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Discussion in 'Laser Cutters' started by joetemus, Feb 20, 2018.
A K40 to ACRO Co2 laser cutter build. Designed and built to expand the work area of the K40
joetemus published a new build:
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Joe, I'll be following your build since that is something I plan on doing too. If you don't mind, can you also post files of parts that you made yourself, like parts from acrylic. The dxf files will be best.
Justin, I plan on posting all the files. I want to make sure they all work before pointing people in the wrong direction. To try to make them easier to see I am making them all from 3mm red, orange, or yellow acrylic except for the tube holders which are currently 6mm black acrylic because I didnt have any other color of 6mm. I'll post the files as dxf, svg, and ipts
Won't let me update the build log tonight for some reason.
Started working on laser stuff tonight! Got the laser mounted( using the k40 stock mounting plates) and the two main mirrors mounted. I have the first two mirrors aligned relatively well, which wasn't nearly as hard as I was expecting. Still not perfect but good enough for me. Laser head is going on tomorrow, and I still need to figure out how to control the laser through pwm. All together though a very productive evening! Hopefully cutting first parts tomorrow?
Can you still cut through 3mm ply at the furthest corner? Just curious how size affects cutting power.
I have not completely dialed in the mirror alignment but I just cut a 20"x20" 1/4" oak board that turned out great. Once I get it properly aligned I plan on testing at all corners to make sure it works properly!
Hey, cool build!
Just noticing a couple serious safety concerns I feel I should bring to your attention (or others reading this with similar plans):
1. Decoupled dual drive Y motors:
I wrote a lenghtier explanation here: A Few General CO2 Questions but basically you always want a rigid mechanical connection between the two sides, preferably a driveshaft driving two belts. Reason being, that if one motor skips a step, the angle of your X gantry changes - can easily then miss the no3 mirror and shoot out the side. I couldnt find the video, but I had one of a local makerspace where someone knocked the mirror just a little while removing material, and the video included pictures of the burnt down booth next door. Even an unfocussed CO2 beam easily ignites cloth. Really, don't take a chance on this one!
2. Enclosure: You really want to enclose that machine:
2.1 Fumes: You will have a hard time extracting fumes from an open frame: in an enclosure, a little negative pressure extraction, means fumes go where they need to be: not into your lungs kicking off the cancer
2.2: Reflections / stray beams: Don't need to say more self explanatory
2.3: Restricting access to the 22kv supply: More than enough to stop your heart!
2.4: Earth path for Arcs: As your tube ages, and moisture in the air breaks down the HV transformers in the PSU, its just a matter of time until the path of least resistance becomes the open air + frame instead of the tube: Every single one of my laser tubes before replacement, arced to the case. In a enclosure, if its properly designed, the path to earth is an enclosed box, usually isolated from the main chassis, around the HV/Tube/wiring with a direct path to earth, usually through an earth spike. Its also wired to mains earth, and the chassis. If an arc to the case happens (well, not if, when, its inevitable) the farraday effect should allow the discharge voltage to flow through the inside skin of the case to the earth wiring. With a bare alu frame, the faraday effect is no longer on your side. My first laser was built the same (except with proper mild steel panels attached, see https://openbuilds.com/threads/v-slot-co2-laser-60-100w.617) - and i have first hand experience of this. In my case it was just a ruined motherboard, and no injury... But that was more luck: When I did version 2 (https://openbuilds.com/threads/openbuilds-freeburn-2-mini-v-slot-co2-laser-40-50w.1112/) I opted for a full enclosure instead!
I had never thought about how bad skipping a step could be on the y-axis, thank you for bringing this up. I will definitely look into trying to implement this for V2 of this build. I was trying to stick to a as stock of an acro frame as possible, but I have definitely found a few areas that I would like to change on that will make it more co2 laser friendly.
Also, I am definitely building a case. I have 15 sticks of 1.5M 2020 sitting right next to the machine, I just ran out of time to build this before the submission for the contest! I would really like to use sheet metal for all the paneling on this enclosure, but we will see how hard that is without a break. Would probably be worth it for the extra safety though. The earth path for arcs is a very good idea, I hadn't thought about that but will definitely include that in my enclosure build/design.
