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Author Topic: laser cutting NOVICE/ROOKIE question  (Read 1472 times)

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Offline nobby

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laser cutting NOVICE/ROOKIE question
« on: December 05, 2015, 09:06:27 AM »
I think I am going to buy an old a2, 420 by 600 or 2' by 1.5' laser cutter.
Its an older model, so wish to do the mach 3 conversion to it.
This particular machine has a moving bed.
it is a RF air cooled machine rather than a glass tube water cooled unit.
The first question is.......
I 'think' its a mere 30w laser, the purpose of its purchase is to cut up to 10mm acrylic,
can I not simply 'using sheetcam tng' set the machine to cut in two or more passes?
I.e. set sheetcam to raise the bed on the second and third pass?
seems too simple..................................................
-simply guessing the power can only cut into the material 3-4mm or 1/4 inch at a time,
does it need to blow the dross out the other side? I think it has air assist.
do they actually vaporize the material?

I gather all the smaller lasers machines use nema 17's? - so I stay 24 volts?

last question is, I don't think I am overly concerned of the machines speed,
so - do I need worry too much about laser on/off - How is this actually controlled

Thanks in advance
« Last Edit: December 05, 2015, 09:08:31 AM by nobby »

Offline Tweakie.CNC

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Re: laser cutting NOVICE/ROOKIE question
« Reply #1 on: December 05, 2015, 10:57:48 AM »
I see no reason why you should not use Sheetcam and cut things in two or more passes, raising the bed between cuts, as you suggest.
Ideally, materials are vaporized when cutting rather than burned but all materials behave differently. Whilst true Acrylic will vaporize and leave no residue wood, on the other hand, will leave a carbon residue which has to be removed by the air assist before subsequent passes.
As there is no tool load on the cutting head drive torque requirements are modest so NEMA 17's will be just fine.
For cutting there is no problems with laser switching M3 / M5 will do but for engraving you will find the the speed of the M11 / M10 is desirable.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

Offline nobby

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Re: laser cutting NOVICE/ROOKIE question
« Reply #2 on: December 06, 2015, 06:17:30 AM »
thanks
I think it does in fact run nema 17 motors,
I will simply fit a new psu, drivers and bob - usb. 24volt

It also appears that sheetcam can be configured as a laser cutter with a buy on add on.
This way, I get looped corners me thinks and lead ins and the like
 however I don't think it has the option to do multiple passes, -I.E. raise the bed
hmm

Offline Tweakie.CNC

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Re: laser cutting NOVICE/ROOKIE question
« Reply #3 on: December 06, 2015, 06:28:03 AM »
Quote
however I don't think it has the option to do multiple passes, -I.E. raise the bed

I am sure you have already worked this out - Edit the Sheetcam generated Gcode  (run Gcode, raise the bed, run Gcode, raise the bed, run Gcode).  :)

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: laser cutting NOVICE/ROOKIE question
« Reply #4 on: December 06, 2015, 07:23:48 AM »
Before you buy the sheetcam laser add-on, read the sheetcam forum as i asked a question and was given an answer about what the plugins actually brought to the party.

The laser one appears to require m10/m11 codes and is a laser engraved type application

...forum link not working on my phone or I would have pasted a link... Either way, ask Les if it does what you want before buying, to check you are happy
« Last Edit: December 06, 2015, 07:26:44 AM by robertspark »
Rob

Albert Einstein ― “If you can't explain it to a six year old, you don't understand it yourself.”

Offline nobby

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Re: laser cutting NOVICE/ROOKIE question
« Reply #5 on: December 07, 2015, 04:13:22 AM »
I THINK I GET IT.
has to be run like a plasma table, on off laser - plus corner looping and lead in and out = I suppose...
 BUT have a means of z axis movement, to cut thicker materials
=don't think it exists.
I.e. a mill will leave the spindle on when doing rapids etc.
a plasma setting won't move the z - axis.
tis probably why none have cut thick acrylic with low powered lasers.

so, corel/illustrator = sheetcam for laser with plasma type laser firing, but with a bed raise between passes, loop corners and lead in.

so a specific g-code generating version for 2d laser with bed raiser
with just the one pair of connections to the breakout board for laser on / off
maybe another to adjust the power setting

It does beg the question then.... IF for example a 10w laser could cut at 2mm,
5 passes............
« Last Edit: December 07, 2015, 04:19:58 AM by nobby »