bill.french wrote:I was going to ask this on Dirk's build thread, but I'll ask here!
What's the significance of tracking direction?
Hi Dirk
This is my first post here on the forum, but I intend to post quite a lot.
I am looking for info to build my own laser cutter just like you guys all do.
The aim is to build a laser which accepts 121x61cm wood plates and acrylic, so its a rather large one. about 4'x2'
Currently I don't know if I'll go for 40 , 60 or 80 watt. The idea is currently to go 60 Watt from cnccoletech.
I found info about your PPI system and will try to understand your exact implementation. I'm also a atmel avr programmer (sometimes also arduino, but if needed I do also plain AVR which is much more powerfull for timing stuff)
If I understand right , then you have found out that the ignition of a laser is a lot more powerfull then the power it puts out in the rest of its burn cycle, so its better to ignite the laser for very short (3ms) pulses and instead of cutting you actually are perforating a row of holes... making the laser work less, provide more power and cut more clearly.
If I calculate right, then when you set a feedrate of 50mm/min at 1200PPI and a pulsewidth of 3ms, then the laser is only burning in about 118 milliseconds per second it is working and the other 882ms it is not burning at all. That means the laser is only on in 13.4% of the time and the rest of the time idle, making it run cooler and in meantime more powerfull ? Am I right with my calculations?
Now can I ask you how many steps has your machine for moving 1 inch in X/Y ? I suppose its the same steprate to ease things?
Also, I can clearly understand that, for example if you have 2000 steps per inch, you can count the steps on X or Y and know exactly how far the head has traveled, but what do you do then with the following example?
1) If X increases by 2000 steps, then the head moved 1 inch
2) If Y increases by 2000 steps, then the head moved 1 inch
3) If X AND Y increase by 2000 steps, then the head moved by 1.4142 inch !!!!!!!!!!!!!!!!!!!!!
Does your system count for that too ?
Kind regards,
Bart
3) Test cut another. If you got through, look at the edges, double PPI and half the Feed Rate and try again. If the edges look burnt or too dark for your liking (wood) or show signs of melting/bubbling especially around sharp corners (plastic), reduce the feed rate. This keeps the linear energy density the same and reduces the power put into the material.
educa wrote:Ow,
You system really looks nice. However, I must say 50mm/min or even 200mm/min is quite slow. Does the system also work if you go ut to for example 600mm/min ? Thats more like 10mm/sec and thats a speed which my cnc router also likes.
Can I also ask you what this does about the width of the cut? I am currently reading your whole buildlog (so I'm still ok for some hours of reading fun), but I dunno yet what laser wattage you have and also not what focus distance.
I understand that for a deepre depth of cut, i need a longer focal distance, but that will also make my cut wider. For engraving its then better to have a shorter focal distance? So what would be the best compromise then ?
educa wrote:Dirk, you say above3) Test cut another. If you got through, look at the edges, double PPI and half the Feed Rate and try again. If the edges look burnt or too dark for your liking (wood) or show signs of melting/bubbling especially around sharp corners (plastic), reduce the feed rate. This keeps the linear energy density the same and reduces the power put into the material.
Don't you mean that if edges look burnt, you have to increase the feed rate instead of reduce? Won't reducing feedrate provide more power to the material?
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