be picking up a false logic state in relation to the direction signal transitions so I tried delaying the direction signals and it worked.
Obviously, and as mentioned earlier, more investigation is required because 150nS is hardly worth considering as a delay so it may just be the Schmitt Trigger outputs which are doing the trick. As time permits I will look at this issue in more depth and post my findings.
The circuit I am using just consists of eight TTL gates, daisy chained for each direction line.

Tweakie.

Thanks Tweakie, Great find BTW.  This is one of those problems that could drive a man mad.

Brett

How do you keep so much knowledge and know-how in your head, Tweakie? I think your part Borg. I have trouble tying my shoes most days.

 

Tweakie.

Hi Sam,

Cast your mind back a while to when I was starting out with this project and having problems laser cutting acrylic with smooth edges.

Who was it that took the time to look at my GCode and discovered that my CAD/CAM created tool-paths were rubbish ?

Before your help. http://www.machsupport.com/forum/index.php?action=dlattach;topic=12444.0;attach=21730;image

After your advice. http://www.machsupport.com/forum/index.php?action=dlattach;topic=12444.0;attach=21738;image

You can’t tell me that you are having troubles with shoe laces.    

Tweakie.

Yeah, but..... that don't even compare. I think the answer to that problem was just so simple, you overlooked it.