Re: Lasers::Comments & Questions fo the List

On Wed, 12 May 1999 21:58:22 -0700, you wrote:

>> >
>> >Thanks for the reply, yes, you will be of great help as I go down this
>> >road. What I need to first know is either the best or safest way of
>> >mounting the laser to the base of the machine table. Should it be
>> >mounted stationary, beside/away from all the axis' and use mirrors to
>> >convey the beam, or mounted on the gantry and use the beam directly
>> >through the focal optics with no mirrors at all?
>> >
>> >Also John, what is the most commonly used software for controlling
>> >lasers in cutting operations. I am mostly wondering about the turning
>> >on/off and the percentages of power control. I will be cutting mostly
>> >lite ply up to 1/4" thick and balsa up to 3/8" thick for model aircraft.
>> >The software would ideally control both the laser and the motion, so I
>> >would need some insight along this road as well. I read in a previous
>> >thread here that IndexerLPT has a great range of uses, do you feel this
>> >may be useful as it uses a HPGL file directly to do the cutting profile?
>> >
>>
>> >Thanks very much,
>> >
>> Firstly let me make it clear that I am a mechanical engineer and have no part
>> with the electronics of the lasers but I can ask and get info on that subject.
>> A bit of background first on the company. They have 6 lasers A to F from 1Kw to 6Kw. the first one [ C ] is in mothballs due to lack of room.
> This is a moving X and Y table machine with the fixed laser mounted above the table firing down through the head by one 45 degree mirror.
>
> By having the lasers mounted this way, are they moving with the gantry?
>If so, does this effect the gases inside the tubes at all? I don't know
>if I mentioned it to you at all, but I plan on using a Synrad 40 watt
>CO2 laser. These do not need to have extra cooling devises and I have
>seen a 25 watt Synrad in operation and it did not quite cut through the
>thickness of the wood that I will be using. Let me clarify that it did
>lase through alright, but there was much distortion and a second cut was
>needed, so it was decided that a 40 watt should do the trick.

Possibly I didn't describe these right.
Image a fixed bridge over a bed that can move under the bridge in the X axis.
The laser is mounted on the top of this fixed bridge and so is also fixed.
On the front of this bridge is a set of horizontal Thompson rails this is the Y
axis. On these Y axis rails runs the head and Z axis.
The laser fires down to a fixed 45 mirror at one end of the bridge and from
there to a second 45 mirror to take it through the head and on to the work.
The Y axis is covered in to prevent any accidents with the exposed beam between
the two mirrors.

> Universal Lasers, of the U.S., markets small application machines that
>have table sizing of 12"x24" and 18"x24 ". This was the system that I
>had demoed for me at the salesman's shop, and he inputted object lines
>by using CorelDraw and another text editor for engraving applications,
>and I did not get the name of that. Now he was able to manipulate the
>power to the laser in percentages and had a stop/start somehow. This is
>the part that I am missing on. Was that machine using an HPGL device
>controllers from typical programs and let's say an AutoCAD plot
>controller for power ranges by the color of pens, and the on/off by the
>pen up/pen down command. If this is the case, then I can use my AutoCAD
>and import to the computer screen and cut from that I would think. Do
>you agree?
>

I asked the question about controlling power and on all these except the latest
the power is controlled manually on the laser by switching from CW [ continuous
wave ] to PW [ pulsed wave ]
The pulsed wave is basically a mark - space relationship that controls the power
input to the laser.
In CW mode there is no way to control the power only by adjusting the feed rate
of the table to prevent burning.
I also asked about these small self contained 40watt type laser and their
opinion was that they were CW and non adjustable but they admit that they
weren't sure.
I think I explained before that the stop start can be done by swinging a heat
sink in the way of the beam at the output mirror. On these lasers it's done with
a 120 degree electromagnetic shutter.

>
> I understand, and many thanks for being patient with me as I start my
>learning curve. Things are coming clearer in certain areas now with
>everyone's input, and especially yours John.
>
>Thanks again,
>Don Hughes
>Vancouver, BC Canada
>>

Regards,
John Stevenson
Nottingham, England