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Author Topic: Add a laser to my CNC  (Read 15585 times)

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Offline Pedio

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Add a laser to my CNC
« on: December 18, 2015, 09:02:15 PM »
This is probably a stupid question  ::)

How do I add a laser to my existing CNC. More specifically how do I activate the laser? I thought about doing it with a micro switch and when the Z axis reaches a certain point it provides power. I have a 12V light on the router head that is connected to a jack. I could use this. I am sure there is a more elegant way of doing this in Mach 4.

Offline Tweakie.CNC

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Re: Add a laser to my CNC
« Reply #1 on: December 19, 2015, 02:07:13 AM »
Within Mach4 two very special commands (which do not have any noticable delay) have been added to switch lasers (and other fast acting devices). These commands switch an Output# of your choice which you have mapped to an output pin number (to provide the actual signal output).
The Mach4 command M62P1 will switch on Output#1 and the command M63P1 will switch off Output#1. Both of these commands need to be followed by an axis (any axis) movement (because activation only occurs at the instant of initial axis movement).
There are other methods and the following short video was made (before the M62/M63 commands had been written into Mach4) using the A axis direction pin for laser switching. My Gcode included the command A0.01 to turn the laser on and A0.00 to turn the laser off. My laser output power was varied between cutting and engraving toolpaths using the spindle speed S### commands.

https://youtu.be/8fUg6ebWut0

Tweakie.
« Last Edit: May 14, 2019, 05:04:02 AM by Tweakie.CNC »
PEACE

Offline Pedio

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Re: Add a laser to my CNC
« Reply #2 on: December 19, 2015, 10:21:17 AM »
I use Vcarve pro for my CAD and toolpaths. I will see if they have an A axis for laser on. I guess I would need a relay to go from 5V on an output to 12V for the laser. I do have extra outputs on my PMDX board that I could use.

Offline Tweakie.CNC

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Re: Add a laser to my CNC
« Reply #3 on: December 19, 2015, 11:02:26 AM »
Your laser would be switched on/off using a TTL signal (5volts or 3.3volts) not sure why you would want to use a relay.
Modifying your Vectric post-processor to replace any Z axis movements with a small A axis movement would seem the easiest way to use the A axis direction signal as the laser trigger.

Tweakie.
PEACE
Re: Add a laser to my CNC
« Reply #4 on: December 19, 2015, 11:18:28 AM »
Most small diode lasers have an input that is designed to take a PWM signal to turn
the laser on and also to control its power level. This input will take a logic level
signal and the main power input is left on continuously. Your breakout board most
likely has some outputs that are logic level that you can use to control the laser
in this way.

I don't know about configuring Vectric, but the most sensible way to configure
Mach4 is to use the spindle controls for the laser. M3 and M5 would turn the laser
on and off while the S word would control the PWM to set the power level.

The above will result in "exact stop" operation with the motion being planned
to come to a complete stop before the M3 or M5 turns the laser on or off.

Mach4 does have provision for some special M codes to turn a signal on or off
without stopping but you may not be able to use these because, first they
do not allow for PWM to control power level, and second, most controllers
do not yet support these codes. This is true for the PMDX SmartBOBs.
Steve Stallings
www.PMDX.com

Offline Pedio

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Re: Add a laser to my CNC
« Reply #5 on: December 19, 2015, 09:06:06 PM »
I was thinking about adding this one http://3dsupplysource.com/L-Cheapo
Re: Add a laser to my CNC
« Reply #6 on: December 19, 2015, 09:33:49 PM »
OK, this guy does NOT have a logic level ON/OFF signal, so you will
need to use a relay or an electronic switch that can handle the 1.77
amperes that it is designed to draw.

With a relay you will not be able to modulate the power level, nor
switch it fast enough to do raster style engraving. You can adapt
to the power level by controlling your motion speed.
Steve Stallings
www.PMDX.com

Offline Pedio

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Re: Add a laser to my CNC
« Reply #7 on: December 19, 2015, 10:06:55 PM »
They have a newer version http://3dsupplysource.com/L-CheapoV3
Re: Add a laser to my CNC
« Reply #8 on: December 19, 2015, 10:13:32 PM »
Their newer units seem to simply offer higher power, but still require
the input power to be switched. Other than lacking a power level
adjustment, this will still work fine for simple vector cutting.
Steve Stallings
www.PMDX.com

Offline Pedio

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Re: Add a laser to my CNC
« Reply #9 on: December 20, 2015, 07:56:01 AM »
Steve - the write up stated "Both the Mark 2 and the Mark 3 are now available with an optional PWM connector that lets you control the output via any logic-level pin, from 15% to 100% (if for some reason, such as engraving grasycale images, you need less laser power)."

Would that work with the PMDX-407 on a PMDX-410 board?

Not sure how I would get this to work with V-carve Pro yet without having to manually edit the Gcode. I did notice they have a couple of laser post processors. Perhaps one of these will work.