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Author Topic: The Laser Project.  (Read 821548 times)

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Offline Tweakie.CNC

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Re: The Laser Project.
« Reply #410 on: June 03, 2011, 06:47:43 AM »
It is difficult to see exactly what is happening from those pictures but it could (as I said earlier) be related to a delay in turning the laser on and therefore vary the spacing of the two images with changes to federate. What I was hoping to see was if each of the two images was created by alternate line scans (one image created by the left to right scan and the other image created by the right to left scan).
Going back over earlier posts in this and the other related thread, I think it would be a good idea to investigate the PWM laser current control aspect. I never managed to succeed with the Mach PWM control and it’s a long shot but perhaps this is what is causing your problems.
As a test, would you consider the following?
As I understand it, you have a board which converts the Mach spindle PWM signal to an analogue voltage from 0 to 5 Volts which is in turn connected to the laser PSU (IN and GND terminals) to control the maximum laser current.
Try disconnecting this board and connecting a potentiometer, as attached diagram.
Set the potentiometer to mid travel (never set it to maximum unless you can monitor the tube current to ensure that the makers maximum recommended current is not exceeded).
Turn off the PWM function within Mach and then repeat the same test as you did before.
I don’t know for certain but Mach really has a lot of work to do running this plugin and it may just be too much to ask for it to generate the PWM as well.
Either way this will at least rule out one possibility.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: The Laser Project.
« Reply #411 on: June 03, 2011, 06:52:54 AM »
Thanks Tweakie.Actually my board sends the pwm signal of mach dirrectly to the Psu.The PSU works either with Pwm or Analog dc 0-5v. The problem with the external potentiometer is that I cannot control on/off the laser!!
Re: The Laser Project.
« Reply #412 on: June 03, 2011, 06:54:31 AM »
I tried to attach a video but was to big.In the video it shows that the to images are made as you said.The left from left to right and the right from right to left!!!

Offline Tweakie.CNC

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Re: The Laser Project.
« Reply #413 on: June 03, 2011, 07:03:27 AM »
Another question comes to mind - How exactly do you control turning the laser on / off ?
Where do you connect the Digital Trigger output ?

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: The Laser Project.
« Reply #414 on: June 03, 2011, 07:05:41 AM »
I connect it to the board of mach where all Mach signals leave!

Offline Tweakie.CNC

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Re: The Laser Project.
« Reply #415 on: June 03, 2011, 07:18:53 AM »
As I see it the Digital Trigger should be set Active Low and the assigned output pin# should be connected to the laser PSU TTL(L) input and this is where the laser is turned on / off.
Are you switching the laser on / off a different way to this ?

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: The Laser Project.
« Reply #416 on: June 03, 2011, 07:25:24 AM »
I do exactly this! I use the same pin (9) that i control the laser when cut.In cutting I  control it like controlling the spindle speed.This only when I cut.For engraving I have made a separate Mach (engrave) where I disable the spindle and I enable pin 9 for the digital trigger.Do you see a problem in that connection?
Re: The Laser Project.
« Reply #417 on: June 03, 2011, 08:00:09 AM »
I will do that
Thanks

Offline Tweakie.CNC

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Re: The Laser Project.
« Reply #418 on: June 03, 2011, 12:53:09 PM »
ntlaser,

From what you have said and after looking again at all the possibilities I think it is definitely a delay issue, but perhaps not as I first thought.
Looking at your double image - if the laser was fired late then the left image would be created during the right to left movement of the axis. The only way in which the left image could be created during the left to right axis movement is if the stream of trigger pulses started early or in other words there is a delay in the start of the axis movement. This would also hold good for different feedrates altering the spacing between the two images and could also explain the non-linearity in your earlier Micky Mouse double image.

I have attached a revised diagram of how I think you should consider connecting your laser PSU and Mach. (Ignore PWM control of laser current and set it manually for both Engrave and Cut operations).

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: The Laser Project.
« Reply #419 on: June 03, 2011, 02:59:11 PM »
Tweakie thanks again I will try it and  tell you as soon as I test it.....