Thanks for all the tips! I actually wanted to build v2 of your laser cutter, but decided to go ACRO so that when my K40 tube/power supply dies I can use this for a standard diode laser and then I can build a 100w version of your laser cutter!
thanks for your info and guidance. I too am building an ACRO based laser cutter I hope. Although my laser is not a CO2 at least to get started. I am starting with a Raspberry Pi with the CNC hat as there are no XPRO available at this time. Great stuff I will be following your work closely.
Questio here??, Why the 5v in the Drain Pin of the mosfet? Im about to start my conversion today just waiting on UPS to arrive with the k40
The Xpro outputs 5v high as the max output for the power settings. The K40 requires 0v to be high and 5v to be low. this mosfet flips it so that is correct.
So are you regulating the k40 tube power with PWM? or just the mosfet as a on off switch?
There is full PWM power control. I set the K40 power controller (most are a pot knob, but mine is an actual board) and set the power to ~75% power to try to prevent the tube from being overpowered. The K40 tube is only meant for 30-35 watts, and the power supply over-volts it to make it 40, so it wont last super long at 100% power. With that mosfet I can control power from 0-75% using 0-100 in the laserweb software.
Can you elaborate a bit on the reverse logic powering the tube power supply, what I understand is that 5v is need it to maintain the laser off?
That is correct. Technically, this is actually flipping the PWM signal, not outputting a specific voltage. It will turn the power supply on and off really quickly simulating the correct power levels.
(theoretical voltage from xpro-theoretical voltage from mosfet-% of pwm signal at 5v on XPro-%of pwm signal at 5v after mosfet-% Power the power supply outputs)
5V -0V -100% -0% -100%
3.75V -1.25V -75% -25% -75%
2.5V -2.5V - 50% -50% -50%
1.25V -3.75V -25% -75% -25%
0V -5V - 0% -100% -0%
Everything in between as well. so with pwm you could tell it to run at 58% and it will be
2.9V -2.1V -58% -42% -58%
Does that make sense or is more confusing? I might've made it too complicated.
Im a airline pilot, so electrical engineering is a bit out of my normal knowledge until a lot of reading and understanding, also in your pics i saw two power supplies plus the tube one, this can be done with 12v or 24 v is need it?
I run my xpro off a 24Vdc power supply and I run my exhaust ventilation off a 12Vdc power supply. All of the control stuff with the mosfet is run off the K40 power supply but has to be tied into the Xpro so they have a common DC "ground".
Does the mosfet make sense on why its required? I can explain more if you'd like.
This is the model im getting today but you know how china products are, as soon i get the box ill confirm that it is a similar product as yours then we discuss if you dont mind that electronic Logic and thanks for your time.
Looks like the exact same model I have. I would recommend running it for a bit to make sure it all works (even if its making the plates for this conversion) things like the water flow meter not working will cause the machine to not run. My flow meter was broken from the factory but I would've been bashing my head against a wall if I hadn't caught it before trying to convert it over to the acro.
ir is here im impresed with the packaging
Pedro. Great new toy!!! I want one.
Hope it works. I still worry about sending soo much money to China and wondering what I'd get back.
Although, they have got so much better over the last couple of years.
It does look well packed, doesn't it!
They are now appreciating the whole Quality Control thing, mostly.
I'll look forward to the next comments.
Really surprise with the package but still the same junk, BTW this thing arrive in two days "free Shipping" from Tennessee, the rail system and belts feels all loose i dont know how this thing can even make perfect circles, ill post the out come later, i need to sleep just came back from a flight and this thing is scary so later tonite ill fire it up.
Didn't know there was a Tennessee in China!!!!
Still, they copy everything else, why not a State.
It works can I put it apart now????
WOW! That was fast. Just like that!
Go for it.
K40 Whisperer, mirrors came very good align
A lot to learn about this dangerous machine i got bite just at 10% of power in my small finger, dam that hurts, but i think is a normal way to learn that this stuff are not toys, power settings speeds etc but impressed how this thing cut a 1/4 inch acrylic like a hot knife thru butter "White Acrylic",, i will experiment a bit more with it before destroying it for this great idea
K40 ACRO Conversion,
It looks like you got one with the actual right powered tube in it, and not a smaller one like a load of other people get.
Pedro, I'd hold of just a week or so. I plan on releasing v3 of the conversion plates that has the tube gantry mounted. Makes aligning the mirrors so much easier.
What size acro did you build?